1970s duo therm gravity propane heater - Fiberglass RV
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Old 02-08-2021, 09:49 PM   #1
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Name: WILLIAM
Trailer: wolf pup
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1970s duo therm gravity propane heater

i have a 1970s duo therm gravity fed propane heater and I'm looking for someone to go over it and install it in a tear drop camper .I'm willing to travel to an expert........maybe some old guy still knows about these heaters
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Old 02-08-2021, 11:49 PM   #2
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Quote:
Originally Posted by yogavnture View Post
i have a 1970s duo therm gravity fed propane heater and I'm looking for someone to go over it and install it in a tear drop camper .I'm willing to travel to an expert........maybe some old guy still knows about these heaters
I posted this where you first asked the question. But it bears repeating now, (White Stripes).

William, I am sorry to inform you that since the furnace that you want to install is no longer approved for use in a trailer, no, "expert" or more accurately, professional will touch your furnace with a ten foot pole. There would be no insurance if they kill you.

The problem is surface temperature. If a blanket, or other combustible material, comes into contact with the front of the furnace, it could start a fire.

That being said, I would not hesitate to install one in my trailer. I love them. No power requirements, no moving parts, they could almost last forever. The only serious failure point is the gas valve. Replacing that is expensive. That is why I posted a complete tear down of the gas valve:
https://www.fiberglassrv.com/forums/...a02-86546.html
And the furnaces:
https://www.fiberglassrv.com/forums/...1hu-94007.html
https://www.fiberglassrv.com/forums/...wer-54226.html
I am preparing an update on the furnace threads. The furnace can be further dissembled. I am also going to experiment with some Peltier generators. I want to see if I can run a fan, maybe an LED light as well.

But, if you are not confident doing the work yourself, (and it sounds like your not) than you may want to abandon your plan. Maybe look into a catalytic heater, and a CO detector. But, no amount of money would convince me to install one on someone else's trailer.
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Old 02-09-2021, 03:42 PM   #3
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I have hooked up many stoves for my own use! as you said they work great but maybe not for him.


i now use a wave 3 with a quick disconnect and yes i vent! no doubt you know a t/r is not very air tight!
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Old 02-10-2021, 12:01 PM   #4
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William, I own about 8 Duo-Therm furnaces, models 65512, 65810-002 and 11HU. They all use the same style of gas valve. The valve has a temperature probe with a volatile liquid inside that, when it boils, it activates the gas valve to close.

There are several model numbers of Duo-Therm furnaces that end in 11. Some are 65211, 65311 and 65411 are some that I am aware of. It would help if you posted a picture of yours. I am especially interested in the gas valve. Because yours has a thermostat, it probably uses a different gas valve then the ones on my furnaces.

As for the safety of the furnace, I have not yet seen a Duo-Therm furnace that the fire box had any rust perforations. Most of the rust seems to be in the exhaust assembly, and that is quite thick steel. Does the exhaust on your fire box telescope into the exterior exhaust assembly? Or has it rusted to the point that it is fused? If it is fused, that makes inspecting it difficult. The inner exhaust tube runs through a seal on the furnace housing. Then it slides inside the exhaust tube that connects to the exterior exhaust assembly. You will not be able to pull the fire box out of the furnace housing if they are fused. That would also complicate installing it in new trailer.

I recommend that you inspect it yourself. Have you disassembled it? Is there an access panel on the front of the fire box? Is the fire box corrugated or smooth? If you plan to disassemble it, I recommend that you soak the nuts and bolts in penetrating oil for a couple of days before you start twisting wrenches. The threaded studs tend to shear off due to corrosion. Though that is not really a big deal, they can be drilled out and sheet metal screws used in their place. You should also source high temperature gasket material.

