how to install a furnace in an enclosed trailer

summ8rmk · Jan 3, 2010

I have an Atwood 8535-ll furnace and an Interstate trailer. Where is the best location? How do I cut the hole in the side of the trailer, it needs to be approx. 17x7? do I need to frame the hole, is there a kit for mounting? What is the most economical and efficient ducting? Any help is greatly appreciated. Some pics would be nice.
Also is it OK to install the propane tank inside the trailer(up in the front of the V)? The tongue is only big enough for the jack, and the horizontal tanks are expensive.

Farmington Motorsports #9 · Jan 3, 2010

I just had a Suburban funace put in my Haulmark trailer. I found a used horizontal mount propane tank out of a motor home that was fairly inexpensive. Keep your eye on craigslist - they are frequently on there. Acutally here is a big 50 gallon tank:

http://spokane.craigslist.org/grd/1535151401.html

I mounted my 25 gallon propane tank in between my axles so it is protected - works very well and doesn't "sweat" inside the trailer. We also mounted my heater vertically instead of horizontally so it doesn't stick out so far.

turbolover · Jan 3, 2010

mounting

I have the heater and want to mount it up by the ceiling. I don't have room underneath for a tank and no room on the tongue either. What would be the draw backs of mounting a tank inside in the nose of the trailer?
yeah I know don't light it up before venting the place of any fumes, just in case. don't want to turn it into a bomb. and I could move it outside when parked for extended periods to keep any leaks and smell outside.

robertyoke · Jan 3, 2010

summitrmk said:
I have an Atwood 8535-ll furnace and an Interstate trailer. Where is the best location? How do I cut the hole in the side of the trailer, it needs to be approx. 17x7? do I need to frame the hole, is there a kit for mounting? What is the most economical and efficient ducting? Any help is greatly appreciated. Some pics would be nice.
Also is it OK to install the propane tank inside the trailer(up in the front of the V)? The tongue is only big enough for the jack, and the horizontal tanks are expensive.

i wouldnt mount the propane inside the trailer because then the regulator will also be inside the trailer and thats not good. if or when it leaks one spark and kaboom! keep looking on ebay they do come around for a good price, think of it like cheap fire insurance.

hole....hole saw, sawzall, skill saw with steel blade
do you have the heater that is removable/serviced from the inside or out? the outside one require a large hole the inside ones just the intake/exhaust holes which are a couple 2.5 inch holes you can make with a hole saw.

Polar Express · Jan 4, 2010

What robertyoke ^^^ just said about the furnace mounting.

I spend the better part of 15 years working on RVs.
If it's a typical RV heater (Atwood or suburban or the like) you should only have to cut a couple of small holes for the exhaust vent, the rest is accessed from inside.

Mounting the tank inside isn't a total no-no. The regulator is not supposed to bleed off. If it does, 1) you will smell the ethyl-mercaptan -the stinky additive they put in propane(http://en.wikipedia.org/wiki/Ethanethiol)- before the gas level reaches the LEL (lower explosive limit) and 2) the regulator has failed and should be replaced. It's a pressure regulator, not a blow-off valve. LP gas is heavier than air, so you can always buy a LP detector and put that on the wall, down low. CO (carbon monoxide) is equal or lighter than air, so, if you buy one of those, I'd put that close to the potential CO source (your furnace). Always check your fittings for leaks! (soapy water in a squirt bottle works great)

That being said, I'd still recommend that you find a ASME tank (the frame mount horizontal units) and put that on the frame, outside. While you're at it, plumb a "T" off, with a shut-off valve so you can have quick disconnect outside for a little travel BBQ, it's a nice feature, and you'll be glad you did. You could even mount an LP/12v fridge to keep the beverages cold!

There is no reason you can't mount your furnace high either. Build a frame out of aluminum angle, that will support the weight of the furnace (I'd suggest putting some pipe foam on the outside corners cuz' you will hit your head at some point.

