Coleman trailer furnace in a RTT

Rubicon_Fan

Adventurer
Hey everyone, I need some help here.
I just got got my hands on Coleman model 4312k from a good friend of mine who just replaced furnace in his RV type trailer.

Here is Furnace, it is Coleman 4312K model, 1987 i guess.
It use propane @ 10mm (ordinary pressure regulator) and 12v supply (1.8 A max).
Input capacity is 12,000 BTU,which will warm up RTT in any weather.
It has build in fan and all controls except thermostat.
In the picture, the Box on right is enclosure where furnace coming in. I took it out so you can have better idea.
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Now I know that I will need to get propane main control valve working or buy new one,which can be about $150. I will need thermostat to fit in my roof top tent if I really want to adjust temperature from tent.LOL.

But before I even start, I just wanted ask you guys if it's even worth doing? Or should I just stick to my coleman Black cat that I'm using now?
Thank you all in advance.
Here is my trailer by the way.
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dwh

Tail-End Charlie
Is it a pilot light version? Model number means what? 12k btu? That's a lot. The Suburban 12k in my camper eats propane and battery like candy. I have a built-in 5g propane tank and I almost never use the heater.

If you can get it working without spending money on it it could be useful for short trips if you carry a 5g tank.
 

Rubicon_Fan

Adventurer
To be perfectly honest with you I don't know of it is pilot light version, but I woul assume so... But anyways, now as I think about it, it might be a big overkill for just my roof top tent...

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Martyn

Supporting Sponsor, Overland Certified OC0018
If you have a thermostat in the tent then the fact is a large heater is really irrelevant. The heater will turn on and off predetermined by the thermostat setting. To give you some idea of heating capacity, we use the HS2000 it generates 6483 BTU and heats up a RTT very quickly, with the thermostat in the tent it has a 25% duty cycle. Your unit is twice as large as ours, and we consider ours to be overkill. The HS2000 is best suited for something with 3 or 4 times the volume of a RTT ,like one of our AT FlipPac applications, but with a thermostat all it effects is duty cycle.

I'd find out if it's a pilot light version or an electronic ignition, check to make sure that the gas valve turns off when there is no flame.

A few other points to ponder.

Is this a direct air heater? By this I mean is the heated air also the combusted air, or does it have a heat exchanger? If it's direct you need to check that the combustion of the propane is complete and no carbon monoxide is being given off. If it's direct it's also going to be pumping in a large amount of water vapor into the tent.

If the unit uses indirect heat, as in there is a combustion box and heat exchanger, is the heat exchanger still sealed from combustion gases? You would need to check the heated air for CO to get some idea on this.

Where is the exhaust from this unit going to go? Depending on the unit the exhaust is going to have to be placed anywhere from 22" -36" away from the air intake.

What is the power draw of the fan? What is the lowest voltage that the unit will work on?

I'm not certain what you mean when you say the unit uses propane at regular pressure 10mm, gas pressure and regulators are measured in inches of water column or mbar.

Finally if this is a direct heat unit I'd recommend you install battery operated CO detector in the tent.
 

greentruck

Adventurer
I could see this working, although as Martyn notes, there are a bunch of issues and caveats that need to be addressed to do this safely.

Here's a thought I had in how to layout the system and may help implementation of some of the above cautions.

The heater goes on the ground (where it's away safely from both the trailer and RTT), is hopefully set up with a heat exchanger, use one flexible duct to carry the exhaust away, and then you use another flexible duct to carry the heat (and it goes up easy, because, well it's heat:)) up to the RTT.

You'll need whatever the thermostat is set up as on a remote, which can hang in the RTT.

