Duotherm Pilot wont go out

[JRC]

I'm working the a Duotherm Furnace on a 1300 Trillium.
Its the Gravity style with a small fan.
The pilot will light with a very weak flame. It doesn't seem to change when I move the adjustment screw.
When the control knob is turned to OFF propane keeps coming to the pilot light.
Something is not sealing the way it should.
Has anyone take the control apart to repair or check?

[Darwin Maring]

The pilot light is to remain lit all the time. It will lite the furnace when the thermostat tells it to.
To put it out, you need to go to the propane cylinder and turn off all propane.

[JRC]

Maybe I didn't explain correctly.
I was thinking if I dont use the furnace during the summer I would turn the dial to OFF.
If I do this there should not be any gas coming out of the pilot?
Is this correct?

[k0wtz]

your furnace s thermocouple is not working! dangerous unless you have an electronic ignition but you have trouble! when the flame is off the pilot all gas should shut off!!

bob

[Jon in AZ]

Sure doesn't sound like the thermocouple to me; it sounds like the valve itself as the OP says. Turning the valve off should shut off all gas flow to the appliance and extinguish the pilot. I've never operated a gravity furnace, but that's how it works with any other gas appliance- home and RV- I've ever used. You should not have to turn off the entire gas supply to the whole house or trailer to shut down one appliance.

As to opening up the gas control unit and attempting to repair it, that's very risky. From what I've read, a reputable shop will not work on the control unit for one of these old gravity furnaces. Beyond that I don't know, but it doesn't seem like a job for anyone who is not certified and experienced in gas appliance repair. Sometimes you just hit the end of the trail.

[Neto]

Pilots remain on as long as propane tank is on. When you turn the heater dial to off, the furnace will no longer lite the main burner but the Pilot will still be lit.
When you store the camper - Turn the gas off at the propane tank. Then as soon as the preasure in the line goes down the pilot will go out.
ALWAYS turn off the propane at the tank when not using the camper.

[gordon2]

Originally Posted by Neto

...When you store the camper - Turn the gas off at the propane tank. Then as soon as the preasure in the line goes down the pilot will go out.
ALWAYS turn off the propane at the tank when not using the camper.

But what the man said was not that he was not using the camper, but that in summer he did not need the furnace...

Originally Posted by JRC

Maybe I didn't explain correctly.
I was thinking if I dont use the furnace during the summer I would turn the dial to OFF.
If I do this there should not be any gas coming out of the pilot?
Is this correct?

Seems to me there should be a separate valve for the furnace gas supply, but I have seen so many shortcuts taken in R/V manufacturing that there might not be one.

[mary and bob]

I don't know about a trailer furnace, but gas cook stoves that I have worked on had an adjusting screw for the pilot. If the furnace has one, gas could be shut off there. Otherwise a manual gas valve would be a good idea.

[k0wtz]

I am thinking he doesn't know for sure how his furnace works. if he shuts the furnace control to off there should be no gas coming out of it at all pilot or furnace burner the cook stove should still work.

if it was mine for the expense involved in redoing it I would get a separate cook stove and a wave 3 for heat!

or he could disconnect the gas line to the furnace and put the cook stove in line if wanted to do that.

bob

[Neto]

On the new heaters, The pilot heats the thermocouple and that keeps the pilot on. If the pilot goes out the thermocouple cools off and the gas to the pilot shuts off. To relite the pilot you turn a valve to pilot and hold down the plunger and that turns the gas on to the pilot and you use a flame to lite the pilot then the pilot heats the thermocouple and when it gets hot enough you let go of the plunger and if the pilot remains lit then the thermocouple was hot enough.

On Old appliances there might not be the safety decice that turns the pilot gas off and if you blow out the pilot, the gas continues to flow. You would not want this because the gas co ti ues to flow so it would be better to just leave the pilot flame on.

[Jon in AZ]

Originally Posted by Neto

...To relite the pilot you turn a valve to pilot and hold down the plunger and that turns the gas on to the pilot...

