CA 02757609 2014-01-20
CONTROL FOR AIR HANDLER
FIELD OF THE INVENTION
The present invention pertains to a control for an air handler and may
comprise a portion
of a thermostat. In an embodiment, the control is for an HVAC system and is
used to monitor
room temperature, allow for programming of desired functions and controlling
heating, cooling
and/or fan recirculation. The present control is focused, in particular, on
controlling the
operation of a fan when no call for heating or cooling is occurring.
BACKGROUND
Controls for air handlers such as, programmable thermostats, have increasingly
more
options and modes available to users, due to the use of fast
microprocessors/microcontrollers.
Careful programming of microprocessors provides for enhanced heating, cooling
and fan control,
operations previously unavailable. Thermostats that maximize the frequent
circulation of air
within a building improve cleanliness and keep the building more comfortable.
If there are long
off cycles for heating or cooling, air may stagnate and reduce cleanliness
because filtration of the
air is not occurring during these off cycles. This is because in typical
systems, the fan is off
between heating and cooling cycles and runs only during the heating or cooling
cycle. Some
systems include a fan-on mode, in which the fan runs constantly. While running
the fan
constantly reduces the stagnate air, such an operation may waste energy.
Nevertheless, it is
known that extending the fan cycle may increase thermal efficiency.
Some systems are known to provide for intermittent fan recirculation modes
that are
triggered by the end of the last operation of the fan during a heating or
cooling cycle. Such a
system has the disadvantage of not including a temperature contingent fan
control variable and
cannot prevent back to back fan on modes. The present invention overcomes the
disadvantage of
previous systems and provides for a system that increases occupant comfort,
while providing
efficient fan control.
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SUMMARY
The present invention provides for an air conditioning system comprising an
air handler,
a circulating fan and a control for activating and deactivating heating,
cooling and fan recirculate
modes. The control is operatively coupled to the air handler and the fan for
controlling the air
handler and the fan. The control has an interval timer switchable between a
timer on (TON) state
and a timer off (TOFF) state. Both the TON and TOFF state durations are
variable according to
comparisons between room temperature and a set point temperature of the
control. The control
activates the fan recirculate mode when the following conditions are met:
a) the control is in the fan recirculate mode;
b) heating and cooling of the air conditioning system are not active;
c) the room temperature deviates from the set point temperature of the
control.
In an embodiment, the air conditioning system may further comprise an interval
spacing
mechanism, wherein the room temperature is compared to the set point
temperature, in order to
avoid back to back fan on states and to allow activation of the fan when the
interval timer is in
the TON state. In an embodiment, the interval spacing comparison may be
calculated according
to the following formula, when the control has the heating mode activated:
T, +0.3 > Tr> Ts+ 0.1
where T, is the set point temperature and Tr is the room temperature.
In an embodiment, the interval spacing comparison may be calculated according
to the
following formula when the control has the cooling mode activated:
T, - 0.3 < Tr < T, - 0.1
where T, is the set point temperature and Tr is the room temperature.
In an embodiment, the interval timer may be activated upon power-up of the
control and
following expiration of the TON state, the TOFF is activated until expiration
and the interval
timer operates in a continuous loop with TON and TOFF states sequentially
running one after the
other and the interval timer being independent of the interval spacing
mechanism. In an
embodiment, the interval timer TON duration is equal to a first value plus the
absolute value of
the difference between of the set room point temperature and the room
temperature multiplied by
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a first scaling factor. In an embodiment, the first value is ten (10) minutes
and the first scaling
factor is 0.1. In an embodiment, the interval timer TOFF duration is equal to
a second value plus
the absolute value of the difference between the set point temperature and the
room temperature
multiplied by a second scaling factor. In an embodiment, second the value is
twenty (20)
minutes and the second scaling factor is 0.2.
In an embodiment, the control may be a thermostat. In an embodiment, the
thermostat
may include one of a mechanical fan switch for setting the fan to recirculate
mode and a
touchscreen input for setting the fan to recirculate mode.
The invention further provides for a method for activating recirculate mode
comprising
the steps of providing a control having an interval timer, the control
operatively coupled to an air
handler and a fan for activating and deactivating heating, cooling and fan
recirculate modes,
powering the control in order to the set the interval timer on (TON) state,
varying the duration of
the TON state by the interval timer to a first value by comparing room
temperature with a set
point temperature of the control, setting the interval timer to a timer off
(TOFF) state, varying the
duration of the TOFF state of the interval timer to a second value by
comparing the room
temperature and set point temperature of the control, setting the control fan
recirculate mode,
monitoring the control to confirm no heating or cooling of the air
conditioning system is active
and activating the fan recirculate mode when room temperature deviates from
the set point
temperature of the control.
