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Humidistat Problems

What is a humidistat?

A humidistat is similar to a thermostat and it responds or is designed to be sensitive to changes in relative humidity. The humidistat is used in several devices such as humidifiers, dehumidifiers and microwaves. In humidifiers and dehumidifiers, setting the humidistat by adjusting its controls can help maintain the relative humidity conditions in a refrigerator or greenhouse. In microwaves it usually is used in conjunction with the “smart cooking” feature.

Listed below are a few questions answered by the Experts on humidistat.

Can I use a Honeywell humidistat as a replacement for my Aprilaire 600 humidistat which is part of my Aprilaire humidifier?

This is dependent on which thermostat you received along with the Aprilaire. They had a wide range of humidistats at different times. Usually the humidistat will have a model number on it. You could use the Honeywell H89 humidistat on the 600 humidifier. However if the old thermostat had more than two wires passing through it, reconfiguration of the wiring may be required.

Explain the mechanical operation or functioning of the humidistat?

When humidity rises above the set point on the humidistat, a switch will get turned on to activate the de-humidification function. A switch can be open or on and closed or off. The switch mechanism and functioning of the humidistat is as detailed. When humidity rises, the switch will close and complete a circuit, which initiates voltage flow to the receiving load. A signal is sent to the air handler to reduce the air flow by 15% to 20%. The load then drops slightly on the evaporator causing it to cool and the lower velocity exposes the coil to air longer causing an increase in the intrinsic moisture capacity of the unit. Similarly when humidity drops below the setting, the switch opens, thereby creating a break in the circuit and turning off the humidification function.

Explain if and how I can wire a humidistat to a swamp cooler?

A humidistat is essentially a switch which is programmed to close at certain humidity levels and open at other levels. Your goal is to locate the spot on the swamp cooler that allows the humidistat or an open or closed switch to start or stop the cooler based on humidity levels. Generally it should be connected where the thermostat would be installed or through the control panel of the swamp cooler. The humidistat is a low voltage (24 volts) connection and most swamp coolers are usually not equipped with 24 volts. In the case of a 120 volt swamp cooler, a 120 volt humidistat will be required, which stops power to the unit similar to a light switch. The other option would be to use an isolating relay, a transformer and a 24 volts thermostat.

I am connecting a furnace and air conditioner (AC). How do I wire a 98001i2 programmable thermostat/humidistat?

Case details: The thermostat has a cable with five wires, with four connected to the thermostat/humidistat. The connections are as follows: Green to G; Red to RC; Yellow to Y, and White to W. There is also a short wire connecting the RC post to the RH post.

Red wire goes into R, yellow into Y1, Green into G and Y into E/W1. If there is no wire connected to the old thermostat in the C or common post, then there is no C wire. This particular thermostat/humidistat requires the C connection and it has no battery power. The fifth wire which is in the wall needs to be connected to the C terminal. Next connect the same color wire to the C terminal of the furnace control board. The air conditioner usually has two wires coming from it. One wire connects with the yellow wire going to the thermostat/humidistat. The other wire of the outdoor A/C hooks to C and the fifth wire is what would need to be hooked to this.

The Humidistat is fairly simple device with a straightforward mechanism. The common problems you can face with it are listed above. With specific instructions you can arrive at the problem area and work upon resolving it. Therefore to understand better, insights and information from Experts will be helpful and useful to tackle the problem immediately and effectively.
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