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Old 12-03-2015, 01:58 PM   #1
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Furnace replacement for 1971 Globetrotter

Hi, this is my first post...
I own a 1971 Globetrotter. It's 21 ft long with the interior of the cabin at about 17 ft. As you can imagine there is very little (if any) insulation so the heat loss is quite high.

On that note, I'm in need of a new furnace. The current model, that is no longer working properly, is the NT-16F (no longer available from what I can see). The BTU rating is 16000.

I am considering installing a new furnace, the NT-20SQ which has a BTU rating of 19000. It looks like an obvious choice. That said, I am planning on using the trailer through the winter as an onsite office and occasional crash pad. With the sub zero temperatures in these parts I am debating whether or not I should consider a larger furnace - thinking of the NT-30 SP.

I'm not sure if I am missing any obvious considerations.

Any advise on which furnace would be the best choice, including any I haven't considered, would be greatly appreciated.

FYI, I also have shore-power of 30 amps so I can use a space heater if necessary.
Thanks
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Old 12-03-2015, 02:21 PM   #2
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If you are not paying for electricity, the space heater is the obvious choice. Due to the minimal insulation and high thermal conductivity of your trailer, heating it will be costly and you will burn a lot of propane in sub zero temps.
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Old 12-03-2015, 02:40 PM   #3
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The various forced-air furnaces have minimum outlet area requirements... without some mods I'm guessing you don't have enough vents/outlets in the trailer now to meet the requirements for the NT30 which is big enough for a large trailer, it's only the longest couple of models that get multiple furnaces. For having propane heat it'll probably be best overall to go with the NT20 or maybe one of the alternate brands. The NT will fit right up to the existing exhaust/intake holes in the outer skin, though it may require you to build a base for it if the new case is a different shape than the old.

You should be able to find the duct/outlet area requirements for each model at the manufacturer's website to get a definitive answer.
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Old 12-03-2015, 06:09 PM   #4
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The NT 20 will work out fine in the small trailer you have.
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Old 12-03-2015, 06:23 PM   #5
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In my 71 25' Tradewind I replaced the old furnace with an NT30. You may have to make some modifications so that the new furnace combustion air and exhaust holes line up with the corresponding furnace holes.

For sub zero I don't know if a NT20 has enough juice for winter weather. In any event you will burn a lot of gas and have to address condensation issues inside the trailer.
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Old 12-03-2015, 07:09 PM   #6
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My son just installed an Atwood 7916 in his 67 20' GT. It's a great compact furnace, replacing the original one that was much bigger and heavier. Jim


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Old 12-04-2015, 08:39 AM   #7
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Thanks for the great info. With the advice I've read, before committing to the NT 20 (which seems to be a better choice over the NT 30) I will look at the Atwood brand. In addition to having the furnace and space heater, I am installing a 2ft X 4Ft 800 watt infra panel on the ceiling. Infrared heat might keep some of the condensation down but will have to wait and see. Thanks for bringing condensation to my attention - no doubt it will factor in and will need to be addressed. Thanks again!
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Old 12-04-2015, 01:27 PM   #8
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I am installing a 2ft X 4Ft 800 watt infra panel on the ceiling.!
Sounds interesting can you post some more info.
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Old 12-04-2015, 02:47 PM   #9
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If you have 30amp power, is your AC capable of having a heat strip installed as a supplemental heater?
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Old 12-04-2015, 03:26 PM   #10
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Not sure if a heat strip can be installed aftermarket, but 30 amps will run it.
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Old 12-05-2015, 11:21 AM   #11
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The infrared panel I plan to install is the "Base IR200 - 800 Watt Standard Heating Panel" which can be seen at irheating.ca.

I have a clean 30 amps running to the trailer. Currently I am using a small space heater that has the typical settings of 750 & 1500 watts. It works well at either setting. I am also powering other small electronic devices and lights. So far no problems with power.

There is just enough room on the ceiling next the AC unit to mount the 2ft X 4ft infrared panel. There are optional mounting brackets for the ceiling but I am reluctant to drill into the interior. I have an approach I believe will keep the original interior intact without drilling holes.

Once installed I'll post some photos. Cheers
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Old 12-05-2015, 07:56 PM   #12
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Hi Fraser and welcome to Air Forums. It's a great place to get advice from experienced Airstreamers who have likely done what you want to do.

It will be challenging to keep your Globetrotter warm in sub zero degrees C temps. Old Airstreams are not as well insulated as the new ones, and Airstreams are not the greatest cold weather campers around.

Here is my story. I installed a NT30 in my 1966 24' Trade Wind. The installation instructions are very specific on the amount of vents you must use to exhaust the hot air, and getting cool air back to the furnace. My old trailer had this strange system from the factory where cold air was drawn to the furnace via floor vents and ductwork under the floor. The hot air exhausted out one big vent in front of the furnace. I did not want to install a flexible above floor 4" vent through the cabinets and under the bed beacuse I loose valuable storage space.

So I decided to reverse the hot air flow. I delivered hot air to the floor ducts and floor vents via an underfloor plenum, and draw cold air into the furnace cabinet in the galley. I also had to heat my under the floor waste water tanks. So I had lots of places to vent hot air. Bottom line is my system is inefficient, but it keeps the trailer warm, including the rear bath.

A new furnace install is a fun project. Maybe you can read the installation instructions on line to insure the NT20 or Atwood will work okay in your Toronto winters.

