DIY Direct Vent Heater?

[Locutus]

Hi everyone. First post here. First let me just say what a great discovery I found this site to be. And the most active forum I've ever seen!

So anyway, I've looked through this Propane section looking for options for economical heating solutions that don't require electricity, don't consume cabin oxygen, don't spew CO, CO2 or water vapor into the cabin, and are either cheap to buy or straightforward to build. But I couldn't find what I was looking for. Maybe such a thing doesn't exist. So that means it needs to be invented....

The only commercial product I've found so far, which meets all the above criteria except price (about $400), is made by US Stove:

Ashley AGDV8L Direct Vent 8,000 BTU Heater LP Propane Gas


The runner up to this would be Sig Marine's Cozy Cabin heater. But it's more expensive (about $500) and uses cabin oxygen to fire the burner, while venting the exhaust up a 1" chimney.

Cozy Cabin Heater


On the other hand, the Cozy Cabin Heater looks like it would be easier to hack a redneck DIY clone, and one could argue that one could also simulate direct venting by running a PVC pipe from the outside to a point near the burner.

Both of these heaters are overkill for a TD or TTT with the Ashley putting out 8000 BTUs (albeit thermostatically controlled), and the Cozy putting out 5000 BTUs (no thermostat, manual operation). I wouldn't put either in a TD, but maybe a larger standie TTT.

I'd like to find for sale, or a DIY design that puts out about 3000 or 4000 BTUs and can be built for about $50.00. I read an Instructable recently that makes an outside unit out of two mailboxes and pumps cabin air around the smaller one (inset into the larger one.) That's fine as far as it goes, but a bit redneck for my tastes. (No offense intended towards rednecks, who are by and large fine upstanding folks.)

The guy who designs and builds portable homeless shelters (forget his name, sorry), came pretty close, using #10 coffee cans and tealight candles.

I envision an indoor unit, scalable to the interior volume, which takes up little space and costs little to build. Something that uses a single propane stove burner (like the Cozy Camp heater does), with a means to draw outside air for combustion, running the flame heat over some kind of dry air heat exchanger, and then purging the exhaust out a side or roof flue. Consider this a challenge to find or invent something that has the potential to benefit this entire TNTTT comunity. Please post your ideas here. I'll put on my thinking cap as well.

[KennethW]

I just did a propane radiant heater that replaces my Wiley window pane. It is fully vented work like the radiant tube heater on my former TD. In runs a propane flame from outside the TD into a big dog dish and outside with the exhaust. The dog dish radiance's the heat into the TD.
It is based on this design but fits in the window opening.
viewtopic.php?f=2&t=58648&hilit=radiant&start=45#p1061891
If there is interest in it. I will take some pictures and go into the details.

[Locutus]

That's a pretty interesting concept Kenneth. Pretty innovative. Is that automotive exhaust pipe you're using? Any idea of fuel consumption per hour?

Fixed your link:
viewtopic.php?f=2&t=58648&hilit=radiant&start=45#p1061891

My critique:

Pros--
Simple to build
Inexpensive parts
Looks like it can use a variety of propane bottles.

Cons--
Looks like you would burn yourself on the pipe if you touch it.
Must be assembled for each use.
Controls are outside.
Sticks out of both sides of the TD, at least a foot on each side?

[KennethW]

That's a pretty interesting concept Kenneth. Pretty innovative. Is that automotive exhaust pipe you're using? Any idea of fuel consumption per hour?

Fixed your link:
viewtopic.php?f=2&t=58648&hilit=radiant&start=45#p1061891

My critique:

Pros--
Simple to build
Inexpensive parts
Looks like it can use a variety of propane bottles.

Cons--
Looks like you would burn yourself on the pipe if you touch it.
Must be assembled for each use.
Controls are outside.
Sticks out of both sides of the TD, at least a foot on each side?

I used electrical conduit.
The pipe is up high so there is a minimum chance of getting burned. One can put a guard on it.
The pipes on the outside is removed when not in use.
I just use the windows and roof vent to adjust the temperature. One can also have a regulator by the tank and open the door to adjust the heater.
Gas use would be about the same as a table top grill on low.

My second teardrop uses a big stainless steel dog dish glued to a piece of cement board that fits in the window opening, rather then the pipe. The heat from the flame goes from the outside in to the dog dish and exit back out side. And yes it could use a guard.
I really need to get some pictures and post them of the full vented Dog Dish Radiant Heater.

[Locutus]

Kenneth,

I think your basic idea is a good one. I also think it could be refined to have the burner and controls be inside, drawing air from outside and sending the exhaust out the flue. That might require a bit of welding and some baffles, and a way to pull the heat out of the baffles.

When I get a chance I'll head down to West Marine and have a close look at their cabin heaters. If I can get a glimpse of their guts I might get some inspiration from them.

[KennethW]

I did try to make it as easy to put together as possible. So that most anyone could do it. It is hard to find a small fully vented nonelectric heater. If you have any questions post them.