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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8533
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Hello, I have a Payne furnace, model #PG9MAB03608, about

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Hello,
I have a Payne furnace, model #PG9MAB03608, about 5 yrs. old, mounted horizontally in my attic. The problem is that it is overheating and tripping the high limit sensors. It has tripped the high limit sensor mounted on the back wall of the unit twice, but the rest of times it trips the flame roll-out sensor. It's done this about 8-10 times in a week. It's getting worse, and won't run for more than 5-10 minutes w/o tripping the roll-out. The wall of the furnace gets very hot directly above the burner box, which is only 3-4 inches away from the roll-out switch. I've pulled the front cover and burner box doors off and looked and listened. When the t-stat calls for heat the inducer motor spins normal, the ignitor lights up normal, the burners fire up and the blower circulates air normal. However when the side of the furnace heats up the roll-out switch shuts off the burners and the furnace goes into a code 33 purge mode. When I look at the flames coming out of the burners, they don't have that "perfect blue" flame. I'd say they're about 70 percent blue and about 30 percent orange, and I can see why the cabinet is getting so hot and tripping the roll-out. It's because the flames don't shoot straight out, they shoot out with several orange-tipped flares, which are contacting the top of the burn box. So my question is this: Could something have changed with regard to the gas pressure regulator valve letting too much gas into the burner? Or is it more likely something to do with either the intake air and exhaust air venting being restricted? Also, this flame pattern is the same whether or not the main blower fan is on or not, it's always 70-30 percent blue to orange, which to me doesn't look like the correct flame pattern that this thing is supposed to be producing. Any insight into this problem would be greatly appreciated by me and my slowly but surely becoming more and more chilled out family members. If you can please give any info. Thank you.

Phil :

Hi,This is risky business in the blind, not responsible for damages on your end. Click 'accept' when satisfied.. or we can get another expert

Phil :

Great description thanks, the flue pipe is likely restricted. If its been off all summer a bird may have built a nest in it.

Phil :

Look that over and get back to me

Phil :

Meantime dont run it other than for testing, it is a major fire hazard the way it is and could easily burn out its electric controls.

Phil :

odds of it being a birds nest are in the 70 to 80 percent range, odds of some issue with installation about 10%.. odds of a gas pressure issue, 5% or so.

Phil :

I will be in for another hour or so, then back in the AM san francisco time

Phil :

Phil

JACUSTOMER-bnccqidb- :

Thanks. Will try to get up there and check out the flue if possible tomarrow

JACUSTOMER-bnccqidb- :

Thanks. I'll try and get up there ASAP tomarrow. But it's Michigan and 35 degrees and I've just installed a new (very slippery) metal roof. In the meantime, the only reason I'm questioning the gas pressure/mixture is because I can't recall the flame pattern in either of my furnaces in this house ever looking like a "normal" clean blue flame is supposed to look like. So I'm wondering could it even be an issue at the propane tank outside, or even the quality of the propane itself? I don't know, I'm just trying to think from all the angles on this. So do you still think the probablility of bad flame from "bad propane" is still pretty low?

Phil :

The orange in a flame is caused by either too much gas (regulator set too high) or not enough air at the air shutter adjustement on each burner. or a combination of both... an orange flame produces carbon monoxide.. thats dangerous if leaks into the house via a cracked heat exchanger or some such.. vent too close a window.

Phil :

I will be here another hour or so, then back in the AM. Phil

JACUSTOMER-bnccqidb- :

Thank you very much for your insight and advice. I will try to get up onto the death trap... er new roof ASAP to check the vent. Thanks again and happy holidays.

Phil and other HVAC Specialists are ready to help you

Hello again, put a rope around your legs and waist at least. tie it off onto something solid. and make a hold on loop in the rope for your hand. been there done that. You dont need an injury in this economy.

 

Phil