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ANY HVAC PROS OUT THERE?


kmsss

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Just hooked up a wall furnace in the garage, it was origianlly setup for natural

gas but I bought the conversion for it to LP. My problem is the furnace runs fine for about 10-15 minutes (seems like after everything gets up to operating temp) then the furnace makes a loud pop and then the flame on the burners flutter and eventually go out. Any ideas other than a new furnace?? Now im just :banghead: !! Thanks

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Checked the regulator on the tank, cleaned the spider web and remains out, seems to be clean now. Also switched propane tanks with one that was just filled. Same problem is there, also noticed that right before it acts up it sounds like the burner has a strong draft blowing on it. The gas valve has been converted to LP and everything looks o.k. there. Thanks for the reply MN C5.

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Humm, if it runs for 10-15 minutes then shuts off it rules a few things out. Not knowing the brand and model # I'll take another guess

 

Does the fan come on? Yes... ?

 

After it shuts off does it restart on its own? If not what its it requiring you to do to get it to recycle?

 

Did you check the Low & High Temp limits? I'd check these next :smash:

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The furnace is a Forcaire wall unit (top vent), not sure of the model number without looking at it. It has a Robertshaw model 7000 gas valve.

 

The fan does come on.

 

When the furnace shuts down, everything goes out including the pilot. Also it takes a while to get the pilot relit.

 

I did not check the high/low limits, I will do that tonight. I should be able to just put a DVOM on the gas valve and run it to see if I loose voltage, Right?

 

Thanks

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The furnace is a Forcaire wall unit (top vent), not sure of the model number without looking at it.  It has a Robertshaw model 7000 gas valve.

 

The fan does come on.

 

When the furnace shuts down, everything goes out including the pilot.  Also it takes a while to get the pilot relit.

 

I did not check the high/low limits, I will do that tonight.  I should be able to just put a DVOM on the gas valve and run it to see if I loose voltage, Right?

 

Thanks

check your gas pressure at the manifold or there should be a small allen screw to check on the outlet of the valve, and make sure your gas pressure is right, not sure how many inches on propane, it is should tell you on the retro kit what to set it at, nat gas is usally 3.5 inches of water colum, also clean the pilot assemblly, you should have changed the orifice for that also when you made the retro fit

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Didn't check the pressures yet, but removed orffices and found them to be almost plugged. Actually the orffices are melted, from the inside out, the alum. looks like it melts and then is pushed threw the hole plugging it more. Could incorrect pressures cause this?

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If its dropping the pilot (obviously it doesn't have electronic ignition) you have a issue with one of the safety limits. High Temp Low Temp Flame Sensor shouldn't be to much else to check. If your pressure is low or to high it could cause problems..

 

I'm no pro as I've never been a HVAC guy but here is what I'd do

 

Check the mounting and function of the Thermo Couple (It senses a flame and allows the gas valve to remain open.) Check to see that the flame remains intact with the Thermo Couple after the burners fire.. I.E. Watch it until it kicks out.

 

Next I'd jump out the High and Low limit switches one at a time. If you jumper one and the problem goes away replace that limit switch.

 

Perhaps a real HVAC tech could chime in.

 

 

LOL walked away from the computer for an hour or so and didn't see your last post :P

 

But yes it could..........If the pressure was to low you could have had a flame right at the oriffices and they aren't made for that..

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