Note: Descriptions are shown in the official language in which they were submitted.
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RANGE HOOD F~N WITH
ATMOSPHERIC ~UMIDITY SENSOR
Field of the Invention
This application relates to a kitchen range hood
fan electrically connectable to a humidity sensor. The fan
motor is automatically activated when atmospheric humidity
readings measured within a dwelling exceed a pre-set limit.
Background of the Invention
15Range hoods having exhaust fans are typically
installed directly above kitchen elements or burners to
ventilate grease-laden air generated during cooking.
Typically such fans are manually activated using a toggle
switch.
Some automatic operating devices for range hood
fans are known in the prior art. Japanese patent No.
0,213,628, which issued to Mitsubishi Electric Corp. on 9
September, 1987, discloses an operating device for activat-
ing a range hood fan in response to changes in atmospherictemperature as measured by a temperature sensing part
located near the range hood.
The need has arisen for a range hood fan which is
automatically activated or deactivated in response to
changes in atmospheric humidity as measured within the
interior of a dwelling. In order to increase energy
efficiency, many newly constructed dwellings are insulated
to substantially prevent release of heated air from the
interior of the dwelling. Such air-tight dwellings may
have insufficient ventilation, resulting in unacceptably
high humidity levels and potentially dangerous concentra-
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tions of gases, such as formaldehyde and radon. Accord-
ingly, if natural ventilation of the dwelling is insuffi-
cient, building codes in some jurisdictions require instal-
lation of mechanical ventilators.
Typically mechanical ventilators, such as exhaust
fans, are installed in relatively accessible locations,
such as bathrooms, to facilitate duct work connections.
Operation of the exhaust fans may be automatically con-
trolled by a centrally located humidity sensor, such as a
dehumidistat. Dehumidistats are usually installed in a
hallway or living room and may be pre-set to activate the
exhaust fan when interior humidity readings rise above a
predetermined level.
The installation of additional mechanical venti-
lators in order to meet building code ventilation require-
ments significantly increases construction costs. Apart
from the cost of additional exhaust fans and dehumidistats,
considerable labour is required to install the extra
ducting necessary to exhaust the ventilated air to the
exterior of the dwelling. The inventor has recognized that
considerable cost savings could result if a kitchen range
hood fan is employed as the mechanical ventilator. Depend-
ing on the size of the dwelling, this would either reduceor eliminate the need to install extra mechanical ventila-
tors and associated ducting.
Conventional range hood fans are not suitable for
providing automatic mechanical ventilation since they are
excessively noisy and would tend to awaken sleeping occu-
pants of a dwelling when automatically activated at night.
Accordingly, the need has arisen for a range hood fan
electrically connectable to a humidity sensor, such as a
dehumidistat, which is operable at a reduced sound level in
an automatic mode. Although exhaust fans wired to humidity
sensors are known in the prior art, such fans do not serve
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the dual function of optionally operating as conventional
range hood fans and sound-rated mechanical ventilators.
Summary of the Invention
In accordance with the invention there is pro-
vided a range hood fan operable in a manual or an automatic
mode. The fan includes a housing having an air inlet
aperture and an air outlet aperture and a fan blower
mountable within the housing. At least one motor mountable
within the housing is provided for optionally driving the
fan blower at either a high speed setting for maximal air
output or a low speed setting for minimal air output. The
fan has a sound level not exceeding 65 dBA when operating
at the low speed setting. Manual control means are pro-
vided for manually operating the motor in the manual mode
at either the high speed setting or the low speed setting.
Automatic control means are also provided for automatically
operating the fan motor in the automatic mode at the low
speed setting. The automatic control means is responsive
to electrical signals received from a humidity sensor
located at a position remote from the fan.
Preferably the humidity sensor is a dehumidistat
and the automatic control means is an electrical circuit
for electrically connecting the dehumidistat directly to
the fan motor.
Advantageously, the minimum ventilation rate of
the fan when operating at the low speed setting is 50 Cfm
and the minimum ventilation rate of the fan when operating
at the high speed setting is 100 Cfm.
The fan may further include an exhaust duct, in
communication with the air outlet, which is readily access-
ible for cleaning or servicing. Preferably the exhaust
duct has a minimum inner diameter of 5 inches and the
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length of the duct accessible for cleaning and servicing
extends for at least 15 inches.
In an alternative embodiment, the range hood fan
may include first and second motors mountable within the
housing for driving first and second blowers and the
automatic control means is adapted to operate one of the
first and second motors at the low speed setting in re-
sponse to electrical signals received from the humidity
sensor.
Advantageously, the manual control means is a
control switch moveable between high, low and stand-by
settings and the fan is operable in the automatic mode when
the control switch is at the stand-by setting. Alterna-
tively, the manual control means may consist of a first
switch moveable between an on and a stand-by setting and a
second switch moveable between a high and a low setting.
