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Old 11-08-2010, 02:28 PM   #1
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Long running furnace hurt heat exchanger?


I set the thermostat down to 66*F at night and to 71*F in the morning.
The furnace runs for an hour or slightly more to regain the temperature, would that long running furnace hurt the heat exchanger?
I check the termperature rise, it is 60* which is well within the specs.
Thanks in advance.

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Old 11-08-2010, 02:34 PM   #2
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Long running furnace hurt heat exchanger?


bad chambers are usually ( but always) related to age of the unit. Expanding & contracting of the metal over time & rust

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Old 11-08-2010, 06:20 PM   #3
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Long running furnace hurt heat exchanger?


OK as long as it stays within the temp rise specs.
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Old 11-09-2010, 12:17 AM   #4
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Long running furnace hurt heat exchanger?


Yuri, can you explain this temperature rise spec a bit more?

I setback my thermostat to 65 degrees at 9:30pm and at this time of year, the heat doesn't come on during the half hour we are getting ready to get out the door. When I return at 3pm, I usually manually bump up the temperature to 71 degrees. I'm home by myself until 5:30pm and don't mind the house slowly warming to 71 degrees. (outside temp about 48 degrees F) I noticed today, being one of the first cooler days, that the temp didn't reach 71 until just about 5:30 (2 1/2 hours later) and the HP ran continuously, but did not need to go into defrost mode.

I have the thermostat set so that my aux propane heat doesn't come on, unless the outside temp is 35 degrees.

Is having my HP run continuously for 2 1/2 hours bad?
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Old 11-09-2010, 06:49 AM   #5
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Long running furnace hurt heat exchanger?


Max allowable temp rise is a spec for gas furnaces so they do not run too hot and cycle on the limit control and overstress the heat ex. Should not be a problem with a heat pump but I am not an expert with them but we have a few on this forum. ACs can run continuously and so can a heat pumps, no heat exchanger to damage and they have pressure controls etc to protect them. Should be professionally checked once a year to make sure the freon level is proper and running at the proper pressures. Lose efficiency DRASTICALLY if low on freon and cost a fortune to run then.
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Old 11-09-2010, 06:58 PM   #6
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Long running furnace hurt heat exchanger?


Quote:
Originally Posted by quincy View Post
I set the thermostat down to 66*F at night and to 71*F in the morning.
The furnace runs for an hour or slightly more to regain the temperature, would that long running furnace hurt the heat exchanger?
I check the termperature rise, it is 60* which is well within the specs.
Thanks in advance.
As long as your within temp rise. it doesn't matter is it runs 24/7.
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Old 11-09-2010, 07:01 PM   #7
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Long running furnace hurt heat exchanger?


Quote:
Originally Posted by GEAF View Post
Yuri, can you explain this temperature rise spec a bit more?

I setback my thermostat to 65 degrees at 9:30pm and at this time of year, the heat doesn't come on during the half hour we are getting ready to get out the door. When I return at 3pm, I usually manually bump up the temperature to 71 degrees. I'm home by myself until 5:30pm and don't mind the house slowly warming to 71 degrees. (outside temp about 48 degrees F) I noticed today, being one of the first cooler days, that the temp didn't reach 71 until just about 5:30 (2 1/2 hours later) and the HP ran continuously, but did not need to go into defrost mode.

I have the thermostat set so that my aux propane heat doesn't come on, unless the outside temp is 35 degrees.

Is having my HP run continuously for 2 1/2 hours bad?
Heat pumps with electric aux heat. Will sometimes run for days without shutting off( Like when its 10 degrees outside). They are designed to be able to run like that.

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