Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEMS AND METHODS FOR CONTROLLING RATE OF CHANGE OF AIR
TEMPERATURE IN A BUILDING
CROSS REFERENCE TO RELATED APPLICATION
The present application claims benefit of U.S. Non-Provisional Application No.
17/139,293,
filed December 31, 2020. This application is a continuation-in-part
application of U.S. Application
Serial No. 16/832,618, entitled "SYSTEMS AND METHODS FOR AIR TEMPERATURE
CONTORL USING A TARGET TIME BASED CONTROL PLAN-, filed on March 27, 2020
which is a divisional application of U.S. Application Serial Number 15/043,134
entitled
"SYSTEMS AND METHODS FOR AIR TEMPERATURE CONTROL USING A TARGET
TIME BASED CONTROL PLAN," filed February 12, 2016, which are herein
incorporated by
reference in their entirety.
TECHNICAL FIELD
The present invention relates to a heating ventilation and air-conditioning
(HVAC) system,
and more particularly to an HVAC system in which HVAC equipment is operated
using a
controller. The present inventions further relates to methods for operating
such a controller.
BACKGROUND
Communicating thermostats and communicating TIVAC equipment generally refer to
HVAC equipment that exchange information and control signals using modern
communications
protocols. The increased flexibility of communicating systems provides several
advantages. For
example, communicating equipment may be automatically identified, including
identification of
available capacity settings and/or the number of stages for the equipment. A
communicating
thermostat may then use this information and the flexibility of the
communications protocol to
issue control signals corresponding to specific capacity settings to the
equipment. Although the
use of such protocols provides increased flexibility in the type and amount of
data possible to be
exchanged between communicating thermostats and communicating HVAC equipment,
there are
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significant tradeoffs. First, communicating thermostats and HVAC equipment are
generally more
expensive than their non-communicating counterparts, making communicating
systems cost
prohibitive for many consumers. Second, communicating systems are generally
inoperable with
non-communicating equipment, older equipment, and equipment from different
manufacturers.
As a result, consumer choice is extremely limited regarding equipment to be
used in a
communicating system. Moreover, this lack of interoperability limits the
ability of a consumer to
retrofit or upgrade a system without a relatively complete replacement.
Finally, while many of
the features and capabilities of communicating systems make installation and
setup much easier,
many of these features have limited use for the end user.
In contrast, legacy thermostats and HVAC equipment generally rely on simpler
control
signals, such as on/off-type signals (typically 24VAC signals), for
communication and control.
As a result, interoperability is generally less of a concern in HVAC systems
implementing only
legacy equipment, and consumers are given more flexibility in installing
equipment that better
suit their specific needs and budget. As used herein, the term "legacy" refers
to equipment that
has the ability to connect with a thermostat that sends 24VAC on/off signals.
In light of the above, there is a need for a system that provides the improved
degree of
control afforded by a communicating system while allowing a broad range of
thermostats and
other HVAC equipment to be used within the system. Preferably, the system
would allow for
both communicating and non-communicating legacy equipment and the device
discovery and
configuration processes would occur using several methods alone or in
combination and may
include reading or retrieving information provided by an installer, customer,
or other user;
reading or retrieving information available in a remote database; reading or
retrieving
information directly from the HVAC equipment; or learning the properties of
the HVAC
equipment using a trial and error approach.
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SUMMARY
Examples of systems and methods are provided for control of the air
temperature of a
building. For instance, examples of systems and methods are provided for
operating a HVAC
system according to a control plan based on a target time. The control plan
may be designed to
reach a desired air temperature in a building in the target time.
The system may include a controller that is coupled to indoor and/or outdoor
HVAC units.
The controller may include equipment terminals for controlling either
communicating or non-
communicating HVAC units. The controller may be communicatively coupled to a
thermostat.
The controller may also include sensor terminals which may be communicatively
coupled to one
or more air temperature sensors. The controller may also include accessory
terminals for
connecting devices such as indoor air quality equipment and dampers and other
zoning
equipment.
The controller may include a communication module. The communication module
may be
communicatively coupled with a computer device using a wired or wireless
connection. The
communication module may be used to send or receive performance and operation
data relating
to the HVAC system. The computer device may use the performance and operation
data to
analyze the HVAC system, providing for maintenance and optimized performance.
The
computer device may also be used to input control plan parameters such as
target time and
desired temperature.
The method for controlling the air temperature of a building may include
discovering
connected devices. The method may further include determining a target time
and an initial
control plan. The control plan may include operating one or more HVAC units at
a variety of
capacity or stage settings to achieve high performance or efficiency ratings.
The control plan
may then be executed by a controller in response to a heating/cooling call.
The controller may
then determine a satisfy time based on how long it takes to satisfy the
heating/cooling call using
the control plan. The actual satisfy time may then be compared with the target
time and used to
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update the control plan. The method may then be repeated using the updated
control plan when a
new heating/cooling call is received.
These and various other features and advantages will be apparent from a
reading of the
following detailed description and drawings along with the appended claims.
While
embodiments of this disclosure have been depicted and described and are
defined by reference to
exemplary embodiments of the disclosure, such references do not imply a
limitation on the
disclosure, and no such limitation is to be inferred. The subject matter
disclosed is capable of
considerable modification, alteration, and equivalents in form and function,
as will occur to those
skilled in the pertinent art and having the benefit of this disclosure. The
depicted and described
embodiments of this disclosure are examples only, and not exhaustive of the
scope of the
disclosure.
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BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the present embodiments and advantages
thereof may
be acquired by referring to the following description taken in conjunction
with the accompanying
drawings, in which like reference numbers indicate like features, and wherein:
FIG. 1 shows an HVAC system incorporating an existing therniostat, according
to some
embodiments;
FIG. 2 shows an HVAC system operating without a thermostat, according to some
embodiments;
FIG. 3 is an illustrative embodiment of a controller for use in an HVAC
system; and
FIG. 4 is a flow chart illustrating an embodiment of a method for controlling
the air
temperature of a building using a control plan based on a target time.
FIG. 5 is a flowchart illustrating an example method for achieving and
maintaining a target
rate of temperature change during a cooling operation in a building, in
accordance with certain
aspects of the present disclosure.
FIG. 6 is a flowchart illustrating an example method for achieving and
maintaining a target
rate of temperature change in a multi-equipment HVAC system, in accordance
with certain
aspects of the present disclosure.
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DESCRIPTION
This disclosure generally relates to a system for controlling a heating
ventilation and air-
conditioning (HVAC) system and methods of controlling HVAC equipment in the
HVAC
system.
For purposes of this disclosure, an HVAC system refers to any system that
provides one or
more of heating, cooling, or ventilation to an environment, such as a
building. The building can
be, but is not limited to, a residential building such as a home, apartment,
condominium, or
similar. An HVAC system may include one or more pieces of FIVAC equipment for
providing
heating, cooling, or ventilation. HVAC equipment includes, but is not limited
to, furnaces, air-
conditioners, heat pumps, blowers, air handlers, and dehumidifiers. HVAC
equipment may be
operable at one stage of operation only (i.e., single stage), at one of
multiple discrete stages of
operation (i.e., multi stage), or along a continuum of operational points,
such as with modulating
furnaces or inverter air-conditioning units. HVAC equipment may also operate
using gas,
electricity, or any other suitable source of energy.
The present disclosure is directed to an HVAC system comprising a controller.
In certain
embodiments, the controller is incorporated into one or more component of the
HVAC system,
such as a thermostat or piece of HVAC equipment, and communicatively coupled
to other
HVAC system components. In other embodiments, the controller is a standalone
unit
communicatively coupled to HVAC system components.
The controller operates by attempting to satisfy heating or cooling calls
received by the
controller within a specified target time. To do so, the controller determines
an initial control
plan for satisfying the heating/cooling call at a target time and then
proceeds to operate the
HVAC system based on the initial control plan. The controller then compares
the actual time
taken to satisfy the heating/cooling call to the target time and adjusts the
control plan
accordingly. The new control plan may then be implemented in the subsequent
heating/cooling
cycle. Based on the results of comparing the actual satisfy time to the target
time in the
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subsequent cycle, the control plan may again be adjusted. This process may
repeat continuously,
gradually converging on a control plan that satisfies the heating/cooling plan
in as close to the
target time as possible.
The control plan comprises settings at which HVAC equipment is to be run in
order to
satisfy the beating/cooling call. The control plan may comprise instructions
corresponding to one
or more of what equipment is to be run, how long a piece of equipment is to be
run, and, if the
equipment is capable of being run at more than one stage or capacity, the
particular stage or
capacity the equipment is to be run. For example, if an HVAC system includes a
three-stage air-
conditioning and is required to satisfy a cooling call within a 20 minute
target time, the control
plan may comprise instructions to operate the air conditioner at the second
stage for 15 minutes
and the first stage for 5 minutes.
