Operating Airstream furnace in closed garage

[Lee_G]

I have a 19' Flying Cloud that I would like to use as a fixed cabin most of the time, but retain the capability of using it on the road when I like. I have an all-metal RV barn that measures 24' x 30' x ~16' tall, with a heated room inside that. The barn is at 8500' in the Colorado Rockies, and probably reaches low temperatures of -25 degF. It has large (16' x 12'), insulated panel type garage doors on each end to allow drive-through with the trailer, but the doors do provide some air leakage. The barn includes a small heated room, about 7' x 22' x 8', to house the well water tank, sink, toilet, and batteries and inverter for the 1.6-kW solar system. All water lines, even across the barn, are underground at 5' depth, with an outside, frost-proof hydrant to supply water to the trailer.

I would like to use the Airstream on occasional weekends throughout the year without having to heat the uninsulated metal barn, at least not full time, and without winterizing the Airstream. I wonder about attaching either a single exhaust pipe with a flexible coupling to exhaust the furnace outside the building, or a coaxial set of tubing for both fresh air intake and exhaust. Exhausting horizontally would only require a 4' extension, or vertically about 14'. Of course, this approach would not allow the use of the hot water heater that appears more difficult to attach an exhaust line to.

Has anyone had experience connecting to the furnace exhaust system, and exhausting outside of an enclosed space.

[DaveP]

How about just using electric heat when you need it?

[OTRA15]

I would guess that your barn has sufficient air flow to us the AS without ducting to the outside, particularly if there is any wind. You could install a roof or sidewall vent to exchange air, like airtight solar homes have, to make this a certain thing.

If your interior low temperature gets below freezing, however, at some point you will have to winterize the trailer, or risk freeze-ups and pipe damage. Your figure of minus 25 was an exterior temp I guess? What is the lowest interior temp on a cold night?

Also, as Dave just said, why not heat with electric portable heaters, and use electric to heat the water too? Is your service big enough for this?

Sounds like you have a perfect setup! Do you rent out space for other Airstreams?

Cheers,

Peter

[Lee_G]

Originally Posted by OTRA15

I would guess that your barn has sufficient air flow to us the AS without ducting to the outside, particularly if there is any wind. You could install a roof or sidewall vent to exchange air, like airtight solar homes have, to make this a certain thing.

If your interior low temperature gets below freezing, however, at some point you will have to winterize the trailer, or risk freeze-ups and pipe damage. Your figure of minus 25 was an exterior temp I guess? What is the lowest interior temp on a cold night?

Also, as Dave just said, why not heat with electric portable heaters, and use electric to heat the water too? Is your service big enough for this?

Sounds like you have a perfect setup! Do you rent out space for other Airstreams?

Cheers,

Peter

It is a nice setup, but I made the heated room a little too big, and may not have room for the Kubota RTV as it is, so not enough room for another Airstream! I assume that the interior temperature of the metal building will be similar to the exterior temperature on a cold night, maybe -15 degF inside and -25 degF on the outside.

The RV barn is off-grid, and has only a small solar-electric system of 1.6 kW peak power. It should collect about 150 kW-hr per month in the worst (and coldest) month (December). I have assumed that solar PV system it is too small to heat the RV barn, but I need to go through the numbers and see if it would heat the Airstream alone using electric resistance heat. The Airstream does not seem to be well insulated, but maybe I could throw an insulating blanket over it, leaving open the areas that need to be open. Anyone know the insulation thickness in the walls of a 2016 Airstream. While I am not there, I only need to keep the water from freezing, and while I am there, I could provide ventilation as needed based on a CO alarm.

I could also consider heating the whole barn with a propane furnace to just above freezing, but that would require spraying in some insulating foam, which is a possibility. I will have a 500-gal. propane tank installed soon.

Thanks for the ideas.

Lee

[Protagonist]

Burning propane makes less carbon monoxide than burning just about any other fuel except pure hydrogen. But it's still not a good idea to run the Airstream's furnace inside a garage. If your furnace depletes the oxygen in the garage by even a small amount, the CO production goes way up because you have less-complete combustion. No garage is airtight, but people die of CO inhalation in enclosed garages anyway.

I won't tell you not to do it. But if you do, then mount at least one CO/smoke detector inside the garage near the ceiling, and an LPG detector in the garage near the floor. And every time you go to the barn to visit your Airstream, open the big garage doors to ventilate the garage for several minutes— longer if either detector is sounding an alarm when you open the door— before entering.

