Propane vented radiant tube heater

[rowerwet]

I would second the gas pilot light set up for keeping the flame safe. a soldering torch is meant to only be used when you are hands and eyes on the torch. Gas water heaters with a pilot light (also gas floor furnaces) have a thermocouple that sticks into the pilot flame, if the flame goes out, the thermocouple shuts the gas off. thermocouple pilot lights are UL listed and required for safety on any gas appliance with a pilot today. Many of them also incorporate an Oxygen sensor, f the O2 level drops below safe the flame goes out.
Don't forget, you will be running the heater outside in the wind where it will be much easier to blow out.

[KennethW]

People don't seem to understand the inventors spirit. Don't listen to the nay-sayers. Educate yourself and try your ideas in as safe a manner as you can.

One thing to think about is the fact that propane is about 1.5 times heavier than air. If for some reason your torch blows out and the propane valve stays open will your tube vent out the unburned propane? If the tube happened to be filled and you tried to re-ignite, the results may be a bit surprising to say the least.

Be careful and have fun.

The tube is open at both ends. one side has the burner . Which is a coupler with a torch in it. the other end will have a elbow to increase draft.
If the flame get blown out the draft will clear the pipe. Unless you park in a hole with no wind at all(bad any time if it rains) any gas leak with blow a way. Unlike most heaters ALL the propane gas and gas components will be out side the camper. As for clearances the dog dish thimble thru the wall will provide at least 2" of vented clearance and at least 4" from the ceiling with a reflector heat shield in between.
A alarm is always a good ideal.

[Mojave Bob]

Hmm... I don't think you intend to be talked out of it, but I gather that you are open to ideas to improve it. Here are the concerns that I have:

1. The end of the tube where the torch is inserted will get ROASTING hot - very likely glowing red inside the camper. The thimbles may protect the structure, but I would be concerned about having something that hot inside the small space.
2. The torch itself is designed for intermittent use. I very much doubt that it will hold up to running for hours on end.
3. Torches use a mixer vent to add air to the propane for combustion, but clean combustion only occurs when there is a good source of air around the flame. By inserting the torch nozzle tip into the tubing, I think the flame will burn very rich, which, combined with the moisture associated with propane, will cause serious soot build-up in the tubing.

I like the idea that has been presented of using a water heater burner, or something similar. Even if a propane leak will dissipate, it is still preferable to shut down the flow of propane instead of venting it to the atmosphere. A water heater burner, with a throttle valve, with a collector over it, reduced into a draft tube, should provide positive flow pressure to push the heated air through the ceiling tube, without super-heating one end of it.

By the way, I use a trucker's 12v mattress pad. I have not camped in sub-zero temps, but it heats the bed VERY nicely. That, combined with a nice down comforter, would be toasty warm. I can easily go three nights on a deep-cycle battery. If the battery were stored in semi-warmed space (in the interior of the camper with a vent to the outside), it shouldn't suffer from amperage loss due to the cold.

Another wonky idea -- what about using a Zodi propane hot water heater (like the camper showers) to create radiant hot water heat? A small water reservoir, a circulating pump, and an expansion jacket, and voila!

[KennethW]

Rob, I understand the inventor spirit...more than you might think. But I also understand risk. I don't want some one experimenting when they are building a bridge it will have to drive over. Engineering principals and safety principals are just that....principals never change, and when you start to play, you can get burned. Carbon monoxide and fire aren't just minor inconveniences like a dripping waterline or a rattle under the dash. They are both things that can easily kill you. Heck, even Bob Henry has experienced problems in trailer that was a little too tight.

I thank you for your concern. I am looking for a design flaw that would allow gas or fire. It is one of the reasons I posted this. The other is to find a safer way for others. Put a lantern or butty heater in a teardrop to preheat a teardrop might fill the camper with bad gases, water vapor and burn all the air up just before you go to bed.

[rowerwet]

Another wonky idea -- what about using a Zodi propane hot water heater (like the camper showers) to create radiant hot water heat? A small water reservoir, a circulating pump, and an expansion jacket, and voila!

I have the Zodi water heater, the heater is intended for showering, it needs continuous flow to keep from overheating the water (no thermostat), more than one reviewer has complained that they couldn't shut the water off to soap up.
too bad they still don't sell the small zodi tent heater, it really is exactly what you want, http://www.zodi.com/tent-heaters

[KennethW]

1. The end of the tube where the torch is inserted will get ROASTING hot - very likely glowing red inside the camper. The thimbles may protect the structure, but I would be concerned about having something that hot inside the small space.
2. The torch itself is designed for intermittent use. I very much doubt that it will hold up to running for hours on end.
3. Torches use a mixer vent to add air to the propane for combustion, but clean combustion only occurs when there is a good source of air around the flame. By inserting the torch nozzle tip into the tubing, I think the flame will burn very rich, which, combined with the moisture associated with propane, will cause serious soot build-up in the tubing.

I like the idea that has been presented of using a water heater burner, or something similar. Even if a propane leak will dissipate, it is still preferable to shut down the flow of propane instead of venting it to the atmosphere. A water heater burner, with a throttle valve, with a collector over it, reduced into a draft tube, should provide positive flow pressure to push the heated air through the ceiling tube, without super-heating one end of it.

By the way, I use a trucker's 12v mattress pad. I have not camped in sub-zero temps, but it heats the bed VERY nicely. That, combined with a nice down comforter, would be toasty warm. I can easily go three nights on a deep-cycle battery. If the battery were stored in semi-warmed space (in the interior of the camper with a vent to the outside), it shouldn't suffer from amperage loss due to the cold.