In certain embodiments, the control plan may be adjusted if the actual satisfy
time is
greater than or less than the target time. For example, if the actual satisfy
time is greater than the
target time, the current parameters of the control plan are generally
inadequate to provide
sufficient heating or cooling. Accordingly, the controller may change the
operating equipment,
timing, or capacity parameters of the control plan to provide more heating or
cooling as
necessary. Conversely, if the actual satisfy time is less than the target
time, it may be assumed
that the current parameters of the control plan are too aggressive. As a
result, the controller may
change the operating equipment, timing, or capacity parameters of the control
plan to provide
less heating or cooling.
The present disclosure is now described in detail with reference to one or
more
embodiments thereof as illustrated in the accompanying drawings. In the
following description,
numerous specific details arc set forth in order to provide a thorough
understanding of the
present disclosure. However, the present disclosure may be practiced without
some or all of
these specific details. In other instances, well known process steps and/or
structures have not
been described in detail in order not to unnecessarily obscure the present
disclosure. In addition,
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while the disclosure is described in conjunction with the particular
embodiments, it should be
understood that this description is not intended to limit the disclosure to
the described
embodiments. To the contrary, the description is intended to cover
alternatives, modifications,
and equivalents as may be included within the spirit and scope of the
disclosure as defined by the
appended claims.
FIG. 1 is a schematic depiction of an HVAC system 100 in accordance with an
embodiment of this disclosure. As depicted, HVAC system 100 is incorporated
into a building
101. The HVAC system 100 includes a controller 102. Controller 102 is depicted
as being
incorporated into and communicatively coupled with an indoor unit 104. Indoor
unit 104 may
comprise, but is not limited to, heating equipment such as a furnace.
Controller 102 is also
communicatively coupled to an outdoor unit 106, which may comprise, but is not
limited to,
cooling equipment such as an air conditioner. Other examples of indoor and
outdoor units
include but are not limited to air handlers and heat pumps, respectively.
Controller 102 is further
communicatively coupled to a thermostat 108.
During operation, controller 102 receives heating or cooling calls from
thermostat 108.
Specifically, sensors within thermostat 108 determine if the current
temperature within building
101 rises above (in the case of cooling) or falls below (in the case of
heating) a temperature set
point. If one of these events occurs, thermostat 108 issues a heating or
cooling call to controller
102. In response, controller 102 may issue control signals to one or more
pieces of HVAC
equipment, including indoor unit 104 and outdoor unit 106.
In the embodiment of FIG. 1, thermostat 108 performs several functions. First,
thermostat
108 senses the temperature within building 101. Second, in response to the
temperature within
building 101 being above or below a desired set point, thermostat 108 provides
a signal to
controller 102 calling for cooling or heating, respectively. Once the desired
temperature is
reached, the heating/cooling call is removed. In certain embodiments, one or
more of these
functions may be performed by the thermostat or by other components of the
HVAC system.
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Thermostat 108 may also provide signals to enable or disable other optional
equipment
including, but not limited to, humidifiers and ventilators (not shown). In the
embodiment of FIG.
2, for example, a thermostat is not required and the functions described are
instead performed by
a temperature sensor alone or in combination with a controller.
FIG. 2 is a schematic depiction of a second embodiment of an HVAC system 200
in
accordance with this disclosure. HVAC system 200, which is incorporated into
building 201,
includes an indoor unit 204 and an outdoor unit 206 communicatively coupled to
a controller
202. Indoor unit 204 may comprise, but is not limited to, heating equipment
such as a furnace.
Outdoor unit 206 may comprise, but is not limited to, cooling equipment such
as an air
conditioner. Other examples of indoor and outdoor units include, but arc not
limited to, air
handlers and heat pumps, respectively. In contrast to the embodiment of FIG. 1
in which
controller 102 was incorporated into indoor unit 104, controller 202 is
depicted as a standalone
unit.
The embodiment of FIG. 2 further includes a temperature sensor 210 for
determining the
temperature within building 201. In certain embodiments, temperature sensor
210 may be
configured to determine one or more of the actual temperature within building
201 or whether
the current temperature within building 201 is above or below a temperature
set point.
Temperature-based signals and data from temperature sensor 210 may be received
and
analyzed by controller 202. For example, controller 202 may generate control
signals to control
HVAC equipment such as indoor unit 204 and outdoor unit 206, based at least in
part on the
temperature-based signals received from temperature sensor 210. In certain
embodiments, sensor
210 may transmit the temperature readings to controller 202. Controller 202
may monitor the
temperature readings provided by sensor 210 to determine if the temperature in
building 201
exceeds or falls below a temperature set point, thereby causing the controller
202 to generate a
heating/cooling call. In response to the heating/cooling call, controller 202
may issue appropriate
control signals to at least one of the indoor unit 204 and the outdoor unit
206. In other
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embodiments, sensor 210 may transmit a signal that the building 201 air
temperature is above or
below a temperature set point. Controller 202 may then generate a
heating/cooling call and issue
control signals to control HVAC equipment such as indoor unit 204 and outdoor
unit 206 in
response to this signal. In certain embodiments, temperature readings from
temperature sensor
210 may also be stored in a memory module of the controller 202. Stored
temperature readings
may be used by the controller 202 to determine temperature trends, response
times to control
signals, and other metrics to be used in refining a control plan implemented
by the controller
202.
FIG. 3 is a schematic depiction of controller 300 according to an embodiment
of this
disclosure in which controller 300 is configured to receive signals from a
legacy thermostat. As
previously noted. controller 300 may be incorporated into an indoor unit, an
outdoor unit, or a
thermostat or may be part of a standalone component. Controller 300 may
include a processing
unit 301A and memory module 301B.
Because controller 300 is intended for use with a legacy thermostat,
controller 300 includes
a terminal block 302 to connect controller 300 to a legacy thermostat.
Terminal block 302 may
include terminals corresponding to one or more corresponding output terminals
of the legacy
thermostat. For example, as shown in FIG. 3, terminal block 302 includes a
24VAC supply line
terniinal (R) 303A, a common ground terminal (C) 303B, a cooling call terminal
(Y) 303C, a
heating call terminal (W) 303D, a fan terminal (G) 303E, a reversing valve
terminal (0) 303F,
and a dehumidifier terminal (Dehum) 303G. In other embodiments, one or more of
terminals
303A¨G may be omitted or other terminals may be added. For example, if a
thermostat is
capable of issuing control signals corresponding to multiple stages of heating
or cooling calls
(e.g., Y2 or W2 terminals), the controller may include corresponding terminals
for receiving
such signals.
Controller 300 may also include one or more equipment terminals for
communicating with
indoor and/or outdoor units. For example, controller 300 may include a RS-485
interface 304
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suitable for communicating data and control signals to communicating HVAC
equipment.
Controller 300 may also include components for controlling non-communicating
equipment
using other signals, such as 24VAC signals. For example, controller 300
includes a cooling relay
306 and a corresponding cooling terminal block 308 for connecting controller
300 to a non-
communicating air-conditioning unit.
Controller 300 may also include interfaces for receiving data or signals from
other
components of the HVAC system. For example, controller 300 includes sensor
interfaces 310A,
310B for receiving data from a return air (R/A) and a supply air (S/A) sensor,
respectively.
Controller 300 may also include an accessory interface 311 for communicatively
coupling other
components of the HVAC system, including, but not limited to, indoor air
quality equipment,
dehumidifiers, humidifiers, ventilators dampers, and other zoning equipment.
Controller 300 may also include a communication module 312 for communicating
with a
computing device. Communication module 312 may include a wired interface. For
example, in
certain embodiments, communication module 312 may include, but is not limited
to, one or more
of a universal serial bus, Ethernet, FireWire, Thunderbolt, RS-232, or similar
interface. Instead
of or in addition to a wired interface, communication module 312 may include a
wireless
interface for communicating with a computing device. Such wireless interfaces
may include, but
are not limited to, Bluetooth, Wi-Fi, and ZigBee interfaces. in certain
embodiments,
communication module 312 may be configured to connect controller 300 directly
to the
computing device. Communication module 312 may also be configured to connect
controller 300
to the computing device over a computer network, including, but not limited
to, a local area
network (LAN), a wide area network (WAN) and the internet.
