I converted my new Goodman 90000 BTU 95% furnace to propane. I have been trouble shooting a yellow flame. My original thought was the opening to the heat exchanger was too small. After Goodman would not talk to me because I'm not licensed. I had to call a technician who couldn't find any problems with my conversion or pressure settings.He finally had me replace my 2.5 inch vent/flue to 3 inch even though I was below the maximum bends and run for a 2 inch. No change. Tried lowering inlet pressure to 10 WC. No change. Blow air into any of the tubes - blue flame. He now agrees it is a air restricting and only internal furnace parts are left and I'm back where I started. The hole in the restrictor plate is 3/4 inches in diameter. The inside diameter of the gasket covering the hole is 1.5 inches. I think I have heat exchanger front cover for a smaller BTU furnace. I've paid for a technician and torn my house apart in the middle of winter. Before I pay my tech to be on the phone with Goodman, does anyone know what size that hole should be? Thanks
It is possible the air flow is somehow restricted but if this is the case the pressure switch should not be allowing the furnace to come on. If the air flow is correct then it maybe a gas flow problem. Double check the orifices installed in the furnace they should be #55 or #56. If you are at a higher elevation they may be #57 or #58.
check to make sure the manifold pressure is correct. It should be 10 in w.c. on the manifold side of the gas valve when running. If you have #55 orifices installed try #56 nad see if this solves the problem. Hope this helps.
If it is an air supply problem, the induction blower is creating sufficient vacuum for pressure switch to operate, but there is not sufficient volume of air through the burner assembly. The part I'm trying to verify is between the outlet of the heat exchanger and the inlet of the induction blower. It is in this document,http://igate.northernplumbing.com/partsb... pg 10, part #131 - 20170906A FRONT COVER. I want to make sure my front cover is not for a smaller furnace. The hole in my cover is 3/4 of an inch. I?m trying to find out if this varies according furnace size and if so, what is correct for 92,000 BTUs. If this isn't the problem, I have to look for a blockage inside the heat exchanger. If it is a gas flow problem, both manifold pressures are good - 10 WC and 6 WC. We have tried the inlet pressure from 13WC to as low as 10 WC. Flame does not change. Currently it is set to about 12.3 WC. My stove and hot water heater are burning fine. The only time we see a correct blue flame with small yellow tip is during the first 5 to 10 seconds of start-up, or when I blow into one of the tubes. According to the conversion kit document,http://www.alpinehomeair.com/viewresourc... pg 5, #23, the #55 orifice is correct up to 7000 feet. Wouldn't changing to #56 just de-rate my furnace to compensate for an unsolved (air or gas) burn problem. My technician says #55 is normal for our location, my pressures are good, my vent/flue is good, and my springs are correct for propane.
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Http://www.goodmanmfg.com/Portals/0/pdf/SS/SS-GMH95.pdf
The part I'm concerned with is not in this document. It is in this document,http://igate.northernplumbing.com/partsb... pg 10, part #131 - 20170906A FRONT COVER. It is the next place to look for an air restriction. I want to make sure my front cover is not for a smaller furnace. The hole in my cover is 3/4 of an inch. I'm trying to find out if this varies according furnace size and if so, what is correct for 92,000 BTUs.
Here is a picture of the part.
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