Another wonky idea -- what about using a Zodi propane hot water heater (like the camper showers) to create radiant hot water heat? A small water reservoir, a circulating pump, and an expansion jacket, and voila!

#1 If the pipe did get red hot I could put a wire cage around it or put a restrictor valve to limit the gas flow.
#2-#3 I will have to run it to see the results.
The way I am building it the heater head can be easily changed to a water heater pilot. I will look in to it. Might be a good way to go.
I use a cpap so a electric heater would need a second battery.
A water(antifreeze) system sounds like a lot of weight.
Good ideals!!

[KCStudly]

Have you tested to see how hot the dog dishes get out at their rims? Might be hotter than you think. I would test that in mockup with the dishes screwed to a test piece like your wall construction (testing in free air is not a fair comparison because they will radiate more heat to free air than they will when they are attached to something more insulating, like your walls).

[KennethW]

Testing on a sample wall.Good ideal. I have the window cut outs to test with(I am bad at not throwing junk away). I will try that. May this weekend.

[KCStudly]

I've done a bit of work with large industrial gas fired generator exhaust, and the commercial "thimbles" (where the exhaust penetrates a roof or wall) have a tube that is larger than the pipe (an air gap) with 4 pieces of flat bar welded on edge axially along the inside walls of the outer tube. This minimizes the contact between the hot and cool pipe, and still allows for thermal movement.

The air gap is key to interrupting thermal transmission. Then there is an outer tube with insulation packed between it and the guide tube. From there the flange of the outer pipe is big enough to provide a good deal of separation between the outer pipe and any combustibles.

http://dmeexpansionjoints.com/wp-content/uploads/2012/10/exhaust_catalog.pdf page 40 (printed page 38) shows it.

We all like to think that we are creative, and smart enough to find a solution to any problem. Before authorizing the budget for this type of commercially produced thimble, an engineer at my work thought he could make his own system work. After setting the roof on fire, he didn't work there much longer.

We essentially ripped out everything he did and started over. Not a commentary on you, just saying, be safe. Make sure.

[Mojave Bob]

Another wonky idea -- what about using a Zodi propane hot water heater (like the camper showers) to create radiant hot water heat? A small water reservoir, a circulating pump, and an expansion jacket, and voila!

I have the Zodi water heater, the heater is intended for showering, it needs continuous flow to keep from overheating the water (no thermostat), more than one reviewer has complained that they couldn't shut the water off to soap up.
too bad they still don't sell the small zodi tent heater, it really is exactly what you want, http://www.zodi.com/tent-heaters

Yes, thermostatic control is the issue. My thought was that with a sufficiently-sized tubing loop, the water would give off it's heat before returning to the heater, so the system wouldn't overheat. It would have to be constantly circulating, though. The trick there would be the "sufficiently sized" thing. That might require some math. I don't think the entire loop would be holding more than a few gallons, so while it has some weight, it isn't prohibitively heavy, and could be designed to be drained for travel.

The tent heaters are very slick, but very expensive, and require 12v electricity, which I think is outside the design spec for our case study.

Back to a variant of the original concept -- to my mind, I don't think the torch will prove satisfactory, although the elegance of simplicity is great. I have concerns about the flame being directly inserted in the tubing, as well. A little separation goes a long way. What about rigging a feeder tube from the camper, with a collector "hood" on the end, that can just be set on a standard campstove? Set the campstove on a little side table, set the collector hood over one burner, and have that feeding heat to the radiant tube. The extra two feet of tubing will dramatically reduce the risk factors, and the stove is more intended for extended use (somewhat, anyway).

I guess one question I have is, how many nights of consecutive use must this thing accommodate? If it is one or two nights, I would highly recommend using a 12v mattress pad - clean, simple, effective, safe, and affordable ($85). An extra battery isn't that big a deal in the grand scheme of things. If it is for more than three nights, then avoiding battery power becomes a bigger deal. But, if a CPAP is being used, there is probably about a 2-night limit in place, anyway.

[KennethW]

last night I also thought camp stove on a shelf with a hood The shelf would be removable with keyhole slots and 2 screws in the side of the camper.

[KCStudly]

The shelf would be removable with keyhole slots and 2 screws in the side of the camper.

...or better yet, a length of Patrick Molding.

[rowerwet]

viewtopic.php?f=2&t=18902 almost all of this has been thrown out there before, the one issue with testing, make sure you are in the tear when doing the comfort test, Mike tested his candle box heater with just the heater in the pod, your own body heat is important in any test.
Personally I'm working with kerosene type heaters, they have more BTU per pound in the fuel, are almost impossible to make explode, already have many tested heat burning appliances, and for me as an airplane mechanic the fuel is free (jet fuel is just super clean kerosene)
Propain and gasoline are not something I want burning around me in a home made rig while I sleep. the kerosene lantern heater idea appeals to me as I already use them for light/bug repelling when camping and as a boat light at night rowing and paddling.

[rowerwet]

The tent heaters are very slick, but very expensive, and require 12v electricity, which I think is outside the design spec for our case study.

you can still find the original small ones on Ebay from time to time, the fan ran on D cells and had a much more reasonable price. Zodi stopped selling them and even would refund buyers after it was discovered the heat exchanger would melt and possibly burn if the fan batteries died. Zodi has been working on this for a few years now, however they seem to have just given up on the portable tent heaters and gone for expedition wall tent types aimed at large groups with a truck to haul gear.
I really can't believe a simple, reed type, air flow switch couldn't have solved everything, but what do I know.
Zodi sells a metal coil to stick into your campfire http://www.zodi.com/portable-fire/zodi-fire-coil run some loops of copper in the tear, force water through with their 12V pump and you have heat...

[bdosborn]

Your design reminds of this one:

Mother Earth Heater

Bruce