Manuals can be found at these links:
https://www.fiberglassrv.com/forums/...do=file&id=159
https://www.fiberglassrv.com/forums/...do=file&id=153
https://www.fiberglassrv.com/forums/...do=file&id=143

Also, check out these links for more information:
https://www.fiberglassrv.com/forums/...ter-49659.html
https://www.fiberglassrv.com/forums/...0-a-61527.html
https://www.fiberglassrv.com/forums/...out-84189.html
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Old 02-10-2021, 02:02 PM   #5
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Trailer: wolf pup
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thanks david

Quote:
Originally Posted by David Tilston View Post
William, I own about 8 Duo-Therm furnaces, models 65512, 65810-002 and 11HU. They all use the same style of gas valve. The valve has a temperature probe with a volatile liquid inside that, when it boils, it activates the gas valve to close.

There are several model numbers of Duo-Therm furnaces that end in 11. Some are 65211, 65311 and 65411 are some that I am aware of. It would help if you posted a picture of yours. I am especially interested in the gas valve. Because yours has a thermostat, it probably uses a different gas valve then the ones on my furnaces.

As for the safety of the furnace, I have not yet seen a Duo-Therm furnace that the fire box had any rust perforations. Most of the rust seems to be in the exhaust assembly, and that is quite thick steel. Does the exhaust on your fire box telescope into the exterior exhaust assembly? Or has it rusted to the point that it is fused? If it is fused, that makes inspecting it difficult. The inner exhaust tube runs through a seal on the furnace housing. Then it slides inside the exhaust tube that connects to the exterior exhaust assembly. You will not be able to pull the fire box out of the furnace housing if they are fused. That would also complicate installing it in new trailer.

I recommend that you inspect it yourself. Have you disassembled it? Is there an access panel on the front of the fire box? Is the fire box corrugated or smooth? If you plan to disassemble it, I recommend that you soak the nuts and bolts in penetrating oil for a couple of days before you start twisting wrenches. The threaded studs tend to shear off due to corrosion. Though that is not really a big deal, they can be drilled out and sheet metal screws used in their place. You should also source high temperature gasket material.

Manuals can be found at these links:
https://www.fiberglassrv.com/forums/...do=file&id=159
https://www.fiberglassrv.com/forums/...do=file&id=153
https://www.fiberglassrv.com/forums/...do=file&id=143