You can use flexible ducting and aluminum ducting tape if you want to direct the airflow, but in an open space like a sled trailer box, you really don't need ducting, unless you are building a glove/boot/helmet dryer, or want to aim air at your clothes rack to dry your gear. If you want to do that, you can use ABS pipe, but the ABS glue can get hot enough that it will let the fittings slip, so just use some high temp silicone and a screw on each fitting. Make sure you support your new pipe structure well though.

Hope that helps,

PE

summ8rmk · Jan 5, 2010

thanks everyone.
the atwood furnace needs a17x7 in. hole in the wall because it slides through the wall from the outside and is completely serviceable through the access door on the outside.

Smoothlander · Jan 5, 2010

I will try to get pics up soon of how we installed our Atwood 8535 last month. The only hole we have is a 4" X 4" one for the exhaust and combustion air intake.

jsledder · Jan 5, 2010

Polar Express said:
What robertyoke ^^^ just said about the furnace mounting.

Mounting the tank inside isn't a total no-no. The regulator is not supposed to bleed off. If it does, 1) you will smell the ethyl-mercaptan -the stinky additive they put in propane(http://en.wikipedia.org/wiki/Ethanethiol)- before the gas level reaches the LEL (lower explosive limit) and 2) the regulator has failed and should be replaced. It's a pressure regulator, not a blow-off valve. LP gas is heavier than air, so you can always buy a LP detector and put that on the wall, down low. CO (carbon monoxide) is equal or lighter than air, so, if you buy one of those, I'd put that close to the potential CO source (your furnace). Always check your fittings for leaks! (soapy water in a squirt bottle works great)

PE

Good advice. But, I can tell you from experience, that you cannot always smell an explosive amount of LP. I was given a very scarey lesson in that one time when I had to fill a vacationing persons LP tank that had run out. Went in the house to check for fumes and didn't notice any, turned off the valve at the furnace while filling the tank and came back in to re-lite the furnace.... dont this hundreds of times, and as soon as I struck the ignitor.... KABOOM, dust came from every joint in the house and I thought I was a goner. Most of those regulator you put on the portable LP tanks say right on them not to use indoors, take the advice. If you get a newly filled bottle of LP and it's cold out, put it in the trailer and start the furnace and get it nice and warm, it can expand the gas and pop off the valve or the vent from the regulator can be enough to cause problems. My LP tank will be mounted on the tongue like a camper. I realize a lot of people have put them in trailers and garages and things like that for years and probably never had a problem, but 1 problem is all you need to have a very bad day.

If nothing else, get a long hose and set the tank outside. You only need about 10psi so regular hose barbs and hose clamps are enough, just check for leaks once the system is complete.

Smoothlander · Jan 5, 2010

Here is pictures of how we installed our Attwood 8535. The wood box in the front of the trailer houses a 20# propane tank and is sealed and open to the bottom to let out any gas. Behind the shield on the lower left hand side of the furnace is a flex exhaust pipe. The shield forces the furnace to take fresh air from the outside for combustion. I still have to fab a cover for the whole thing to protect it from damage.

summ8rmk · Jan 5, 2010

VINNEE said:
Installed the same furnace this weekend "Between the studs" and slid through the wall from the outside..... Took some modifying but it turned out good!

can you post some pics? i would appreciate it.

94fordguy · Feb 6, 2010

mmaxcarver · Feb 18, 2010

Smoothlander said:
Here is pictures of how we installed our Attwood 8535. The wood box in the front of the trailer houses a 20# propane tank and is sealed and open to the bottom to let out any gas. Behind the shield on the lower left hand side of the furnace is a flex exhaust pipe. The shield forces the furnace to take fresh air from the outside for combustion. I still have to fab a cover for the whole thing to protect it from damage.

I have one of those same furnaces but my exhaust is where you are saying you fresh air intake is??? Confused??

wiseguy · Feb 19, 2010

Here's how I mounted my heater and bottles in my trailer. I then have a cover that goes over the bottles and also have 2 2" vents in the floor.

