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Why Does My Furnace Keep Shutting Off Early?


When you live in a climate such as ours, it’s essential that you have a fully functional and highly efficient heating system in place. So when your furnace starts acting up, it can definitely be frustrating.

One of the most common calls we get in regards to a malfunctioning furnace is about a heater that shuts off earlier than it’s meant to–before it completes a full heating cycle. This is a process called short-cycling.

While short-cycling doesn’t pose a danger, like other problems with a gas-powered furnace might, it can certainly cause damage to your furnace, leading to expensive repairs or even a premature system breakdown and replacement need.

So what causes this? Well, there are a few different potential culprits, which we’ll dive into below. Read on!

What Causes Short-Cycling?

As we mentioned above, your furnace may be shutting off early due to short cycling, which has a few potential causes.

One possible culprit is a malfunctioning thermostat that may be causing the furnace to receive incorrect commands. This is an easy fix for our technicians!

Another potential cause of short cycling is that the furnace wasn’t properly sized, to begin with, and is actually too large for your living space. This, unfortunately, is not a simple fix. Short cycling actually exacerbates wear and tear, so your furnace will wear down a lot faster than it otherwise would have if it was sized correctly to begin with. If you think this might be the problem, reach out to our team to learn about your replacement options.

The most likely cause of a furnace’s short cycling is that there is heat trapped in the system. This usually happens as a result of a malfunctioning air handler or a clogged-up air filter. Essentially, if something is restricting airflow in the furnace, then your furnace can’t properly circulate air and it remains trapped in the system.

As the temperature in the furnace increases, the equipment will eventually activate a limit switch, which causes the furnace to shut down as a safety feature. This will then allow the furnace to cool down, at which time it will restart.

If you allow this to continue, the furnace will just keep overheating and shutting down. You’ll notice that instead of running in 15-minute increments 2-3 times an hour, your system will instead run in very short bursts.

Why Short Cycling Is So Bad

The biggest problem with short cycling, as we briefly touched on, is that it increases the rate at which various components of your heating system wear out. Ultimately, this means your furnace becomes more and more likely to develop problems over time, and this, in turn, shortens the lifespan of the system by years.

If you notice your system short-cycling, or if you notice any other strange symptoms, like sounds coming from the system that you’ve never heard before, the best thing you can do for your system and for your peace of mind is give our team a call.

Contact us today for professional Hillsboro, OR furnace repairs. Clawson Heating & Air Conditioning is “Connecting People to Comfort”!

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