Yes, and when you turn that valve back to off, the pilot should go out, but it doesn't, according to the OP. That's how I am understanding this problem, and that points to a bad gas control unit.

I'm waiting for some with training and experience in gas appliance repair to tell us whether the control unit is repairable. This is a very old furnace.

[Tom 72]

Thermocouples have been in use a long time, probably our entire lives. It seems to be working fine and its function has been described correctly above (Neto post #10). In residential units, rotating the gas valve on the unit, (not at the tank) back to off, shuts off all gas, including the pilot. It's hard to imagine the unit's gas valve wouldn't work that way, but you never know.

There sure seems to be a lot of "folklore" posted about this potentially dangerous subject.

[Mike_L]

I haven't had a gravity furnace in a while but I always liked them. The pilot light heats the thermocouple and ignites the burner when the thermostat calls for heat. When the burner shuts off the pilot stays lit. If the pilot goes out, the thermocouple cools and the gas shuts off so as not to cause an explosion or fill your unit with gas.
IN THE OFF POSITION THERE SHOULD BE NO GAS ENTERING THE FURNACE
If the main switch is malfunctioning, it should be replaced, not fixed.

[k0wtz]

neto I wouldn't consider running that furnace under any conditions if the pilot gas doesn't shut off with a safety thermocouple. I cannot image them making such a gas valve even in those days!


I just redid a Vermont castings gas stove that a guy wouldn't spend a bunch of money on I didn't blame him I took a risk also so he sold it to me. I put in a new Robertshaw gas valve with a new thermocouple and I had to put in a different pilot gas line but all is good now. I have a 2k stove for 300bux. as I read up on this robertshaw gas valve it is made for rvs by the way they are made to run everyway but upside down! there is a ton of those Vermont castings stoves out there just setting because Honeywell quit making the gas valve and no one wants to work on them. I have helped get several going!

[k0wtz]

mike I stayed in a motel one time it had the old style wall furnace the stove went out but the pilot kept letting gas through I could hear the gas but no smell. I reported it they called a gas guy to work on it I asked him about it and he said it was legal with the flue they had that blew my mind.


I moved out of there but in thinking back if all the gas fumes went up the flue was he telling me the truth or was that furnace legal.


it was an old motel looked like one of those route 66 jobs each motel room was individual maybe it was grandfathered in. now I am thinking as old as that furnace is maybe it is a legal stove in that camper. dangerous to me but legal!


bob

[k0wtz]

i wonder what the name of the furnace was?


bob

[k0wtz]

i just did a search for durotherm and they are still in business i would start with them.

bob

[Tom 72]

Mike L is correct. The main gas valve on the unit controls gas flow. The thermocouple only senses whether the the pilot is lit.

Please people, don't be posting your guesses on this topic.

[Gerry]

Originally Posted by Tom 72

Mike L is correct. The main gas valve on the unit controls gas flow. The thermocouple only senses whether the the pilot is lit.

Please people, don't be posting your guesses on this topic.

Guesses are not good when dealing with a propane problem and if not sure bring it to an expert.
On my Duotherm heater, when the furnace gas valve was turned to the OFF position, the pilot went out.
Sounds like a bad gas valve to me.
REPLACE

[Mike_L]

I had an old '78 Scamper some years back with a gravity furnace. It had a red control knob on the bottom with 3 positions; OFF, no gas coming through, PILOT, gas to the pilot light only, not the burner and if the pilot went out the thermocouple would cool and cut the gas to the pilot and ON, the burner would cut in if the thermostat called for heat which would be lit by the pilot.
The fridge also had a pilot light which I had to light with a piezo-electric ignitor similar to those found on BBQs. There was a small window in the bottom of the fridge so I could see the pilot.
Both appliances had the same red master switch which you had to hold in until the pilot heated the thermocouple. Otherwise all gas would shut off.
Gas coming through the pilot without flame is basically a gas leak. Propane is heavier than air so it would not likely travel up the flue like heated lighter-than-air combustion products would.