In an embodiment, the fan recirculate mode may be activated when the interval
timer is in
the TON state only after an interval spacing mechanism is executed by
comparing the room
temperature to the set point temperature of the control. In an embodiment, the
interval spacing
mechanism value is not preselectable. In an embodiment, the interval spacing
mechanism
operates according to the following formula when the control has the heating
mode activated:
T+0.3 > Tr> Ts+ 0.1
where Ts is the set point temperature and Tr is the room temperature.
In an embodiment, the TON spacing mechanism operates according to the
following
formula, when the control has the cooling activated:
Ts - 0.3 < Tr < Ts - 0.1
where Ts is the set point temperature and Tr is the room temperature.
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In an embodiment, the method may further comprise the step of setting the TON
duration
that is equal to a first value plus the absolute of the difference of the set
point temperature and
the room temperature multiplied by a first scaling factor. In an embodiment,
the TOFF state is
not dependent from an end of the last operation of the fan. In an embodiment,
the first and
second value and first and second scaling factors are not user selectable.
In an embodiment, the method may further comprise the steps of activating the
interval
timer upon power-up of the control, activating the TON state until expiration,
activating the
TOFF state until expiration and operating the interval timer in a continuous
loop with TON and
TOFF states sequentially running one after the other and the interval timer
being independent of
the interval spacing mechanism. In an embodiment, the control may
simultaneously process the
comparing, monitoring and activating steps. In an embodiment, the control may
include a
microprocessor for simultaneously processing the comparing, monitoring and
activating steps.
In an embodiment, the TON duration is between five (5) and fifteen (15)
minutes. In an
embodiment, the TON duration is approximately fifty-percent (50%) of the TOFF
duration. In
an embodiment, the TON and TOFF durations are not preselectable by a user. In
an
embodiment, a fan auto mode and a fan on mode are provided and further
comprising the steps
of monitoring the control to confirm no auto fan nor fan on mode are active.
In an embodiment,
the air handler may be a household HVAC system including an air filter and air
ducts for
circulating indoor and outdoor air.
The invention also provides for a control for activating and deactivating
heating, cooling
and fan recirculate comprising an interval timer switchable between a timer on
(TON) state and
timer off (TOFF) state, both the TON and TOFF state durations are variable
according to
comparisons between room temperature and a set point temperature of the
control, and the
control activating the fan recirculate mode when the room temperature deviates
from the set
point temperature of the control.
In an embodiment, the control may provide for an interval spacing mechanism,
wherein
the room temperature is compared to the set point temperature in order to
avoid back to back fan
on states and to allow activation of the fan when the interval timer is in the
TON state. In an
embodiment, the interval timer is activated upon power-up of the control and
following
expiration of the TON state, the TOFF state is activated until expiration and
the interval timer
operates in a continuous loop with TON and TOFF states sequentially running
one after the other
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and the interval timer being independent of the interval spacing mechanism. In
an embodiment,
the interval timer TON duration may be equal to a first value plus the
absolute value of the
difference between the set point temperature and the room temperature
multiplied by a first
scaling factor. In an embodiment, the interval timer TOFF may be equal to a
second value plus
the absolute value of the difference between the set point temperature and the
room temperature
multiplied by a second scaling factor.
In a further embodiment the invention provides for a control for activating
and
deactivating heating, cooling and fan recirculate modes comprising an interval
timer switchable
between a timer on (TON) state and a timer off (TOFF) state, an interval
spacer to prevent back
to back fan on states, the interval timer setting TON and TOFF state durations
that are variable
and are set independently from the operation of the interval spacer and the
control activating the
fan recirculate mode when the room temperature deviates from the set point
temperature of the
control following operation of the interval spacer. In an embodiment, the
interval spacer may
operates according to the following formula:
ABS (Tr - Ts) < Value A
where Ts is the set point temperature and Tr is the room temperature.
In an embodiment, the interval spacer may operate according to the following
formula:
CALLON/(CALLON + CALLOFF) <A%.
In an embodiment, the interval spacer may operate according to the following
formula:
CALLON/(CALLON + CALLOFF) <B%.
In an embodiment, the interval spacer may operate according to the following
formula:
LASTOFF > Value A.
In an embodiment the interval spacer may operate by comparing the room
temperature to the set
point temperature of the control to allow activation of the fan when the
interval timer is in the
TON state. In an embodiment, the interval spacer may operate according to the
following
formula subsequent to a heating mode:
Ts+0.3 > Tr> Ts+ 0.1
CA 02757609 2014-01-20
. where T, is the set point temperature and Tr is the room temperature.
