High limit switch cutting out


  #1  
Old 01-03-04, 09:12 PM
k55378
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High limit switch cutting out

The furnace will run for ~5 minutes and the limit switch will turn off the burner, while the blower continues. After the temp drops and ~30seconds the burner will than turn back on.

Is this normal?

I have replaced the limit switch (original limit switch rated for 150degrees F). The one I replaced it with is adjustable. Granted the manual says 150, however just to see how high before it wouldn't kick off, it was 165. I don't want to run it at this, but wanted to find out the limit.

I have put a new filter in, made sure all the vents are open, but still the same problems.


BTW, I am interested in this because earlier (see post in mid Dec) I had a problem with the Honeywell smartvalve failing. I ordered this and one of the first thing I read in the manual is under normal conditions (furnace kicks on ~3 times/hr) the valve should last much longer than 5 years. Hence I was guessing that if the limit switch is kicking the burner off every ~5minutes then the smartvalve will prematurely fail again.

The furnace is a : Comfortmaker GGNE125J20A1

Thanks in advance for your help!
 
  #2  
Old 01-04-04, 08:19 AM
Ed Imeduc's Avatar
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Location: Mountain Williams Missouri
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Lightbulb limit

INFO:Is this a down flow furnace? Is there and AC coil on this furnace? 3 times an hour, dont think ,it's all in how cold it is outside.Also are the blades on the blower clean ? ED
 
  #3  
Old 01-04-04, 12:21 PM
k55378
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I don't believe it is a downflow furnace... the return air comes from the side and is blown up through the heat exchanger. Yes there is an AC coil, which I have not inspected. Nor have I inspected the fan blades.

With the old high limit switch, I have noticed that the high limit is reached even if the lower fan access dor is off. Therefore removing any of the obstacles of the return air side.

I probably wasn't clear before, however in an hour the burner will cycle ~10 times. The furnace will reach the target temp, however the limit switch will cut out 4-5 times.

Is this normal behavior for the high limit switch to cut out during a normal heat cycle?

Regarding the AC coil ... does this need to be blown out once an awhile? The house is 5yrs old

The same question regarding the fan?

Thanks for your help!

--Rod
 
  #4  
Old 01-04-04, 03:24 PM
Ed Imeduc's Avatar
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Location: Mountain Williams Missouri
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Lightbulb FURNACE

Blower door off and still hit limit. Id go for that A coil of the AC for dirt on it and clean it. With the power off look at the fan blades on the blower they have a cup like in them if that gets full of dirt the blower cant put out the air it should. ED
 
 

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