Propane fiireplace won't stay lit

[94SupraTT]

I believe I have a vented fireplace. Its a propane fireplace. The fireplace will light and stay lit for about 20mins. The logs will then go out and the pilot will stay lit. I was told by a friend it was probably the thermocouple and an easy fix. Any advice is welcome. The unit was made by a company that is no longer around, Martin Industries.

[FurnacePro]

Supra,

Have you checked the voltage (DC) coming from the thermocouple? Should be somewhere around 250mv or higher to keep valve open. Sometimes they can get crud built up on them and a green scrubby pad will do the trick.

The thermocouple and thermopile need to be directly in the pilot flame. If your pilot is not adjusted correctly or if you have a little back-drafting due to wind, that could be pushing the heat of the flame away from it.

Unless you know what you are doing, I would strongly suggest calling a certified technician..... gas can sometimes make an interesting noise when not happy; sounds kinda like..... BOOM!

The after affects can look worse than a $2 walmart haircut!

[korben]

Your friend does not know what he is talking about you need to get a pro in there to fix it.

[show me the money]

you want the pilot flame to contact the powerpile, but not the thermocouple.
The small thermocouple should not have flame contact! That device is your oxygen depletion sensor, the flame is close but not touching, when the oxygen is low the pilot flame with shrink ever so little allowing the thermocouple to turn the pilot out, stoping the ignition process.

If the pilot stays lit the thermocouple is ok.
The job of the powerpile is to power the gas valve open.
First with out any way to measure the DC signal of the powerpile, all you can do is check the electrical connections, which must be tight, and clean the pilot assembly.
If the pilot flame is strong and the DC signal is within limits, you may have a mulitude of possiblities wrong. For example, gas pressure problem, when the gas valve opens the pressure drops shrinking the pilot flame. Check the gas pressure on both sides of the gas valve. The gas valve may be going bad. Check the chimney for obstuctions, openings, seems like dumb advice as most chimneys have tight capping, but that doesn't keep wasps out. I had a totally blocked chimney from paper wasps.

Assuming you are not as stupid as most DIY'ers are thought to be by contactors I assume you know that fuel gas is explosive and flamable.
You could aquire a simple tool set of a DC ampmeter/voltmeter, and a gas simple digial type gas pressure gauge for under 50 bucks.

Sorry for the double post, I thought I only pushed the reset button once.

[show me the money]

you want the pilot flame to contact the powerpile, but not the thermocouple.
The small thermocouple should not have flame contact! That device is your oxygen depletion sensor, the flame is close but not touching, when the oxygen is low the pilot flame with shrink ever so little allowing the thermocouple to turn the pilot out, stoping the ignition process.

If the pilot stays lit the thermocouple is ok.
The job of the powerpile is to power the gas valve open.
First with out any way to measure the DC signal of the powerpile, all you can do is check the electrical connections, which must be tight, and clean the pilot assembly.
If the pilot flame is strong and the DC signal is within limits, you may have a mulitude of possiblities wrong. For example, gas pressure problem, when the gas valve opens the pressure drops shrinking the pilot flame. Check the gas pressure on both sides of the gas valve. The gas valve may be going bad. The gas pressure maybe to high causing over firing, and shuting off due to open high limit. Check the chimney for obstuctions, openings, seems like dumb advice as most chimneys have tight capping, but that doesn't keep wasps out. I had a totally blocked chimney from paper wasps.

Assuming you are not as stupid as most DIY'ers are thought to be by contactors I assume you know that fuel gas is explosive and flamable.
You could aquire a simple tool set of a DC ampmeter/voltmeter, and a gas simple dial type gas pressure gauge for under 50 bucks.

[logdoc_rob]

First thing, vented units do not have an oxygen depletion senso, second.....save $50 on buying those tools and pay someone that knows what is going on. Propane is a a heavier than air gas and will pool in a low spot, then ignite when you least expect it. Don't take chances.......make a call.

[jtp10181]

It could be the thermocouple and be an easy fix.... but it might be about 100 other things too. Call a fireplace pro.