Also, check out these links for more information:
https://www.fiberglassrv.com/forums/...ter-49659.html
https://www.fiberglassrv.com/forums/...0-a-61527.html
https://www.fiberglassrv.com/forums/...out-84189.html
thanks for responding david. my heater is sitting at the erv guys shop where he inspected it. he is the same guy that sold it to me 23 years ago. i never had an issue with it. i have a new teardrop i want to put it into. the new teardrop so airtight that u here a pressurized sound when you shut the door!! good and bad right? good in that something that airtight wont take much to heat it. bad in that if nasty fumes get inside u wont wake up. some of these rv guys put the fear of god in you regarding heaters. my rv guy says same as you that they were banned years ago cause people put blankets on them . buy hey blankets ain't the same as co2 poisoning. my guy inspected it recently and put i think a thermo coupler on it a new one
whatever that is. i think it starts the unit up. after 20 years of sitting it didn't want to start up but then it did and the rv guy put a new part on it. that is readily available. david i will try to get a pic for you. i need to tread lightly with my rv guy as he's gonna put the unit in my camper. david let me ask you ...................i know it has a vent to outside. do you think in summer their might be a way to remove the heater? yet keep the vent to outside system on the camper. a quick release idea>? just wondering. i have studied and studied and i had a wave 3 but returned it as my gut says the old duo therm is actually gonna be safer. remember any time you burn propane the soot gotta go somewhere. and on the duo therm I'm pushing it outside via the vent. but on wave 3 they say the unit burns up all the fumes. cmon man as biden would say, the propane soot just magically disappears on the wave 3? I'm skeptical. i should be happy though my duo therm I'm pretty sure has two knobs on it. one is to turn up and down . let me ask you this david. if for some reason the pilot light would turn off . on the old duo therm would the propane gas still be emitted into my camper?
in other words if the gas is running and the furnace is on, and lets say you think its burning , but somehow u fall asleep and the pilot goes out, wouldn't you die then. don't you see how I'm living on the cutting edge?? so now we know why nobody is using these heaters anymore. my life is dependant on the pilot light?
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Old 02-10-2021, 02:12 PM   #6
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Trailer: wolf pup
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david one thing i did to mine on my last camper is i cut off the long vent to outside and halved its size. i would assume its only long to dissipate heat. and i will put a metal plate on wall where i hook up vent. david the long vent is to dissipate heat right>?? its way to long for a tiny camper. since i have a tiny camper, i never crank it up.. and on my previous camper i never noticed heat on vent on outside. so i think I'm fine. i had to cut it down or my heater would have stuck half way into my camper
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Old 02-11-2021, 01:28 PM   #7
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Originally Posted by yogavnture View Post
thanks for responding david. my heater is sitting at the erv guys shop where he inspected it. he is the same guy that sold it to me 23 years ago. i never had an issue with it. i have a new teardrop i want to put it into. the new teardrop so airtight that u here a pressurized sound when you shut the door!! good and bad right? good in that something that airtight wont take much to heat it. bad in that if nasty fumes get inside u wont wake up. some of these rv guys put the fear of god in you regarding heaters. my rv guy says same as you that they were banned years ago cause people put blankets on them . buy hey blankets ain't the same as co2 poisoning. my guy inspected it recently and put i think a thermo coupler on it a new one
whatever that is. i think it starts the unit up. after 20 years of sitting it didn't want to start up but then it did and the rv guy put a new part on it. that is readily available. david i will try to get a pic for you. i need to tread lightly with my rv guy as he's gonna put the unit in my camper. david let me ask you ...................i know it has a vent to outside. do you think in summer their might be a way to remove the heater? yet keep the vent to outside system on the camper. a quick release idea>? just wondering. i have studied and studied and i had a wave 3 but returned it as my gut says the old duo therm is actually gonna be safer. remember any time you burn propane the soot gotta go somewhere. and on the duo therm I'm pushing it outside via the vent. but on wave 3 they say the unit burns up all the fumes. cmon man as biden would say, the propane soot just magically disappears on the wave 3? I'm skeptical. i should be happy though my duo therm I'm pretty sure has two knobs on it. one is to turn up and down . let me ask you this david. if for some reason the pilot light would turn off . on the old duo therm would the propane gas still be emitted into my camper?
in other words if the gas is running and the furnace is on, and lets say you think its burning , but somehow u fall asleep and the pilot goes out, wouldn't you die then. don't you see how I'm living on the cutting edge?? so now we know why nobody is using these heaters anymore. my life is dependant on the pilot light?
david why do you have 8 of these? i think these type of heaters will be more in demand as off grid grows. unless someone comes up with a modern day answer to heating. i bought a wave 3 but returned it. it says its ventless and no fumes come out.. how do they do that magic??? i mean propane has off gases u just cant magically make them disappear. thus the vent is needed.
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Old 02-11-2021, 03:06 PM   #8
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William, So many questions:
Thermocouple: A device that generates a small amount of power when heated. This is used to keep the gas valve open when the pilot light is on. When the thermocouple gets cold, it no longer generates enough voltage to hold the gas valve open. This prevents an extinguished pilot light from filling you trailer up with an explosive mixture of propane and air. So no, your life is not dependent on the pilot light.
This furnace is basically a fire in a vented metal box. As long as there are no leaks, you won’t die.
CO, (carbon monoxide) is deadly. CO2 makes your pop fizzy. It can kill you, but only at very high concentrations. See Apollo 13.
Since I don’t know what furnace you have, I can’t say on the quick release idea. The three styles of Duo-Therm furnaces that I have can be pulled from the inside, leaving the exterior exhaust/air intake installed. However that would let the mosquitos in. Also reinstalling the furnace would be more difficult as you would have to blindly fit the exhaust and air intake ducts into their mating exterior fittings.
There are two issues with a catalytic heater, like the Wave 3. The products of combustion, (catalytic reaction?) are dumped into the interior of the trailer. For the most part, water is the problem here. You might find your trailer to be kind of humid after a while. The catalytic reaction of the Wave 3 will not product soot, and very little carbon monoxide, (mostly just water an carbon dioxide) until your perfectly sealed trailer starts running low on oxygen. Then the Wave 3 will start generating carbon monoxide, enough to kill you. The same thing could happen if you try to run it at a high altitude. That is why the manufacture recommends running the Wave 3 with a window cracked open and they publish a maximum operational altitude. I think you are correct that pulling your combustion air from outside and also dumping the products of combustion outside, is a safer solution.
Cutting the telescoping vent will reduce the distance that your furnace can be from the trailer wall. In Trillium trailers the furnace is in front of the wheel well. The vent has to be able to reach past the wheel well to get to the side wall of the trailer. Since it sounds like you will have the furnace very close to the wall, cutting the vent should not be a problem. However, I would use some aluminum tape to seal the joint in the vent. The outside of the vent is the combustion air intake, so it will not get very hot.
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Old 02-11-2021, 04:38 PM   #9
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thanks dave i will try to get my model number

