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Getting Technical: How Thermostats Work

All HVAC systems use thermostats to control their operation. While some use complicated electronics, chips and programming, they all work off the principle of thermal change. A bimetal thermostat uses a thin strip of brass bolted to an equally thin strip of iron. A gas-bellows thermostat operates on the same principle as a bimetal unit, but gas reacts more quickly to temperature changes.

Both metal and gas expand or contract depending on temperature, which makes them move closer or further from a circuit, turning on the power when it makes contact with the circuit, or off when it moves away.

When the thermostat opens the circuit, the electrical signal to the motor inside the blower stops, and the HVAC system shuts off. When it closes, the circuit closes and power is transmitted to the motor, which turns the system on. That starts a sequence of events that triggers the rest HVAC system to work. When the temperature reaches your desired settings, the circuit opens and the system stops.

Thermostat Issues

Although thermostats don’t power the systems, it does turn them on. If anything goes wrong, they won’t work as intended. Issues might include: 

How Thermostats Work

    Short Cycling

    A thermostat on the fritz may turn your system on and off repeatedly within a short period of time, regardless of the actual temperature indoors.

    Thermostat Doesn’t Work

    The most obvious causes are dead or weak batteries, but in a hardwired thermostat, the reason could be age. Although they last a long time, they do need replacing periodically.

    Inaccurate Temperatures

    If the thermostat isn’t perfectly level, it won’t work properly. Check it with a level. It could also be in an area that is hotter or cooler than the rest of your home, is close to open doors or windows, or the sun hits it during the day. The thermostat could also be dirty.

    It’s important to pair your system with a compatible thermostat and set it up properly for the most efficient thermal management indoors. For more in-depth information and assistance with thermostats, contact Arpi’s Industries, providing trusted HVAC services for Calgary-area homeowners.