David
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Old 12-05-2015, 08:28 PM   #13
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Quote:
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It will be challenging to keep your Globetrotter warm in sub zero degrees C temps.
David
Being in Canada I would guess Fraser is talking about sub zero fahrenheit not celsius which is a whole other kettle of frozen fish.
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Old 12-06-2015, 09:36 AM   #14
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Hi David, thanks for the additional info. I realize heating the AS in the dead of winter, especially up here in Canada will be a challenge. The subzero temps can be as low as -25Cº but usually not much lower than -15Cº.
I am leaning towards installing the NT20, which as I mentioned is an upgrade from the current smaller model, NT-16F.
The pics of your NT30 installation are very helpful. Based on your approach I might be in a position to consider something similar when the warmer weather permits a more elaborate retrofit.
My Globetrotter has a duct system already in place. It needs to be reworked as there are many gapping holes and other deficiencies to address. All things considered I will likely simply do a straight swap if the new NT20 allows.
I'll be sure to read the installation instructions as you suggest. Thanks
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Old 12-06-2015, 03:25 PM   #15
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I lived in beautiful Minnesota for 25 years and learned all about cold winters. It gets so cold that you can take a hot cup of coffee outside and throw the liquid up into the air. It will all freeze before it hits the ground. The ice on the lakes was 2' thick. My Airstreams sat in the yard from November until April. Too cold and icy for me.

Good to know your Globetrotter has hot air ductwork from the furnace already installed. Maybe there are three runs of ductwork? My 86 Limited has 4" round flex ductwork installed. One run goes to the center bath, and one goes to the water tanks under the floor to keep them from freezing. The others spill out into the living areas.

This summer we moved to Colorado. We are at 8300 feet above sea level, much closer to the sun, but less atmosphere to hold the heat in. It's warmer here. My son has a 69 Globetrotter that he takes snowmobiling in the mountains. He says he stays warm, but I wonder what his definition of warm is.

Get the specs and installation instruction on the furnace of your choice and see what happens.

David
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Old 12-06-2015, 04:25 PM   #16
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size doesnt always matter with furnances.

I lived in Idaho winters in a 69 31 foot soveriegn. It had a 30k btu furnance that worked fine with water flowing through system constantly. I am currently restoring a 1966 24 foot tradewind (20' box) in the western mountains of North Carolina and am replacing a 50 year old 20k btu system with a 19k btu system. My only concern about the 19k btu system is that the air flow is too low. It uses a fan versus a squirrel cage air mover for the 30k btu model. I will let you know if the 19k works.
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Old 12-06-2015, 04:39 PM   #17
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Hi geodazed. You mentioned 66 Trade Wind so I had to chime in. I've had mine 2 years now. I "fixed up" mine, restoration is not the right word. But I have enjoyed working on the thing all these hours. Paying the bills for parts and supplies wasn't as much fun.

After replacing a rotted through rear bath floor and all the appliances I have the trailer "travel ready". The NT30 furnace moves air in the underfloor ducts adequately. I have not tested it in freezing weather yet.

I'm always glad to meet another vintage Airstream enthusiasts and compare notes. I'll post a coule of pictures later as Air Fourms isn't working for me right now. "503 service error" what ever that is.

David
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Old 12-06-2015, 06:46 PM   #18
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Quote:
Originally Posted by Fraser View Post
The infrared panel I plan to install is the "Base IR200 - 800 Watt Standard Heating Panel" which can be seen at irheating.ca.

I really like this idea for when one has shore power. It will provide heat, help eliminate condensation, and it is quiet. My little electric heater with a fan does an adequate job of keeping the bedroom area warm on a 30' but we don't like the noise. The heat pump is just plain obnoxious. Thanks for the info. Jim


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Old 12-06-2015, 07:34 PM   #19
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Here is why we install furnaces in our Airstreams. Looks like a fun time, doesn't it. It is a 69 Globetrotter. I'm more of a fair weather traveler myself.

David
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Old 12-08-2015, 06:19 AM   #20
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Quote:
Originally Posted by dbj216 View Post
Hi geodazed. You mentioned 66 Trade Wind so I had to chime in. I've had mine 2 years now. I "fixed up" mine, restoration is not the right word. But I have enjoyed working on the thing all these hours. Paying the bills for parts and supplies wasn't as much fun.

After replacing a rotted through rear bath floor and all the appliances I have the trailer "travel ready". The NT30 furnace moves air in the underfloor ducts adequately. I have not tested it in freezing weather yet.

I'm always glad to meet another vintage Airstream enthusiasts and compare notes. I'll post a coule of pictures later as Air Fourms isn't working for me right now. "503 service error" what ever that is.

David
Hi David
Thanks for the reply. Great to hear about your tradewind rebuild. I loved the nt30 in my current tradewind. I still have 2 nt30s if you need them. One works great and the other is for parts. When I rebuilt the frame I had to rebuild the collection boxes for the subfloor duct work. Mine were set up as return flow for the furnance, one return vent in the rear bath and the other return under the front couch near the water tank. My nt 30 was a direct discharge unit with a return air metal collar around the unit housing.
I am installing the fridge cabinet at the moment, then kitchen cabinet with new nt 20 which will go under the stove. Will send you photos if you send your email. Mine is jpitt52@frontier.com
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