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Natural Gas to LP gas conversion .. orifices
My 95% efficient furnace was installed by a licensed contractor in November 2012. This furnace is a 90,000 BTU with 6 in-line burners. Upon the furnace installation ..the installer converted this furnace from NG to LP. But, he installed size 54 orifices even though the owners manual specified size 1.15 orifices.
The furnace failed in December 2013 due to the secondary HX completely plugged with soot.
The furnace has had a new HX put in. When the new HX was put in and the furnace turned back on, it started short-cycling immediately ..approximately 6 minutes burners on then approximately 2 minutes burners off ..all the while the blower motor was on. Note: It had been short-cycling like this since I can remember. I originally assumed it was the new 2-stage blower kicking in. (I am not an expert in furnace operation!)
Eventually I asked for the improper gas orifices to be replaced with the correct size orifices, and the furnace seems to be working properly.
The original installer told me that the old HX might not be covered by warranty, and that he would not accept responsibility for the cost. He said that improper size gas orifices will never cause soot.
It seems to me after a bit of internet research that he may be wrong. It seems an improper (oversized) gas orifice will cause incomplete combustion, and that the 2 products of incomplete combustion are soot and CO.
(Also, as a side note, ..during the time this furnace had operated on the oversize gas orifices, my propane usage increased by nearly 30% even though last winter was relatively milder than most in my area.)
I would like to ask the furnace installer to assume the cost for fixing the furnace, but again, he says his improper size gas orifices would never cause soot. He says it might have been my outside regulators at the tank and at the house are probably faulty. If I could get the manufacturer to honor the warranty on the HX, then I would only have the costs for labor to fix the furnace. Unfortunately, hHe also says it is not his responsibility to pay for labor to fix the furnace even if it were possible that the wrong gas orifices were part of the problem (which he insists was not the cause).
Is my furnace installer correct that the oversize gas orifices will not cause any soot and that he has no responsibility at all? Also, is there any possibility that the oversize gas orifices might have resulted in increased propane usage.