But 12k BTU is a crazy amount of heat for this IMO, unless you've got the world's largest RTT.
 

gasman

Adventurer
ok . so i know a little bit about gas furnaces, i have been in the heating industry all my life ,, what you have will work, but do ya really want to?

martyn raised some good questions, the unit you are looking at is a direct vent furnace, yes it is sealed combustion , no it will not fill your tent with water vapour, and no you dont have to worry about carbon monoxide with this unit if,,,, it is installed properly,
as you can see there are 2 pipes coming out the end, one smaller pipe inside a larger pipe , the center pipe is the exhaust and the combustion air is drawn in thru the outer pipe, . now as long as you dont have the intake sucking in the exhaust , the gas press and orifices are correct and the burners are clean , that unit should make very little CO, and would be exhausted ok.

what would you have to do to make this work in a rtt, ?
you would need to have a stove jack sewn into the canvas for the exhaust to exit, i imagane at 12,000 btu's the exhaust pipe would be a couple hundred degs, the exhuast would have to be extended away from the tent ,preferably above it,

this a a very basic direct vent furnace and im not sure how critical having a balanced intake and exhaust would be, you would have to experiment there.

it is also designed to suck its combustion air from outside the RV,

as far as the thermostat issue , most of the basic units like this the tstat is built into the gas valve . ( a closer picture and i can tell you right away )

how much power will that fan draw ? prolly lots

what about clearnce to combustibles ? it should be on the units rating plate,
it is most likely a zero clearance unit,

would i want to sleep beside that thing ? even if it was set up properly ?
no thanks.............
 

gasman

Adventurer
I could see this working, although as Martyn notes, there are a bunch of issues and caveats that need to be addressed to do this safely.

Here's a thought I had in how to layout the system and may help implementation of some of the above cautions.

The heater goes on the ground (where it's away safely from both the trailer and RTT), is hopefully set up with a heat exchanger, use one flexible duct to carry the exhaust away, and then you use another flexible duct to carry the heat (and it goes up easy, because, well it's heat:)) up to the RTT.

You'll need whatever the thermostat is set up as on a remote, which can hang in the RTT.

But 12k BTU is a crazy amount of heat for this IMO, unless you've got the world's largest RTT.

leaving outside and ducting it could work, , if you were to seal the louvers on the sides and cut a round hole on the top to attach a 4'' round duct, cut some louvers at the other end of the box for supply air (to be heated ) the fan might be strong enough to push the air up and into the tent, there is a limit switch on the side of the heat exchanger, if you didnt get enough air flowing past the heat ex, it would overheat and shut off, and thats ok as long as the limit dosnt kill the pilot light , then your gettin outta bed to relight it,
another option for the thermostat you could hook up an infared remote tstat from a gas fireplace. they are battery operated and would probably work very well,

it would be fun trying to get this unit to work for ya, but after all of that, then there is the legality of the whole thing, basically to make it work you would be altering the manufactures specs, and that aint allowed
 

greentruck

Adventurer
it would be fun trying to get this unit to work for ya, but after all of that, then there is the legality of the whole thing, basically to make it work you would be altering the manufactures specs, and that aint allowed

Well, it was a thought.:) I think my idea might work if you rolled your own, which might help with the legal side of things, DN:coffeedrink:

But this is not the kind of thing you want to hack together without knowing everything about exactly what you're doing, for your own safety and that of others.
 

gasman

Adventurer
in the old days,,, we used to heat rocks in the fire , wrap them in a towel and stuff them into the sleeping bag. they would stay warm till morning, not the most comfortable but it works,,,,,,,,,,
 

Engineer Guy

New member
Random Heater Observations

I've worked on some Tent Trailer and Hardside Trailer Furnaces, and can add some info.

12k and 16k BTU Furnaces typically use larger Fans and draw ~6 Amps. Yes, they do draw down Batteries mighty fast. However, from the pic of the Fan and the hard data that it draws 1.8 Amps total, that modest current draw will allow ~3x the operating time of larger Fan Furnaces. Amps is Amps.

There's a Pilot Flame-sensing Thermocouple evident next to the Pilot Light Gas Tube. I don't see a port for match lighting your Furnace. A Pal's '88 Wilderness Trailer - about the same vintage - with a 12k Furnace has a push button Piezo Pilot lighter. Putting these factoids together suggests you've inherited a push button Pilot style. Pilot lighting instructions, or a Match port 'hole', will decide that detail.