In an embodiment, the interval spacer may operate according to the following
formula
subsequent to a cooling mode:
T, - 0.3 < Tr < T, - 0.1
where T, is the set point temperature and Tr is the room temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and form a part of this
specification, illustrate embodiments of the invention and, together with the
description, serve to
explain the principles of embodiments of the invention:
Fig. 1 is a plan view of the control of the present invention;
Fig. 2 is a partial circuit diagram of the control of the present invention;
Fig. 3 is a partial circuit diagram portion of the control of the present
invention;
Fig. 4 is a partial circuit diagram portion of the control of the present
invention;
Fig. 5 is a partial circuit diagram portion of the control of the present
invention;
Fig. 6 is a flow diagram of a first embodiment of the control logic for the
present
invention;
Fig. 7 is a flow diagram of a second embodiment of the control logic for the
present
invention;
Fig. 8 is a flow diagram of a third embodiment of the control logic for the
present
invention;
Fig. 9 is a flow diagram of a fourth embodiment of the control logic for the
present
invention; and
Fig. 10 is a flow diagram of a fifth embodiment of the control logic for the
present
invention.
DETAILED DESCRIPTION
Fig. 1 depicts a control, such as a thermostat 100 of the present invention.
The control
100 includes a housing 110 for enclosing a printed circuit board and
components therein and a
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display screen 120. The control 100 includes a mechanical switch 130 for
operating the control
100. The display screen 120 may be any well-known display, such as an LCD or
LED type
screen. The screen includes display areas for alpha numeric displays and touch
sensitive areas
for touch buttons. The embodiment of the invention of Fig. 1 alpha-numeric
display area 151
displays the current room temperature. The control 100 includes a sensor
within the housing 110
for sensing room temperature which has an output that provides for the display
151 as an alpha
numeric representation. The room temperature display 151 in the embodiment
depicted in Fig.
1, shows an alpha numeric display of "88". This alpha numeric display is
indicating that the
current room temperature is currently 88 F.
A display area 153 is provided for displaying the day and time. The day and
time alpha
numeric display 153 may be programmed by the user of the control 100 via the
touch buttons.
The day and time display area 153 in the embodiment of Fig. 1 provides for an
alpha numeric
display of "M MORN 11:07am." This indicates that it is Monday morning at 11:07
a.m.
The display screen 120 also includes a display area 155 for an alpha numeric
display of
the set point temperature. As depicted in Fig. 1, the set point temperature
display area 155
includes an alpha numeric display of "SET AT 72". This indicates that the user
has input a
temperature set point of 72 F.
The display screen 120 also provides for symbol displays or icons displays
157. For
example, the icon 157 provides a graphical depiction of the blades of a fan.
In the embodiment
depicted in Fig. 1, when the icon 157 is present it indicates that the fan is
currently running.
The display screen 120 also includes an alpha numeric or icon display for the
current
mode display area 158. As depicted in Fig. 1, the mode display area 158
includes "HEAT".
This mode display indicates that the system has been set to a heating mode.
The display 120 also
includes a fan mode display area 159. In the embodiment depicted in Fig. 1,
the fan mode
display area includes a "CIRC" icon. This fan mode display area 159 indicates
that the fan
mode has been set to the recirculate mode.
The display screen 120 also includes touch sensitive areas that provide for
touch buttons
each having a generally rectangular outline to identify the button. The
display screen includes a
system button 161, fan button 162, program button 163, hold button 164,
day/time button 165,
clean button 166 and configuration button 167. Each of these buttons has an
operation that is
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described by U.S. pending application 12/982,959 filed 12/31/2010, which is
incorporated herein
by reference.
The fan button 162 operates the control with respect to the selection of
multiple fan
modes. In a preferred embodiment, the fan modes include an auto mode, an on
mode and a
recirculate mode. By sequentially depressing the fan button 162, a user may
scroll through each
of these three fan modes and the particular alpha numeric representation or
icon for each mode
will appear in the fan mode display area 159. As is depicted in the embodiment
of Fig. 1, the
recirculate mode has been selected and as evidence of that selection, the
alpha numeric
representation of "CIRC" is presented in the fan mode display area 159. The
fan recircluate
mode allows for the fan to run intermittently, when there is no call for
heating or cooling. The
fan auto mode provides for the running of the fan during a heating or cooling
call. The fan on
mode provides for the fan to run continuously during heating and cooling and,
also, when there is
no call for heating and cooling. The control 100 of the present invention
includes circuitry for
operating all parts of the air conditioning system, including each of the
three fan modes. The
main focus of this application pertains to the operation of the fan
recirculate mode.
