jhvac

I installed an 90% upflow goodman furnace. The furnace will only run with the burner door off. I have checked the gas flow, pressure it has 3.75 inches of water column, 12.7 inches of water column on the inlet side.
Sometime with the door on it wont start on the first attempt. When it goes to the second attempt it creates somewhat of a explosion/roll out.
But yet if I leave the door off the furnace workes well. On the exaust side it is vented with 2" pvc pipe less than 15' plus 2 long sweeping 90's. On the inlet air is ran with less than 10' of pipe plus 2 90's. I have checked the inlet air side for obstructions and found none. Does anyone have a sugestion to how I can make it run with the door on. Model GKS90904

jhvac

I installed an 90% upflow goodman furnace. The furnace will only run with the burner door off. I have checked the gas flow, pressure it has 3.75 inches of water column, 12.7 inches of water column on the inlet side.
Sometime with the door on it wont start on the first attempt. When it goes to the second attempt it creates somewhat of a explosion/roll out.
But yet if I leave the door off the furnace workes well. On the exaust side it is vented with 2" pvc pipe less than 15' plus 2 long sweeping 90's. On the inlet air is ran with less than 10' of pipe plus 2 90's. I have checked the inlet air side for obstructions and found none. Does anyone have a sugestion to how I can make it run with the door on. Model GKS90904

genecarp

CALL TECH SUPPORT, THEY SHOULD TROUBLE SHOOT IT with you.

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BigMikeB

First of all 12.7 inches wc is high on the inlet side if it's natural gas. I second the call to their tech support, there is a venting issue, it isn't getting enough air in for proper combustion.

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hf05

is there a hose on the burner box going to a pressure switch check that..or put door back on ,cut inlet about a foot up if it fires whats that tell ya ??

Dr Heat

you need to run 3" on both int and ex the limit on 2" IS 25' EACH 90 IS 5' IF THEY ARE LONG SWEEP. You are very close we only run 3' Because we ran into this several times.

MechAcc

Need to check the draft with a magnehelic or digital manometer. You'll have to tee into the hose from the burner box to the pressure switch attached to positive side of meter and tee into the hose from the inducer/collector box depending upon where the negative side is tapped into the negative side of the meter. Most pressure switches will have a pressure range on it. If the pressure is nominal close to the range the possible causes sagging vent pipe trapping water or some other obstructions (children just love tossing rocks and other things down vent pipes wondering where they have gone), under sized vent, inducer running slow either from bearing or from low voltage to inducer, drain trap dirty, and finally heat exchanger leakage.

On the heat exchanger leakage leave only one side of the magnehelic hooked up. Turn thermostat heat off fan switch to ON. Block intake and exhaust pipe. Turn power on and watch magnehelic if meter moves the heat exchanger has a leak. Crimped rings broken off or crack in the heat exchanger.

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hvaclover

12" is excessive. our gas valve regulator is probably malfunctioning and passing excessive gas. Ain't enough air to ignit with the door on.

Call the gas supplier to check the meter. But if they are dicks like they are here you might want to close down your gas cock til you gt around 7" supply gas.

If your furnace gas control hasn't been ruined it should light. Have the HO call the gas utility and watch him measure the pressure at the meter.

Unless i miss my guess the meter is screwed.

jrobbins

Thats a 90,000 btuh furnace right? It calls for 3" PVC on both the exhaust and intake piping in the goodman installation manual. The gas pressure also needs to be turned down to around 7" WC at the gas meter. You problem will go away if you do these two things.

jwiehagen76

I agree with the others flue size too small gas pressure to high whats the pressure coming out of valve? You could add a regulator before furnace as well