Fireplaces, Heating Stoves, Flues and Chimneys - Fireplace won't stay lit

It's an older natural gas fireplace (GTI - Gas Technologies, Inc) with a manual switch in the unit - no wall switch. The fire will light, but in about 20 min the flame extinguishes as well as the pilot light. If you go through the process to re-light the pilot and fireplace, it will re-light, but then goes out again in another 20 min or so. I don't know how long the wait period is in between re-lighting - relatives in a condo. It has been fine for the past couple weeks, up until last night.

I've done several internet searches with some results - those include the high limit switch, and cleaning the thermopile and/or thermocouple.

I can't even find a company web address or listing in internet yellow pages.

I have looked at the parts diagram and see where the limit switch would be located, as well as the thermopile. I do not see a thermocouple.

Which of these (or other) parts are serviceable? Are these parts typically interchangeable (if the company has gone out of business)?

Thanks. Any and all help is appreciated.

It sounds like you are having problems with flame lift-off. The venting has probably become corroded and needs replacing, but the vent piping is no longer made which means time to replace the unit. If the unit is over 10 years old, it may be time to call a professional.

logdoc_rob,

Can you explain to me what flame liftoff is?
Also, the corroded venting you're talking about - do you mean the external exhaust venting? Is there any chance a cleaning will help it?

Is there a way to diagnose it?

Flame lift-off happens when the seal between the inner and the outer exhaust piping degrades and allows the exhaust gasses to be sucked back into the firebox and starve the flames for oxygen. You can see this happening. Do the flames start off looking blue with yellow tips, then turn blue, then become very thin and look like ghosts dancing on the burner, the flames lift off the burner and within a few seconds the fireplace shuts off. If this happens, then you have venting issues....which are one of the biggest headaches that I have to deal with.