In this alternative embodiment, the fan is operable in the
automatic mode when the first switch is at the stand-by
setting.
Brief Description of the Drawings
In drawings which illustrate embodiments of the
invention, but which should not be construed as restricting
the spirit or scope of the invention in any way,
Figure 1 is an exploded, bottom isometric view of
the range hood fan assembly of the present invention;
Figure 2(a) is an electrical wiring diagram of a
first embodiment of the invention having a single manual
control switch and showing the switch configured for manual
operation at the low speed setting.
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Figure 2(b) is a wiring diagram of the fan of
Figure 2(a) showing the control switch configured for
manual operation at the high speed setting.
Figure 2(c) is a wiring diagram of the fan of
Figure 2(a) showing the control switch configured for
automatic operation at the low speed setting.
Figure 3(a) is an electrical wiring diagram of a
second embodiment of the invention having a pair of manual
control switches showing the switches configured for manual
operation at the low speed setting.
Figure 3(b) is electrical wiring diagram of the
fan of Figure 3(a) showing the control switches configured
for manual operation at the high speed setting.
Figure 3(c) is an wiring diagram of the embodi-
ment of Figure 3(a) showing the control switches configured
for automatic operation at the low speed setting.
Figure 4 is an electrical wiring diagram showing
the switch configuration of Figure 3 for use with two
separate fan motors for driving dual fan blowers.
Figure 4(a) is an electrical wiring diagram of an
alternative embodiment of the invention showing the humid-
ity sensor wired to two separate fan motors for maximal air
output in the automatic mode.
Detailed Description of the Preferred Embodiment
The present invention contemplates the provision
of a range hood fan which may be installed in the kitchen
of a multiple-room dwelling. With reference to Figure 1,
range hood fan 10 is mountable above kitchen elements or
burners to ventilate steam, grease and related odours
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generated during cooking. Range hood fan 10 includes a
housing 12 for enclosing one or more fan blowers 14. In
the embodiment illustrated in Figure 1, two blowers 14 are
provided which are each driven by a respective fan motor
16.
Fan housing 12 includes a bottom panel 18 having
a pair of air inlets 20 underlying blowers 14 and a top
panel 22 having at least one air outlet 24. Outlet 24 is
in communication with an exhaust duct 26 extending above
housing 12 for ventilating air to the exterior of the
dwelling. The length of exhaust duct 26 readily accessible
for periodic cleaning and servicing should preferably
extend for at least 15 inches.
The present application relates specifically to
a range hood fan 10 which is operable in either a manual or
an automatic mode. With reference to the wiring diagrams
shown in Figure 2, fan 10 includes a three-position toggle
control switch 28 for operating fan blowers 14 in the
manual mode to ventilate grease-laden air generated during
cooking. Switch 28 is preferably mounted on the exterior
of fan housing 12 in a conventional manner for easy access.
When switch 28 is manually adjusted to the "low"
position shown in Figure 2(a), fan motor 16 is electrically
activated to drive a corresponding blower 14 at a low speed
for minimal air output. Similarly, with reference to
Figure 2(b), when switch 28 is adjusted to the "high"
position, fan motor 16 is electrically activated to drive
the corresponding blower 14 at a high speed for maximal air
output.
Fan 10 may also be automatically activated when
switch 28 is in the "off" or "stand-by" position shown in
Figure 2(c). In this automatic mode, operation of fan 10
is controlled by a humidity sensor, such as a dehumidistat
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30, which is wired directly to at least one of the fan
motors 16. Dehumidistat 30 measures the atmospheric
humidity within the dwelling in question and includes a
contact switch 32 for closing the electrical circuit to fan
motor 16 when humidity readings rise above a pre-set level.
Usually dehumidistat 30 is set for between 40%-60% relative
humidity. A suitable dehumidistat is manufactured by Broan
Limited of Mississauga, Ontario.
An important feature of the present invention is
that it is not possible to disable the operation of fan
motor 16 in the automatic mode. That is, it is not poss-
ible to turn fan 10 "off" in the automatic mode by adjust-
ing control switch 28 (adjustment of switch 28 will cause
fan 10 to operate manually at either the high or low speed
settings). If control switch 28 is left in the "off" or
"stand-by" position, fan 10 will continue to operate in the
automatic mode at the low speed setting until humidity
readings within the dwelling fall below the pre-set level
and dehumidistat 30 is deactivated.
Figures 3(a) - 3(c) illustrate an alternative
embodiment of the invention having a pair of two-position
toggle control switches 34 and 36. Switch 34 is provided
for activating fan motor 16 in the manual mode and is
adjustable between an "on" and an "off" or "stand-by"
position. Switch 36 is provided for switching fan motor 16
between the "low" and "high" speed settings when switch 34
is in the "on" position.
