DIYbanter - View Single Post - Furnace cycling too often? Oversized perhaps?

wrote:
How often should a gas furnace cycle on and off for those living in
colder climates (Canada)? I have noticed that during winter, when
maintaining the temperature of the house steady, my furnace tends to
turn on every 5-10 minutes, staying on for about 10 minutes each time.
I find this to be a little to frequent.

Why do you find that too frequent? Most thermostats have an adjustable
anticipator and if that is improperly adjusted it can cause fast cycling as
can a poor location of the thermostat.

I have the specs from the
previous owner, and the furnace is 13 years old, 72,000 BTU (82%
efficiency) in a 1200 sq foot 2 story home. I am thinking about
getting it replaced as it had 3 separate problems this year with
components breaking down (hot surface igniter, blower, flame sensor,
etc.) and am wondering if perhaps it is oversized (i.e the frequent
cycling) and I should get a smaller model?

I would say you are iffy age for replacement. I would likely replace it
myself in order to take the opportunity for a higher efficiency model. I
would not do it because of the cycle issue. I likely would use the
opportunity to work out a deal from my tech so it can be replaced at his
convenience and that might make it a little cheaper.

I would let the tech do a proper study of your home to determine the
correct size for the unit. This can only be done by measuring and computing
a number of factors. I know on my home when the time comes (likely
sometime in the next ten years) I will have the duct work re-done and maybe
add a two zone system.

From the information you provided there is no way anyone can answer your
size question unless they are just guessing.

How long do gas furnaces typically last anyways? I have read on the
Internet that gas furnaces can last 20-25 years, but I'm wondering if
perhaps that is reflective for warmer climates where furnaces aren't
used as much. Over here the furnace is probably on from early October
until mid-May.

Properly sized the local weather does not matter related to the useful
life.

--
Joseph Meehan

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