Communication module 312 generally permits controller 300 to exchange data
with the
computing device. In certain embodiments, the data exchanged between the
controller 300 and
the computing device may include system configuration data. System
configuration data may
include data regarding the HVAC system in which controller 300 is installed,
including
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information regarding any HVAC equipment or components that are included in
the HVAC
system. Configuration data may include general information about the basic
types of equipment
included in an HVAC system, but may also include specific details regarding
particular pieces of
HVAC equipment. For example, if an HVAC system includes a multi-stage air
conditioner, the
configuration data may include product details including the brand, model,
product number, and
serial number of the unit. The configuration data may also include performance
details including
the number of stages and corresponding capacities of the air conditioner.
Communication module 312 may also be configured to send and/or receive
operating
parameters. As previously discussed, controller 300 generally operates by
developing and
executing a control plan to meet heating and cooling calls to reach a desired
temperature set
point in as close to a target time as possible. During operation,
communication module 312 may
be used to send or receive operating parameters such as the temperature set
point and target time
to set or retrieve the operational goals of the HVAC system.
Communication module 312 may also be used to exchange historical performance
data
with a computing device. For example, controller 300 may store temperature
readings received
from a temperature sensor of the HVAC system in memory module 301B and
transmit or
otherwise make the temperature data available to a computing device.
Controller 300 may also
transmit historical perforniance data that may be used to assess the general
effectiveness of the
system and to determine whether maintenance may be required. For example, the
controller may
provide data regarding the amount of time which a particular piece of HVAC
equipment is
operated. Such usage information may then be used to determine the likely life
of HVAC
equipment parts and to develop a corresponding maintenance schedule.
FIG. 4 is a flow chart illustrating an embodiment of a general method for
operating an
FIVAC system in accordance with this disclosure. In one or more embodiments,
any one or more
of the steps described may not be performed. In other embodiments, any one or
more of the steps
depicted may be performed in any suitable order or in any combination.
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The method begins at step 402 with the controller initiating device discovery.
Device
discovery generally refers to the process of identifying the equipment present
in an HVAC
system and may include determining one or more of the type, capacity, number
of stages, or
other characteristics of that equipment.
Device discovery may occur using several methods alone or in combination and
may
include reading or retrieving information provided by an installer, customer,
or other user. For
example, in certain embodiments, the user may configure a series of dip
switches located at a
controller, a thermostat, a piece of I-1VAC equipment, or any other suitable
location within the
HVAC system to indicate the characteristics of one or more pieces of HVAC
equipment within
the system. During device discovery, a controller or other suitable piece of
equipment in the
system may read the dip switches to determine the characteristics of installed
HVAC equipment.
In certain embodiments, device discovery data may be stored in and retrieved
from
memory. For example, device discovery data may be stored locally in the memory
of a controller
of the HVAC system. In other embodiments, the device discovery data may be
stored in a remote
location, for example in a remote server. In either embodiment, the device
discovery process
may comprise executing instructions to retrieve the device discovery data from
the memory,
regardless of where the memory is located.
The device discovery data may be stored in memory that is read-only memory.
For
example, the memory may include device discovery data that is fixed during
manufacturing of
the HVAC system. In certain embodiments, the read-only memory may store
default information
corresponding to a default HVAC system and may permit an installer or other
user to reset the
HVAC system to the default HVAC system if an error, system failure, or other
problem is
encountered.
In certain embodiments, the memory may be reprogrammable by a user. In such
embodiments, the user may be able to input information corresponding to the
HVAC system to
be stored in memory. Any suitable method may be used to program the memory.
For example,
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the user may use a software application to configure the HVAC system and input
device data.
Such software may be run on any suitable platform. For example, in certain
embodiments, device
data may be input using a panel or terminal specifically designed for the HVAC
system. In other
embodiments, a user may use a computing device having a program or application
installed that
allows the user to input or modify device data. Such general computing devices
may include, but
are not limited to, laptops, notebook computers, tablets, smartphones,
netbooks, and desktop
computers. Inputting of device data may be done by directly connecting the
computing device to
the HVAC system using any suitable interface or by remotely providing the
device data,
including by providing data over a wired or wireless connection. For example,
in certain
embodiments, a user may input device data by directly connecting a computing
device to a piece
of equipment in the HVAC system using a wired connection which may include,
but is not
limited to, one or more of a universal serial bus, Ethernet, FireWire,
Thunderbolt, RS-232, or
similar interface. In other embodiments, the user may provide device data to
the HVAC over the
internet or through any suitable wireless technology, including but not
limited to Wi-Fi,
Bluetooth, and ZigBee.
In certain embodiments, device data may be stored and retrieved from a
database. The
database may be stored locally in memory connected to the HVAC system or may
be remotely
accessible from a server or other remote data source. In certain embodiments,
device data
corresponding to a given piece of HVAC system may be retrieved from the
database based on
information provided by a user or by components of the HVAC system.
For example, in certain embodiments, information may be provided to a database
regarding
a particular piece of HVAC equipment to include in an HVAC system. Based on
the information,
one or more database entries may be returned. For example, if a product name
or product ID
corresponding to a particular piece of HVAC equipment is provided, device data
for the
particular product may be returned. Alternatively, if more generic information
(e.g., heating or
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cooling, number of stages, capacity, etc.) is provided, multiple entries may
be returned from
which a selection or further refinement of the retrieved entries may be made.
Device data may also be reported to the HVAC system by the connected
equipment. In
certain embodiments, a piece of HVAC equipment may automatically report its
device data to
the T-1VAC system when first connected to the HVAC system. The HVAC equipment
may also
provide its device data in response to a device data request received from
other components of
the HVAC system.
In certain embodiments, device characteristics may also be determined using a
trial and
error approach. For example, if a cooling command is issued and temperature
does not drop, the
attached equipment is likely a furnace or other heating equipment. A similar
approach may be
used to determine if a piece of 1-1VAC equipment is capable of operating at
multiple capacities or
stages. For example, after determining that a cooling unit is connected, a
cooling command may
be issued, requesting the HVAC equipment to provide cooling at a first stage
and a second stage
corresponding to different capacities. If cooling following issuance occurs
faster when operating
in one stage or the other, the connected HVAC unit is likely a two-stage unit.
Conversely, if no
change is observed or if cooling does not occur, then the HVAC unit is likely
a single-stage unit.
After discovery has occurred, the controller determines the desired target
time 404. Target
time may be input directly by a user or installer or may be determined
automatically based on
user preferences. For example, a user may indicate a preference that the
system operates to
maximize performance, maximize user comfort, maximize efficiency, or to
achieve a preferred
balance of performance, comfort, and efficiency. In response, the controller
may automatically
determine an appropriate target time corresponding to the preferences. For
example, if a user
prefers performance over efficiency, the controller may apply a short target
time such that the
FIVAC equipment is operated at a relatively high capacity for a shorter period
of time. On the
other hand, if a user prefers efficiency over performance, the controller may
select a longer target
time such that the HVAC equipment is operated at a lower capacity for a longer
time.
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In certain embodiments, the user may input the desired target temperature
directly into a
thermostat that is communicatively coupled to the HVAC system controller. In
other
embodiments, the HVAC system controller may have a means for directly
inputting the desired
target temperature. In still other embodiments, the user may input the desired
target temperature
by directly connecting a computing device to the HVAC system using any
suitable interface or
by remotely providing the device data, including by providing data over a
wired or wireless
connection. Such general computing devices may include, but are not limited
to, laptops,
notebook computers, tablets, smartphones, netbooks, and desktop computers. A
suitable wired
connection may include, but is not limited to, one or more of a universal
serial bus, Ethernet,
FireWire, Thunderbolt, RS-232, or similar interface. A suitable wireless may
include, but is not
limited to Wi-Fi, Bluetooth, and ZigBee.
Once a target time has been determined, the controller develops an initial
control plan 406
for operating the HVAC equipment to satisfy a heating/cooling call in as close
as possible to the
target time. Establishing the initial control plan may occur in various ways
and may differ
depending on whether the equipment to be controlled is staged, and therefore
has discrete
capacity levels, or modulating, and is therefore capable of a continuous range
of capacities.
In certain embodiments in which staged equipment is to be controlled, the
initial control
plan may be established by detemiining satisfy times for each of one or more
stages. A satisfy
time is generally the time required for HVAC equipment operating at a
particular stage or
capacity to satisfy a heating/cooling call. Based on the satisfy times, the
controller may then
determine at which stage or stages one or more pieces of HVAC equipment should
be operated
and approximate the time required to run at each stage(s) in order to satisfy
a subsequent
heating/cooling call in a time that is as close as possible to the target
time.
In certain embodiments, the actual satisfy time for any given stage or
capacity setting may
be determined by running the equipment at the stage until the heating/cooling
call is satisfied.
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This approach may be repeated for each stage of the HVAC equipment to
determine the full
range of satisfy times.
