Solar Air Heater w/ Propane Backup/assist

[Off Grid Rving]

Hi guys, as you may know, I built a 6x8 travel trailer from scratch that I am living in for a year long project. it is now the winter months and I can see for myself how my options are fairing.

The 10,000 btu blueflame propane heater is keeping this place plenty warm. and only kicks on a minute or so every 20-30 min id say. on a thermostat.

the problem is when you burn propane it produces moisture. and quite a bit of it.

my solution.../idea

I bought this heater for only 10 bucks at a local barn sale last fall.

It has all of the parts I need to salvage and build my idea.

I want to build a solar air heating panel, similar to the popcan solar air heaters found on youtube. with some modifications of my own.

utilizing aluminum rain shoots instead of pop cans for a "factory look" and running a flue pipe inside the solar air heating panel,

I need to build an external burner chamber to mount the burner, pilot light, piezo ignighter assembly from this blueflame heater. and route the thermostat inside the travel trailer/Ogre.

in theory, it will be a dual "fuel" either sun rays or propane used to heat up the air inside the panel this inturn heats up the air inside the aluminum downspouts that feeds into the Ogre's living space.

it will provide nice dry heat day and night and supplement the use of solely using propane for heating during the daytime.

[Shadow Catcher]

I am not quite seeing how you plan on executing this. What I think I hear is a solar heater with propane heater grafted on to makeup heat when too cold or no sun...?
The problem as I see it is that unless you are getting some solar gain the propane burner will be either heating the solar collector, or losing heat from air passing through it, if you are using the down stream air from the collector.
I am kind of going through this exercise in trying to figure out how to supplement heat in Compassrose when off grid/boondocking and looking at the Espar/Eberspacher RV Propane heaters. The most fuel efficient lowest power draw appear to be the Espar/Eberspacher.
The main problem I see in building your own heat exchanger (Blue flame burner inside housing) is the risk of explosion, CO leak or burn through (over heat) and CO leak.
Commercial (Espar, RV furnaces) units have safeguards built into the electronics e.g. the Espar first starts the combustion fan to purge the combustion chamber it then starts the glow plug and injects fuel and if it fails to ignite shuts down, it will go through a number of cycles and if it fails five times will lock down and power must be removed before it will try again. With what you want to do you run the risk of an explosion and or CO death.
Used RV furnaces are available on Ebay for about $100. You can build a free standing housing hosed into your trailer.
I trust you already have a CO/fire detector?

[GPW]

OGRv , did you see this ... http://tnttt.com/album_ ... c_id=71947 I'm working on making one or two for my house... No fuel , no fumes , no moisture ... Easy enough to tie in an auxiliary heater...
Already doing Solar cooking ... working on water heating too .... Solar works for the simple stuff ... Still too expensive for making home electricity , but on a camper ...Hmmm???

[bobhenry]

I recently moved my A/C unit outside and see no reason a heater needs to take up precious interior room either. Perhaps using the small LP heater to warm the air in a larger insulated plenum and then let it enter the solar collector by natural convection or assisted by a small fan.
By mounting the thermostat remotely inside you could control the air temp most conveniently. If the solar gain satisfies the thermostat the heater would not even come on. A blue foam board insulated cover could be fitted to insulate the solar collector during inclement , non producing, weather and after dark.



There would be no reason a water coil could not be added in either or both cabinets to pre warm the water as well ! It may not be scalding hot but it would gather a good bit of warmth.

[bobhenry]

After looking at that pic a few minutes I had a thought.

We are worried about avoiding the musty smells that accumulates during off season storage. perhaps this little bare bones solar collector would help to eliminate the moisture build up that causes these problems. I know my clear roof adds enough heat I never have experienced that problem in the past 2 winter layups.

In fact on a sunny 23 degree day in Dec/Jan it is mid 50's inside the trailer.

[Off Grid Rving]

no risk of co poisoning in my design, I am moving the propane burner to the outside of the Ogre's interior air system. basically building a normal solar air heater, and running a flue pipe through the footer to heat the air via propane when the sun is not producing.

thermostat will be located inside the Ogre. so it kick on when the Ogre is not up to temperature.

[S. Heisley]

BobHenry wrote:

I know my clear roof adds enough heat I never have experienced that problem in the past 2 winter layups.

In fact on a sunny 23 degree day in Dec/Jan it is mid 50's inside the trailer.

...When you get tired of using it for camping, you can use it for a greenhouse and start your tomato plants in there!

(If it is 50 on a 23 degree day, I wouldn't want to be in it on a 100 degree day.)

[Off Grid Rving]

not the place to post this... but I really really want a full set of porter cable 18-volt cordless tools! heh

[bobhenry]

BobHenry wrote:

I know my clear roof adds enough heat I never have experienced that problem in the past 2 winter layups.

In fact on a sunny 23 degree day in Dec/Jan it is mid 50's inside the trailer.

...When you get tired of using it for camping, you can use it for a greenhouse and start your tomato plants in there!

(If it is 50 on a 23 degree day, I wouldn't want to be in it on a 100 degree day.)

And now you know why I have the barn as my summer / winter trailer of choice.

I stuck my head in the teardrop last july to retrieve something and noticed it was unbelievably hot and glanced at the thermometer on the wall it was pegged at 140 who knows how hot it really was ? We went camping this fall in it and I had a difficult time telescoping out the privacy pull out and when I got in I figured it out. It had gotten so hot in there over the summer it had sagged the 2 1/2 schedule 40 pvc and the 2" schedule 80 pvc leg of the pullout. It was drooping almost 4 inches.

NOW THAT"S HOT !!!!

[jimqpublic]

Not to discourage innovation---

If the Blueflame only goes 1-2 minutes every 20-30, that means it's burning only about a pound of propane per day. Even if it's double that it isn't much. How about just providing more ventilation and increasing the burn time? Would that reduce condensation or would the increased vapor output still be a problem? Seems an easy test.

When the kids and I camp in the winter we get a lot of condensation even though our furnace doesn't put any inside. Three bodies plus the stove so plenty. My solution is to keep the heat running while we're out to drive off moisture.

[Shadow Catcher]

What you are building is a heat exchanger and depending on how you do it it will be either a fairly efficient one or a very inefficient one. The Blue Flame is efficient because you are getting all of the heat inside, along with the products of combustion including moisture. With a heat exchanger your efficiency is directly related to how much is transmitted to the air to be heated and how much is waste heat that is vented, a finned heating coil will extract more heat than "Just a piece of pipe" an insulated plenum as Bob Henry suggested will increase that efficiency, running warmed air through your solar collector means you have a nice heater for the outdoors. A simple bypass cures that problem. And we are back to my original concerns explosion, CO etc. Propane combustion is much cleaner than gasoline combustion, though not as clean as natural gas combustion. The presence of C–C bonds, plus the multiple bonds of propylene and butylene, create organic exhausts besides carbon dioxide and water vapor during typical combustion. These bonds also cause propane to burn with a visible flame.
Yes you can do it and it will probably not kill you and it will probably work, but why risk waking up dead.

[tk]

I'm no HVAC expert by anyone's estimation but the original post here raises a question for me. You state, "the problem is when you burn propane it produces moisture." If everything is working properly, shouldn't the humidity be vented outside with the exhaust? Or am I missing something?

Best,
Tom

[Off Grid Rving]

this heater is not a vented model.