Humidistat and interface

The present invention provides for a humidistat which can be connected to a humidifier through a thermostat and its existing wiring. The thermostat has a plurality of output leads for a heating signal, a fan signal and/or a cooling signal. The humidistat includes a first input for receiving the heating signal from the thermostat, a sensor associated with the first input for sensing the relative humidity of the air in the enclosed volume, a second input for receiving the cooling signal from the thermostat, and a first switch with a heating position and a cooling position for switching between the first and second inputs, respectively, and an interface module for selectively energizing either a humidifier when the first switch is in the heating position or a cooling system when the first switch is in the cooling position. The interface module can further include a second switch for switching between the humidification position and the cooling position and a timing device for timing a predetermined period of time after receiving the cooling signal to delay switching the second switch to the cooling position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a humidistat and more particularly to a 
humidistat having an interface module for use in conjunction with an 
existing thermostat. 
2. Description of the Prior Art 
Various thermostats and humidistats for controlling the temperature and 
humidity levels in an enclosed area have been developed., In a building or 
other structure with an installation of a thermostat connected to a 
heating and cooling system, the addition of a humidifier and a humidistat 
to moisturize the air in the enclosed volume presents particular problems 
and disadvantages. Typically, the thermostat is placed in a central 
location within the building and is electrically connected to the heating 
and cooling system at another location. As such, these existing 
installations do not provide for the easy addition of the humidifier 
because new wiring is needed and must be passed through the walls of the 
structure so as to connect the humidistat to the humidifier and the 
humidifier to the heating system. The humidistat, like the thermostat, 
also should be located centrally within the enclosed volume and adjacent 
the thermostat. The installation of additional wires often requires 
opening a hole in the wall, drilling holes between floors, rebuilding the 
wall and other laborious tasks. These problems increase the time and 
overall cost of the installation. Thus, a need exists for a humidistat 
having an easy installation procedure that overcomes the disadvantages of 
the known humidistats. 
SUMMARY OF THE INVENTION 
The present invention provides for a humidistat for sensing the humidity of 
air in an enclosed volume and sending a humidity signal to a humidifier 
when the humidity falls below a preselected value. The humidistat is 
specially adapted for use with a thermostat having a plurality of output 
leads for a heating signal, a fan signal and a cooling signal. The 
humidistat has a first input for receiving the heating signal from the 
thermostat. A second input of the humidistat receives the cooling signal 
from the thermostat. The humidistat has a first switch with a heating 
position and a cooling position for switching between the first and second 
inputs, respectively, wherein the first switch supplies the cooling signal 
at an output of the humidistat when in the cooling position. A sensor is 
connected between the first input and the heating position to sense the 
humidity of the air in the enclosed volume wherein the first switch 
supplies a humidity increase signal at the output of the humidistat when 
the switch is in the heating position and the sensor calls for increased 
humidity. An interface module is provided for selectively energizing 
either a humidifier when the first switch is in the heating position or a 
cooling system when the first switch is in the cooling position. The 
interface module includes a second switch for switching between the 
humidifier and the cooling system. The interface module can include a 
relay for switching the second switch between a first position to energize 
the humidifier and a second position to energize the cooling system and 
the relay is energized when the fan signal is applied to the interface 
module. Alternatively, the interface module can include a timing device to 
delay switching the second switch to the second position for a 
predetermined period of time after receiving the fan signal. The timing 
device includes a relay and a timer, whereby when the timer signals the 
expiration of the predetermined period of time, the relay is energized to 
close the second switch to the second position thereby energizing the 
cooling system. The humidistat of the present invention can be 
electrically connected to the humidifier through the existing wiring 
between the thermostat and the heating and cooling systems, thereby 
eliminating the need for the additional excess wiring and installation 
procedures and expense normally associated with the installation of a 
humidifier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1-4 illustrate the humidistat 10 of the present invention for use 
with an existing thermostat 12. The present invention will be described 
using a thermostat 12 which controls a heating system 14 that includes a 
relay center 16 and an electrically energizable gas valve 18. The heating 
system 14 is described generally because, while other elements of a 
heating system exist such as a furnace and blower (not shown), the present 
invention principally uses existing connections of the heating system 14 
such as a terminal strip (relay center) having a connection for the gas 
valve 18. Additionally, the thermostat 12 can control a cooling system 20 
such as an air conditioning unit having a compressor and fan. The present 
invention will be described when the humidistat 10 and a humidifier 22 are 
connected to the thermostat. 12 for controlling an existing heating system 
14 and cooling system 20 in a building or other structure. 
