U.S. patent application number 10/973960 was filed with the patent office on 2005-10-27 for crawl space ventilation system.
This patent application is currently assigned to TB&B Partners. Invention is credited to Reese, Timothy A..
Application Number | 20050239393 10/973960 |
Document ID | / |
Family ID | 35463713 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050239393 |
Kind Code |
A1 |
Reese, Timothy A. |
October 27, 2005 |
CRAWL SPACE VENTILATION SYSTEM
Abstract
The present invention provides a fan unit centrally located
within a crawl space. The fan unit includes a fan, a fan motor, an
inlet grill, and an outlet grill. A timer connected in the power
supply activates the fan motor at periodic predetermined time
intervals to move the crawl space air through the fan unit. The fan
unit is located and orientated to create a negative pressure to
pull air into the crawl space through wall inlet vents and to also
create a positive pressure to force air out of the crawl space
through wall outlet vents. An outside humidity sensor can be used
to insure the outside air has a lower percent humidity than that
desired in the crawl space and an inside humidity sensor is used to
turn the fan unit off if the crawl space humidity is below an
acceptable limit. A temperature sensor is used to turn the fan unit
off when the crawl space air temperature gets too low.
Inventors: |
Reese, Timothy A.;
(Greenville, SC) |
Correspondence
Address: |
Patent Consultants & Services, Inc.
204 Bouchillion Drive
Greenville
SC
29615
US
|
Assignee: |
TB&B Partners
Greer
SC
29650
|
Family ID: |
35463713 |
Appl. No.: |
10/973960 |
Filed: |
October 26, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10973960 |
Oct 26, 2004 |
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10829634 |
Apr 22, 2004 |
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6926602 |
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Current U.S.
Class: |
454/251 |
Current CPC
Class: |
F24F 2110/20 20180101;
F24F 11/0001 20130101; F24F 11/0008 20130101; F24F 2110/22
20180101; F24F 11/30 20180101 |
Class at
Publication: |
454/251 |
International
Class: |
F24F 007/007 |
Claims
What is claimed is:
1. An electrically powered ventilation system for a building crawl
space to reduce the moisture content of enclosed air within walls
of the crawl space, said system comprising: a fan unit having a fan
operated by an electrical motor, said fan unit centrally located
and orientated within the crawl space; said fan unit includes at
least one inlet grill and an outlet grill for moving air within the
crawl space through said fan unit to establish relatively high and
low air pressure areas within the crawl space relative to the
outside ambient air pressure; inlet vents in the walls adjacent to
low air pressure areas allow for movement of relatively low
moisture content outside ambient air into the crawl space; outlet
vents in the walls adjacent to high air pressure areas allow for
movement of relatively higher moisture content crawl space air to
be discharged from the crawl space; a timer unit manually set to
transmit a first electrical signal to activate said fan unit for
ventilation periodic time periods that are set to optimally reduce
the moisture content of the crawl space air; a controller unit
having a control switch is connected between said timer unit and
said fan unit to turn the fan unit on and off; and a main switch of
said controller unit for directly transmitting electrical power to
said control switch to turn on said fan unit in one position, and
to activate control logic circuits for air temperature and humidity
controls before selectively transmitting electrical power to said
control switch to turn on said fan unit in the other position.
2. The ventilation system of claim 1 including: a transformer of
said controller unit to provide a low voltage signal; a crawl space
temperature sensor powered by said low voltage signal to sense the
crawl space temperature and transmit a temperature signal to
indicate the crawl space temperature; and a temperature control
logic circuit of said controller unit that receives both said low
voltage signal and said temperature signal, wherein said low
voltage signal is transmitted directly to said control switch to
turn the fan motor off when said temperature signal is below a
predetermined temperature value.
3. The ventilation system of claim 2 including: an outside humidity
sensor powered by said low voltage signal, to sense the percent
moisture content of the outside ambient air and transmit a second
electrical signal to indicate the outside air humidity; and a first
control logic circuit of said controller unit that receives both
said low voltage signal and said second electrical signals, wherein
said low voltage signal is transmitted directly to said control
switch to turn the fan motor off when the outside humidity is above
a first threshold value.
4. The ventilation system of claim 1 including: an inside crawl
space humidity sensor powered by said low voltage signal to sense
the percent moisture content of the inside crawl space air and
transmit a third electrical signal to indicate the inside crawl
space air humidity; and a second control logic circuit of said
controller unit that receives both said low voltage signal and said
third electrical signal, wherein the low voltage signal is
transmitted directly to said control switch to turn the fan motor
on when the inside crawl space humidity is above a second threshold
value and to turn the fan motor off when the inside crawl space
humidity is below a second threshold value.