In certain embodiments, determining satisfy times may comprise determining the
satisfy
time for a subset of stages and then calculating, estimating, looking up or
otherwise determining
satisfy times for any remaining stages based on the satisfy times of the
subset of stages. For
example, the satisfy time for the maximum capacity of a piece of HVAC
equipment may be
determined as previously described. Once the maximum capacity satisfy time has
been
determined, the satisfy times of any remaining stages or capacity settings may
be calculated,
estimated, looked up, or otherwise determined based on the maximum capacity
satisfy time.
Doing so eliminates the need to run the HVAC equipment at each stage or
capacity setting to
establish the satisfy times.
In certain embodiments in which satisfy times are determined from a subset of
satisfy
times, a proportional capacity map may be applied to the known satisfy times
in order to
determine satisfy times for any remaining stages or capacity settings. One
such method of doing
so is to apply a proportional capacity map that determines satisfy times based
on the relative
capacities of stages to the capacities of stages for which an actual satisfy
time has been
determined. For example, a system having a first, second, and third stage
corresponding to 40%,
60% and 100% (i.e., maximum) capacity may first be run at maximum capacity and
a
corresponding maximum capacity satisfy time of 10 minutes may be achieved.
Applying a
proportional capacity map based on capacity may then result in estimates for
the first and second
stage satisfy times of 25 minutes and 17 minutes, respectively.
More sophisticated mappings may also be implemented. For example, instead of,
or in
addition to, the ratios of stage capacities, the capacity map may be based on
a model that takes
into account thermodynamic effects, equipment characteristics, room
characteristics, or any other
factor that may affect the time in which a given piece of HVAC equipment is
able to satisfy a
heating/cooling call. In certain embodiments, the capacity map may be created
based in whole or
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in part on empirical data, which may include data generated during testing of
the HVAC
equipment or similar units or data collected during actual operation once
installed.
Because a low stage may not be able to satisfy the heating/cooling call within
a reasonable
time, or at all, certain embodiments may include a timeout if a
heating/cooling call is not
satisfied within a given time. In embodiments implementing a timeout, the
process of
determining the initial control plan may be abbreviated by not determining the
satisfy times for
any stages with capacities below that of a timed out stage.
Based on the satisfy times, the controller may establish an initial control
plan comprising
instructions for the HVAC system including, but not limited to, what equipment
to operate, at
what capacity thc equipment should be operated, and for how long. As a result,
the initial control
plan is a best guess of how to operate the 1-Ps/AC equipment in order to
satisfy a heating/cooling
call in as close to the target time as possible.
In one embodiment, the initial control plan is established by first
determining the minimum
stage capable of satisfying the heating/cooling call in less than the target
time. Because the
minimum satisfying stage will not properly satisfy the heating/cooling call in
the target time, the
target time may be more closely achieved by running the HVAC equipment at the
minimum
satisfy time for a first period of time then switching the HVAC equipment to
the next higher
stage for a second period of time. The length of the first and second periods
of time may be
based off of the satisfy times of the two stages. For example, if a target
time is 10 minutes, a
third stage satisfies in 6 minutes, a second stage satisfies in 8 minutes, and
a first stage satisfies
in 16 minutes, the second stage is the minimum satisfying stage. Accordingly,
the second stage
and the first stage are used in the initial control plan. Based on these
specific numbers, the initial
timing would be to operate at the first stage for 2.5 minutes and the second
stage for 7.5 minutes.
After the initial control plan is determined, the controller receives a
heating/cooling call at
408. In certain embodiments, the heating/cooling call may be received from a
legacy thermostat
communicatively coupled with the controller. In other embodiments, the
heating/cooling call
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may be received from a communicating thermostat coupled with the controller.
In other
embodiments, the heating/cooling call may be generated by the controller
itself in response to a
temperature signal received by the controller from a communicatively coupled
air temperature
sensor. In response to the heating/cooling call, the controller runs the HVAC
equipment based on
the current control plan until the heating/cooling call is satisfied. In
certain embodiments, the
controller may be programmed to time out if the heating/cooling call is not
satisfied within a
particular time period. Doing so may avoid situations in which the initial
control plan
underseryes a heating/cooling call such that the heating/cooling call cannot
be satisfied in a
reasonable time, or at all.
Once the heating/cooling call is satisfied, the controller determines the
actual satisfy time
using the current control plan at 412. The controller then compares the actual
satisfy time to the
target time at 414. Based on whether the actual satisfy time is greater than
or less than the target
time and, in certain embodiments, by what degree the target time and satisfy
time differ, the
controller updates the control plan at 416. When the controller receives a
subsequent
heating/cooling call, the controller implements the updated control plan,
determines the satisfy
time based on the updated control plan, compares the satisfy time under the
updated control plan
to the target time and updates the control plan again to account for any
differences. This process
may repeat continuously with the controller updating the control plan after
every heating/cooling
cycle.
As previously mentioned, the control plan may be updated based on whether the
heating/cooling call was satisfied in more or less than the target time and,
in certain
embodiments, the degree to which the target time was missed. If the
heating/cooling call is
satisfied in more than the target time, the control plan is adjusted to
provide additional
heating/cooling accordingly. To do so, the controller may adjust the control
plan in various ways,
including by changing one or more of the HVAC equipment used in the control
plan, the stages
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or capacities at which a piece of HVAC equipment is run, and the time during
which a piece of
HVAC equipment is run.
As an example, an embodiment of the current disclosure may include a
controller
communicatively coupled to a two-stage air-conditioner that implements a
control plan
comprising running the air-conditioner at the first stage for a first period
of time and at the
second stage for a second period of time. After implementing the control plan,
the controller may
determine that the time required to satisfy a cooling call is greater than or
less than the target
time. In response, the controller may adjust the first and second time periods
to account for any
discrepancies between the actual satisfy time and the target time. For
example, if the cooling call
was not satisfied within the target time, the control plan may be adjusted to
increase the amount
of time during which the air-conditioner is run at the second stage.
To the extent the controller is configured to adjust timing, the times for
which pieces of
HVAC equipment are operated or the times at which HVAC equipment is operated
at particular
stages or capacities may be adjusted by a fixed amount. For example, the
timing may be adjusted
by a set number of seconds in favor of the lower stage if the heating/cooling
call is satisfied too
quickly or the same number of seconds in favor of the higher stage if the
heating/cooling call is
not satisfied within the target time.
In other embodiments, timing adjustments may be variable. For example, one or
more
equations may be used to calculate new timing after each heating/cooling
cycle. Such equations
may adjust the timing based on the degree to which the satisfy time for the
more recently
completed cycle differs from the target time. An example of such an equation
is as follows:
( Target Time)
New Low Stage Time = Current Low Stage Time x ______________________ x C.F.
Satisfy Time
As shown in the equation, the new run time for the low stage is based on the
current timing
of the low stage and the ratio of the target time to the actual satisfy time
for the current cycle. An
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optional correction factor (C.F.) may also be included in the equation to
account for non-linearity
and other adjustments to the newly calculated timing.
In certain embodiments, the control plan may be adjusted by changing the
capacity at
which one or more pieces of HVAC equipment are operated. Adjusting the
capacity may
comprise changing the stage at which HVAC equipment is operated or, in the
case of modulating
HVAC equipment capable of operating along a continuum of capacities, changing
the operating
point of the modulating HVAC equipment. Capacity adjustments may be made in
addition to or
instead of timing adjustments.
In certain embodiments in which the control plan is adjusted by changing
capacities,
determining the initial control plan 406 may comprise determining an initial
capacity. The initial
capacity may be the minimum capacity that will satisfy a heating/cooling call
in as close to the
target time as possible. Determining the initial capacity may be achieved in
various ways. For
example, in certain embodiments, the controller may complete multiple
heating/cooling cycles at
various capacities and determine the actual time required to satisfy the
heating/cooling call at
each capacity. The capacity with a satisfy time that deviates the least from
the target time may
then be chosen as the initial capacity.
In other embodiments, the HVAC equipment may be run at a test capacity and the
initial
capacity for the control plan may be estimated, calculated, or otherwise
determined based on the
satisfy time of the test capacity. For example, in certain embodiments, the
test capacity may be
the maximum capacity of the HVAC equipment. Accordingly, if a target time is
20 minutes and
the heating/cooling call is satisfied in 15 minutes when operating at maximum
capacity, the
initial capacity for the control plan may be determined to be 75%.
After the initial capacity is determined, the controller may implement a
control plan based
on the initial capacity in response to a heating/cooling cycle. Once the
heating/cooling call is
satisfied, the satisfy time is compared to the target time and the control
plan is adjusted. In
general, if the satisfy time is less than the target time, the capacity
parameters for the control plan
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are decreased. Conversely, if the satisfy time is more than the target time,
the capacity
parameters of the control plan are increased. In certain embodiments, this
process repeats,
continuously adjusting the capacity of the HVAC equipment to hone in on the
target time.