Referring to FIG. 1, the thermostat 12 controls the operation or 
energization of the heating system 14 and cooling system 20. The 
thermostat 12 can be a known three-lead or four-lead thermostat having 
input and output leads to control the heating system 14 and cooling system 
20. Typically, a three-lead thermostat includes an input lead for power 
and output leads for a heating signal and a fan signal whereas a four-lead 
thermostat includes an additional output lead for a cooling signal. In 
FIGS. 1-3, a four-lead thermostat 12 is utilized to illustrate the 
operation of the present invention. The thermostat 12 has a power lead 24, 
a cooling lead 26, a heating lead 28 and a fan lead 29. The thermostat 12 
is placed in a central location in the building with wires connecting 
leads 24, 26, 28 and 29 to the heating and cooling systems which are at a 
separate location. 
A preferred embodiment of the present invention provides for the humidistat 
10 to be connected to the existing thermostat 12. The humidistat 10 and 
thermostat 12 are energized by an appropriate connection to the power lead 
24. An interface module 30 forms a part of the system to utilize existing 
wiring that transmit the cooling and fan signals from the cooling lead 26 
and fan lead 29 so as to operate the humidifier 22 without installing 
additional wiring directly between the humidistat 10 and humidifier 22. 
The purpose of the present invention is to utilize an existing wire to 
energize either the cooling system 20 or humidifier 22. This is 
advantageous because the humidistat 10 can be located adjacent the 
existing thermostat 12 and can utilize existing wiring throughout the 
building without having to run new wiring from the humidistat 10 to the 
humidifier 22. 
The humidistat 10 includes a humidity sensor 32, a summer/winter switch 34 
having a heating (winter) position 36, shown in FIG. 2 and cooling 
(summer) position 38, as shown in FIG. 3, inputs 40 and 42, and an output 
44. The inputs 40 and 42 receive the heating and cooling signals, 
respectively, from the thermostat 12. The humidity sensor 32 is connected 
between the input 40 and the summer/winter switch 34. The humidistat 10 
further includes an output 44 so as to supply either a humidity signal 
from the humidity sensor 32 to increase the humidity in the enclosed 
volume or a cooling signal from input 42 depending on the position of the 
summer/winter switch 34. 
The humidistat 10 is connected to the thermostat 12 by making a connection 
from the heating lead 28 to the input 40. The existing wire connected to 
the cooling lead 26 providing the cooling signal is split using one end to 
connect to the input 42 and the other end to the output 44, thereafter the 
wire continues through the walls or the like to the separate location for 
the heating system 14 and cooling system 20. Thus, the humidistat 10 of 
the present invention advantageously uses a single wire to signal for an 
increase in the cooling or in the moisturizing of the air in the enclosed 
volume so as to eliminate installation problems of the prior art. 
The summer/winter switch 34 can be a single pole double throw switch having 
pole 46 and contacts 48 and 50. As illustrated in FIG. 2, when the 
summer/winter switch 34 is in the heating (winter) position 36, the 
contact between pole 46 and contact 48 is closed. Thus, when humidity 
sensor 32 of the humidistat 10 closes to generate a call for an increase 
in moisture, the heating signal at input 40 is modified and used as a 
humidity signal. The humidity signal is generated at output 44 and 
supplied to the interface module 30. As illustrated in FIG. 3, when the 
summer/winter switch 34 is in the cooling (summer) position 38, the 
contact between pole 46 and contact 50 is closed. Thus, when the 
thermostat 12 generates a call for cooling or otherwise for an decrease in 
temperature, the cooling signal at input 42 is also generated at output 44 
and supplied to the interface module 30. 