Fig. 2 is a circuit diagram for the present invention. Such circuitry may be
provided on a
printed circuit board mounted within the housing 110 of the control 100 (Fig.
1). The control
includes an electrical connector for connection with HVAC components including
an air handler
190 such as a furnace or cooling unit or boiler, a fan, humidifier,
dehumidifier or air filter. The
fan 200 may be connected through air ducts to an outside air damper. The
circuit depicts micro-
controller 201, which is connected to a fan relay 203 via a switching
transistor 204. When the
touch button 162 (discussed above in Fig. 1) is operated to place the system
in recirculate mode
159, the micro-controller 201 will operate according to the specific flow
diagram logic
programmed therein and based on characteristics, such as room temperature and
set point
temperature, the micro-controller 201 will activate the fan relay 203. As
depicted in Fig. 2, the
fan relay 203 is currently shown de-energized as a result of the micro-
controller 201 selecting a
deactivate mode for the fan 200. As will be discussed in greater detail below,
when the flow
logic of the preferred embodiment determines appropriates conditions, the G
terminal 208 will be
energized in order to run the fan 200.
In the fan "on" mode, pole 207 connects fan terminal 208 to 24-volt power from
RC
terminal 209. In the fan auto and recirculate modes, fan 200 operation is
controlled by a latching
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relay 203 shown with its contacts in the de-energized mode in Fig. 2. In the
recirculate or auto
modes, the fan 200 operation is controlled by the relay state, which is in
turn controlled by the
output of the microprocessor 201 through switch 204.
The control circuitry is illustrated in Figs. 2 - 4. As depicted in Fig. 3 and
Fig. 4 a 1P, 1T
switch 210, 220 with poles 221, 222 provide an output to the input 231, 232 of
the
microprocessor 201 to tell the microprocessor the state of the fan relay 203
(Fig. 2). A gas-
electric switch 210 shown in Fig. 3 provides an input to the microprocessor
201 so that the
furnace logic and not the thermostat controls the fan 200 (Fig. 2) operation
during the gas
heating cycle.
Fig. 4 depicts a portion of the circuitry for selecting a heat pump or
conventional system
depicting the power input 232 for the microcontroller 201.
Figs. 3 - 5 depict a portion of circuit diagrams for an embodiment where a
mechanical
switch is provided on the control 100 (Fig. 1) for setting the fan modes or
gas, electric or heat
pump configurations. Such configurations may also be accomplished via software
by using an
installer menu to input the settings using a display of the control 100
(Fig.1). As depicted in Fig.
5, a 1P, 3T switch 240 includes a fan 200 (Fig. 2) on pole 241, a fan
recirculate pole 243 and fan
auto pole 245. Each pole 241, 243, 245 is selected by a mechanical button or
switch on the
thermostat 100 (Fig. 1). While in the fan auto mode, as depicted in Fig. 2,
the fan terminal 208 is
essentially controlled utilizing furnace logic or the microprocessor 201. That
is, the fan terminal
208 is energized upon call for cooling and de-energized after the set point
temperature is
reached. When in the heating mode, fan terminal 207 may be energized upon call
for heat, and
de-energized when the call is satisfied in an electrical heat system.
A first embodiment of the control logic of the invention is depicted by the
flowchart in
Figure 6. The unit starts the ON-OFF interval timer (loop B) at power-on or
reset 310 and then
(loop A) checks the fan mode 320. The first interval timer (loop B), is the
timer ON (TON) state
of the timer 410, 420. The length of the TON state is a first value, Value A
assigned to TON.
Following expiration of TON 420, additional TON duration is calculated at step
430 by the
absolute value of the difference between the set point temperature and the
room temperature,
multiplied by a first scaling factor, Factor 1. When the ON state interval
expires 440, the timer
OFF state interval (TOFF) starts 450. The length of TOFF state is a second
value, Value B,
assigned to TOFF. Following expiration of the TOFF 460, additional TOFF
duration is
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calculated at step 470 by the absolute value of the difference between the set
point temperature
and the room temperature, multiplied by a second scaling factor, Factor 2.
When the TOFF state
interval expires 480, the timer begins the TON state interval again 410.
During operation of loop A, if the fan 200 (Fig. 2) is in the AUTO mode, the
control of
the fan mode is determined solely by heating, cooling, humidification or
dehumidification calls
321 (e.g., Normal Fan Control). If the fan 200 (Fig. 2) is in the constant ON
mode, the fan 200
(Fig. 2) is on constantly 321 (e.g., Normal Fan Control). If the fan 200 (Fig.