5. The ventilation system of claim 1 wherein the crawl space
includes a remote crawl space such that the ventilation system
further comprises: a discharge plenum of the fan unit; a duct to
extending from said discharge plenum into the remote crawl space,
wherein a portion of the discharge air from the discharge plenum of
said fan unit is diverted and discharged into the remote crawl
space to produce an increase in the air pressure within the remote
crawl space; remote outlet vents for movement of relatively high
moisture content within the remote crawl space to the exterior of
the remote crawl space, wherein the air pressure in the crawl space
is reduced to a balanced air flow.
6. The ventilation system of claim 1 including: flexible straps
attached to and extending from floor structure of the building for
supporting the fan unit and limit the amount of noise and
vibrations produced by operating the fan and fan motor.
7. The ventilation system of claim 1 including: a support frame
setting on a ground surface for supporting the fan unit within the
crawl space to limit the amount of noise and vibrations produced by
said fan unit, said fan and said electrical motor.
8. The ventilation system of claim 7 wherein said support frame
includes: main support members resting on the ground surface; a
pair of cross members connecting said main members together as a
unit; and a pair of support brackets affixed to said main support
members to support and hold said fan unit within the crawl
space.
9. The ventilation system of claim 1 including an outlet baffle
associated with said outlet grill of said fan unit to provide a
back pressure in said discharge plenum so that said fan motor will
operate at a desired speed and power rating.
10. A multiple ventilation system for multiple crawl spaces under a
building structure with exterior wall vents to reduce the moisture
content of the air within at least one crawl space, said multiple
ventilation system comprising: a fan unit having a fan operated by
an electrical motor centrally located and orientated within said at
least one crawl space; a timer unit associated with fan unit that
is set to transmit a first electrical signal for ventilation time
periods that are determined to optimally reduce the moisture
content of the air in a respective crawl space; a temperature
sensor to determine a temperature within the at least one crawl
space and transmit a temperature electrical signal that generally
indicates a temperature value in the crawl space used to determine
if said fan unit should be activated; an outside humidity sensor to
determine the percent moisture value of the ambient air and
generate a second electrical signal to indicate the ambient air
moisture value to further determine if said fan unit should be
activated; an inside humidity sensor to determine the percent
moisture value of the at least one crawl space air and generate a
third electrical signal to indicate a percent moisture value for
the at least one crawl space air to also help determine if said fan
unit should be activated; and a controller unit associated with
each crawl space having a main switch, a transformer, a plurality
of logic control circuits and a control switch that receives said
temperature, second and third electrical signals and compares these
signals with predetermined limits of temperature and humidity,
whereby the fan unit may be activated.
11. The multiple ventilation system of claim 10 wherein said fan
unit includes at least one inlet grill, an outlet grill and an
outlet baffle for moving air within the at least one crawl space
through said fan unit to establish relatively high and low pressure
areas within the at least one crawl space, so that air flows in and
out of the at least one crawl space through respective exterior
wall vents.
12. The multiple ventilation system of claim 10 wherein said
controller unit includes a main switch wherein electrical power is
transmitted directly to said control switch to activate the fan
motor when said main switch is in one position and said transformer
and logic control circuits are activated when said main switch is
in a second position.
13. The multiple ventilation system of claim 10 wherein said
plurality of logic control circuits includes a temperature logic
control circuit for comparing said temperature electrical signal of
said crawl space air moisture value with a predetermined
temperature threshold limit value, wherein said control switch is
free to activate the fan motor when the crawl space air temperature
is above the temperature threshold limit value and turns the fan
motor off when the crawl space air temperature is below the
temperature threshold limit value.
14. The multiple ventilation system of claim 13 wherein said
plurality of logic control circuits includes a first logic control
circuit for comparing said second electrical signal of said outside
air moisture value with a predetermined first threshold limit
value, wherein said control switch is free to activate the fan
motor when the outside ambient air humidity is below the first
threshold limit value and turns the fan motor off when the outside
ambient air humidity is above the first threshold limit value.
15. The multiple ventilation system of claim 14 wherein said
plurality of logic control circuits includes a second logic control
circuit for comparing said third electrical signal of said crawl
space air moisture value with a predetermined second threshold
limit value, wherein said control switch activates the fan motor
when the inside crawl space air humidity is above said second
threshold limit value and turns the fan motor off when the inside
crawl space air humidity is below the second threshold limit
value.