The interface module 30 includes a terminal strip 54 having contacts 56, 
58, 60, 62 and 64. The terminal strip 54 allows for making connections for 
input and output signals at the interface module 30. The interface module 
30 further includes a switch 66 having a first position 68 to effectuate 
humidification, shown in FIG. 2, and a second position 70 to effectuate 
cooling, as shown in FIG. 3. The switch 66 can be a single pole double 
throw switch having a pole 72, a contact 74 and a contact 76. The 
interface module 30 includes an electrically energizable relay 78 
operative to throw or close switch 66 to the second position 70 from the 
first position 68. In operation, when the fan signal is applied at relay 
center 16, 24 VAC is generated and applied by a connection to contact 62 
of the interface module 30. This energizes relay 78 to close and throw 
switch 66 to the second position 70, allowing for energization of the 
cooling system 20. Additionally, interface module 30 can include a timing 
delay circuit 80 as illustrated in FIG. 4 so as to delay the energization 
of the cooling system 20 for a predetermined period of time, for example, 
to delay the energization of the compressor of the cooling system 20 for 
30 seconds. 
As illustrated in FIG. 4, the timing delay circuit 80 includes a rectifier 
82, a relay 84 and a timer 86 to control the energization of the cooling 
system 20. Typically, known heating and cooling systems 14 and 20, 
respectively, are energized using 24 VAC. When the fan signal is applied 
at relay center 16, 24 VAC is generated and applied to contact 62 of the 
interface module 30. The 24 VAC is first applied to the rectifier 132 to 
generate direct current output voltages of +24 VDC to energize one side or 
leg of the relay 84 and +5 VDC to energize the timer 86. Once energized, 
the timer 86 begins a timing cycle 88 adjustable to time a predetermined 
period of time. The timing cycle 88 can be adjusted from, for example 0 
seconds to 180 seconds. Upon expiration of the predetermined period of 
time, the timer 86 energizes the other leg of relay 134 to close and throw 
switch 66 to the second position 70 from the first position 68. The timer 
86 can use a programmable timer chip made by Motorola bearing number 
NC14260BCP/FFXA9213. Likewise, the relay 84 can be a 24 VDC relay made by 
Aromat bearing number JS1E-24/AJ 813423B. 
Installation of the interface module 30 is simplified according to the 
present invention. The interface module 30 can be connected at the 
location of the heating and cooling systems and use the existing wires 
from the thermostat 12 supplying the cooling and fan signals as these 
terminate at this separate location. The relay center 16 is often present 
in known heating and cooling systems 14 and 20. In the present invention, 
the relay center 16 includes contacts for power 90, cooling 92, heating 
94, energization of a fan 96 and a common ground 98. The power lead 24, 
heating lead 28, and fan lead 29 of the thermostat are connected to the 
relay center 16 at contacts 90, 94 and 96, respectively. The relay center 
16 is located separate from the thermostat 12 with the heating and cooling 
systems 14 and 20. In addition, the relay center 16 can be present as a 
bus bar or terminal strip of the heating or cooling systems 14 and 20. 
While the interface module 30 is described having various input and output 
connections between the relay center 16 and the interface module 30 so as 
to have uniformity between FIGS. 1-4, the present invention is not 
specifically limited to such because direct connections can be made to the 
interface module 30 such as to the humidifier 22 and the cooling system 
20. 
The interface module 30 is connected to the existing wires of the 
thermostat 12. At the separate location of the heating and cooling systems 
14 and 20, the wire supplying the cooling signal is split having one end 
connected to contact 56 and the other end connected to contact 60. Contact 
58 is connected directly to the humidifier 22. The existing wire 
containing the fan signal is connected the contact 96 of the relay center 
16 and then is supplied to contact 62 of the interface module 30. The 
circuits between the relay center 16 and each of the interface module 30, 
cooling system 20 and humidifier 22 are completed by having common or 
ground wire 98 connected to contact 64 of the interface module 30, to 
contact 102 of the cooling system 20, and to contact 104 of the humidifier 
22. 