And for the record, I recommend the detectors for the garage even if you do run an extended exhaust pipe from the furnace through the roof or through an outside wall. Leaving any fire unattended in an enclosed space, even a small furnace in a very big barn, calls for at least that much precaution.

[OTRA15]

Thanks for the reply Lee. Here is a recent thread about CO winter AS use, with other older threads linked in Post #7 there. It is a tougher row to hoe than most realize IMO:

http://www.airforums.com/forums/f48/...am-170763.html

Among other reasons, the exterior walls are fairly thin, and the R-value probably around 6-8, but don't quote me. There is quite a bit of thermal loss because the aluminum ribs are connected to both the outer and inner skins with no thermal break. Condensation from water vapor is another major problem with the single-pane non-insulated glass in the windows.

Good recommendations in Protagonist's post for CO and propane detectors.

Good luck.

Peter

[Lee_G]

Originally Posted by Protagonist

Burning propane makes less carbon monoxide than burning just about any other fuel except pure hydrogen. But it's still not a good idea to run the Airstream's furnace inside a garage. If your furnace depletes the oxygen in the garage by even a small amount, the CO production goes way up because you have less-complete combustion. No garage is airtight, but people die of CO inhalation in enclosed garages anyway.

I won't tell you not to do it. But if you do, then mount at least one CO/smoke detector inside the garage near the ceiling, and an LPG detector in the garage near the floor. And every time you go to the barn to visit your Airstream, open the big garage doors to ventilate the garage for several minutes— longer if either detector is sounding an alarm when you open the door— before entering.

And for the record, I recommend the detectors for the garage even if you do run an extended exhaust pipe from the furnace through the roof or through an outside wall. Leaving any fire unattended in an enclosed space, even a small furnace in a very big barn, calls for at least that much precaution.

Actually the carbon monoxide (CO) problem is likely much worse than what you might have if you duplicated this experiment in Louisiana. Since my property is at 8500', the air density is about 72% of that at sea level. I don't know the fuel-air ratio the furnace is normally designed to operate at, but I assume that the combustion is occurring at 39% richer than it would at sea level.

I agree that having CO and propane detectors will be required if I run the furnace to keep the plumbing from freezing.

[Lee_G]

Upon further thought, the CO problem is probably not as bad as I have suggested. I assume the furnace burns as a diffusion flame with excess air. I just don't know exactly how much excess air that it is designed with, so the extent of the CO problem is unknown to me.

[Protagonist]

Originally Posted by Lee_G

Upon further thought, the CO problem is probably not as bad as I have suggested. I assume the furnace burns as a diffusion flame with excess air. I just don't know exactly how much excess air that it is designed with, so the extent of the CO problem is unknown to me.

A quick look — if you can actually see the flame— will tell the tale. If it burns blue, you're good. If it burns yellow, you're getting incomplete combustion.

[Ted S.]

I think I'd play it safe. You never know.

So my Airstream is in a metal warehouse space minimally insulated/heated to 40 degrees F with propane infrared heater. Not expensive at all and well worth it. I can work on it and wash it all I want. Does not use much propane and it is a 22' x 60' high bay space. Heater is on the ceiling.

[dandraws]

good suggestion . . . (AS Forums needs a LIKE button similar to Face Book).

[Lee_G]

Originally Posted by Protagonist

A quick look — if you can actually see the flame— will tell the tale. If it burns blue, you're good. If it burns yellow, you're getting incomplete combustion.

Yep, good suggestion. I am not sure how easily visible the flame is, but I will check into it.

Lee

[Lee_G]

Originally Posted by Ted S.

I think I'd play it safe. You never know.

So my Airstream is in a metal warehouse space minimally insulated/heated to 40 degrees F with propane infrared heater. Not expensive at all and well worth it. I can work on it and wash it all I want. Does not use much propane and it is a 22' x 60' high bay space. Heater is on the ceiling.

That is interesting that you can minimally heat that large a space without sucking down too much propane. You are slightly warmer in Massachusetts than I am in the Colorado mountains, but I get a lot more sun that does provide some heat to my barn. I am a bit of an energy Nazi, so I hate to use more than absolutely necessary. Heating the whole RV barn to 40 F would definitely solve the freezing problem, but that would still leave me with a problem when I am staying in the Airstream and want a higher temperature. At those times I could add some ventilation and fire up the furnace. Life is a series of choices.