Q&A / 

Furnace Comes On Too Often

Bonnie Speeg lives in a chilly apartment in the gaslight district of Clifton in Cincinnati, OH. She reached out and here's her paraphrased situation:

"Tim, my forced-air furnace comes on too often and it's driving me nuts. It's hard to sleep and it's annoying. My landlord says everything is fine and I'm under the impression I probably just have to suck it up thankful that I even have heat and am not huddled around a steel barrel outdoors burning old wood pallets.

Is this normal? What's going on? Is there an easy fix?"

Well Bonnie, without be being there to inspect it, the first thought that comes to mind is the furnace could be oversized.

Many people don't realize that furnaces and air conditioning units are like clothes and shoes. They come in all different sizes.

You have to match the Btu output of the furnace closely to the Btu heat LOSS of the space you're trying to heat.

Here's an extreme example. Imagine you have a tiny shed you're trying to heat, but in the center of it is a giant stove with a roaring hot coal fire inside. It would produce so much heat, you couldn't stand being in the shed. Or, how about trying to heat this shed with a kitchen match? No way the tiny flame on the match head produce enough heat to offset the heat loss out of the shed.

When an oversized forced-air furnace turns on and the hot air blasts from the supply registers, the bubble of invisible hot air floats over to the thermostat. Within a minute or two, the thermostat senses that the temperature in the room is correct and it tells the furnace to shut off.

But, the furnace has not yet run LONG ENOUGH to heat up you, the objects in the room, etc.

When a forced-air furnace is sized correctly, it might normally run for about ten minutes or so gently bringing up to temperature everything in the space that's being heated. Then it shuts off and might not come on for ten or fifteen minutes assuming it's not bitter cold outdoors.

One other issue is your thermostat could be in the wrong location. It could be close to an exterior wall or window where it's being subject to a cold convection draft. A cold draft could be then dropping the temperature at the thermostat and it then commands the furnace to come on, even though the rest of the room is comfortable.

Thermostats should be located as far away from windows, exterior doors, etc. as possible. They should be on interior walls in the center of the space that's being heated.

As for an easy fix, I don't know that there is one if the furnace is oversized. Sorry!


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