Propane Direct Vent Fireplace - Gas leak at pilot?


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Old 02-18-16, 08:49 AM
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Propane Direct Vent Fireplace - Gas leak at pilot?

Before I tell the story, let me say that I will not be turning the gas back on to this thing until I'm 100% sure it's fixed. If that means calling a pro I will, but I'm looking for some advice around how it's supposed to operate and some basic troubleshooting.

Here goes....

I have a Lennox-brand gas fireplace. I've lived in the house about 2 months now. The fireplace was working fine until I ran out of propane one night. Upon the refill I got a strong gas smell when lighting the pilot. Well it turns out that was just the odorant from having run the tank empty. I had it behind my oven, too, and the gas company tech leak tested that, too. Anyway, while looking under the fireplace I barely touched the pilot tube and it snapped off. It had been bent at a tight radius and cracked by the installer. It was a matter of time before it failed.

I took the valve and pilot assembly out and replaced the tube. It worked fine for the past couple of days with the pilot on constantly. It's a manual pilot (SIT gas valve assembly) I shut off the pilot early today to let it cool so I could install the "burning embers" and vermiculite. When I re-lit it, there was a poof! and flame out the bottom of the plate to which the pilot assembly is attached. Fire where there should not be fire! I shut off the gas and contemplated my situation. For fun, I re-lit it with my nose under there. Definite gas smell. It did the same thing, but this time with more vigor and fire. It's doing it apparently at the point when the thermocouple heats up enough to allow the pilot to continue without holding the button in.

So what's going on here? Another leak at the pilot somewhere? Is there another source of gas to the pilot once the thermocouple opens the valve? It seems fine until that point.
 
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Old 02-18-16, 09:03 AM
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I'm not quite following you. Normally you'd need to hold the pilot button down to light the pilot and continue holding it until the the thermocouple was hot enough to hold it engaged.

There is a gas valve with two ports....one to the pilot and the main burner valve.

You replaced the pilot tube.... maybe it's leaking where it attaches to the valve ?
 
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Old 02-18-16, 09:19 AM
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Thanks for the reply.

I hold the button down to light the pilot. It lights okay. I can hear the "click" in the valve when the thermocouple is hot enough. That appears to be when the badness happens. I've only done it twice, though, and don't want to do it again. It might just be coincidence. The flame is out the bottom of the fireplace through a hole cut for the pilot tube so I assume the leak is up at the pilot assembly and a draft is taking it down through the hole. I also should add that there was black mortar-like sealant on the fireplace floor where the tubes went down through to the valve. I chipped it out in order to replace the tube. I doubt the absence of that sealant would be causing the issue but I will be replacing it as soon as I solve this issue.
 
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Old 02-18-16, 09:39 AM
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That black sealant is not a gas seal.

Can you post the model number for that Lennox fireplace ?
 
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Old 02-18-16, 09:51 AM
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Oh - I know it's not a gas seal. It looks like it's for heat and/or draft.

It's a MPD-4035CPM-B
 
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Old 02-18-16, 11:17 AM
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Well it turns out my pain was once again self-inflicted. That pilot tube was loose. I didn't want to make it too tight because it's a brass compression fitting on an aluminum tube. I guess the heating and cooling over the past couple of days allowed it to loosen up. I cranked it down and put it back together and it's fine.

Thanks PJMax for the replies!

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