"Open High Limit Device " Error

Old 03-03-05, 09:25 AM
Andy Beet
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"Open High Limit Device " Error

I live Massachusettsm in a 2 bedroom cape style house. I have a American Standards Freedom 80 single stage furnace (http://www.amstd-comfort.com/Product...erCategoryID=1), running on gas, in the basement. I have single zone heat.

We left our heat on at 59F for 4 days while we were away. The outside temperature was just below freezing (25F) the entire time (i believe). When we returned i went to the basement. The furnace seemed to be fine, the ductwork was hot.

Withing the hour I turned the heat up to about 65F. 2-3 hours later i noticed that cold air was blowing out of the registers. I went to the furnace and saw the red light flashing 4 times, indicating the error -"Open High Limit Device".

I am not really sure what this is. I cleaned the filter (which was dirty!) but i still get the same error message and cold air.

I have now shut off the gas and electric to the burner to see if it resets.

Any ideas what is happening? Is there something that i can do remedy this problem or at least diagnose the problem, before i call in an expert? Does anyone know where i can get a manual for this furnace?

I appreciate any help

Old 03-03-05, 10:33 AM
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You may have a problem with airflow through the furnace and that is the reason it is overheating. Dirty filter, plugged air conditioning coil, closed registers etc...

It may be a flame roll out switch inside the furnace has been tripped. They are manually resetable(?) and are identified by a little red button. Often they are located directly above or adjacent to the burners or near the exhaust pipe and switch the burners off if they overheat. Try reseting these switches and see if it will fire, but be careful as these switches have uncovered contacts with power going to them.

If trying to reset these switches does not work, then it may be the high limit switch is defective. Ordinarilly a high limit should allow the furnace to re-ignite after a certain amount of cool down time has passed, but in your case this switch might be defective and not reseting itself.

In any case it would be advisable to get someone out to look at your furnace, as the problem may persist or even be dangerous. (!)

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