Smoothlander · Feb 21, 2010

mmaxcarver said:
Smoothlander said:

Here is pictures of how we installed our Attwood 8535. The wood box in the front of the trailer houses a 20# propane tank and is sealed and open to the bottom to let out any gas. Behind the shield on the lower left hand side of the furnace is a flex exhaust pipe. The shield forces the furnace to take fresh air from the outside for combustion. I still have to fab a cover for the whole thing to protect it from damage.

I have one of those same furnaces but my exhaust is where you are saying you fresh air intake is??? Confused??

Click to expand...

The combustion air is sucked in on the bottom third of the furnace where the exhaust pipe is, the other two thirds is cold air return.

j_w10 · Feb 21, 2010

heater

so iwould like to put one of these heaters in my trailer as well was wondering if someone couldtell me how much they cost and were too get in in the calgary or med hat area

DUKHTR3 · Feb 28, 2010

I am in the process of buying a rv furnace and tank. How big of propane tank do i need? I now a 25lb wouldn't be big enough but how long would it last. I would need enough propane for 3 nights.

turbolover · Apr 4, 2010

HEATER INSTALL

WTF next posting

turbolover · Apr 4, 2010

HEATER INSTALL

This is my toybox about an hour after I picked it up

OK so I got my furnace installed.
It is an Atwood 8940 ACLC (110 AC 40,000 BTU)

I bought the heater off of EBAY. (didn't realize it was an AC model until after I bought it.) I've got an inverter so I can run it off of the generator or battery power.

I mounted it on some brackets inside mounted directly to the wall struts.

I just used a 2 1/2 hole saw and cut a hole through the sidewall. I used some prebent tubing to kick the exhaust sideways and vent it through the sidewall.

I had to get some starter flanges from STATE TRAILERS (local rv parts store, its awesome ALMOST as good as goin to a sled store) to hook up to the furnace box. It was setup for a floor duct. I made a closeoff plate and ducted it out through the sides of the case in the holes already made there. Just had to remove the round close off plates. You can see the aluminum close off plate on the left side and the starter flanges here.

I used some reducers (4" to 3") and some furnace duct 90* elbows I got at Lowes. Then I got some Plastic pipe (3") and hung it up with the white plastic carpenters strap. I used self tapping screws to hold all of the joints. (Not sure but have heard of the heat softening glue and having problems with the glued joints coming apart, so they are all screwed together)
I vented everything down to the floor and used 90* elbows to turn it and direct it across the floor. I also mounted my thermostat over by the door, that way I can reach in and turn it on without having to crawl over things to get to it. (Not too close don't want it to get a blast of cold air every time I open the door.)

I still have to make and mount some cabinets in the front. I plan on having a small tank that I can use for weekend sled trips and being able to drop the propane hose outside to be able to hookup to a big bottle for longer camping trips in the summer.
Its still a work in progress but WOW heat is nice. 40,000 BTUs will heat it up to 65* in a few minutes then it just cycles for a few minutes to keep things nice and toasty. I have a plug on the house I can keep the trailer plugged into but have a little 800W generator that will run the lights and heater. (already tried it out) I also have a bigger generator to run a fridge and everything else in the summer.

I'm open to suggestions on things if you can see where I need to improve something. So whada ya think guys?

Doc Zoom · Dec 8, 2010

Check out this video from Mountain Mod Mania's "Ultimate Trailer"
http://www.youtube.com/watch?v=WfxLJs2b2Us

sledjunky3 · Sep 25, 2011

I will be installing an 8535 this week and my trailer does not have room at the v as well because of the jack. what i was thinking was to take the top wind jack off and have another square tube jack welded to the side of the trailer tongue. Has anyone else gone this route? if i move the jack i think i can mount a single 30lb tank directly on the tongue and use some kind of bracket to hold it?

how to install a furnace in an enclosed trailer

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