Help, replacement furnace?

knjobrien5 · 11-23-2005, 12:01 PM

Our 31ft Overlander came to us with a very rusted and failing Suburban NT-30 furnace. A local RV shop told me a "New" NT-30 wouldnt fit and he wanted to put a new furnace that would require cutting a door into the skin. I quikly went and picked it up.

Any reason why I can't just order an NT-30 and place it back in? The old box measures the same as new advertised NT furnaces.

Anyone know why I can't upgrade to a NT-40? The 40 only draws a couple more amps.

I've searche old forums and havent found anything yet that answers these questions.

thanks

markdoane · 11-23-2005, 12:23 PM

knj,

The only reason not to use a NT-40 is higher propane consumption, and you need to add one more outlet duct and more return air grill area, in order to keep the temperature rise within specs.

You're handling 100 cfm more air flow.

knjobrien5 · 11-23-2005, 12:34 PM

If I installed the NT-34 would I also need to add another duct and more return air?

I've never been in the camper when the furnace worked and we will be using it in the mountains of New Mexico 6000 to 9000 ft elevations.

Is the NT 30 sufficinet for the size?

markdoane · 11-23-2005, 12:45 PM

You're ok with the N-34 if you have 3 of the 4" outlets discharging into open areas. With the N-40 you need 4 - 4" outlets.

The 'rule of thumb' according to the Suburban guy that was on "Classic Rides" a few weeks ago, is 1000 btu per ft of trailer.

knjobrien5 · 11-23-2005, 01:51 PM

thanks a bunch.

**Pick** · 11-23-2005, 02:41 PM

And remember a 31' Airstream actually has a 29' coach length, so a 30,000 BTU furnace should work just ducky!

knjobrien5 · 11-23-2005, 02:55 PM

so your saying no reason to change from the NT-30. OK

Was the guy at the RV shop full of it as I figured.

He was trying to tell me that the vent location on the new NT-30's is different than my old one. My old one has a crome plate with two vent tubes located one above the other. The new ones look just the same from the pictures Ive looked at. Is there any difference that anyone knows of with the new furnace from the old?

Thanks for everyones help so far.

j54mark · 11-23-2005, 05:58 PM

I would stay with the NT 30. The NT 40 would have to cycle on and off more frequently even if you run the extra duct.

I personally removed and replaced the original NT-30 with a new NT-30 in less than one hour. It is hard to imagine anything more simple in the world of Airstream repairs.

Mark

markdoane · 11-23-2005, 06:21 PM

Quote:

Originally Posted by knjobrien5

Was the guy at the RV shop full of it as I figured?

He was one of the anti-airstreamers who think we are all millionaires.

TomW · 11-23-2005, 06:54 PM

I believe I have a 22,000 Btu furnace in my 26' Overlander. If nothing else, it is the original furnace.

After last weekend's camping trip in slightly below freezing weather, I would NEVER replace that furnace with anything with more Btus. Setting aside the fact that my wife adjusted the thermostat after I had fallen asleep, I woke up sweating just before the furnace cycled off, and was peacefully asleep basking in the coolness before it cycled on. Say what you want about the thermostat, but the point is that the furnace had the heat to supply.

The point is that, if you plan to have a three-season Airstream, there is no reason to upsize your furnace. The small airspace in a travel trailer will result in larger temperature swings than your house will.

Four-season campers, especially in zero-degree climates, are the only people who might benefit from a more powerful furnace.

Tom

3Ms75Argosy · 11-23-2005, 07:24 PM

Hi, I just replaced my NT 22 with a NT30 (26ft trailer). It heats it fine. What IS different is this.... you will need to lift the new furnace about 1" higher to get the furnace ducts to line up with the outside...and my gas line for the new furnace was on the opposite side as the old one. I had my RV supplier make me a short copper line with flared ends (and nuts) to go from the one side to the other (just bent it to fit around the top of the furnace). The new furnace is slightly shorter (even being lifted up the 1") in height, and a tad shorter in overall depth.

Otherwise, it was a piece of cake (less than 2hrs total to replace)! I'd do it yourself.

I did have to buy an additional blankout for the furnace (it comes with one, I needed two). I didn't bother replacing the thermostat (my old one worked fine -it comes with a new thermostat).
Marc

tom3061 · 11-24-2005, 01:04 PM

I would like to replace the original furnace in 30 ft 61 model that has a old luver window in front. with 25000 BTU vent-free fireplace? I would appreciate an comments.

knjobrien5 · 11-24-2005, 08:30 PM

First let me say thank you to everyone for your input and help. I will be ordering a NT-30 and installing as soon as it comes in.

Ref the fireplace idea. I dont' know why it wouldnt work but maybe one of these other more knowledgable people will speak on this. My parents heat their guest house with a small gas ventless gas fireplace.

Darol Ingalls · 11-24-2005, 08:53 PM

Any vent-free heat propane heat source is going to add moisture to the interior of the trailer since propane gives off water vapor as it burns. Catalytic heaters do the same thing. This effect increases in cold weather and the result is "rain" from all the ceiling rivits and the windows all condense moisture. If you're considering a "fireplace" type of heater, check out the marine versions with a vent. They are pretty efficient and have the moisture problem under control. The advantage of the forced air furnaces is the dryer heat they produce. The disavantages are the hot exhaust wasted outside and the electricity it takes to run the fan. I prefer bigger propane tanks and extra batteries over inside rain. Darol