16. The multiple ventilation system of claim 10 wherein the
controller unit includes a transformer to reduce the first
electrical signal to a low voltage signal used to power the
humidity and temperature sensors and logic control circuits of the
controller unit.
17. The multiple ventilation system of claim 10 wherein the at
least one crawl space includes a remote crawl space of the multiple
crawl spaces said remote crawl space system comprises: a plurality
of outlet vents associated with the exterior wall vents of said
remote crawl space; and a duct extending from a discharge plenum of
said fan unit into the remote crawl space, wherein a portion of the
discharged air from said fan unit is diverted and discharged into
the remote crawl space through said duct to produce an increase in
the air pressure within the remote crawl space and move the
relatively high moisture content air within the remote crawl space
to the exterior of the remote crawl space through said outlet
vents.
Description
BACKGROUND OF THE INVENTION
[0001] This invention is directed to providing ventilation for a
crawl space under a house or similar structure, and in particular
to provide a fan system for the introduction of air into and from
the crawl space as well as circulation within the crawl space to
reduce the amount of moisture present in the crawl space.
[0002] The moisture content within a crawl space is the result of
having a space between the ground and the floor that is subjected
to a moisture buildup from various sources. Some of these sources
include leaking pipes, condensation on the exterior surfaces of
heating and air conditioning ducts and natural ground water
intrusion into the crawl space. Very little opportunity exists for
the moisture to be discharged from the crawl space. Openings in the
exterior walls are generally small and not properly located to keep
the moisture content of the crawl space air from reaching a high
percentage. The need exists to provide a positive flow of the air
not only within the crawl space but also from a source having a
lower percentage of moisture introduced into the crawl space and
discharging the air within the crawl space having a high percentage
of moisture.
[0003] The lack of circulation or movement of air within a crawl
space results in higher concentrations of radon gas and the
inability of the air to carry moisture from the crawl space that
has evaporated into the air from damp surfaces. The harmful effects
of radon gas are well known in the building industry and special
construction features are used to keep concentrations low,
including a ground cover, vent pipes and crawl space vents. In
addition. air moving across a moist surface will collect moisture
from the surface by evaporation from the surface and transport this
excess moisture in the air away from the surface. The better the
air circulation the more moisture will be removed from the crawl
space by evaporation. This moisture reducing effect is in addition
to replacing air having a high percentage of moisture with air
having a lower percent moisture as previously discussed.
[0004] Some of the bad effects of high moisture content in the
crawl space air include wood rot, mold, mildew, fungi, bacteria
growth and insect infestation, to mention a few. The crawl space
air can have an odor which is also objectionable. Radon gas content
of a crawl space having a high moisture content is generally found
to be higher than that in a crawl space with a low moisture
content. A lower moisture content air of a crawl space has many
advantages including: helping prevent termite infestation; helping
prevent rusting and corrosion of heating and air conditioning
equipment; helping maintain floor insulation "R" factors; and
helping prevent high moisture content air from reaching the living
space in a home.
[0005] Typical crawl space ventilation systems have been disclosed
in U.S. Pat. Nos. 3,368,756; 4,702,149; 4,829,882; and 4,877,182.
The ventilator systems of '756 and '149 are passive systems where
the air is not being forced through the crawl space and depends on
the natural flow as a result of temperature differences. The
ventilation systems of '182 and '882 depend on both intake and
exhaust units at the exterior openings and vents of the crawl
space. Numerous dehumidification systems are available in the
industry to actively remove moisture from a space to reduce the
moisture content of the air. These systems are generally used to
condition the living area air and are not cost effective for use in
conditioning air in a crawl space.
[0006] The need remains to have an efficient and cost effective
ventilation system for the crawl space under the lower floor of a
home or building not built on the ground. The ventilation system
should be easy to install as an aftermarket device.
[0007] Accordingly, an object of the present invention is to
provide a ventilation system for a home or building crawl space
which is easily installed and operated but effective in reducing
the moisture content of the air within the crawl space.
[0008] An additional object of the present invention is to provide
air circulation within a crawl space that reduces the concentration
of radon gas and helps reduce the moisture in the crawl space by
removing moist air caused by evaporation from damp surfaces.
[0009] Another object of the present invention is to provide a high
velocity and high cubic feet per minute ventilating system which is
cost effective to produce, install and operate.
[0010] A further object of the present invention is to provide a
control system which operates with limited changes and can be set
to provide the low moisture content air for the crawl space.
[0011] Yet another object of the present invention is to provide a
crawl space ventilation system that accounts for the relative
humidity of the crawl space compared with the ambient air and the
crawl space temperature.