2) is in the
recirculate mode 320, and there is no heating, cooling, humidification or
dehumidification call
330, the fan mode is activated and deactivated via step 380, according to the
interval timer loop
B. If the fan 200 (Fig. 2) is in the recirculate mode, and there is a heating,
cooling,
humidification or dehumidification call 330, control of fan mode is determined
according to the
requirements of the call type 340 (e.g. Normal Fan Control), 350. At the end
of the call 360, the
room temperature is compared to the set point, and if they are not within a
fixed value, Value C,
of each other, fan mode control again passes to the timer until the next call,
or until the fan 200
(Fig. 2) is moved from the recirculate mode 320.
As a example of the control described by the above method, if the thermostat
100 first
has power applied in the heating mode with the fan 200 (Fig. 2) in the
recirculate mode, and is
set at 50 F, but the room temperature is steady at 75 F, there is no heating
call because the
room temperature is greater than the set point temperature 330. Fan 200 (Fig.
2) control is
therefore passed to the ON-OFF interval timer 380 (loop B). If Value A is
programmed to be 10
minutes, and Factor 1 is programmed to be .1, then the length of the first fan
200 (Fig. 2) ON
cycle will be ten minutes plus the absolute value of 75 minus 50, multiplied
by .1 minutes.
Expressed as an equation, this would be 10 + ABS (75-50) x .1 in minutes, or
12.5 minutes 430.
If Value B is programmed to be 20 minutes, and Factor 2 is programmed to be
.2, then the
length of the first OFF cycle would be 20 minutes plus the absolute value of
75 minus 50,
multiplied by .2 minutes. Expressed as an equation, this would be 20 + ABS (75-
50) x .2 in
minutes, or 25 minutes 470.
As a further example of the control described by the above method, if the room
temperature drops to 45 F, there will be a heating call because the room
temperature is less than
the set point temperature 330. Fan 200 (Fig. 2) control is therefore
determined by the thermostat
100 to match the type of heating system being used 340. When the heating call
is completed
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350, 360, the room temperature is subtracted from the set point temperature
and the absolute
value is compared to Value C 370 to provide an interval spacing
mechanism/interval spacer to
prevent back to back fan 200 (Fig. 2) on states. Immediately after the call is
completed, the
room temperature will match the set point temperature, so that the difference
between the two
will be close to zero. If Value C 370 is programmed to be .1 deg., the fan 200
(Fig. 2) will
remain off 350 until the temperature drifts further from the set point
temperature. If the
temperature drifts lower to 49.8, then fan 200 (Fig. 2) control passes to the
interval timer 380
(loop B) at whatever state it is in at that point, because the condition of
370 "is ABS (Room
Temperature ¨ Set Point Temperature < .1?" would be met.
A second embodiment of the control logic of the invention is depicted in Fig.
7. The unit
starts the ON-OFF interval timer (loop B) at power-up or reset 510 and then
(loop A) checks the
fan mode 520. The first interval timer (loop B), is the ON state of the timer
610, 620. The
length of the ON state is a first value, 10 minutes assigned to TON. Following
expiration of the
TON timer, an additional duration for TON 630 is calculated by the absolute
value of the
difference between the set point temperature and the room temperature,
multiplied by a first
scaling factor (i.e., 0.1 or by dividing by 10). When the ON state interval
expires 640, the TOFF
state interval starts 650. The length of TOFF state is a second value, 20
minutes, assigned to
TOFF. Following expiration of the TOFF timer, an additional duration for TOFF
670 is
calculated by the absolute value of the difference between the set point
temperature and the room
temperature, multiplied by a second scaling factor (i.e., 0.2 or by dividing
by 5). When the OFF
state interval expires 680, the timer begins the ON state interval again 610.
If the fan 200 (Fig. 2) is in the AUTO mode, the control 100 is determined by
loop A,
solely by heating, cooling, humidification or dehumidification calls 521
(e.g., Normal Fan
Control). If the fan 200 (Fig. 2) is in the constant ON mode, the fan 200
(Fig. 2) is on constantly
521 (e.g., Normal Fan Control). If the fan 200 (Fig. 2) is in the recirculate
mode 520, and there
is no heating, cooling, humidification or dehumidification call 530, the fan
mode is activated and
deactivated according to the interval timer 580 (loop B). If the fan 200 (Fig.
