I have a Lennox gas log with an SIT valve. If I take out the front log, I get the required mV (320) to open the valve. The man burner lights with no problems.

When I put the front log back in place, the mV's quickly drop to 250, main burner will not light.

The pilot stays lit, but the log being there is somehow affecting mV's from my thermopile (just got a new one).

Any ideas what's going on?

Thanks to anyone who can help me.

 

Is the pilot assembly near the front log? Does the front log hit, touch or get close to the pilot light, thermopile? The thermopile needs a full, proper pilot light flame on it to generate the required current. If the log is blocking or somehow interfering with the pilot then you don't get the correct voltage.

 

The front log is about an inch or two ahead of it, not even close to touching. The only thing it can be doing is blocking air somewhat. If this can have such an effect on the pilot, I'm just wondering if the pilot is adjusted correctly (it's fully touching the Thermopile and it works just fine if that front log is removed). Also, I don't see any visible change to the pilot with the log in or out. Strange isn't it?

 

Odds are the pilot orifice needs to be taken out and cleaned.

 

I recently installed a direct vent fireplace and was about to take it out to the trash. it was a very basic install and I followed the instructions exactly. Watched videoes and spoke to the factory inside technical support on several occaisions. This resulted in basically doing it over several times. My pilot would light and stay lit forever, but when I turned it to on to ignite the logs, it would burn(the logs) for a few minutes and go out every time, pilot and all. The inside support guy gave me the cell # of the field supervisor(the guy making the videos) for some extra advise. He told me to move the back log about a qtr of an inch closer to the pilot and call him back. I thought no way, and he probably wouldn't answer the phone again. Well, it worked and has worked great ever since(couple of weeks). I called him back and he said it is all about the air flow. Granted this is a direct vent and obviously they work differently than conventional fireplaces, but I thought it was very strange.