dave at my house at the moment i only have the vent parts. some are rusted a bit surface and discolored metal. (but they are intact. should i use some sanding tool to get the surface rust off? here's my idea dave. i know my rv gu gonna install this but he ain't gonna be anal about servicing it . yes he put a new thermo coupler in it. and from what u say above the thermo coupler is unique as if the pilot goes out the unit will not keep producing gas in the chamber. am i reading that right what the thermo coupler does? its kind of a gas monitor ? BOTTOM LINE DAVE . WHAT IF THE PILOT LIGHT GOES OUT? THEN WHERE DO THOSE GAS FUMES GONNA GO? TOMORROW I RECIEVE A TRAILER TONGUE BOX AND I PLAN ON DRIVEING TO MY DEALER AND I WILL TAKE PICS OF MY HEATER. FROM WHAT I REMEMBER the worst of the rust is on the vent to outside. in the tube ........yes i feel like an apollo astronaut , doing something nobody else does. i again state that these heaters will be come valuable to off grid users. as hardly nobody knows about these heaters.
i did sleep in my new camper . one night with an electric heater. its very airtight 5 x8 outbound extreme. in the rear of the unit it has installed two feet up from the ground a bunk bed is what they call it . its basically a board up from the ground across the back in back of camper. i was gonna install my heater their. as it would be above my head or feet depending on what way i sleep. but heat rises. would i be better off mounting heater on ground as the spot below the bunk bed would be harder to get heat. I'm not sure. my gut says even if the heater is mounted 2 feet above the ground level the camper is so small it still would heat ok, i would put my head below the bunk bed so that area would get the least heat. if you look on outbound trailers in nebr. you will see what i have its a bunk bed addition to the unit.
more soon. apollo 11 signing off..................ps. my rv guy seems to want to build a box for my heater. I'm confused about that. why would my rv dealer want to build a box. is it an insurance policy? if he built a box for my heater would that keep a leak at bay? somehow?
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Old 02-11-2021, 05:18 PM   #10
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William, You are correct. If the pilot goes out, the gas valve will close so that no gas will escape. You will be safe, assuming that the gas valve works correctly. I would test that though.
As for a box around the furnace, the only thing that is meant to be seen, on the furnaces that I am familiar with, is the front grill. Everything else is too ugly.
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Old 02-11-2021, 10:49 PM   #11
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William, You are correct. If the pilot goes out, the gas valve will close so that no gas will escape. You will be safe, assuming that the gas valve works correctly. I would test that though.
As for a box around the furnace, the only thing that is meant to be seen, on the furnaces that I am familiar with, is the front grill. Everything else is too ugly.
I'm hoping tomorrow my tongue box comes and i will take my camper to where my heater is locatednow at the rv dealer. I'm on shaky ground with him he doesn't like me much.. but I'm tempted to use him to put it in as he knows about these things. i don't have touse him though. my heater is set up with a two burner on top of it..............and in back a y connector links the two units together. i do wonder if going down the road something might giggle something loose in the heater. I'm pretty sure my heater has two control buttons one for starting and the other is a button with numbers 1 to 5. so i can put it on low to high. as i remember it ( from 20 years ago) if i put it too low the heater wants to not stay lit. anyways i looked at your 200 dollar co2 unit. i will try to get one cheaper than that. considering i i consider myself an apollo astronaut. i thought i would just make a mask for my mouth and nose and drill a hole in side of camper an put a hose from my mask to the hole outside. i just hope a bee don't come in that hose whilst i sleep....i see the pics of the units here mine looks like the one that has the corrogated front of the heater box.
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Old 02-17-2021, 12:53 PM   #12
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David if u send me your email to yogavnture1@gmail.com i will send u pics of my heater...i dont know how to post here. Maybe u could post here my pics.
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Old 02-17-2021, 01:22 PM   #13
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Originally Posted by yogavnture View Post
I'm hoping tomorrow my tongue box comes and i will take my camper to where my heater is locatednow at the rv dealer. I'm on shaky ground with him he doesn't like me much.. but I'm tempted to use him to put it in as he knows about these things. i don't have touse him though. my heater is set up with a two burner on top of it..............and in back a y connector links the two units together. i do wonder if going down the road something might giggle something loose in the heater. I'm pretty sure my heater has two control buttons one for starting and the other is a button with numbers 1 to 5. so i can put it on low to high. as i remember it ( from 20 years ago) if i put it too low the heater wants to not stay lit. anyways i looked at your 200 dollar co2 unit. i will try to get one cheaper than that. considering i i consider myself an apollo astronaut. i thought i would just make a mask for my mouth and nose and drill a hole in side of camper an put a hose from my mask to the hole outside. i just hope a bee don't come in that hose whilst i sleep....i see the pics of the units here mine looks like the one that has the corrogated front of the heater box.