When switch 34 is in the "off" or "stand-by"
position, fan motor 16 may be automatically activated by
dehumidistat sensor 30 when humidity levels within the
dwelling exceed a pre-set limit as described above. As
shown in Figure 3(c), fan 10 is wired so that motor 16 will
operate at the low speed setting in the automatic mode,
irrespective of the position of switch 36. As discussed
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above, it is not possible to disable operation of fan motor
16 in the automatic mode.
Figure 4 illustrates a further alternative
embodiment of the invention showing a suitable wiring
diagram if two fan motors 16 are provided for driving a
corresponding pair of dual blowers 14. Each motor 16 is
controlled by a pair of two-position control switches 34
and 36 as described above. In the embodiment shown in
Figure 4, dehumidistat 30 is wired to only one of the fan
motors 16 for operation of one of the dual blowers 14 in
the automatic mode. Again, the fan motor 16 wired to
dehumidistat 30 will be automatically activated at the
"low" speed setting in response to elevated humidity
readings, even if each of the switches 34 is in the "off"
or "stand-by" position.
Alternatively, dehumidistat 30 may be wired to
activate both motors 16 as shown in Figure 4(a) for maximal
air output in the automatic mode. An electronic control
device (not shown) could be provided for activating one or
both of fan motors 16 depending upon humidity levels as
measured by sensor 30. For example, if humidity levels are
extremely high and a large volume of interior air must be
ventilated from the dwelling, both fan motors 16 could be
automatically activated.
The primary advantage of the present invention is
that fan 10 serves the dual function of operating as a
conventional, manually controlled kitchen range hood fan
for ventilating odours and steam generated during cooking
and an automatically controlled exhaust fan to maintain
humidity levels within the dwelling at an optimum level.
At present, exhaust fans for regulating humidity
levels are typically installed by building contractors in
washrooms to facilitate duct work connections. However, in
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g
many residential dwellings, washrooms are located immedi-
ately adjoining the sleeping quarters. Accordingly, when
such exhaust fans are automatically activated at night in
response to elevated humidity readings, as measured by a
dehumidistat sensor, the occupants of the dwelling may be
awakened. Such occupants may well be inclined to switch
the dehumidistat sensor off completely in order to avoid
further disturbance, which obviously defeats the purpose of
the automatic ventilation system. By contrast, kitchen
range hood fans are typically located far enough away from
the dwelling's sleeping quarters such that the building
occupants would not be disturbed at night when the fan is
automatically activated.
As indicated above, the applicant's fan 10 is
designed so that it will operate in the automatic mode only
at the low speed setting. This ensures that fan 10 will
operate relatively quietly in the automatic mode, preferab-
ly at a sound level not exceeding 65 dBA. By contrast,
most conventional range hood fans are far too noisy to
function as automatic mechanical ventilators and could not
meet regulatory requirements. Accordingly, building
contractors are compelled at present to install a separate
sound-rated automatic ventilation system as described above
which significantly increases the cost of constructing new
dwellings.
It is also important that fan 10 have a suitable
ventilation output in both the automatic and manual modes
in order to comply with regulatory requirements. The
Building Code of British Columbia, Canada may be usefully
considered by way of example. This Code provides that all
new dwelling units must include a mechanical ventilation
system capable of providing, during the heating season, at
least 0.5 air changes per hour. Other Code provisions
stipulate minimum ventilation rates calculated with refer-
ence to the interior volume of the dwelling in question.
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For example, a building having a floor area of 2,400 square
feet and standard eight foot ceilings must have mechanical
ventilators installed having a minimum capacity of 180 CFM
(cubic feet of air per minute).
As indicated above, in order to comply with the
above provisions, building contractors at present ordinar-
ily install one or more exhaust fans in washrooms or other
easily accessible locations within the dwelling. For
larger dwellings both a manually controlled fan and an
automatically controlled fan wired to a dehumidistat must
be installed to meet the minimum ventilation rate require-
ments. For larger residential dwellings, the Code require-
ments cannot be met with an automatically controlled fan
alone since such a fan would be excessively noisy.
The present invention eliminates or reduces the
need to install a separate automatic ventilation system by
providing a kitchen range hood fan 10 which may be operated
in both a manual and an automatic mode. When operating at
the low speed setting, in either the manual or automatic
mode, the minimum capacity of fan 10 is preferably 50 Cfm.
The minimum capacity of the fan at the high speed setting
in the manual mode is preferably 100 Cfm.
As will be apparent to those skilled in the art
in the light of the foregoing disclosure, many alterations
and modifications are possible in the practice of this
invention without departing from the spirit or scope
thereof. Accordingly, the scope of the invention is to be
construed in accordance with the substance defined by the
following claims.
