Official Test Results: Five Ways to Heat a Tent

[MattJ]

I decided the carrying-case-and-weather-cover system wasn't optimal. So I came up with a better option:

1) Get rid of the case and use a simple tarp to cover the unit and protect it from the weather
2) Get rid of the exhaust system (flexible metal conduit) since the tarp will channel the exhaust away from the tent
3) Use a circular carrying case for the hoses (I tried a drum case but it was too big, finally found a fire pit carrying case that worked perfectly)
4) Pack the Propex unit separately

This system should make it easier for me to pack the two pieces of the heating system independently (three pieces, if you count the propane tank). And the tarp is much more flexible than the hard plastic tote. Most of the time, I would expect that I can use the tarp folded into just a few feet of coverage and held in place with some spring clamps. But if necessary, the tarp can unfold to 8' x 6'.

 

[Victory_Overland]

Love the heating system ideas and someday maybe I'll be at the level where I can complete all my other tasks and work on this one......lol

On that note, I use my JetBoil to boil water and then pour it into my BPA Nalgene bottles and toss them in the sleeping bags for radiant heat. Something we've been doing in high-altitude-cold-weather-survival for quite a few years. You'll be surprised at how well it works, especially if you have a bivvy for your sleeping bag.

Not trying to take away from the heater thread, just trying to add to ideas!

 

[john61ct]

2) Get rid of the exhaust system (flexible metal conduit) since the tarp will channel the exhaust away from the tent

I think not a good idea, since a mistake could be fatal.

 

[MattJ]

Not trying to take away from the heater thread, just trying to add to ideas!

No worries! This thread is about all methods to heat a tent, and so far the list is five:

Warm gear and hot water bottles
Electric blankets or mattress warmer
UCO candles
Mr. Heater Buddy catalytic heater
Propex portable heater kit

Wood stoves are another portable option that we've discussed, but aren't really an option for most tents . . .

I think not a good idea, since a mistake could be fatal.

Thanks - I definitely am focused on the risks. But two facts get me comfortable

1) The Propex unit is outside the tent, several feet away, and the tent is zipped shut
2) CO is heavier than air (although wind can push it anywhere)

I do have a CO monitor that I use for all of this testing. But I think the CO will dissipate rather quickly and it would be difficult to get any meaningful concentration back inside the tent from the exhaust port of the Propex unit several feet away.

Having said all that, there is certainly room to stuff the exhaust conduit into my circular carrying case and just hook it up anyway.

Thanks for your input! Am hoping to do another field test soon . . .

 

[mmp3823]

How hot is the exhaust? I have a camper and the exhaust for the furnace is quite warm and would melt that tarp pretty quick.

 

[john61ct]

Last night https://fox4kc.com/2018/11/04/2-men-overcome-by-carbon-monoxide-at-texas-nascar-speedway/

 

[Bruce988jl]

Last night https://fox4kc.com/2018/11/04/2-men-overcome-by-carbon-monoxide-at-texas-nascar-speedway/

That unit was inside the vehicle... Matt's unit is located outside the vehicle on the ground and likely under his truck out of the elements. Slight difference in placement.

 

[MattJ]

How hot is the exhaust? I have a camper and the exhaust for the furnace is quite warm and would melt that tarp pretty quick.

Yes - the exhaust is hot (I measured the exhaust port at 150-160F earlier in this post, I think). But the tarp is a few inches away from where the exhaust puffs out of the port, so I'm assuming that ambient temperatures of 20 - 40F will cool the exhaust vapor very quickly and avoid damage to the tarp. But maybe I'll just use the exhaust conduit that I spent so much time and money designing. I was also trying to figure out a way to recapture some of the exhaust heat to warm up the propane tank so it doesn't get sluggish in the cold, but I gave up on that idea.

That unit was inside the vehicle... Matt's unit is located outside the vehicle on the ground and likely under his truck out of the elements. Slight difference in placement.

Yes - lots of stories online about deaths from CO poisoning. Combustion in a closed space is the most direct way to commit suicide by heater. I've also read stories about heaters that were underneath campers in closed spaces and built up enough CO to seep back inside the camper.

I'll post pictures after another test this weekend. One additional factor that should provide more safety to my setup: when the heater is on and the exhaust is chugging out of the port, the unit is also pumping a large volume of warm, dry air into my tent. So presumably there is positive air pressure in the tent as the warm air leaks out through the soffit vents. So even if a cloud of CO built up on the roof of my Jeep a few feet away from the tent, presumably it wouldn't somehow start pushing into the tent that is zipped shut.