2) is in the
recirculate mode, and there is a heating, cooling, humidification or
dehumidification call 530,
control of fan relay 203 (Fig. 2) is determined according to the requirements
of the call type 540
(e.g. Normal Fan Control) 550. At the end of the call 560, the room
temperature is compared to
the set point temperature 570, and if there is a deviation, fan relay 203
again passes to the
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interval timer until the next call, or until the fan 200 (Fig. 2) is moved
from the recirculate mode
520. The interval timer (loop B) operates independent of the other operations
(loop A).
As an example of the control described by the above method, if the thermostat
100 first
has power-on applied in the heating mode with the fan 200 (Fig. 2) in the
recirculate mode, and
is set at 50 F, but the room temperature is steady at 75 F, there is no
heating call because the
room temperature is greater than the set point temperature 530. Fan 200 (Fig.
2) control is
therefore passed via 580 to the ON-OFF interval timer 610 (loop B). The first
fan timer ON
(TON) cycle will be ten minutes. Following expiration of TON 420 additional
TON duration is
calculated at step 630 by the absolute value of 75 minus 50, divided by 10
minutes. Expressed as
an equation, this would be ABS (75-50) / 10 minutes, or 2.5 additional TON
minutes. The first
fan timer OFF (TOFF) cycle 650 is 20 minutes. Following expiration of TOFF
460, additional
TOFF duration is calculated at step 670 by the absolute value of 75 minus 50,
divided by 5
minutes. Expressed as an equation, this would be ABS (75-50) / 5 minutes, or 5
additional
TOFF minutes. In an embodiment, the initial TON and TOFF durations are input
at the factory
at the time the microcontroller is programmed.
As a further example of the control described by the above method, if the room
temperature drops to 45 F, there will be a heating call at step 540 because
the room temperature
is less than the set point temperature. Fan 200 (Fig. 2) control is therefore
determined by the
thermostat 100 to match the type of heating system being used (e.g. Normal Fan
Control).
When the heating call is completed 550, 560, the room temperature is compared
to the set point
temperature at 570, using the following formulas to provide an interval
spacing mechanism to
prevent back to back fan 200 (Fig. 2) on states:
Ts + 0.3 > Tr? Ts + 0.1 (subsequent to a heating mode)
Ts - 0.3 < Tr < Ts - 0.1 (subsequent to a cooling mode)
where Ts is the set point temperature and Tr is the room temperature.
Immediately after the call
is completed, the room temperature will match the set point temperature, so
that the difference
between the two will be close to zero, so no call to the interval timer (loop
B) is made and there
will again be a determination at step 550 as to whether there is a call for
cooling, heating,
humidification or dehumidification. The fan 200 (Fig. 2) will remain off 560,
until the
temperature drifts further from the set point temperature. The room
temperature is again
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=
compared to the set point temperature at 570, using the following formula to
provide an interval
spacing mechanism to prevent back to back fan 200 (Fig. 2) on states:
Ts + 0.3 > Tr > Ts + 0.1 (subsequent to a heating mode)
Ts - 0.3 < Tr < Ts - 0.1 (subsequent to a cooling mode)
where Ts is the set point temperature and Tr is the room temperature. Once the
temperature drifts
lower, for example, to 49.8, then according to 580, a fan 200 (Fig. 2) on
state may occur based
on the interval timer (loop B) at whatever state it is in at that point,
because the condition of 570
would be met.
A third embodiment of the control logic of the invention is depicted by the
flowchart in
Figure 8. The unit starts the ON-OFF interval timer at power-up or reset 710
and then checks the
fan switch mode 720. The first interval, is the ON state of the timer. The
length of the ON state
is a first value, value A, assigned to TON 810. When the ON state interval
expires, the OFF
state interval starts 820. The length of OFF state is a second value, value B,
assigned to TOFF
830. When the OFF state interval expires, the timer begins the ON state
interval 840 again.
During operation of loop A, if the fan 200 (Fig. 2) is in the AUTO mode, the
control of
fan mode is determined solely by heating, cooling, humidification or
dehumidification calls 721
(e.g., Normal Fan Control). If the fan 200 (Fig. 2) is in the constant ON
mode, the fan 200 (Fig.
2) is on constantly 721. If the fan 200 (Fig. 2) is in the recirculate mode
720, and there is no
heating, cooling, humidification or dehumidification call 730, the fan mode is
activated and
deactivated according to the interval timer 780. If the fan 200 (Fig. 2) is in
the recirculate mode
720, and there is a heating, cooling, humidification or dehumidification call
730, control of fan
mode is determined according to the requirements of the call type 740. At the
end of the call
750, the fan relay 203 is turned off 760 and the room temperature is compared
to the set point
temperature, and if they are not within a fixed value, Value C, of each other
770, the fan mode
control again passes to the timer 780 until the next call, or until the fan
200 (Fig. 2) is moved
from the recirculate mode.