SUMMARY OF THE INVENTION
[0012] The above objectives are accomplished according to the
present invention by a combination of a fan unit suspended from the
building floor structure within the crawl space. The fan unit
includes a fan, a fan motor an inlet grill and an outlet grill. A
timer connected to the power supply activates the fan motor at
periodic predetermined time intervals to move the crawl space air
through the fan unit. The fan unit is located and orientated to
create a negative pressure to pull air into the crawl space through
inlet vents and to also create a positive pressure to force air out
of the crawl space through outlet vents. Inlet and outlet vents are
located in the exterior walls of the crawl space and generally
exist in most homes and buildings without adding any new vents. The
location and orientation of the fan unit determines which existing
vents become inlet vents and which become outlet vents depending on
positive and negative pressures created within the crawl space by
the fan unit. The wind direction exterior to the crawl space can
also influence which vents are inlet vents and which become outlet
vents. However, during certain periods of time, the moisture in the
outside air may be too high. An outside humidity sensor can be used
to insure the outside air has a lower percent humidity than that
desired in the crawl space before the fan motor is activated. A
temperature sensor is also used to help protect the system from
freezing conditions which may cause ice to form in the crawl
space.
[0013] In one embodiment of the present invention an electrically
powered ventilation system is provided for a building crawl space
to reduce the moisture content of enclosed air within walls of the
crawl space. The system comprises a fan unit having a fan operated
by an electrical motor. The fan unit is centrally located and
orientated within the crawl space and includes at least one inlet
grill and an outlet grill for moving air within the crawl space
through said fan unit to establish high and low air pressure areas
within the crawl space relative to the outside ambient air
pressure. Inlet vents in the walls, adjacent to low air pressure
areas allow for movement of relatively low moisture content outside
ambient air into the crawl space. Outlet vents in the walls,
adjacent to high pressure areas allow for movement of relatively
higher moisture content crawl space air to be forced from the crawl
space. A timer unit is manually set to transmit a first electrical
signal to activate the fan unit for periodic ventilation time
periods that are set to optimally reduce the moisture content of
the crawl space air. A controller unit having a control switch is
connected between the timer unit and the fan unit to turn the fan
unit on and off. A main switch of the controller unit is for
directly transmitting electrical power to said control switch to
turn on said fan unit in one position, and to activate control
logic circuits for air temperature and humidity controls before
selectively transmitting electrical power to said control switch to
turn on said fan unit in the other position.
[0014] In one aspect of the invention a transformer of the
controller unit provides a low voltage signal. A crawl space
temperature sensor is powered by said low voltage signal to sense
the crawl space temperature and transmit a temperature signal to
indicate the crawl space temperature. A temperature control logic
circuit of said controller unit receives both said low voltage
signal and said temperature signal, wherein said low voltage signal
is transmitted directly to said control switch to turn the fan
motor off when said temperature signal is below a predetermined
temperature value.
[0015] In another aspect of the invention an outside humidity
sensor is powered by the low voltage signal to sense the percent
moisture content of the outside ambient air and transmit a second
electrical signal to indicate the outside air humidity. A first
control logic circuit of said controller unit receives both the low
voltage signal and the second electrical signal, wherein the low
voltage signal is transmitted directly to the control switch to
turn the fan motor off when the outside humidity is above a first
threshold value. An inside crawl space humidity sensor is powered
by said low voltage signal to sense the percent moisture content of
the inside crawl space air and transmit a third electrical signal
to indicate the inside crawl space air humidity. A second control
logic circuit of the controller unit receives both the low voltage
signal and the third electrical signal. The low voltage signal is
transmitted directly to the control switch to turn the fan motor on
when the inside crawl space humidity is above a second threshold
value and to turn the fan motor off when the inside crawl space air
humidity is below a second threshold value.
[0016] In another embodiment of the invention a multiple
ventilation system is provided for multiple crawl spaces under a
building structure with exterior wall vents to reduce the moisture
content of the air within at least one crawl space. The multiple
ventilation system comprises a fan unit having a fan operated by an
electrical motor. The fan unit is centrally located and orientated
within the one crawl space. A timer unit associated with fan unit
that is set to transmit a first electrical signal for ventilation
time periods that are determined to optimally reduce the moisture
content of the air in the one crawl space. A temperature sensor to
determine a temperature within the one crawl space and transmit a
temperature electrical signal that indicates a temperature value in
the crawl space is used to determine if the fan unit should be
activated. An outside humidity sensor determines the percent
moisture value of the ambient air and generates a second electrical
signal to indicate the ambient air moisture value to further
determine if the fan unit should be activated. An inside humidity
sensor determines the percent moisture value of the one crawl space
air and generate a third electrical signal to indicate a percent
moisture value for the at least one crawl space air to help
determine if the fan unit should be activated. A controller unit
associated with each crawl space includes a main switch, a
transformer, a plurality of logic control circuits and a control
switch. The controller unit receives the temperature signal, second
and third electrical signals and compares these signals with
predetermined limits of temperature and humidity. The fan unit may
be one of either activated or turned off by comparing the signals
with the predetermined limits.
