Small RV furnace for cab heat.........

[linrick1]

I'm not familiar with that heater but it looks interesting. If there's some way to control the output (fan speed, fire level, etc) I'd test drive it in cold weather before swapping to a smaller orfice.

The heater I have is rated at 20,000 BTU's and there have been a few days that I was glad to have that output. I can vary the heat output via the fan at OFF/LO/HI speeds and by regulating the valves for water flow.

Morning, Chim. I believe that the furnace requires a certain minimum airflow for both combustion and to keep the exchangers from overheating so a variable speed fan is out. I need to keep the same gas pressures and volumes to maintain a good burn so I can't alter those either. I am hoping to locate a non mercury switch type thermostat to control the temp in the cab. It isn't terribly difficult to change the orifice so perhaps I will leave the stock one in and see how that works before I install the smaller one. I have to say I hope this works as well as I think it should because as you said, it will be a real pleasure snow blowing in a heated cab....Thanks for the interest and input, Rick.

 

[Colonel Monk]

I think using one of these is a fine idea. They can be finicky though, be forewarned....

The electric ignition units require the fan to start up and sometimes they run a few minutes before they start - basically there's a switch called the "sail switch" which must be blown by the fan to tell the control the fan is working, then the valve opens, some seconds later it will try to light.

The tricky part is that when this isn't working, in an RV you basically have to remove the **** things and disassemble to get to these parts, like the sail switch.

I recommend that you clean it before you install so you're not having to remove it if you have an issue.

FWIW, I think that you could do pretty well also with a catalytic heater, like the Lil Buddy or the Coleman black cats, or whatever.

But with some creative ducting I suppose you can keep your windshield clean and all with the RV one.

Our old plow jeep hasn't had working heat in years. Still not too bad in there.

good luck, take pictures!

 

[pat32rf]

My first real RV had a furnace that did not need voltage. It was designed as a convection unit and the hot air just came out the top vent. Later on the same units came with fans, safeties, electric ignition etc....
I once saw an aircooled engine that had 1/4? inch copper lines wrapped around it. This line was filled with light oil that got pumped thru a small rad by an electric fuel pump....Looked good but I never saw it working in the winter...

 

[pat32rf]

My first real RV had a furnace that did not need voltage. It was designed as a convection unit and the hot air just came out the top vent. Later on the same units came with fans, safeties, electric ignition etc....
I once saw an aircooled engine that had 1/4? inch copper lines wrapped around it. This line was filled with light oil that got pumped thru a small rad by an electric fuel pump....Looked good but I never saw it working in the winter...

 

[linrick1]

Made some progress on the heat project. I have been acquiring material and parts for the past couple of weeks and today began actual construction. First I made an adapter to go from the 4" by 4 1/4" square furnace outlet to a 4" round 90 degree duct. This will enter the back of the cab and connect to a T, splitting the airflow into two ducts, one to my feet and one along the roof of the cab aiming toward the windshield. Next was the furnace mount itself, which I fabricated from some light angle and is bolted through the back of the cab. For the body of the enclosure I had a piece of 16 gauge bent on a brake to a 90 and will use this as the top and front. The bottom, rear, exhaust end panels, and intake end ducting will be fabricated out of 16 gauge sheet as well. Here are some pics of todays events. Thanks for your input and interest, Rick

 

[linrick1]

Made a little more progress on the body of the furnace housing. Fabricated the panels and hood yesterday and will bring the whole shooting match to work tomorrow so I can weld it up. I still have to cut the holes for the hot air duct and for the exhaust. Not sure if it is clear in the pictures but the idea is to draw the intake air in from underneath, around the baffle and over the exhaust elbow in an attempt to minimize the amount of snow that reaches the furnace itself. Still have to cut the hole in the cab and run the ductwork, wire the thermostat, and make the propane tank mount - sooner rather than later 'cause this morning I woke up to snow on the deck...........Thanks for the input and interest, Rick

 

[Travelover]

I think this will work, well. If fact it will almost work too well, unless you can de-rate it. Nice work!

 

[linrick1]

I think this will work, well. If fact it will almost work too well, unless you can de-rate it. Nice work!

Thanks. I can de-rate it to 9K BTU's if necessary - temperature control and airflow are what I'm trying to figure out. It's going to take a balance between all of it to get it to run as evenly as possible, minimize the on/off cycles and maintain an even cab temp. The furnace moves a decent volume of air at I think enough velocity to still be effective when ducted.......I come out of the furnace to a 4" 90 which will be close coupled to a 4" tee with opposite outlets reduced to 3" then through 3" flex duct to the windshield and footplates - all of which still has to be made and installed. I hope this will work well, I think it ought to, but I think there is going to be a fair amount of tweaking involved before this thing runs the way want it to.

 

[chad22]

Cool idea there. I installed an rv furnace in my little camper and boy did it work. It worked too good. lol

It was over powered for the little camper but that was alright with me. Better to be roasting than freezing.

 

[dieselbeef]

yer gonna fry in that little cab with that..