Trouble keeping flame lit (HnG ST-TRC Thermopile)

[edschminke]

I have a Heat-n-Glo Model ST-TRC gas fireplace and I'm having trouble keeping the main burner lit.

(oooo... oooo.... I know the answer!! you have a bad thermopile! replace that and you'll be good)

Sorry, but I already tried that. I bought a brand new thermopile which according to the vendor, was the specific part for that application/model, etc. Also, due to my keen attention to detail, the thermopile was replace eXACTly as before and everything was put back together eXACTly as it was.

With pilot flame only, I'm seeing 570mv (+/- 5mv) using a multi-meter. When I turn on the main burner, I see a significant drop in voltage.. down to ~120mv. From there the voltage continues to fluctuate .1-.2 mv every second or so. A little up, a little down, but generally the trend is down. The valve inevitably clicks off at around 60mv. I would say around the 10 minute mark.

I replaced it because the previous one was doing that, only much faster. (Starting voltage ~250mv, down to 100mv and then clicked off in 60-90 seconds)

Did I get the wrong thermoile? It looked almost identical to the old one. Is it just possible it was a bad one?Anyone have any other ideas?

Thanks!

 

[DAKSY]

Your readings shouldn't drop much below 200 when the burner is on. Did you try to turn the pilot adjustment screw to see if you can raise the flame? I wouldn't go much above 600mV tho...How much of the T-Pile is engulfed by flame? IIRC, the top 3/8" should be in the flame. Another question I'd ask, is do you have metal-braided wires on your T-Pile? Sometimes I've seen that type short itself out when it contacts the sheet metal.

 

[edschminke]

I don't recall if there is a way to adjust the pilot any.. at least, I didn't mess with it at all. The T-couple, the pilot, and the T-pile (in that order) were run through a single piece of metal, holding the whole thing together. I can check, though.

The new T-pile: yes, the two wires coming out of it are wrapped in another, insulated, metal wire/mesh type thing. Is that what you're referring to?

 

[DAKSY]

I don't recall if there is a way to adjust the pilot any.. at least, I didn't mess with it at all. The T-couple, the pilot, and the T-pile (in that order) were run through a single piece of metal, holding the whole thing together. I can check, though.

The new T-pile: yes, the two wires coming out of it are wrapped in another, insulated, metal wire/mesh type thing. Is that what you're referring to?

Look for the word "PILOT" on the front of the gas valve. There may be a silver, slotted screw that you have to remove before you can access the adjustment screw.

Yes that braiding can sometimes ground out. Try to coil it so it doesn't contact anything...

 

[edschminke]

Found it.. and actually, that pilot flame was burning WAY hotter than I remember it burning in the past. Not sure how that would happened; I hat not adjusted it any.. didn't even know where it was.

So I choked the pilot down a little and after some tweaking (at one point the pilot wasn't staying lit), I'm able to keep the main burner lit. Everything has been going steady for an hour or so now. I'm probably good now.

I did not do anything with the wire wrap around the T-pile wires.

Thanks for the help, DAKSY!

 

[Heatsource]

if you were getting over 500mV you shouldn't need to adjust the pilot
i'd look for turbulence around the pilot when the main burner comes on causing the t-pile to cool down

 

[edschminke]

I hate to do this, but I am STILL having trouble keeping this fireplace running.

My unit runs on a thermostat (when I turn it on). After a week so of not running it, it will cycle on and off for 24 or so. The very next day, after 5 minutes or so running, *CLICK*.. the thermopile has tripped causing the main valve to kill both the burner and the pilot.

I originally thought it was a failing thermopile, so I replaced it. I kept having the same problem. But now that I actually look closer, I see the problem. The flame is weakening under these conditions; from both the main burner and the pilot. The color of the flame overall is considerably bluer than normal. Very little orange. The flame that is produced burns higher and higher from the gas jets. That is, the ones that remain burning. One by one, the flame disappears from the holes, but the gas is cut off before they all go out.

It is almost as if there is not enough gas in the line.. That the pressure is going down. It's natural gas and every other appliance in my house is fine. Maybe a question of fuel/aix mixture? If that is the case, I'm not really sure how to solve it myself.

Any advice would be appreciated!

Update:

This might help. If I unscrew the glass face and pull it away from as the burner is going, the fire roars back to life. Replace the face, it weakens. I'm guessing this is evidence of it being starved for air. (?)