Intertherm standing pilot LPG burner 77 BTU IN gas valve mounting plate gets hot ( not warm).

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Posts: 48
Joined: Mon May 31, 2010 12:32 pm

Mobile Home Intertherm (now Nordyne) Standing Pilot LPG Burner 77 BTU IN
Model # MGHA 077 Serial number MGA9703 (20 yr. old furnace).

Original Gas Valve had date code of 94 something. 20 yr. old original gas valve also evidently (Robertshaw confirmed this for me). Replaced it with new gas valve cause someone stripped the OUT PRESS port Allen screw/plug. Had too much trouble trying to remove it. When I got it home in my vice, and knowing I was going to install new valve, I jammed a flat blade screwdriver/cordless-type bit into it with maximum bite, and still wouldn't budge it, after a little penetrating oil. Only tore up the plug's metal.

Gas valve mounting plate gets HOT, not warm. Was opening the small hinged door covering the inspection window (access door) with my fingers and when I touched the the back of my hand on the metal next to it, had to pull away sharply.

New gas valve Robertshaw Model or part #720-472 installed with #40 drill size orifice spec'd on the furnace data plate. 11" wc OUT PRESS, 13"wc IN PRESS. Regulator Converter in the proper LP position (red stripe closest to top of valve body).

No flue obstruction from roof-top down to the horizontal piece in top of furnace cabinet where the 4" dia. fresh air duct connects and goes down on right side of cabinet to connect to and feed combustion chamber.

This 4" fresh air duct ( no inducer motor) is clear also.

The only thing regarding air flow that hasn't been checked for obstruction is the outer part/chamber of the concentric flue pipe (the fresh air part). This furnace hasn't been used for two years, prior to me starting it up with new gas valve, pilot burner and t-couple. This outer chamber could be a problem regarding blockage? Well actually, we did disconnect the flue pipe at the top of furnace cabinet and slide pipe up a bit. No obstruction there at the bottom of the pipe where it meets the top of furnace cabinet

Blower motor amp draw per data plate is 5.9A/heating (5.8A cooling). Actual draw is 6.8A. However, air is escaping the duct system somewhere under the home, because we opened a small section of skirting, and felt heated air coming out that skirting section. Less resistance to blower (air escaping from duct system under home) would mean higher amp draw me thinks. Just checked that with a Youtube video. Gradually covering a bench-mounted blower outlet with a cardboard, gradually dropped the amp draw. So maybe that eliminates a weak blower motor not pushing sufficient air over the heat exchanger.

Is it possible this mounting plate getting HOT ( not warm) is normal for this old furnace?
Posts: 5
Joined: Thu Nov 22, 2018 1:33 am

What is the source of your heat. Is the coil in the gas valve getting hot, or is your 3/4 " burner tube conducting from the burner it's self. If the burner is heating up the gas valve, try adjusting the placement of your pilot flame, check your orifice as well, make sure it is a lpg orifice, that it's clean, and tight. Other than that what temperature is the plate reaching? Hot can mean a wide range.
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