A thermostat is the main point of interface between you and your HVAC system. When your thermostat is accurate, it’s easier to make fine adjustments that will keep your home comfortable and your utility bills low. Like all components of your home HVAC system, thermostats require periodic repairs and maintenance to keep working their best over the long term. Here’s what you need to know to calibrate your thermostat.
There are three main types of thermostat found in homes today: manual thermostats, programmable thermostats and smart thermostats. The most simple thermostats may require nothing more than occasional cleaning to work accurately. Other, more advanced digital units have batteries that must be changed, software that must be updated and other service considerations.
Your first step in ensuring thermostat accuracy should be to consult your owner’s manual to see what periodic maintenance the manufacturer recommends.
Checking a Thermostat’s Calibration
Checking the calibration of your thermostat is easy and should be done once a year, typically in the fall. To do so, locate your home’s thermostat and tape an accurate thermometer on the wall next to it. Wait 15 minutes and check the temperature reading on both devices.
A variance of +/- 3˚F is generally acceptable, but anything outside that range means your previously accurate thermostat may require service.
Cleaning a Thermostat
From time to time, a thermostat’s mechanical contacts will require cleaning to maintain accuracy. This simple maintenance procedure can be easily done at home. First, carefully remove the thermostat cover. Then, brush away any dust or dirt you find using a soft cloth or Q-tip. If you notice any surface corrosion, remove it using electrical contact cleaner (available in any hardware store).
Adjusting a Thermostat
If cleaning your thermostat doesn’t fix the problem, there are a number of adjustments you can make that may do the trick:
- Moving the heat anticipator: If your furnace cycles on and off too frequently, adjust the heat anticipator. Look for a small lever below a scale with an arrow marked “longer.” Moving the level in that direction will increase the length of your HVAC system’s cycling time. Bear in mind, however, that longer cycle times will be less effective at keeping your home at the desired temperature.
- Checking the level: Certain types of thermostats contain a small vial of mercury that must be level to ensure proper temperature control. This can be confirmed with a standard carpenter’s level. If the measurement is off, adjust the placement of the thermostat itself until it’s straight.
- Adjusting the calibration screw: Screw-type thermostats can be adjusted for accuracy using a small screw located on a coil inside the unit. Different products have different calibration techniques, so consult your manual before doing anything.
If you’re still struggling with thermostat problems, or don’t want to perform the above adjustments yourself, get in touch with a trained HVAC professional for assistance. Remember: thermostat problems aren’t something you should ignore for long. The better your thermostat works, the more reliable and economical your HVAC system will be overall.