[0017] In another aspect of the present invention, ventilation of
another crawl space of the building is realized. A remote
ventilation system comprises a duct extending from said discharge
plenum of the fan unit in the one crawl space into the remote crawl
space. A portion of the discharge air from the adjacent fan unit is
diverted and discharged into the remote crawl space to produce an
increase in the air pressure within the remote crawl space. The
relatively high moisture content of the air within the remote crawl
space is exhausted to the exterior of the remote crawl space
through the wall vents in the remote crawl space.
DESCRIPTION IF THE DRAWINGS
[0018] The construction designed to carry out the invention will
hereinafter be described, together with other features thereof.
[0019] The invention will be more readily understood from a reading
of the following specification and by reference to the accompanying
drawings forming a part thereof, wherein an example of the
invention is shown and wherein:
[0020] FIG. 1A is a plan view of typical crawl spaces between a
floor structure and the ground surface within walls of a building
having a fan unit centrally located in one crawl space to discharge
air in one direction to draw outside air into the crawl space
through inlet vents and discharge air through outlet vents to
provide ventilation for the crawl spaces;
[0021] FIG. 1B is a plan view of the typical crawl spaces between a
floor structure and the ground surface within walls of the building
of FIG. 1 having the fan unit again centrally located in the one
crawl space but reversed to discharge air in an opposite direction
and draw outside air into the crawl space through different inlet
vents and discharge air through different outlet vents to again
provide ventilation for the crawl spaces;
[0022] FIG. 2A is a perspective view of a fan unit suspended from a
typical floor system of the building using flexible straps and
including a power supply, sensors and a timer unit connected to a
controller unit for operating the crawl space ventilation
system;
[0023] FIG. 2B is a perspective view of a fan unit sitting on the
ground under the floor system of the building a support frame and
including the power supply, sensors an the timer unit connected to
the controller unit for operating the crawl space ventilation
system;
[0024] FIG. 3 is a flow diagram of how the crawl space ventilation
components are interconnected and how the controller logic circuits
of the controller unit function for periodic operation of the fan
unit to provide proper ventilation subject to predetermined
threshold humidity and temperature limits; and
[0025] FIG. 4 is a graphic chart of the threshold humidity limits
levels in relation to the fan operating time showing the fan
operating regime when applying inside and outside humidity limits
and when the crawl space temperature is greater than a threshold
limit for temperature.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0026] Referring now to the drawings, the invention will now be
described in more detail. A fan unit 20 is positioned within a
crawl space 10 at a somewhat central location within the crawl
space area, as illustrated in FIGS. 1A and 1B. The fan unit
includes a fan motor 22, inlet grills 24, a discharge plenum 25 and
an outlet grill. The fan unit is located and orientated to pull air
into the crawl space through inlet vents 12 and force air out of
the crawl space through outlet vents 14. Inlet and outlet vents are
located in exterior walls 18 of crawl space 10 and generally exist
in most homes and buildings and usually include a screen or grill
and a hinged cover for closing the vent when ventilation of the
crawl space is not wanted or needed. These vents normally exist in
buildings to obtain natural or free ventilation of the crawl space.
The location and orientation of fan unit 20 determines which
existing vents become inlet vents and which become outlet vents;
depending on negative pressure locations 10a created within the
crawl space adjacent inlet vents and positive pressure locations
10b created within the crawl space adjacent outlet vents. The wind
direction exterior to the crawl space can also influence which
vents are inlet vents and which become outlet vents. The plan view
of FIG. 1A shows fan unit 20 discharging air in an opposite
direction to that shown in FIG. 1B. In this case the location on
inlet vents 12 and outlet vents 14 has changed. The essential
operation is to draw an equal quantity of air into the crawl space
as there is being discharged from the crawl space. According to the
present invention it is not important which vents become inlet
vents and which become outlet vents as long as a flow and
circulation of air is maintained to achieve more changes of air in
the crawl space per unit of time compared with the crawl space
having no fan unit. The serpentine arrows of FIGS. 1A and 1B
illustrate a possible direction of the flow of air within the crawl
space as well as in and out of the crawl space.
