Is your furnace turning off and on?

November 1, 2019

You’re not alone. Furnace cycling – when your furnace turns off and back on again in an endless loop – is one of the most common reasons we get service calls.

But before you call in one of our technicians, there are a couple of things you can check out for yourself first.

Check your filter to make sure it’s clean. A clogged filter restricts airflow which slows air blowing across the heat exchanger. When the heat exchanger gets too hot, it shuts itself off as a safety measure. Clean the filter and air will flow freely over the heat exchanger, allowing everything to run more smoothly.

Once you’ve noticed a clogged filter, cleaned it, and returned it to its place, there’s a chance your furnace will remain stubbornly off. No need to call us in yet! Some models go into a hard lockout mode once they’ve been tripped a number of times. Try turning off the breaker and waiting 30 seconds before turning it back on.

If a clogged filter isn’t the issue and it’s been cold outside, check the condensate drain. On high-efficiency furnaces (those rated at 90% and higher), the drain is made of PVC piping that can get blocked by ice or snow. Typically, this piping exits the structure through an outside vent block that’s located near the furnace.

Not sure if your furnace is rated at 90% or higher? Just look at the furnace and see if the largest pipe that exits the equipment is metal or plastic. If they are plastic, you have a 90% efficient furnace and should check the pipe for ice or snow buildup.Furnaces rated 80 or higher have metal piping that aren’t vulnerable to this kind of blockage.

And what to do if neither of these solutions work? That’s when it’s time to call us. We’d be happy to send someone from our service team out to assess your equipment, diagnose the problem, and give our best recommendations for getting it fixed.

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