HVAC Tech

tomturkey · Sep 13, 2014

I bought a used furnace for my shop. It was advertised as "LP". When I went to look at it, it had no stickers indicating it had been converted to LP from NG. I ask the gentleman and he assured me it was LP. Well, being the skeptic/worryer I need to make my self perfectly sure. I took the manifold apart to check the orfice size. So now the question, this furnace has 4 burners, each has an orfice marked 55. It is an 88,000 btu input furnace. I checked some charts and I don't understand them. Sooo, has this furnace been converted to run on LP. I did not check the spring in the gas valve. Thank you for your educated experienced wisdom. gobble

Bob · Sep 13, 2014

At standard LP pressure, a #55 orifice flows about 18,888 BTU's, on natural gas, likely less than half that, so the answer seems to be "yes" for 4 orifices.

But there's more to it. You have already figured out you need to check the pressure, determined by the gas valve spring.

AND, for LP, the gas valve MUST be "100% shutoff" and listed for LP.

tomturkey · Sep 13, 2014

Thanks Bob. I'll look the gas valve over, II had not looked at it to see what stickers it has on it. I appreciate you sharing your knowledge. All of us are smarter than one of us! gobble

Bob · Sep 14, 2014

Look for a mfg name/part# on the gas valve (likely Honeywell or White Rogers) and GOOGLE it for a spec sheet to see if it is approved for propane and what needs to be done to convert it, then verify that it has been done.

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tomturkey

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Bob

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tomturkey

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Bob

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