[0027] A remote crawl space area 11 may exist which is separated
from the main crawl space 10. For these remote areas a duct 28 is
provided as illustrated in FIGS. 1A and 1B. The duct connects to
discharge plenum 25 with vanes in the discharge plenum to direct
air into the duct. Air is discharged into the remote area from an
end 29 of the duct to increase the pressure in the remote area.
This higher than ambient pressure moves the air in the remote area
out through outlet vents 15 to the outside. Additional remote areas
can be ventilated in the same way.
[0028] The overall objective is to circulate air in crawl space and
reduce the moisture content of the crawl space air by moving the
air within the crawl space and replacing the air within the crawl
space. Therefore, it is necessary to pull air into the crawl space
that has a lower moisture content than the air within the crawl
space without ventilation. One aspect of the crawl space
ventilation system of this invention depends on the outside ambient
air having a lower moisture content. An outside humidity sensor 60
is included to monitor the percent moisture of the outside ambient
air. If the outside ambient air has a higher moisture content than
the inside crawl space air, little or no advantage is achieved by
bringing outside air into the crawl space. In addition, an inside
humidity sensor 64 is included to monitor the percent moisture in
the crawl space air. If the crawl space air already has a low
moisture content, the crawl space moisture is under control and
there is also little or no advantage in bringing outside air into
the crawl space. However, the movement of air for evaporation of
moisture from damp surfaces and the lowering of radon gas
concentrations may continue to yield positive results, regardless
of the inside or outside humidity.
[0029] Another aspect of the crawl space ventilation system of this
invention depends on the crawl space temperature having a lower
value than a predetermined value for safe operation of the system.
A crawl space temperature sensor 70 is included to monitor the
temperature of the inside crawl space air. If the crawl space
temperature is below a predetermined value that creates a problem
in operating components within the crawl space that are damaged by
a low temperatures, such as ice buildup, the ventilation system can
be turned off. The temperature sensor transmits a temperature
signal that can be compared with the predetermined value to decide
if continued operation of the ventilation system is desirable.
[0030] The ventilation system of this invention has the option of
using or not using the inside and outside air humidity values and
the crawl space temperature value to operate the fan unit. The
humidity and temperature sensors are those commonly found in the
building industry to measure percent moisture and temperature and
transmit a proportional electrical signal.
[0031] A detailed view of the working components of one setup for
the ventilation system for a building crawl space is illustrated in
FIG. 2A. A fan unit 20 is suspended within the crawl space below
the building floor 5 from floor structural members 7 using flexible
straps 30. The straps are attached at the top to the floor members
using fasteners 30a and at the bottom to the fan unit by fasteners
30b. This suspension means allows the fan unit to operate without
structural vibrations and noise.
[0032] A detailed view of the working components of another setup
for the ventilation system for a building crawl space is
illustrated in FIG. 2B. Fan unit 20 is supported above a ground
surface 4 within the crawl space below the building floor 5 using a
support frame 80. The support frame includes main support members
82 held together by cross members 84. Support brackets 86 are
affixed to the main support members for holding and supporting the
fan unit above the ground using fasteners 86a. The fan unit can
alternately be made without a plenum 25 if a duct to serve a remote
crawl space is not needed.
[0033] Once again, the fan unit includes a fan motor 22, inlet
grills 24, a discharge plenum 25, and an outlet grill 26, as
illustrated in FIGS. 2A and 2B. A timer unit 41 is connected to a
controller 40 to activate fan motor 22 at periodic predetermined
time intervals to move the crawl space air through the fan unit. An
inlet grill 24 is provided on at least one side of the fan unit
pulls air into the fan unit from the crawl space and an outlet
grill 26 is provided for discharging air from a discharge plenum 25
back into the crawl space, as indicated by the arrows in FIGS. 2A
and 2B. An outlet baffle 27 associated with the outlet grill of the
fan unit provides back pressure in the discharge plenum so that the
fan unit operates at a desired speed and power rating. A power
cable 52 is brought from the building electrical power system into
the crawl space to the fan unit. The power cable is first
terminated in a power receptacle 50, located near the fan unit, to
be further extended to a timer device 41 through a system cable 54.
When the timer device is requesting the fan unit be turned on,
electrical power is transmitted through a timer conduit 42 to a
controller unit 40. The controller unit contains logic control
circuits to decide if further conditions are satisfied to allow the
fan unit to be operated. A previously discussed, these conditions
may include the existing percent moisture in the crawl space, the
percent moisture in the outside ambient air and the temperature in
the crawl space. For convenience, the power receptacle, the timer
device and the controller unit can be located near the fan
unit.