In certain embodiments, adjustments to the capacity may occur in fixed
increments. For
example, the capacity may be adjusted by one of a fixed percentage of the HVAC
equipment's
total capacity, a fixed amount of volumetric output, and a fixed amount of
energy output (e.g.,
watts or BTU/hr).
In other embodiments, capacity adjustments may be variable. For example, one
or more
equations may be used to calculate new capacity after every heating/cooling
cycle. Such
equations may adjust the capacity based on the degree to which the satisfy
time of the most
recently completed cycle differs from the target time. An example of such an
equation is as
follows:
( Satisfy Time)
New Capacity = Current Capacity x _____________________________ x C.F.
Target Time!
As shown in the equation, the new capacity for the subsequent cycle is based
on the current
capacity and the ratio of the target time to the actual satisfy time for the
current cycle. An
optional correction factor (C.F.) may also be included in the equation to
account for non-linearity
and other adjustments to the newly calculated timing.
Notification that a heating/cooling call has been satisfied may occur in
various ways
depending on the equipment in the system. For example, in systems with legacy
thermostats, the
notification may correspond to the removal of a cooling or heating request by
the thermostat. In
systems that include temperature sensors, the notification may be generated in
response to a
temperature sensor detecting that a temperature set point has been reached. In
certain
embodiments, the notification may be generated by the temperature sensor. In
other
embodiments, the controller may generate a notification internally based on
temperature readings
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received from the temperature sensor or sensors. Alternatively, the sensor
itself may generate a
signal indicating that the temperature set point has been reached.
In certain embodiments, the HVAC system of the present disclosure is not
limited to a
single sensor. The system may include multiple sensors located throughout a
building. In some
embodiments, the sensors may be located in the rooms of the building. in still
other
embodiments, the sensors may be located in the ductwork of the HVAC system
itself It should
also be understood that the sensors of the present disclosure are not limited
to temperature
sensors. The sensors may include, but are not limited to, temperature and
humidity sensors. The
HVAC system controller may incorporate all information received from these
sensors, for
example temperature and humidity readings, into the control plan. Furthermore,
the information
from any of these receivers may be sent to a computing device, as discussed
above, for direct
monitoring by a user or other system.
In certain embodiments, additional inputs or data, such as a temperature set
points and real-
time temperature readings, may be used to adjust timing or capacity settings
of the control plan.
Such data may be useful in determining the effectiveness of a particular
control plan or in
developing a more suitable control plan in fewer cycles than would be required
without the
additional data. For example, if a sensor provides real-time temperature data,
a rate of
temperature change associated with particular stages or capacities may be
determined. The rate
of change may then be used to correct or otherwise refine stage timing or
capacity
determinations.
In certain embodiments, the control plan does not require a satisfy time to
operate. If the
temperature of the building is provided to the controller, then the controller
may design a control
plan using an algorithm that does not require calculation of a satisfy time.
In certain
embodiments, the controller may determine an initial control plan based on the
temperature
inside the building, the HVAC equipment available, and the preferences of the
user. The
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controller may then monitor the temperature inside the building and update the
control plan
based on the user's desired preferences of performance, comfort, and
efficiency.
As previously discussed, the control plan is generally established by
determining initial
control plan parameters, which may include timing and/or capacity settings,
and iteratively
adjusting the control plan parameters to develop a control plan that satisfies
a heating/cooling
call in as close to a target time as possible. Because of the iterative
process, a controller
operating in a relatively steady-state environment and with a consistent
target time and
temperature set point will generally converge on a particular control plan. In
other words, the
degree of adjustments required for the timing and capacity settings will
eventually diminish as
more heating/cooling cycles are performed. However, the environment in which
the HVAC
system is operating and the operating parameters of the HVAC system may be
changed during
operation. For example, the environment being controlled by the HVAC system
may be subject
to changes in temperatures caused by, for example, the opening of a window or
door, changes in
exterior temperatures, or uses of heat-generating appliances. Operating
parameters of the system,
such as the desired temperature set point and/or the desired target time, may
also be changed.
In general, the previously disclosed approach will adjust for such changes and
will
converge on a new control plan that accounts for the changed conditions
provided that the
FIVAC equipment is capable of meeting the resulting heating/cooling calls.
However, under
certain circumstances, such as when changes are particularly sudden or
drastic, it may be more
efficient for the system to begin from a new initial control plan than to
adjust the current control
plan over the course of multiple heating/cooling cycles.
In certain embodiments, the control plan may recognize when an unexpected
change in
performance can be ignored. For example, if a control plan is repeatedly
satisfying a cooling call
based on a 20 minute target time, and an unexpected event, such as the opening
of a door, causes
the next cooling call to be satisfied in 10 minutes, then the control plan
would recognize that this
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was not a permanent change to the cooling requirements of the building, and
would not adjust
the control plan accordingly.
Restarting the control process by determining a new initial control plan may
be triggered
by various conditions and events. In certain embodiments, for example, the
controller may restart
from a new initial control plan based on the degree to which the satisfy time
or the most recent
heating/cooling cycle differs from that of the second-to-last heating/cooling
cycle. Large
differences in satisfy times for consecutive heating/cooling cycles may
indicate that a significant
change has occurred in one or more of the controlled environment or the
operating parameters.
Accordingly, in response to discrepancies in satisfy times, the system may be
configured to
restart from a new initial control plan.
Restarting from a new initial control plan may also be triggered by a timeout
event caused
by the currently implemented control plan failing to satisfy a heating/cooling
call within a
particular time. The timeout may be based on an absolute time, such as a
particular number of
minutes. The timeout may also be based on a different parameter such as the
target time. For
example, a timeout may occur if the current control plan fails to satisfy a
heating/cooling call
within twice the target time.
Implementing a timeout may be particularly useful in multi-stage machines. For
example,
if a three-stage air-conditioner is operated using its first and second stages
only, a sufficient
inflow of heat may prevent the air conditioner from satisfying a corresponding
cooling call
within the target time even if the second stage were to run continuously. To
avoid continuously
n_inning at the second stage, a timeout may be implemented to stop the current
control plan and
develop a new initial control plan, which may include operating the air-
conditioner at the second
and third stages. Alternatively, a timeout may cause the system to increment
or decrement the
currently operational stages of the equipment without requiring a new initial
control plan.
Controlling Rate of Temperature Change in a Building
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In one or more aspects, the controller 300 may be configured to selectively
operate one or
more heating or cooling equipment of the HVAC system to achieve and maintain a
target rate of
change in air temperature within a building. This allows a user to control how
fast the air
temperature changes within a building both during cooling and heating
operations. In an aspect,
a rate of temperature change may be specified as a change in temperature value
in a specified
time period, for example, 5 degrees temperature change in one hour.
In one or more aspects, the controller 300 may receive a "rate of temperature
change"
setting from a user. For example, a user may provide a desired or target "rate
of temperature
change" setting using a computing device (e.g., a smartphone) communicatively
coupled to the
communication module 312 of the controller 300. As described above, the
communication
module 312 allows the controller 300 to exchange data with the computing
device. The
communication module 312 may include a wired interface. For example, in
certain
embodiments, communication module 312 may include, but is not limited to, one
or more of a
universal serial bus, Ethernet, FireWire, Thunderbolt, RS-232, or similar
interface. Instead of or
in addition to a wired interface, communication module 312 may include a
wireless interface for
wirelessly communicating with a computing device. Such a wireless interface
may include, but is
not limited to, one or more of Bluctooth, Wi-Fi, and ZigBee interfaces. In
certain embodiments,
communication module 312 may be configured to connect the controller 300
directly to the
computing device. Communication module 312 may also be configured to connect
controller 300 to the computing device over a computer network, including, but
not limited to, a
local area network (LAN), a wide area network (WAN) and the internet.
Computing devices may
include, but are not limited to, laptops, notebook computers, tablets,
smartphones, netbooks, and
desktop computers.
In an alternative aspect, the user may provide the target "rate of temperature
change"
setting by inputting a "rate of temperature change" value (e.g., 5
degrees/hour) in a thermostat
(e.g., thermostat 108) which is communicatively coupled to the controller. In
an aspect, the
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thermostat may transmit the target "rate of temperature change- value using a
wired connection
or a wireless connection to the controller 300. The thermostat may be
configured to exchange
data with the communication module 312 of the controller 300 using at least
one of the wired
interface or the wireless interface of the communication module 312. For
example, the
communication module 312 and the thermostat may connect to a Wi-Fi network and
may
exchange data with each other over the internet or a local area network (LAN).
