Quote:
Originally Posted by abogart
For a while now I had noticed that my gas warm-air furnace tended to be running short cycles, starting right back up after the cool-down sequence....
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I was having exactly the same issue with our furnace. The problem was an old and malfunctioning thermostat.
Quote:
Originally Posted by abogart
I shortly after checked the filter and noticed that it was completely plugged  . It was one of the high-filtration, disposable types which apparently clog up easily and don't allow much air to pass through. So I bought one of the basic blue fiberglass types today and put it in. After that the outlet plenum topped out at around 145 deg. F, eliminating the over-temp issue  . |
Unfortunately those blue fiberglass "filters" are nearly worthless for filtering air. I use mid-range, pleated paper filters and replace it every 2 months.
Quote:
Originally Posted by abogart
... I don't like how the thing runs such short cycles. The inducer fan runs for a good 45 seconds before the igniter lights up, then another 30 seconds or so before the gas kicks in. With the 90 seconds that it runs after the gas shuts off, the thing is running for 2 minutes and 45 seconds during the total cycle that isn't even producing heat. When the flame is only on for a couple minutes, this makes for a lot of wasted energy and excess wear on the equipment.
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I agree with Daox here - I think that your current thermostat has too small a temperature swing or is malfunctioning. By allowing a larger temp. swing (+/- 1 to 1.5 deg. F) the furnace will run longer and more efficiently.
If you can't adjust the temperature swing (range) on your current thermostat, it's probably time to buy a new one. I picked up a programmable thermostat for $25 (on sale) and will be comparing the next heating bill to the same period from last year.
My experience -
$25 Thermostat vs. $250 Thermostat | EcoDaddyo.com
FWIW,
Tim