The larger diameter wires have/need more insulation because they carry high voltage out of the small Transformer that 'sparks' the Ignitor I see at the rear of the Plenum. The White wire looks detached, so there wouldn't be ignition until it was reattached to an intact Ignitor. Rust never sleeps...

While it's true the Thermostat will cycle heat on/off, there will be wider temp swings in a small volume as the hot Plenum heats up and cools down. One of the black circular Switches - NO - works like a mechanical 'Frog Clicker' Toy and keeps the Fan running until the Plenum cools down, and also typically controls the heat cycle on/off IF the Thermostat is calling for heat. The other 'clicker' Switch - a NC type also the size of a Quarter - opens if something fails and prevents a Fire by interrupting the heat cycle until the Plenum cools down. Just below the Fan may be the 'Sail Switch' that senses that the Fan is moving air. I'm not positive about that from the pic resolution. Confirm the operation of these Components with an Ohmmeter.

There's 25.4 mm to 1 inch. So, the 10 mm spec is a rounded-off, Metric way to state the Furnace needs the usual ~1/2 inch of LP pressure by referencing the Water Column unit-of-measure standard to the Industry.

To cut to the chase... Hunters here in W. CO., and elsewhere, routinely run Wood Stove Flues up and out of Tents through metal sleeves in sheet metal squares. However, as with the Poster above, I'd skip using this Furnace in a Tent out of safety/fire concerns. Also, given the typical appearance of the Plenum, and Furnace age, it's not unusual for CO Gas leaks to occur in older Plenums through rust pinholes. This causes you to wake up dead. You can almost snag 2 'Little Buddy' Heaters with integral Oxygen Sensors on sale at end-of-Season for the possible repair $$$ you mentioned.

Pop the repaired Furnace instead into a larger volume, like a Tuff Shed, etc., if you want to muck with it 'just because', and have a working CO Detector installed. As a Guitar Repairman pal used to say, 'you can't polish a Turd'.
 

TBRV

New member
I worked for a tent trailer manufacturer in the early eighties. We didn't use coleman as it wasn't much of a furnace. The round cap on the front of the combustion chamber is where you stick the match to light the pilot. I don't remember seeing that model with a piezo lighter. The exhaust is an issue it needs lots of clearance from combustibles on the outside of the unit. That furnace will also take a lot of space on the interior.
 

Rubicon_Fan

Adventurer
Thank you everyone for great suggestions and help.

I was basically was going to do what you guys have advised,
I wanted to:

1.Modify enclosure box by blinding the front outlet and fit small stud piece of round pipe 2" or 3".
2.Use flexible heat resistant hose ( type you use for home laundry dryer or exhaust ) to supply air to your tent or wherever you want.
Fresh air will be sucked from right and left side of enclosure and blow around furnace into the hose.
3.Furnace will be inside ensclosure ,while combustion inlet air and exhaust from furnace burning will be arranged from rear of enclosure.
With smal 2" elbow I could lead exhaust straight up to prevent any suction of exhaust into fresh air supply.

I think It is safe. There is no chance of fumes entering fresh air supply. I could position furnace as far from my tent as long is my hose.
Furnace is light weight and easy to hook up for 12v or propane.

4. Temperature control

*Easy way,as is now. Short circuit everything: thermostat full blast, pilot on, adjust temperature by propane supply or by opening flap in the tent.
I know I will need to get propane main contrl valve working or buy new one,which can be about $150 an I will need thermostat to fit in the tent if I really want to adjust temperature from tent.LOL.

Bur after speaking to my best friend, my dad, we decided that it's too much, overkill for what we need. And it's too complicated. We are trying to keep my trailer as clean, simple as possible.
Anyways, just wanted to say Thank You one more time for your help and advice.







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