[FurnacePro]

you want the pilot flame to contact the powerpile, but not the thermocouple.
The small thermocouple should not have flame contact! That device is your oxygen depletion sensor, the flame is close but not touching, when the oxygen is low the pilot flame with shrink ever so little allowing the thermocouple to turn the pilot out, stoping the ignition process.

If the pilot stays lit the thermocouple is ok.
The job of the powerpile is to power the gas valve open.
First with out any way to measure the DC signal of the powerpile, all you can do is check the electrical connections, which must be tight, and clean the pilot assembly.
If the pilot flame is strong and the DC signal is within limits, you may have a mulitude of possiblities wrong. For example, gas pressure problem, when the gas valve opens the pressure drops shrinking the pilot flame. Check the gas pressure on both sides of the gas valve. The gas valve may be going bad. The gas pressure maybe to high causing over firing, and shuting off due to open high limit. Check the chimney for obstuctions, openings, seems like dumb advice as most chimneys have tight capping, but that doesn't keep wasps out. I had a totally blocked chimney from paper wasps.

Assuming you are not as stupid as most DIY'ers are thought to be by contactors I assume you know that fuel gas is explosive and flamable.
You could aquire a simple tool set of a DC ampmeter/voltmeter, and a gas simple dial type gas pressure gauge for under 50 bucks.

WTF? What exactly is a powerpile? What exactly is an "oxygen depletion sensor"? I'm not sure about most DIY'ers, but you definitely steal the show!

Clogged chimney ....might contain brain.

[hearthman]

Man, this discussion is like cow patties---all over the place!

Can we agree on some definitions here?

Thermocouple--two dissimilar metals when joined and heated at the hot junction with a 400F temp. difference btw hot and cold junctions produces about 25-30 millivolts dc open circuit. Connects to the Electro Magnetic Power Unit or EPU, which is an electromagnet. Used for flame proving and burner ignition. This is your "primary safety control".

Thermopile--sometimes called a thermogenerator or powerpile. Essentially, a collection of 2 dozen thermocouples connected in series to multiply the voltages. Produces about 325-700 mv dc open circuit. Connected to TP and TH/TP terminals on the main operator head, it provides the power to open and close the operator which sends gas to the main burner.

Oxygen depletion sensor or ODS. Used exclusively on ventfree appliances. A highly engineered component that is NOT field adjustable. You can blow out the dust bunnies but you cannot replace just the pilot orifice, which is an industrial ruby shot full of holes like a spider web and will crush if you probe it. As long as there is about 18.5-20.9% room oxygen, the pilot flame is stable on the thermocouple. However, as the room oxygen drops below 18.5%, the flame speed slows to the point the flame is past the tip of the thermocouple causing the EPU to shut down. Low O2 does not shorten the flame but the opposite. An ODS does NOT sense CO.

If the pilot flame does not impinge on the tip of a thermocouple or thermopile, you won't get your 400F temp. differential so it won't produce the voltage required and you'll get a failure. While it appears the flame does not touch the tip of the TC on an ODS, it is close enough to heat it by conduction and radiation. A weak short yellow tipped ODS is dirty and has nothing to do with ambient room oxygen levels.

If his pilot is staying lit, the thermocouple and EPU in the valve are not the culprit. Look to the thermopile, pilot burner, pilot orifice, venting, log placement, vent restrictor, inlet gas pressure under full load, adverse wind effect on the vent termination, thermostat circuit, limit switches, and glass/ firebox seals for a start. Since you have LP, the second stage regulator could be suspect along with the size, type, and length of gas piping as well.

Site rules prevent explaining how to check these items so the most a DIY can do is suggest them to a Qualified Technician, who is the only one who should be servicing this appliance.

HTH

[korben]

Well said Hearthman

It is amazing how a guy who reads half a manual on some unit somewhere knows all about every fireplace.

[SeattlePioneer]

Show Me The Money----


But don't dispense advice about gas fireplaces. Your advice is largely wrong and could be dangerous.