In an aspect, the
user may select a 7-day weekly schedule for the target rate of temperature
change setting.
In an aspect, the user may specify different target rate of change values for
heating and
cooling operations. The controller 300 may receive the desired target rate of
temperature change
setting and save the setting in a non-volatile memory (e.g., memory 301B) of
the controller. In
an aspect, the controller 300 may determine the target rate of temperature
change automatically,
for example, based on user preferences. For example, the controller 300 may
determine a target
rate of temperature change based on a target temperature to be achieved and/or
a target time in
which the target temperature is to be achieved. As described above, the target
temperature and
the target time may be specified by the user.
In one or more aspects, the controller 300 may control a rate of temperature
change in a
building by selectively operating one or more equipment of an HP/AC system
(heating or cooling
equipment as required) at different capacities. For example, heating and/or
cooling equipment of
the HVAC system may be operable at a range of capacities. The controller 300
may adjust the
capacities at which one or more cooling and/or heating equipment operates to
adjust the rate of
temperature change within a building in order to achieve a target rate of
temperature change in
the building. For example, the controller 300 may change a capacity parameter
(e.g., a
percentage of the total capacity of the equipment) of an operating HVAC
equipment to provide
more or less heating/cooling as necessary in order to achieve the target rate
of temperature
change in the building.
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Adjusting the capacity of an HVAC equipment may include changing the stage at
which
HVAC equipment is operated or, in the case of modulating HVAC equipment
capable of
operating along a continuum of capacities, changing the operating point of the
modulating
HVAC equipment. The HVAC equipment includes, but is not limited to, one or
more air
conditioners, one or more heat pumps, one or more furnaces and one or more air
handlers. The
controller may operate a cooling equipment such as an air conditioner or
heating equipment such
as a heat pump or furnace depending on whether it received a heating call or a
cooling call from
a thermostat. Additionally or alternatively, as described above, the
controller may generate a
heating call or a cooling call based on ambient temperature readings received
from a thermostat
or temperature sensor and a target temperature setting specified by the user.
In one or more aspects, upon receiving (or generating) a heating call or a
cooling call, the
controller 300 initiates operation of an HVAC equipment at a predetermined
initial capacity. The
controller initiates operation of a cooling equipment (e.g., air conditioner)
in response to a
cooling call, or initiates operation of a heating equipment (e.g., heat pump
or furnace) in
response to a heating call. The following discussion applies to heating as
well as cooling
operations. In an aspect, the initial capacity of the HVAC equipment may be
set to a minimum
capacity of operation supported by the equipment. For example, the HVAC
equipment may bc
set to 25% of a maximum capacity supported by the equipment.
Once the operation of the HVAC equipment is initiated, the controller 300
periodically
samples the ambient air temperature in the building. For example, the
controller samples the
ambient air temperature in the building every 3 minutes. In an aspect, to
sample the air
temperature in the building the controller may poll a thermostat (e.g.,
thermostat 108) or a
temperature sensor (e.g., temperature sensor 210) installed in the building
and in response
receive a temperature measurement from the respective thermostat or
temperature sensor. In an
alternative aspect, the ambient air temperature may be recorded at regular
intervals by a
thermostat or temperature sensor in the building and the controller 300 may
periodically sample
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the latest temperature measurement recorded by the thermostat or temperature
sensor. It may be
noted that the controller 300 is not limited to sampling the ambient air
temperature in the
building at fixed intervals and may sample the air temperature according to
any predetermined
schedule or randomly. In an aspect, after initiating operation of the HVAC
equipment in
response to the cooling or heating call, the controller 300 may optionally
wait for a
predetermined stabilization period before initiating sampling of the ambient
air temperature in
the building. The stabilization period allows sufficient time for the HVAC
equipment to attain
stabilized operation at the initial capacity setting. For example, assuming
that the controller
initiates operation of the HVAC equipment at t=0, the stabilization period is
set to 10 minutes
and the sampling period is set to 3 minutes, the controller samples the air
temperature at t=10
min, t=13 min and so on.
At each sampling event (e.g., t=10 min, t=13 min ...), the controller 300
determines
whether the air temperature in the building has changed from the air
temperature sampled at the
previous sampling event. If the controller 300 detects no change in air
temperature since the
previous sampling event, the controller 300 increases the capacity of the HVAC
equipment by a
predetermined amount 'a'. At each sampling event, if the controller 300
detects that the air
temperature has changed since the previous sampling event, the controller 300
calculates a rate
of change (ROC) value. For example, the ROC value represents the rate of
change in
temperature over one hour (e.g., 5 degrees/hour). If the ROC value is smaller
than the target
ROC value (e.g., as specified by the user) indicating that the air temperature
is changing slower
than desired, the controller 300 increases the capacity of the HVAC equipment
by a
predetermined amount 'b'. The predetermined amounts 'a' and 'b' may be the
same or different
values. If the ROC value equals or is larger than the target ROC value
indicating that the air
temperature is changing at a rate that is same as the target rate or is
changing faster than the
target rate respectively, the controller 300 decreases the capacity of the
HVAC equipment by a
predetermined amount 'c'. The predetermined amount 'c' may be same as or
different from at
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least one of `a. or `b.. In an aspect, the value `b. increases by a multiple
of n (where n is a
positive integer) every subsequent sampling event, when the calculated ROC
value is smaller
than the target ROC value. Each of the predetermined amounts 'a', b' and 'c'
may be set to a
fixed percentage of the total capacity supported by the HVAC equipment or a
fixed percentage
of a current capacity at which the HVAC equipment is operating.
FIG. 5 is a flowchart illustrating an example method 500 for achieving and
maintaining a
target rate of temperature change during a cooling operation in a building, in
accordance with
certain aspects of the present disclosure. The method 500 may be implemented
by the controller
300 as shown in FIG. 3. It may be noted that while the method 500 has been
described with
reference to a cooling operation, the method 500 applies to a heating
operation as well.
Controller 300 triggers method 500 in response to initiating a cooling
equipment (e.g., air
conditioner) and after expiration of any pre-set stabilization period. As
described above, the
controller 300 may initiate the cooling equipment at an initial capacity in
response to detecting a
cooling call. For example, the initial capacity is set to 25%. In FIG. 5, the
capacity of the HVAC
equipment is represented by the term "demand".
In one or more aspects, the initial capacity at which the cooling or heating
equipment is
initiated (e.g., before step 502) may be dynamically adjusted by the
controller. For example, the
controller may set the initial capacity equal to the minimum capacity (e.g.,
25%) for night time
operation or if outdoor temperature is low (during cooling operation) or high
(during heating
operation). This allows the capacity to slowly ramp up if needed when the HVAC
system cycles
through method 500.
The controller may set the initial capacity to the maximum capacity (e.g.,
100%) if outdoor
temperature is high (during cooling operation) or low (during heating
operation). This allows the
capacity to slowly ramp down if needed when the HVAC system cycles through
method 500.
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The controller may set the initial capacity to the minimum capacity (e.g.,
25%) if the
previous heating/cooling call ended recently (e.g., less than 15 mills ago).
This may prevent
equipment short cycling.
The method 500 begins, at 502, by checking whether a predetermined sampling
period
(tRoc) has expired since the previous sampling event. tRoc may be a fixed time
interval such as 3
minutes. "Run Timer" represents a timer which is started when the method 500
is triggered and
"Timeouf represents a time of the previous sampling event. At 502, the
controller 300
determines that the predetermined sampling period tRoc has expired since the
previous sampling
event when (Run Timer - Time OLD > tRoc). When the controller 300 detects that
the
predetermined sampling period tRoc has expired since the previous sampling
event, the method
500 proceeds to step 504 where the controller increments a 'strike 1' counter
by 1. The strike
counter is initialized at '0'.
At 506, the controller 300 checks whether a new value of the ambient air
temperature
(RATNEw) in the building has been recorded. RAT (Return Air Temperature)
represents the
ambient air temperature in the building as recorded by a thermostat (e.g.,
thermostat 108) or a
temperature sensor (e.g., temperature sensor 210). RATNEw may represent an air
temperature
value recorded at or after the latest sampling event occurred (that is, at or
after expiration of the
latest sampling interval tRoc). Thus, at 506, the controller checks whether a
new air temperature
value RATNEw has been recorded after the latest sampling event occurred. If a
RATNEw has been
recorded after the latest sampling event occurred, the method proceeds to step
510. On the other
hand, if a RATNEw has not been recorded after the latest sampling event
occurred, the method
proceeds to step 508 where RATNEw is set to a current value of the air
temperature (shown as
RATcuR). RATcuR may represent a latest value of the air temperature recorded
by the thermostat
or the temperature sensor.