Referring to FIGS. 1 and 2, the humidifier 22 can be energized when switch 
66 is in the first position 68. Any humidity signal supplied from output 
44 to contact 60 is also supplied from contact 58 connected to contact 
100, thereby energizing the humidifier 22. Common wire 98 of the relay 
center 16 is connected to contact 104 of the humidifier 22 to complete the 
circuit. 
Referring to FIGS. 1 and 3, the cooling system 20 can be energized when 
switch 66 is in the second position 70. Any cooling signal supplied from 
output 44 to contact 60 is also supplied from contact 56 to contact 106 to 
energize the cooling system 20. Likewise, the cooling signal can be 
supplied to contact 92 of the relay center 16 and then supplied to contact 
106 of the cooling system 20. Common wire 98 of the relay center 16 is 
connected to contact 102 of the cooling system 20 to complete the circuit. 
Referring to FIG. 2, the operation of the humidistat 10 having the switch 
34 in the heating position 36 is described. When the thermostat 12 calls 
for heat, a heat signal is generated at the heating lead 28 to energize 
the gas valve 18 and the heating system 14. The same heat increase signal 
is supplied to input 40 of the humidistat 10. With the switch 34 in the 
heating position 36 and the humidity sensor 32 closed or otherwise calling 
for an increase in humidity, the humidity signal is supplied to contact 60 
of the interface module 30 from the output 44. At the interface module 30, 
switch 66 is in the first position 68 wherein pole 72 and contact 74 are 
closed to provide the humidity increase signal as output from contact 58 
of the terminal strip 54. The output from contact 58 is supplied to the 
humidifier 22 so as to energize the same and to provide moisture to the 
enclosed volume. 
Referring to FIGS. 1 and 3, the operation of the humidistat 10 having the 
switch 34 in the cooling position 38 is described. The cooling lead 26 of 
the thermostat 12 is connected to humidistat 10 at input 42. The cooling 
signal generated is supplied to contact 60 of the interface module 30 from 
output 44 of the humidistat 10. Upon a call for a decrease in temperature, 
the thermostat 12 generates the cooling signal from cooling lead 26 as 
well as the fan signal from fan lead 29. The fan signal is supplied to 
contact 96 of the relay center 16 which is connected and supplied to 
contact 62 of the interface module 30. The fan signal applied at contact 
62 energizes the relay 78 to throw and close switch 66 from the first 
position 68 to the second position 70 to energize the cooling system 20, 
as shown in FIG. 3. In the absence of the call for cooling, no fan signal 
is supplied to contact 62, the relay 78 is de-energized and the switch 66 
returns and closes to the first position 68. 
Alternatively, as illustrated in FIG. 4, the fan signal from contact 96 is 
supplied to contact 62 for energizing the time delay circuit 80. Upon 
expiration of the predetermined time interval, the relay 84 is energized 
to close switch 66 to the second position 70. The predetermined period of 
time is adjustable and can be set at a thirty second interval so that upon 
expiration of 30 seconds, the time delay circuit 80 energizes relay 84. In 
the second position 70, the cooling signal is provided as output from 
contact 56 of the terminal strip 54 to the cooling system 20 to thereby 
energize and provide cooling to the enclosed volume. The advantage of 
having the time delay circuit 80 and relay 78 is to allow a short, 
predetermined period of time to expire so that unnecessary fiddling and 
fidgeting of a person with the thermostat 12 does not blow or destroy an 
existing compressor of the cooling system 20. 
Many modifications and variations of the present invention are possible in 
light of the above teachings. Thus, it is to be understood that, within 
the scope of the appended claims, the invention may be practiced otherwise 
than as specifically described above.