[0034] To determine the conditions of the outside ambient air,
exterior humidity sensor 60 is monitored. A low voltage signal is
transmitted to the outside humidity sensor through sensor cable 62
and a second electrical signal is returned to indicate the percent
moisture of the outside ambient air measured by the outside
humidity sensor. To determine the conditions of the inside crawl
space air, interior humidity sensor 64 is monitored. A low voltage
signal is transmitted to the inside humidity sensor through sensor
cable 66 and a second electrical signal is returned to indicate the
percent moisture of the inside crawl space air measured by the
inside humidity sensor. Logic control circuits in controller unit
40 are used to operate the fan unit when considering humidity
values (percent moisture) and temperature (degrees) in the present
ventilation system. This operation will be discussed later.
[0035] If the decision from the controller is to operate the fan
unit, electrical power is allowed to flow from controller 40
through fan cable 44 to a fan connector box 23. Power is further
transmitted to the electrical fan motor 22 through the motor
conduit 21 to ventilate the crawl space.
[0036] A flow diagram of the crawl space ventilation system is
shown in FIG. 3. The building electrical power is transmitted
through power cable 52 to power receptacle 50 located near the fan
unit. System cable 54 transmits power directly to timer device 41.
Operating parameters are set within the timer device using the
timer dial 41a to adjust how often the fan should be turned on and
the amount of time to operate the fan unit each operating interval.
A nominal operating time may be to turn on the fan unit each hour
for about 15 minutes. Depending on the layout of the crawl space
and the moisture conditions within the crawl space the timer device
can be set to operate more or less than the nominal conditions.
Each installation will need to be evaluated as to what is optimum
depending on the amount of air circulation achieved by the fan
unit, the amount of excess moisture normally present within the
crawl space and the building location and nominal outside
environmental conditions, including wind direction and average
velocity. Test installations have indicated that little change is
needed once the general layout of the crawl space, existing
moisture problems and the location of the building and surrounding
structures are all accounted for.
[0037] If the timer device sends a first electrical signal
indicating the fan unit should be turned on, power is transmitted
to controller unit 40 through timer conduit 42 to the main control
switch "S". The main control switch is used to select whether
temperature and humidity conditions will be used or not to operate
the fan unit. With the switch in a first position, the temperature
and humidity sensors are bypassed and electrical power is
transmitted directly through cable 42a from main switch S to turn
on the control switch. Power is further transmitted through fan
cable 44 to fan connector box 23 and fan motor 22 through motor
conduit 21 to turn on the fan unit. If the switch is in a second
position, the inside temperature, outside humidity and the inside
humidity will be monitored to determine if existing temperature and
moisture conditions outside and inside the crawl space are within
limits for optimum operation of the fan unit. Electrical power is
transmitted through timer cable 42b to control switch 40d which can
be turned on or off by the logic control circuits 40b and 40c of
the controller unit. Power is transmitted directly to a transformer
40a to produce the low voltage electrical power for the temperature
and humidity monitoring circuits. The temperature and humidity
monitoring circuits use low voltage sensors and components to
transmit temperature, second and third electrical signals to and
from temperature and humidity sensors 60, 64 and 70.
[0038] If the crawl space temperature is too low the advantages of
circulating air within the crawl space may be limited. A crawl
space temperature sensor 70 is used to help protect the system from
freezing conditions which may cause ice to form in the crawl space
and damage other components within the crawl space. The temperature
sensor receives a low voltage signal through sensor cable 72 and
transmits back to the controller unit a temperature signal for the
crawl space air. A logic control circuit 40e of the controller unit
compares the crawl space temperature with a predetermined low
threshold temperature for safe operation of crawl space fan unit.
The predetermined threshold temperature is set by temperature
sensor dial 70a. If the temperature of the crawl space air is above
the low threshold temperature the fan unit can operated. If the
crawl space air is below the threshold limit value, control logic
circuit 40e tells control switch 40d to terminate any power from
being transmitted beyond the control switch. For example, if the
crawl space temperature is below freezing, the circulation of air
in the crawl space may cause ice to form and build on electrical
equipment and other components.
[0039] If the outside humidity is too high the advantages of
drawing outside air into the crawl space are diminished. In
addition, if the humidity inside the crawl space is already low at
a particular time, it may not be economical to ventilate the crawl
space at that time. Humidity logic control circuits 40b and 40c
allow these two conditions to be checked and the crawl space
ventilation system to be turned off during the time it would
normally be operating.
