Furnace cycles, warms slowly


  #1  
Old 10-24-01, 01:33 PM
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I have a Coleman Furnace in my mobile home. Model #7680, series 859 - natural gas burning.

Everything seemed to work fine last year. This year however, it seems to take quite a bit longer to heat the home. With an indoor temp of 60 degrees, setting the thermostat to 68 will cause the burner to come on. Then the blower will come on for about 1 minute and turn off. The burner remains lit throughout this. About 4 minutes later, the fan again turns on for a minute. This cycle continues until it reaches the desired tempurature. It goes up a degree after about 4 - 6 cycles.

It's as if the tempurature inside the furnace isn't hot enough.
 
  #2  
Old 10-24-01, 03:47 PM
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Hello NorskiMan. Welcome to the Heating and Cooling Appliance forum and the Do-It-Yourself Web Site.

Thanks for posting an excellent problem discription.

Based upon the problem symptom discribed, it is possible the gas valve isn't allowing enough gas to get to the burners. The gas valve itself could be defective or not enough gas is actually getting to the valve from the supply feed.

Check the appliances gas valve control and be sure it's turned ON fully. Check the shut off valve on the supply pipe and verify if it is turned on fully.

If no other appliance in the house is having a gas supply problem, the problem may be isolated to only the heater. In which case, it may be either of the two conditions mentioned above effecting the furnace.

The visual signs may be seen when watching the burners flames while the heater is on. If the fireboxes flames do not appear to be as large as they where last year, the problem may be one of the two problems discribed above.

Another rare possibility may be one or two restricted orifices. In the case, one or two etc. burners flames may not be as large as the others. This is an indication of restricted orifices. Usually they are restricted by spiders which build a tiny nest in the holes of the orifices.

Check the manufacturers online web site for additional product information, problem discriptions and problem solving methods, pictorials and schematics.

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Check the ARCHIVES, within this forum, for other postings on this topic and the replies offered.

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Old 10-25-01, 11:25 AM
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Right the temp inside the furnace is not hot enough. The flame will either be small or uneven. If the flame is too small, you need to set the gas pressure on the outlet side of the furnace to 3.5"WC (natural gas LP varies depending on the furnace retrofit kit) If the flame is uneven, pull the burners and clean them with a wire brush. Paint them if they are not cast. Get a good look at the orifice while the burners are out. If an orifice is clogged, pull the manifold and rod out the hole. Be careful not to damage or enlarge the orifice hole. Tap on the manifold with your pipe wrench to clear any other debris out of the manifold. (That is good advice for any gas pipe you intend to reuse.)
You might want to get a tech to look at it to prtect the life of yourself and family.
 
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Old 10-29-01, 09:27 AM
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[QUOTE]Originally posted by kkim
pull the burners and clean them with a wire brush. Paint them if they are not cast.

KKim,

Paint the burners??? I never heard of that! If you paint then your going to plug up the burner ports, and also since it's next to the flame, and the area is really hot, the paint is going to burn, and going to make a mess in the firebox. New burners are stainless steal, and should not rust!

Anyway, I've had this trouble once on a coleman, and found out that fan switch was bad.. some how it was a lower temp setting so it's cycling the fan more.. I replaced it and it worked fine.. These swich are not adjustable.
 
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Old 10-30-01, 06:16 AM
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Most stainless burners are not rust free stainless. If the burner has ruston it, brush as much rust off as possible with a wire brush, and paint with high temp aluminum automotive spray paint. You do not want spray the paint thick enough to fill the burner holes. Just a light coat to prevent rusting.
 
 

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