As an example of the control described by the above method, if the thermostat
100 first
has power-on applied in the heating mode with the fan 200 (Fig. 2) in the
recirculate mode, and
is set at 50 F, but the room temperature is steady at 75 F, there is no
heating call because the
room temperature is greater than the set point temperature. Fan 200 (Fig. 2)
control is, therefore,
13
CA 02757609 2014-01-20
passed to the ON-OFF interval timer 780. If Value A is programmed to be 10
minutes, then the
length of the fan 200 (Fig. 2) ON cycle will be ten minutes 810. If Value B is
programmed to
be 20 minutes, and then the length of the OFF cycle would be 20 minutes 840.
As a further example of the control described by the above method, if the room
temperature drops to 45 F, there will be a heating call because the room
temperature is less than
the set point temperature. Fan 200 (Fig. 2) control is therefore determined by
the thermostat to
match the type of heating system being used 740 (e.g., Normal Fan Control).
When the heating
call is completed 750, 760, the room temperature is subtracted from the set
temperature and the
absolute value is compared to Value C 770 to provide an interval spacing
mechanism to prevent
back to back fan 200 (Fig. 2) on states. Immediately after the call is
completed, the room
temperature will match the set temperature, so that the difference between the
two will be close
to zero. If Value C is programmed to be .1 deg., the fan 200 (Fig. 2) will
remain off until the
temperature drifts further from the set point temperature 760. If the
temperature drifts lower to
49.8, then fan 200 (Fig. 2) control, according to 780, passes to the interval
timer at whatever state
it is in at that point, because the condition of 770 "is ABS (Room Temperature
¨ Setpoint
Temperature < .1 ?" would be met.
A fourth embodiment of the control logic of the invention is depicted by the
flowchart in
Figure 9. The unit starts the ON-OFF interval timer at power-on or reset 910
and then checks the
fan mode 920. The first interval, is the ON state of the timer 1010. The
length of the ON state is
a first value, Value A, assigned to TON. When the ON state interval expires
1020, the OFF state
interval starts 1030. The length of TOFF state is a second value, Value B,
assigned to TOFF.
When the OFF state interval expires 1040, the timer begins the ON state
interval 1010 again.
If the fan 200 (Fig. 2) is in the AUTO mode, control of fan mode is determined
solely by
heating, cooling, humidification or dehumidification calls 921. If the fan 200
(Fig. 2) is in the
constant ON mode, the fan 200 (Fig. 2) is on constantly 921 (e.g., Normal Fan
Control). If the
fan switch is in the recirculate mode 920, and there is no heating, cooling,
humidification or
dehumidification call 930, the fan mode is activated and deactivated according
to the interval
timer 950. If the fan switch is in the recirculate mode 920, and there is a
heating, cooling,
humidification or dehumidification call 930, control of fan mode is determined
according to the
requirements of the call type 940 (e.g., Normal Fan Control). At the end of
the call, fan mode
14
CA 02757609 2014-01-20
control again passes to the timer 950 at whatever state it is in until the
next call, or until the fan
200 (Fig. 2) is moved from the recirculate mode 920.
As an example of the control described by the above method, if the thermostat
first has
power applied in the heating mode with the fan 200 (Fig. 2) in the recirculate
mode, and is set at
50 F, but the room temperature is steady at 75 F, there is no heating call
because the room
temperature is greater than the set point temperature 930. Fan 200 (Fig. 2)
control is therefore
passed to the ON-OFF interval timer 950. If Value A is programmed to be 10
minutes, then the
length of the fan 200 (Fig. 2) ON cycle will be ten minutes 1010. If Value B
is programmed to
be 20 minutes, and then the length of the OFF cycle would be 20 minutes 1030.
As a further example of the control described by the above method, if the room
temperature drops to 45 F, there will be a heating call because the room
temperature is greater
than the set point temperature 930. Fan 200 (Fig. 2) control is, therefore,
determined by the
thermostat to match the type of heating system being used 940. When the
heating call is
completed, the fan 200 (Fig. 2) control passes to the interval timer at
whatever state it is in at that
point 950.
A fifth embodiment of the control logic of the invention is depicted by the
flowchart in
Figure 10. The unit starts the ON-OFF interval timer at power-on or reset 1110
and then checks
the fan mode 1120. The first interval, is the ON state of the timer 1310. The
length of the ON
state is a first value, Value A, assigned to TON. When the ON state interval
expires, the OFF
state interval starts 1320. The length of TOFF state is a second value, Value
B, assigned to
TOFF 1330. When the OFF state interval expires, the timer begins the ON state
interval again
1340.
