Are this settings correct?


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Old 01-15-07, 12:12 PM
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Question Are this settings correct?

After some maintenance work was done to my furnace,forced air oil [ BROCK LO-1MQH]I notice the fan seems to stop too soon [45 secnds] after the burner shuts down.I measured the temps and the fan comes on at about 200 degrees,140 while running and fan stops at about 100 degrees[ it seems to me furnace still hot] Are this temp correct? if fan shuts down prematurelly is there a risk of cracking the HE?
Thanks for help
 
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Old 01-15-07, 12:27 PM
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100 degrees sounds reasonable to me. Your temp checks indicate that the air temp over the heat exchanger drops 40 degrees in 45 seconds. If the blower continued to run, you could be down to 70 degrees in a minute and a half. That sudden temperature drop could cause harm due to rapid contraction of the metal in the heat exchanger.
 
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Old 01-15-07, 12:39 PM
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Wink

Most of the time the fan control is set for fan on about 110F and off at 95F. You dont want it to blow cool air before it stops.
 
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Old 01-15-07, 09:34 PM
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Thanks so much for replies, I checked again temps and the fan comes on and off at around 100 F ,the pointers on the control dial are set to 90 ,110 and 200F
 
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Old 01-16-07, 11:01 AM
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I take it then you have a fan limit control there . That 200o is what the limit is set at. 110 fan on and 90 fan off
 
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Old 01-16-07, 12:47 PM
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Not too sure what your problem is but 45 sec is way too short. My oil furnace runs in excess of 5 minutes before the fan stops. I would call the tech back to fix the short fan. I will bet it did not do that before service. Mine is set 110 F on and 90 F off.
 
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Old 01-16-07, 10:17 PM
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Yes the limit is set to 200 F ,I did meassure temp again and fan off came at 98 F,is this too hot? then temp rises to 105F for few seconds and drops again. I didnt timed how long the fan run
 
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Old 01-17-07, 01:34 PM
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110 sounds low for an on setting , ive never set on below 140. the 100 degree off setting is correct.
 
 

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