Attention, scavengers of Detroit.

October 10, 2009 2:52 PM

My Westinghouse gas furnace has been disconnected because it wouldn't shut off the gas when the pilot light was out. The fault apparently lies in the part pictured. Is there any hope of getting a replacement? Inquiries about town have been unsuccessful so far.

This seems a long shot, as I can't even find any information. The furnace is old. I've included several pictures of the part in question. Any suggestions would be appreciated.

Model FGBE137MA
Series NIBE
Serial M38778

Alternately, is it possible to put a gas shut-off valve on the intake pipe, so that it doesn't have to be furnace-specific? This is speculation on my part.

This is in San Francisco.

posted by alexei to home & garden (11 comments total)

Ah, forgot the link to the pictures.
posted by alexei at 2:55 PM on October 10

I'd be surprised if you can't find some sort of equivalent, since the basic function is something that every gas furnace and water heater needs. This looks like the sort of thing you need. You may not be able to find an exact equivalent, since pilot lights may be passe, but I bet there are electronic ignition retrofit kits.
posted by Good Brain at 3:13 PM on October 10

Your pictures show a bunch of parts, but you describe something that could be caused by a bad thermocouple. If you do not know enough about how furnaces work to know what I am talking about, call a pro before you blow yourself up.
posted by TedW at 4:43 PM on October 10 [1 favorite]

My guess was also thermocouple which is not really something you should be messing with on your own because the catastrophe you could cause by doing it wrong is sort of a big deal. The good news is they're not that expensive [mine was $200, not cheap but not like "new roof" expensive] and putting it in didn't take my furnace guy too terribly long. The gas company should be able to send someone out to you with the part and then fix it.
posted by jessamyn at 4:52 PM on October 10

I don't think the thermocouple is the problem. If the thermocouple is bad, the pilot light won't stay lit. If the pilot light isn't lit, the gas valve is not supposed to open. Your problem seems to be that the gas valve is bad and isn't closing. You need a new gas valve, I would think. The gas valve is what Good Brain linked to. Any furnace repair guy should be able to fix this quickly and easily, but maybe not cheaply. Unless you know what you're doing, it's probably not a good idea to attempt this repair yourself. Google "natural gas house explosion". Bad stuff!
posted by Daddy-O at 10:05 PM on October 10

BTW, the thermocouple is a bimetal device that sticks into the flame of the pilot light at one end and connects to the gas valve at the other end. The gas valve is actually 2 gas valves: the main valve that supplies gas to the furnace and a small valve that supplies gas to the pilot light. If the pilot flame is present and heating the thermocouple, the heat creates a small electric voltage in the thermocouple that is sensed by the gas valve letting it know that it is safe to open the main valve. If the voltage from the thermocouple is not present, the small valve is closed shutting gas off to the pilot light and disabling the operation of the main valve. A bad thermocouple can't create any voltage, so the pilot light won't stay lit. That's not your problem.
posted by Daddy-O at 10:19 PM on October 10

Bite the bullet and call a pro. They will be able to determine exactly what is wrong and fix it right. The possible ramifications of you performing a flawed DIY are, well, disastrous.
posted by Thorzdad at 8:40 AM on October 11

Thanks for the answers. We've actually had a pro come look at it, but though he promised to have a look for the part, he did not seem optimistic or enthusiastic. Advised us to install a new furnace.

I just called PG&E. They're sending out a guy in a week who can apparently test/replace the thermocouple for $95. I don't know why we didn't do it before-- probably because the PG&E guy who disconnected the furnace when the auto-shutoff failed didn't mention any repair service.

Also, my scouring for parts have come up with this item which is very similar indeed to the one we have, except that the model number is V8146A 1033 instead of V8146A 1017 (I don't suppose anyone can say what the difference is and if it's important?). One plan is to buy it along with a new thermocouple and ask a pro to install it. That said, I do get the impression that any generic version of the thing is fine. I'll ask the PG&E guy about it.

So that's that. I'll post in a week with results.
posted by alexei at 1:38 PM on October 12

I can't imagine why a pro wouldn't see this as a straightforward repair. I doubt an exact match is required. In fact, I'd guess that the size of the input and output pipes tells you almost everything you need to find a replacement, and those are likely highly standardized.

I suspect the pro showed a lack of enthusiasm because they'll make more if you install a new furnace. But here is the thing, maybe you should. New furnaces can be significantly more energy efficient. You should figure out the breakeven on a new furnace and decide whether it is a good investment at this point. If it isn't, I'd keep looking until you find someone who is both competent, and willing to give the repair a shot.
posted by Good Brain at 12:18 PM on October 13

Hi again.

PG&E guy came out, but was not allowed to do any repairs. He did provide some info, though. Apparently the issue is not the thermocouple (thanks Daddy-O): if it was the thermocouple, the previous guy would not have disconnected the gas pipe. So I need a new valve. He also said I didn't need an identical replacement, just a similar model.

I've measured the outer circumferences of the gas pipes are
input:
2 + 5/8 in. (also inner diameter is 9/16 in.)
output:
3 + 7/16 in.

Judging by this and this, I'm pretty sure that's a nominal 1/2 in. input and 3/4 in. output pipe. According to the PG&E tech, I also need a valve which is +/- 5% of the rated input BTU/hr, which is in my case 137,500 BTU/hr.

Now the question:

I'm having a little trouble finding a valve with both the right input power rating and input/output pipe sizes. On Good Brain's page there's a 1/2 in. input x 1/2 in. output 130,000 BTU/hr model and a 1/2 in. input x 3/4 in. output 190,000 BTU/hr model but not one with both. Is one of these negotiable? I'll call the furnace guy tomorrow and ask him what he thinks, but it's always nice to be forearmed with some info.
posted by alexei at 7:20 PM on October 25

In the end, I asked at http://forum.doityourself.com/ and someone pointed out the tool on Honeywell's somewhat poorly designed webpage which allowed me to enter the old model number and get the model of the recommended replacement, which turned out to be one I hadn't looked at, though I suspect almost any one of them would've worked. Furnace works now.

I also found out that modern furnaces are in fact more efficient, due to better heat exchangers, and less heat going up the chimney (I had been dubious-- fire is fire after all). So replacement is probably not a bad idea in the long run. However, I've successfully put it off.

Thanks all.
posted by alexei at 1:42 AM on November 11