If the fan 200 (Fig. 2) is in the AUTO mode, the control of fan mode is
determined solely
by heating, cooling, humidification or dehumidification calls 1121 (e.g.
Normal Fan Control). If
the fan 200 (Fig. 2) is in the constant ON mode, the fan 200 (Fig. 2) is on
constantly 1121 (e.g.,
Normal Fan Control). If the fan 200 (Fig. 2) is in the recirculate mode 1120,
and there is no
heating, cooling, humidification, or dehumidification call 1130, the fan mode
is activated and
deactivated at 1260 according to the interval timer loop B. If the fan 200
(Fig. 2) is in the
recirculate mode 1120, and there is a heating, cooling, humidification or
dehumidification call
1130, a CALLON timer is started 1140, and control of fan mode is determined
according to the
requirements of the call type 1150 (e.g., Normal Fan Control). When the call
ends 1160, the
CA 02757609 2014-01-20
CALLON timer is stopped 1170, and a CALLOFF timer is started, along with a
LASTOFF
timer. When the percentage of time that the fan 200 (Fig. 2) has been running,
since of the last
call started, is less than a first percentage value, Percentage A 1180, the
fan 200 (Fig. 2) will start
1190 to provide an interval spacing mechanism to prevent back to back fan 200
(Fig. 2) on states
so long as there is no heating or cooling call 1200. When the percentage of
time that the fan 200
(Fig. 2) has been running, since the last call started, exceeds a second
percentage value,
Percentage B 1210, so long as there is no heating or cooling call 1220, the
fan 200 (Fig. 2) stops
1230. This process repeats unless a heating, cooling, humidification or
dehumidification call
1210, 1220 occurs, or unless the period of time fan has not run exceeds a
third value, Value C
1250, in which case all timers are reset, and the process repeats 1180. The
LASTOFF timer is
initialized and started at step 1240
As an example of the control described by the above method, if the thermostat
first has
power-on applied in the heating mode with the fan 200 (Fig. 2) in the
recirculate mode 1120, and
is set at 50 F, but the room temperature is steady at 75 F, there is no
heating call because the
room temperature is greater than the set point temperature 1130. Fan 200 (Fig.
2) control is
therefore passed to the ON-OFF interval timer 1260. If Value A is programmed
to be 10
minutes, then the length of the fan 200 (Fig. 2) ON cycle will be ten minutes
1310. If Value B
is programmed to be 20 minutes, and then the length of the OFF cycle would be
20 minutes
1330.
As a further example of the control described by the above method, if the room
temperature drops to 45 F, there will be a heating call because the room
temperature is less than
the set point temperature 1130. Fan 200 (Fig. 2) control is therefore
determined by the
thermostat 100 to match the type of heating system being used 1150, and the
CALLON timer is
started 1140. If, after the call starts, it takes 15 minutes for the system to
bring the room
temperature to the set point temperature 1160, the value of CALLON is stopped
at 15 minutes
1170, and CALLOFF begins incrementing from zero. If there are no further
heating calls for 36
minutes step 1180 is taken to provide an interval spacing mechanism to prevent
back to back fan
200 (Fig. 2) on states when. If Percentage A is set to 30%, the calculation of
CALLON /
(CALLON +CALLOFF) becomes less than .3, so the fan 200 (Fig. 2) is activated
1180.
CALLON begins incrementing from its last value, 15 minutes. If there are no
further heating
calls, and Percentage B is set to 40 %, CALLON / (CALLON +CALLOFF) exceeds .4
after 9
16
CA 02757609 2014-01-20
=
,
additional minutes of fan 200 (Fig. 2) run time, and the fan 200 (Fig. 2) is
deactivated 1210.
Any heating call will cause timers CALLON and CALLOFF to reset 1220, 1230,
1240. If Value
C is set to 60 minutes, any time the fan 200 (Fig. 2) has been off for a
period of time greater than
60 minutes 1250, then passes to the interval timer described above, at
whatever state it is in
1260.
The previous description of the disclosed embodiments is provided to enable a
person,
skilled in the art to use the present invention. There is modifications to
these embodiments
would be readily apparent to those skilled in the art, and the generic
principle applied herein may
be applied to other embodiments within departing from the spirit or the scope
of the invention.
Thus, the present invention does not intend to be limited to the embodiments
shown herein, but
is to be accorded to the widest scope consistent with the principles and novel
features disclosed
herein and as defined by the following claims.
17