[0040] Outside humidity sensor 60 receives a low voltage first
electrical signal through sensor cable 62 and transmits back to the
controller unit a percent moisture signal for the outside air. The
logic control circuit 40b of the controller unit compares the
outside humidity with a predetermined high threshold humidity value
acceptable for continuing to ventilate the crawl space. If the
humidity of the outside air is below this high value, the fan unit
can be operated. However, if the outside air is above this high
value, first logic control circuit 40b tells control switch 40d to
terminate any power from being transmitted beyond the control
switch. For example, if it is raining outside, it would not be
helpful to bring this 100 percent moisture content air into the
crawl space. The high threshold limit value can be set by either a
dial on the controller or a sensor dial 60a on the humidity sensor,
as shown in FIG. 3.
[0041] Inside humidity sensor 64 receives a low voltage first
electrical signal from sensor cable 66 and transmits back to the
controller a percent moisture signal for the air inside the crawl
space. The second control logic circuit 40c of the controller
compares the inside humidity with a predetermined second threshold
limit value acceptable for continuing to ventilate the crawl space.
If the humidity of the air inside the crawl space is above this
relatively low value, the fan unit will be operated. However, if
the moisture content of the crawl space air is below this second
threshold limit value the control logic circuit 40c tells control
switch 40d to terminate any power from being transmitted beyond the
control switch. For example, if it is a time of very low humidity,
say 20 percent indicating the crawl space ventilation system has
been working well, it may not be economical to bring this 20
percent moisture content air in the crawl space any lower. The
system can actually bypass some operating cycles when it would
normally be ventilating the crawl space. If both the outside air
has a moisture content below a high value and the inside air has a
moisture content above a low value, the control switch 40d is
turned on and power is again delivered to fan motor 22 and the
crawl space is ventilated.
[0042] Operation of the system with humidity sensors 60 and 64
limiting on-time for the fan unit is illustrated in the graph of
FIG. 4. During the time for ventilation set by the timer device,
when the fan motor is to be turned on and before it is to be turned
off, the fan unit is normally operating to ventilate the crawl
space if the temperature of the crawl space is above a threshold
temperature value. However, if main switch S of the controller is
in a position to consider existing temperature and humidity
conditions, the fan unit may be turned off. With an acceptable
outside first threshold limit value for the humidity of the ambient
air established and set by sensor dial 60a, the fan unit only
operates when the outside humidity is below this value. With an
acceptable inside second threshold limit value on the humidity of
the crawl space air established and set by sensor dial 64a, the fan
unit only operates when the crawl space humidity is above this
second threshold limit value. These two limiting conditions defines
a fan operating region, as illustrated in the graph of FIG. 4. When
conditions exist within this operating region the crawl space will
be ventilated; provided the crawl space temperature is above the
temperature threshold limit.
[0043] It is possible to operate the ventilating system with only
outside ambient air humidity being a factor by simply setting the
inside threshold limit to zero and the temperature threshold limit
is at a very low value. The ventilating system will then operate
considering the timer device and ambient air humidity conditions
only. In a similar mode, it is possible to operate the ventilating
system with only inside crawl space air humidity being a factor by
simply setting the outside threshold limit to 100 percent and again
setting the temperature threshold limit at a very low value. The
ventilating system will then operate considering the timer device
and crawl space air humidity conditions only.
[0044] The ventilation system can also be made to be controlled by
crawl space air temperature alone with the timer unit. The humidity
threshold values can both be set to always allow the control switch
to be turned on. If the inside humidity threshold limit is set to
zero percent and the outside humidity threshold limit is set to 100
percent, the humidity conditions will not become a limiting factor
and temperature logic control circuit 40e governs the operation of
the ventilation system along with the timer unit.
[0045] Once again, there are other considerations beside the air
temperature and moisture content to consider. The advantages of
circulating air within the crawl space are important in removing
radon gas concentrations and in removing moisture from damp
surfaces that may rust of otherwise be damaged by moisture. The
recommended method for radon gas is to provide a ground cover of
polyethylene sheeting with a plumbing tee beneath the sheeting
having a vent pipe through the sheeting and up through the roof.
The vent pipe would not need to be extended through the roof with
the present ventilating system as the air is being removed from the
crawl space.
[0046] While a preferred embodiment of the invention has been
described using specific terms, such description is for
illustrative purposes only, and it is to be understood that changes
and variations may be made without departing from the spirit or
scope of the following claims.
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