 

[nated]

Found this regarding proper balancing of the combustion chamber in the propex:

Routing requirements to follow:

• The combustion intake and exhaust pipes should not be trimmed to ensure that the combustion is balanced and that the unit function properly in the long run.
• The combustion exhaust pipe should have a constant downward slope: this is because condensation forms in the pipe and will block the air flow if it’s not evacuated.
• The combustion exhaust pipe should be dumped outside the vehicle edge: carbon monoxide is heavier than air and will pool under the vehicle; if so, carbon monoxide could enter inside the vehicle through the floor (it’s not perfectly hermetic) and through floor vent (if you have some). Safety first!
• The combustion intake and exhaust pipes should be 0.5 meter apart: this is to prevent exhaust air to recirculated into the intake pipe (the unit will malfunction in the long run).

 

[MattJ]

Found this regarding proper balancing of the combustion chamber in the propex:

Yep - all good. The downward slope of the exhaust pipe requires some work, depending on how you set it up. It generates quite a bit of condensation, especially in colder environments.

 

[Ark]

Obviously you're a long ways into a good solution but I see that Total Composites has a pretty slick offering now as well. Have you seen it yet? Basically just an Espar in a box like the Propex but it looks like a solid solution!

https://totalcomposites.com/product/portable-diesel-air-heater-planar-3d-12-volt/

Upsides are no icing propane tanks and a very dense fuel that should last quite a while.

Downsides are messy/stinky fuel, not as efficient as yours since there is no return air hose and the possibility of the diesel turning into jelly at low temps if you're not careful. Slightly harder to reverse than an iced up propane tank.....

 

[MattJ]

Obviously you're a long ways into a good solution but I see that Total Composites has a pretty slick offering now as well.

Interesting - I wonder if you can rig it to circulate air from inside the tent by adding an intake extension hose. I can tell you from experience it makes a HUGE difference in the efficiency of the heater.

 

[Ark]

Interesting - I wonder if you can rig it to circulate air from inside the tent by adding an intake extension hose. I can tell you from experience it makes a HUGE difference in the efficiency of the heater.

I'm sure you could. The out-side air intake is just a little grille in the side of the box. It wouldn't be too difficult to imagine removing that grille and stuffing another hose in the hole instead.

Have you had issues with excessive condensation with your setup? You definitely gain a whole lot of efficiency by recirculating the internal air and not having to heat up super-cold outside air but one of the issues with recirculating 100% of your air is building up humidity from breathing. Theoretically you eventually will soak out your walls or frost everything up if it's cold enough.

Up here in Alaska there is a local company that makes tents. It's not immediately obvious but they have a couple of strategically places vents here and there to allow you to bring in a little bit of super-dry cold air down low and exhaust a small amount of humid air up top. That definitely will cost you a little bit in the form of fuel having to heat up that cold air but if you have a good outside vs inside air mixing system you can manage your moisture without expending too much.
https://arcticoventent.com/

Perhaps this isn't an issue with your RTT and that's kind of what I'm curious about. I have seen a few other people on this forum have issues with not getting in enough dry air though. Maybe not a problem for a weekend trip but it sure sounded miserable for a long term cold weather trip!
https://expeditionportal.com/forum/threads/a-hawk-in-the-arctic.163254/

 

[MattJ]

Have you had issues with excessive condensation with your setup? You definitely gain a whole lot of efficiency by recirculating the internal air and not having to heat up super-cold outside air but one of the issues with recirculating 100% of your air is building up humidity from breathing.

Interesting question. Every time I've used it, the air from the Propex has been wonderful, warm and dry. I don't know enough about how it actually heats the air to say that it somehow scrubs moisture out. But I do know it is designed for use in buses and vans, which probably hold recirculated air better than my tent. So maybe the Propex is designed to keep condensation low?

The other reality is that my tent has two open air soffits at the top and leaks at the windows and zippers where the hoses come in. Moisture probably stays in better than the heat does, which leaks out rather fast, even with the reflective blankets installed. My whole design is basically a permeable bubble of warm air that tries to fight the cold air outside to a draw. Not really efficient. But certainly dry, as far as I can tell.

The Mr. Buddy catalytic heaters are a VERY wet heat. With a bit of "something chemical" odor. They are powerful and much cheaper, but do create quite a bit of condensation.

 

[john61ct]

Any unvented propane heater does that, humidity condensation, about 1.64 pounds of water per gallon of propane used.

Raising air temp inherently "dries out" the existing moisture, until it hits cold surfaces again.

Having a flexible intake you could choose inside or out would be ideal.

When from inside you don't want the space too airtight, need a low-O2 sensor, but that's likely not an issue here.