At step 510, the controller 300 checks whether RATNEw < RAToup, where RATow
represents a value of the air temperature recorded at or after the previous
sampling event (that is,
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at or after the expiration of the previous sampling interval tRoc).
Essentially, at step 510, the
controller 300 checks whether the latest recorded air temperature RATNEw is
lower than a
previously recorded air temperature RAToEc. If RATNEw is found to be not lower
than RAToup,
the method 500 proceeds to step 512.
At step 512, the controller 300 checks whether the strike counter is greater
than 1 (strike 1
> 1). If the strike counter is not greater than 1, the method 500 proceeds to
step 516 where the
capacity of the HVAC equipment is set to 50% (shown as Demand = 50%).
Alternatively, if the
strike counter is greater than 1, the method 500 proceeds to step 514 where
the capacity of the
HVAC equipment is incremented by 25% (shown as Demand = Demand + 25%). The
method
500 proceeds to step 528 from each of the steps 514 and 516.
At step 510, if RATNEw is found to be lower than RATaip, the method 500
proceeds to
step 518 where the controller 300 calculates a current rate of change (ROC) of
the air
temperature in the building as ROC =I RATNEw - RAToLe I . For example, the
calculated
current ROC value represents the current rate of temperature change per hour
between two
consecutive sampling events.
At step 520, the controller 300 checks whether the rate of change (ROC) of the
air
temperature in the building equals or is greater than a target ROC (shown as
ROC > Target
ROC). As described above, the target ROC may be provided by the user or may be
automatically
determined by the controller based on one or more parameter such as target air
temperature and
target time. If ROC is found to be equal or greater than the target ROC, the
method 500 proceeds
to step 522 where the capacity of the HVAC equipment is reduced by 5% (shown
as Demand =
Demand ¨ 5%). The strike counter is then reset to 0 at step 524.
Alternatively, if ROC does not
equal or is not greater than the target ROC, the method 500 proceeds to step
526 where the
controller increments the capacity of the HVAC equipment by a multiple of 5%
as a function of
the strike counter (shown as Demand = Demand + (strike 1 ¨ 1) * 5%). By
increasing the
capacity as a function of the strike counter, the controller increases the
capacity of the HVAC
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equipment by a higher value every time the ROC does not equal or is not
greater than the target
ROC in consecutive sampling events. The method proceeds to step 528 from each
of the steps
524 and 526.
At step 528, the controller sets RAToLD to RATNEw (shown as RAToED = RATNEw).
At step 530, the controller 300 sets TIMEoLo to the current value of the Run
Timer (shown
as TIMEoLD = Run Timer).
At step 532, the controller 300 resets RATNEw to 0 (shown as RATNEw = Empty).
At step 534, the controller 300 checks whether the capacity value of the HVAC
equipment
equals or is less than a minimum capacity at with the HVAC equipment is
operable. As noted
above, in the context of example method 500, the minimum capacity of the I-
1VAC equipment is
assumed to be 25%. Thus, as shown, step 534 checks whether Demand < 25%. If
the capacity
equals or is less than the minimum capacity at which the HVAC equipment is
operable, the
method 500 proceeds to step 536 where the controller sets the capacity to the
minimum capacity
of the HVAC equipment (shown as Demand = 25%). This step ensures that the
capacity of the
HVAC equipment is not set below the minimum supported capacity of the
equipment. The
method proceeds to step 538 from step 536. Alternatively, if the capacity is
found higher than the
minimum capacity at which the HVAC equipment is operable, the method 500
directly proceeds
to step 538.
At step 538, the controller 300 checks whether the capacity exceeds a maximum
capacity
(e.g., 100%) of the HVAC equipment (shown as Demand > 100%). If the capacity
exceeds the
maximum capacity supported by the HVAC equipment, the method proceeds to step
540 where
the controller 300 sets the capacity to the maximum capacity of the HVAC
equipment (shown as
Demand = 100%). This step ensures that the capacity is not set higher than the
maximum
capacity of the HVAC equipment. It may be noted that the maximum capacity
supported by the
HVAC system may be less than 100%. The method proceeds to step 542 from step
540.
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Alternatively, if the capacity does not exceed the maximum capacity of the
HVAC equipment,
the method 500 directly proceeds to step 542.
At 542, the controller checks whether the cooling call has been removed (shown
as cooling
call = active). If the cooling call is removed, the method 500 ends here. If
the cooling call is still
active, the method loops back to step 502 and runs another cycle of method 500
upon expiration
of the next sampling interval tRoc. The cooling call is generally removed when
the desired air
temperature is achieved in the building. Thus, as long as the cooling call is
active, the method
500 repeats steps 502 to 542 in order to achieve the target rate of
temperature change (Target
ROC) and to maintain the Target ROC once the Target ROC is achieved.
It may be noted that while the method 500 has been described with reference to
a cooling
operation, the method 500 applies to a heating operation as well. For a
heating operation, the
method 500 may be triggered in response to a heating call. Further, decision
block checks
whether RATNiEw > RAToLu and the decision block 542 checks whether the heating
call has been
removed.
In one or more aspects, some HVAC systems may include heating and/or cooling
equipment capable of multi-stage operation. Additionally or alternatively. an
HVAC system may
include multiple cooling and/or heating equipment providing multiple cooling
or heating
sources. For example, an HVAC system may include two different types of
heating equipment
such as a heat pump and a furnace. Similarly, the HVAC system may include
multiple cooling
equipment such as multiple air conditioner units. In such a case, the
controller 300 may leverage
the multiple stages of an equipment or multiple equipment to achieve and
maintain the Target
ROC. For example, when operating an equipment at a lower stage is not
sufficient to achieve the
Target ROC, the controller may operate the equipment at a higher stage to
provide a higher
degree of cooling or heating as necessary to achieve the target ROC.
Similarly, when the HVAC
system includes multiple heating or cooling equipment, the controller may
switch from a low
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capacity equipment to a high capacity equipment or simultaneously operate
multiple equipment
to achieve a higher target ROC.
In one or more aspects, when a system includes two or more heating and/or
cooling
sources, the controller 300 may initiate operation of a first source (e.g.,
heating or cooling source
depending on the heating or cooling call respectively) in response to a
heating/cooling call and
run the method 500 to achieve and maintain a target ROC. When the capacity of
the first source
reaches a maximum capacity of the first source (e.g., 100%) with the current
ROC still falling
short of the Target ROC, the controller may switch to a second source having a
higher
heating/cooling capacity than the first source and may run the method 500 by
operating the
second source. When the capacity of the second source drops below a minimum
threshold
capacity, the controller 300 may switch back to the first source to save
resources (e.g., power,
fuel etc.). The minimum threshold capacity of the second source may be set to
the minimum
capacity supported by the second source or any other value higher than the
minimum supported
capacity.
FIG. 6 is a flowchart illustrating an example method 600 for achieving and
maintaining a
target rate of temperature change in a multi-equipment HVAC system, in
accordance with
certain aspects of the present disclosure. The method 600 is shown as an
extension of the method
500 as shown in FIG. 5. The multi-equipment HVAC system may include multiple
heating
equipment and/or multiple cooling equipment providing multiple sources for
heating and/or
multiple sources for cooling respectively. The example method 600 applies to
both heating and
cooling operations.
The method 600 assumes that the 1-VAC system includes a source 1 and a source
2.
Sources 1 and 2 may represent heating sources or cooling sources depending on
a heating
operation or cooling operation respectively. For example, in the context of a
heating operation,
source 1 may represent a heat pump and source 2 may represent a furnace. In
the context of a
cooling operation, sources 1 and 2 may represent two different air
conditioning units. Method
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600 initiates operation of source 1 (before initiating step 502 in FIG. 5) in
response to a heating
or cooling call whichever the case may be.
At step 538, if the capacity exceeds the maximum capacity supported by source
1, the
method proceeds to step 540 where the controller 300 sets the capacity to the
maximum capacity
of source 1 (shown as Demand = 100%). The method 600 then proceeds to step 602
where a
second strike counter "strike 2" is incremented by one. Strike 2 is
initialized at '0'. At step 604,
the controller 300 checks whether strike 2 has equaled or exceeded a maximum
threshold value.