turn off propane while driving!
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Old 02-17-2021, 01:30 PM   #14
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Old 02-17-2021, 01:37 PM   #15
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i have pics of my duo therm but don't know how to share them here
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Old 02-17-2021, 01:55 PM   #16
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thanks david

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Originally Posted by David Tilston View Post
William, You are correct. If the pilot goes out, the gas valve will close so that no gas will escape. You will be safe, assuming that the gas valve works correctly. I would test that though.
As for a box around the furnace, the only thing that is meant to be seen, on the furnaces that I am familiar with, is the front grill. Everything else is too ugly.
david if u send your email address to yogavnture@yahoo.com i will send u pics of my duo therm. its a 65211-2
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Old 02-18-2021, 12:45 AM   #17
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Excellent heaters, used them for years. Indirect fired gravity heaters. Fuel efficient, no power required.

Back in the day I traveled with the gear necessary to test air quality and I did many times. Not once did I detect levels of either CO, CO2 or propane above levels outside the trailer. Rain, snow, wind didn't matter, no leaks.
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Old 02-18-2021, 09:22 AM   #18
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Originally Posted by Mike_L View Post
Excellent heaters, used them for years. Indirect fired gravity heaters. Fuel efficient, no power required.

Back in the day I traveled with the gear necessary to test air quality and I did many times. Not once did I detect levels of either CO, CO2 or propane above levels outside the trailer. Rain, snow, wind didn't matter, no leaks.



I like the wave heaters KISS principal for me!
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Old 02-18-2021, 11:23 AM   #19
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Name: WILLIAM
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v my duo therm
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Old 02-18-2021, 11:25 AM   #20
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thanks david

david here are pics
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