In any forced air heating system, you’re going to find an air filter. The air filter is installed in the air return duct for the system, and is designed to protect it from any dust or debris that might damage it while simultaneously allowing air to flow through unimpeded. Though it does this job well, the air filter has one major problem: it has no way to get rid of the particles it captures. As such, if the air filter isn’t cleaned or replaced every few months, it becomes clogged and starts causing problems. Let’s take a look at how ignoring a dirty air filter can lead to heating repair.
Restricted Air Flow
An air filter that becomes clogged with dust and other particles can restrict or even completely block the flow of air through the system. This has two effects. First, it deprives the heater of its supply of air to heat. This prevents the heater from actually distributing heat to the home. Second, it causes the internal temperature of the heater to rise to dangerous levels. Normally, the heater relies on the steady flow of cooler air to keep its temperature in check. Without that cool air, the system will overheat.
There are safety measures in place to prevent the system from damaging itself from overheating. The limit switch is a device that monitors the temperature inside the heater. When the internal temperature rises above the safety limit, the limit switch activates and shuts down the system to prevent damage from overheating. Unfortunately, this does not address the cause of the overheating.
If the source of the overheating isn’t taken care of, another problem occurs. Once the system has cooled off after being shut down by the limit switch, it restarts in response to the thermostat and overheats again. This causes the limit switch to shut down the system again, and the entire cycle repeats endlessly. This is called “short cycling”
Short cycling puts the system under an incredible amount of stress, far more than it was designed to handle. The combination of the increased heat and the strain of the start/stop cycle causes parts to wear out much faster, like the heat exchanger. Eventually, the system will breakdown and require extensive heating repair.