In the example method 600, the threshold strike 2 value is set to 5, and thus,
step 604 checks
whether strike 2 > 5. If strike 2 equals or is greater than the threshold
value, the method proceeds
to step 606 where the controller 300 switches from source 1 to source 2 and
resets the strike 1 to
'0'. Source 2 generally is a more powerful heating/cooling source than source
1 and is capable of
achieving higher ROCs than source 1. Alternatively, if strike 2 is less than
5, the method
proceeds to step 542. In an aspect, switching from source 1 to source 2 only
when the strike 2
reaches a threshold value allows a minimum number of chances (equal to the
threshold strike 2
value) for source 1 to achieve the target ROC at its maximum capacity before
switching to the
source 2. For example, when source 1 is a heat pump and source 2 is a furnace,
source 2 may be
associated with a higher energy cost than source 1. In this case, it may be
more efficient to
operate source 1 at its maximum capacity for a few extra cycles before
switching to source 2.
At 534, if the capacity equals or is less than the minimum capacity at which
the HVAC
equipment (source 1 or source 2 whichever is currently operating) is operable,
the method
proceeds to step 536 where the controller sets the capacity to the minimum
capacity of the
HVAC equipment (shown as Demand = 25%). The minimum capacities of source 1 and
source 2
may be set to the same value, different values, or to the actual minimum
capacities supported by
sources 1 and 2. The method 600 then proceeds to step 610 where the controller
checks whether
source 2 is operating. If source 2 is not operating (e.g., when source 1 is
operating) the method
proceeds to step 538. Alternatively, if source 2 is operating, the method 600
proceeds to step 612
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where the controller decreases strike 2 by one (shown as strike 2 = strike 2 ¨
1). At step 614, the
controller checks whether strike 2 equals a minimum threshold (shown as strike
2 = 0). If strike 2
does not equal zero the method 600 proceeds to step 538. However, if strike 2
equals 0, method
600 proceeds to step 616 where the controller switches back from source 2 to
source 1 and resets
strike 1 to zero (strike 1 = 0). in an aspect, the strike 2 minimum threshold
may be set to any
value below the maximum strike 2 threshold value.
In one or more aspects, the controller 300 may be configured to automatically
select or
adjust the rate of temperature change setting based on one or more factors.
The controller may reduce the rate of temperature change in order to save
power and/or
increase efficiency of operation of the HVAC system. For example, the
controller may reduce
the rate of temperature change if a conditioned space is unoccupied for
extended periods of time.
The controller may reduce the rate of temperature change if outdoor
temperature is low and the
HVAC system is cooling, or if outdoor temperature is high and the HVAC system
is heating.
The controller may reduce the rate of temperature change during night time
when occupants are
asleep.
The controller may adjust the rate of temperature change based on electric
utility
automated demand response (ADR) signaling. For example, the controller may
select a slower
rate of temperature change if the electric utility's ADR clamping is in
effect.
The controller may lower the rate of temperature change in order to reduce
equipment
noise. For example, if the user is in a meeting, the controller may lower the
rate of temperature
change in order to reduce duct noise due to high air flow. This applies to any
other activity that
requires the HVAC noise to be reduced while still meeting cooling/heating set
points from the
thermostat.
The controller may dynamically adjust the rate of temperature change for a
zoned system.
For example, the controller may select a lower rate of temperature change when
a majority of
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zones are closed. The controller may select a higher rate of temperature
change when a majority
of zones are open.
The controller may select or adjust the rate of temperature change based on
which one or
more accessory is currently being used. For example, the controller may lower
the rate of
temperature change when a dehumidifier is running during a cooling operation.
Lowering the
rate of temperature change extends the cooling cycle time, which allows the
dehumidifier to
dehumidify more effectively. Similarly, the controller may lower the rate of
temperature change
when a humidifier is running during a heating operation. Lowering the rate of
temperature
change extends the heating cycle time, which allows the humidifier to humidify
more effectively.
In one or more aspects, the controller 300 may be configured to select or
alter the sampling
period (tRoc) based on one or more factors.
The controller may select or adjust tRoc based on outdoor temperature and/or
humidity. For
example, a shorter tRoc is selected if the outdoor temperature and/or humidity
is too high. The
controller may receive outdoor temperature and/or humidity readings from
various sources
including, but not limited to, one or more outdoor thermostats, one or more
outdoor
temperature/humidity sensors and from an online weather service over the
intemet.
The controller may select a new tRoc in response to detecting a drastic change
in air
temperature within the building. For example, the controller may select a tRoc
that is shorter than
a current tRoc in response to detecting a temperature spike (positive or
negative spike) within the
building. The controller may temporarily implement the shorter tRoc till the
temperature spike
subsides, after which the controller may reset the tRoc to a previously
selected value. In an
aspect, the newly selected tRoc may depend on how significant the change in
temperature is. For
example, a larger change in temperature may result in a shorter tRoc being
selected by the
controller.
The controller may select a new tRoc in response to detecting a drastic change
in return air
temperature. Return air temperature may be measured by a temperature sensor
installed in a
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return air flow duct. The controller may temporarily implement the shorter
tRoc till the
temperature spike subsides, after which the controller may reset the tRoc to a
previously selected
value.
The controller may select a new tRoc in response to detecting a substantial
change in the
capacity at which a heating or cooling equipment is operating. In some cases,
when the controller
rapidly raises the capacity setting of a heating or cooling equipment, there
may be a delay in the
higher heating or cooling output being reflected by temperature readings. In
such a case, the
controller may select (e.g., temporarily) a longer tRoc value to allow for the
higher heating or
cooling output to be reflected by the thermostat or temperature sensor
readings.
In a zoned installation, thc controller may select a new tRoc if a zone is
closed. This is
because any previously taken temperature readings taken for a previous zone
configuration may
no more apply for the new zone.
The controller may select tRoc as a function of a sensitivity of a temperature
sensor
installed in the building and feeding temperature readings to the controller.
Different temperature
sensors may have different sensitivities, wherein the sensitivity of a
temperature sensor depends
on various factors including, but not limited to, the material used for
constructing the sensing
bulb (e.g., metal, glass, plastic etc.), amount of epoxy used for
waterproofing the sensor and the
paint used for the sensor.
The controller may select or adjust tRoc depending on a level of occupancy
within a
building or an area of the building. For example, the controller may select a
shorter tRoc in
response to detecting that an area of the building is occupied and/or
detecting constant activity/
occupancy in area. Occupancy and/or activity data for the building may be
obtained by various
means including, but not limited to, motion detectors, infrared cameras,
ultrasonic sensors, ultra-
wide band geolocation sensors, global positioning system (GPS) geolocation
systems, and
wearable devices (e.g., smart watches, ibeacons etc.). User activity may also
be ascertained from
the stability of return air temperature. For example, more jitter in the
return air temperature
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implies a constantly changing system load, which may be due to increased
activity in a
conditioned space for example during daytime. By contrast, night time return
air temperature
trends relatively follow a smoother trajectory, therefore a higher tRoc may be
selected.
The controller may select tRoc based on the rate of temperature change
setting. A shorter
tRoc may be selected for a larger rate of temperature change setting (e.g., 10
degrees per hour),
and a larger tRoc may be selected for a smaller rate of temperature change
setting (1 degrees per
hour).
The controller may select or adjust tRoc based on how close a current capacity
at which a
heating or cooling equipment is operating is to the maximum capacity of the
equipment. For
example, the controller may increase the tRoc to a larger value if the
equipment is operating close
to the maximum capacity supported by the equipment.
The controller may select tRoc based on which accessories are currently
running. For
example, the controller may select a longer tRoc if a ventilator is running.
Herein, "of' is inclusive and not exclusive, unless expressly indicated
otherwise or
indicated otherwise by context. Therefore, herein, "A or B" means "A, B, or
both," unless
expressly indicated otherwise or indicated otherwise by context. Moreover, -
and" is both joint
and several, unless expressly indicated otherwise or indicated otherwise by
context. Therefore,
herein, "A and B" means and B, jointly or severally," unless
expressly indicated otherwise or
indicated otherwise by context.
The scope of this disclosure encompasses all changes, substitutions,
variations, alterations,
and modifications to the example embodiments described or illustrated herein
that a person
having ordinary skill in the art would comprehend. The scope of this
disclosure is not limited to
the example embodiments described or illustrated herein. Moreover, although
this disclosure
describes and illustrates respective embodiments herein as including
particular components,
elements, feature, functions, operations, or steps, any of these embodiments
may include any
combination or permutation of any of the components, elements, features,
functions, operations,
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or steps described or illustrated anywhere herein that a person having
ordinary skill in the art
would comprehend. Furthermore, reference in the appended claims to an
apparatus or system or
a component of an apparatus or system being adapted to, arranged to, capable
of, configured to,
enabled to, operable to, or operative to perform a particular function
encompasses that apparatus,
system, component, whether or not it or that particular function is activated,
turned on, or
unlocked, as long as that apparatus, system, or component is so adapted,
arranged, capable,
configured, enabled, operable, or operative.
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