A comfort controls system regulates the heating, cooling, and humidity on a central air conditioner, furnace, heat pump,boiler, and other heating and cooling systems. This Fix-It Guide on comfort controls repair tells how comfort controls work, what often goes wrong, how to identify the problem, and what parts and tools you will need to fix comfort controls. It then tells how to clean and adjust a mechanical thermostat, how to test a thermostat, and how to test and replace a humidistat.
How Do Comfort Controls Work?
The main comfort controller is a thermostat, which is basically a switch that turns a furnace or central air conditioner on or off at a preset temperature. Comfort controls may also include a humidistat, which is a device that senses changes in the moisture of your home.
A thermostat controls the temperature by sensing a temperature change at its location and turning the furnace on or off to maintain the preset temperature. Your comfort system’s thermostat may be either mechanical or electronic. An automatic thermostat can be set to lower or raise the temperature in the home during preset times by using microprocessors and thermistor sensors.
A humidistat can change the humidity in your home by controlling a humidifier or dehumidifier in your comfort system.
What Can Go Wrong with Comfort Controls?
Thermostats usually work without problem for many years, but they eventually may become inaccurate or fail. You can clean, adjust, and replace a mechanical thermostat. An electronic thermostat, beyond replacing the backup battery, will require either replacement of the entire unit or repair by a professional technician.
If a mechanical thermostat is acting up, consider replacing it with a programmable digital thermostat. They’ve become inexpensive and can help you save energy costs because of their efficiency.
The location of your thermostat can greatly affect the efficiency of the comfort system. Make sure your home’s thermostat is not placed in direct sunlight, in a draft, or near an exterior door or window. If it is, you can move it, or, if it is located within a wall, you can pack insulation behind it.
How Can I Identify the Comfort Controls Problem?
- If your comfort (heating and/or cooling) system fails to come on, first check your electrical service panel for a blown fuse or tripped circuit breaker. Next, try cleaning the thermostat (see below). If that fails, test the thermostat (see below) and replace if faulty (see below).
- If the comfort system short-cycles, that is, it turns on and off repeatedly, clean the thermostat contacts.
- If the comfort system does not turn off, clean the thermostat. If that fails to resolve the problem, test the thermostat and replace it if it is faulty.
- If the humidifier does not turn on, check the electrical service panel for a blown fuse or tripped circuit breaker; test the humidistat; replace a faulty humidistat.
Save money with a programmable thermostat–it pays for itself in energy savings within just a few seasons. For example, if you lower the temperature in your home from 70° to 60° for an eight-hour period every night, you’ll save about 9 percent of your energy use.
What Do I Need for Comfort Controls Repair?
Replacement parts typically are not available for temperature and humidity sensors. However, many other components within comfort controls may be available through the manufacturer or dealer. Electronic comfort controls typically are replaced as a unit. The tools you’ll need to access and check a comfort controller include these:
- Small brush
- Coarse paper (such as a paper grocery bag)
- Room thermometer
- Insulated jumper wires
What Are the Steps to Comfort Controls Repair?
Clean and adjust a mechanical comfort controls thermostat:
- Remove the comfort control’s cover by unscrewing or pulling on it.
- Verify that the wall plate is absolutely level. If it is not, loosen the mounting screws and level the unit.
- Use canned air or a small brush to clean all the parts.
- Insert coarse paper (grocery bag or other heavy, rough paper) under each lever and clean by moving the lever and sliding the paper around.
- If the furnace turns off and on too often or too seldom, move the anticipator pointer slightly toward or away from the longer setting.
- To determine if the thermostat is accurate, hold an accurate room thermometer nearby while adjusting the thermometer coil.
Test a comfort controls thermostat:
- Remove the thermostat body.
- Clip an insulated jumper wire to the R (red) and W (white) terminals on the baseplate. If the furnace goes on, the thermostat is faulty; if the furnace doesn’t go on, the problem is with the furnace, its relay, or the transformer.
- If you’re testing a mechanical thermostat, clean and retest it. Replace it if necessary. If you’re testing an electronic thermostat, replace it.
Test and replace a comfort controls humidistat:
- Set the humidistat higher than the humidity in the room. You may need a humidimeter for this task.
- Turn off power to the comfort system at the electrical service panel.
- Open the humidistat body.
- Attach a jumper wire clip to the two terminal screws with wires on them.
- Turn on power to the comfort system. If the humidistat drum operates, the humidistat is faulty.
- To replace the humidistat, first turn off power at the electrical service panel . Then disconnect the humidistat from the wiring and install a replacement unit.
If you’re replacing an older thermostat with a new programmable unit, get one that allows at least two daily cycles. Select one that allows you to vary the settings for the weekend or daily requirements.