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Old 05-15-2014, 10:11 PM   #1
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1970 27' Overlander
Belmont , California
Join Date: Mar 2013
Posts: 49
NT-30SP or NT-20SQ for Overlander

Hi, I'm remaking my kitchen cabinets and have already junked the old rusty and dead NT22 so I have free choice of a new furnace.

Based on the advice of 1,000 BTU per ft of living space it seems like the NT-20 is about right.. but it only has side ducts. If I want to replicate the original flat ducting with a plenum I'd need to go for the NT-30 that has a bottom duct.

Any advice, pros / cons of either installation? Am I underspec'ing at 1,000 BTU per ft?

Alex
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Old 05-16-2014, 06:08 AM   #2
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1986 34' Limited
1966 24' Tradewind
Conifer , Colorado
Join Date: Jun 2009
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I replaced the furnace in my 66 Trade Wind with a NT-30. I configured this furnace to blow warm air down, under the floor. I'm sure this will be inefficient, but the NT-30 has the capability to make up for it. The original Trade Wind furnace routed warm air out the front, and then collected cool air return through under the floor ducts in the bathroom and under the gaucho. I reversed this method of heating, warm air under the floor ducts, and cold air return to the front of the furnace.

Suburban requires 3 of the 4 four inch round exhaust ports be used to keep the furnace from over heating. This is roughly 36 square inches of warm air exhaust. I did not want to run 4" round duct work throughout my trailer as I would quite a bit of storage room. So I purchased the bottom ducting kit (4 by 10 square or 40 square inches) and blow into a plenum under the floor and then routed three 4" round ducts under the floor to the living room, bath room, and waste water tank compartment.

I have yet to test this new furnace arrangement other than to verify I get decent air flow out of the ducts.

I have had good luck with the Suburban NT 30. It seem quite reliable and long lasting. Your Overlander is the next size up from my Trade Wind. You will have the capacity to stay warm on cold mountain mornings.

David
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Old 05-16-2014, 06:24 AM   #3
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1993 21' Sovereign
Colfax , North Carolina
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The reason you want more BTUs in a furnace is that you also have a duct going to the holding tanks to keep them from freezing. An NT30 or NT32 would be good for your Overlander.
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Old 05-16-2014, 10:03 PM   #4
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1970 27' Overlander
Belmont , California
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Interesting, I hadn't thought of running the air under the floor. I'm just at the floor up stage relocating tanks and will give it some thought.
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Old 06-01-2014, 05:50 PM   #5
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1969 27' Overlander
columbia , Illinois
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How much modification do I need to do on my 1969 Overlander if I buy a NT 30 SP?
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Old 06-02-2014, 05:26 AM   #6
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1986 34' Limited
1966 24' Tradewind
Conifer , Colorado
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It will be a sizable project.

I had to modify the galley cabinet, Make a shelf for the furnace to sit on so it lined up with the exterior opening, make new interior aluminum pieces around the furnace, alter the exterior aluminum for the new combustion air exhaust and intake, configure the ductwork, change the propane line routing, change the thermostat, and lengthen the 12v wiring.

It's a sizable project.

David
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