Gas furnace running to long ?

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  #1  
Old 02-24-15, 08:51 AM
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Gas furnace running to long ?

Well first off we live where it has been neg 10 degrees Fahrenheit. So that doesn't help I'm sure.

Our furnace is running 75% of the time -- whether the thermostat is set at 66 or 72. Outside temp varies from -10F to 30F. I'm getting this runtime from the digital thermostat filter timer. You can reset this to zero at any time. I assume it's giving us the actual furnace run time, not just the fan.

Is this excessive? Also takes 3 hours to raise temp 5 degrees F.

100 year old home, remodeled and insulated, 2 story, 2200 sq ft, new filter, 60,000 btu Carrier system that is 25 years old. Wow a long time!

Thx appreciate your ideas.
 

Last edited by Iluvteak8; 02-24-15 at 09:10 AM.
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Old 02-24-15, 09:06 AM
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Welcome to the forums.

I'm assuming a natural gas furnace.

Bases on the size of your house and the size of the unit.... it sounds about normal to me. I'm experiencing the same thing here and my temps aren't quite as cold as yours.

Make sure the air filter(s) are clean.
 
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Old 02-24-15, 03:21 PM
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The run time indicator on the thermostat is more likely the fan on time.

Your operation is entirely normal. In the coldest weather the furnace should run continuously and maintain the "design" indoor set point. Most cases the design indoor setpoint is 74 degrees although I find that high a temperature to be way too much for me. That your furnace only is running 75% of the time even in the coldest weather tells me it is only somewhat oversized for your home rather than grossly oversized as is the norm.
 
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Old 02-24-15, 04:56 PM
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Good to know. Thx to you both.

Furd you mentioned the filter timer measures fan time. Does the fan run when the gas flame is not burning ? I have the tstat set to 'auto', not 'on'. So I'd think the fan and flame would be in sync ?
 
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Old 02-24-15, 06:06 PM
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No, the flame and fan are not always on together. When the thermostat "calls for heat" it initiates a sequence in the furnace that may take as long as 45 seconds to establish the flame. Then it heats up for a few more seconds before the fan starts so as not to blow an excessive amount of cold air out the registers. When the thermostat signals the house is at set point the flame goes out and the fan continues to run for up to 90 seconds to push the heated air from the furnace and ductwork. (All these times are approximate and will vary according to the specific furnace.)

Also, if you have cooling the fan on time will be recorded as the filter needs changing during the cooling season as well as the heating season. Of course, for only rough measurements of burner on time the fan time will be good enough. If you were, however, trying to estimate fuel consumption then you would really prefer to use the actual burner time rather than the fan time.
 
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