Official Test Results: Five Ways to Heat a Tent

[MattJ]

Well, the rebuilt insulated hoses worked GREAT. The air coming out of the hose into the tent was so hot you couldn't hold your hand close to it for more than a few seconds. And that hot air is beautiful, dry, and odorless. I think it really helps that the Propex heater was cycling warm air from the tent through the heater.

Unfortunately, I learned the hard way that the Propex heater consumes a LOT of propane unless you set the thermostat to cycle on/off every few minutes. I had the thermostat set to run the heater constantly since I wanted to see how much it could raise the temperature in the annex and tent (the annex alone is nearly 500 square feet). As you can see in the photos, I was using a 4.4-pound tank (1 gallon). At 2am, the system shut down. I had to climb down from the tent to see why. I was worried the system had malfunctioned, but in fact the tank was empty. So I certainly didn't get a good night of sleep!

I guess I could try again with a 20-pound tank and test various settings for the thermostat on/off cycle. This project is a LOT of work, but I think I am finally getting closer to the perfect tent heating system . . .

 

[danfromsyr]

one gallon of propane is about = 91,333 Btu or 21,548 per pound.
the propex is how many BTUs per hour?

 

[MattJ]

I don't know. Is it possible to convert from kW to BTU?

 

[chet6.7]

The picture is a joke,but,one of those open military trailers could hold a 100lb tank and some gear.

 

[aearles]

I don't know. Is it possible to convert from kW to BTU?

Yes, 1kWh = 3412BTU/hr. So at the rated 2.1kW (7165BTU) input, the heater should last 12.7 hours on 1Gal with continuous duty.

An easier way to remember that: It should run for ~3 hours per 1lb propane.

Keep in mind that most places only fill your tank to 75-80% capacity though, pay attention when you have it refilled.

 

[MattJ]

Yes, 1kWh = 3412BTU/hr. So at the rated 2.1kW (7165BTU) input, the heater should last 12.7 hours on 1Gal with continuous duty.
An easier way to remember that: It should run for ~3 hours per 1lb propane.
Keep in mind that most places only fill your tank to 75-80% capacity though, pay attention when you have it refilled.

You are absolutely correct! I took both of the the 1-gallon tanks to refill today and BOTH still had propane in them. The person at the fill station banged on the tanks with a rubber mallet and said "sometimes the valves get stuck".

I always bring twice as much propane as I need, just in case there is a problem with a tank. But on this trip, BOTH tanks failed. And both are new. Why?

1) Something wrong with the 1-gallon tank design in cold weather?
2) Is the Propex connection hose or the Propex system causing the valve in the tanks to shut down after a few hours of use in cold weather?
3) Did banging the tanks with a rubber mallet fix the problem? Maybe the valve gets stuck on new tanks but loosens over time?

Maybe this project will never end . . .

 

[aearles]

Some explanation and tips here:
https://www.bournesenergy.com/news/propane-in-cold-weather-800937483

I wonder if you could circulate the warm return air around the propane tank via a small enclosure?

[EDIT] I was originally thinking a propane box with two flanges on it, in-line with the return air hose, but maybe that's not a good idea in case of a propane leak you'd be circulating that gas mix through the heat exchanger and living space. Maybe just routing the warm hose through the propane box and insulating it would be sufficient. Or... maybe a bigger propane tank is just easier.

 

[Lucky j]

You are absolutely correct! I took both of the the 1-gallon tanks to refill today and BOTH still had propane in them. The person at the fill station banged on the tanks with a rubber mallet and said "sometimes the valves get stuck". I always bring twice as much propane as I need, just in case there is a problem with a tank. But on this trip, BOTH tanks failed. And both are new. Why? 1) Something wrong with the 1-gallon tank design in cold weather? 2) Is the Propex connection hose or the Propex system causing the valve in the tanks to shut down after a few hours of use in cold weather? 3) Did banging the tanks with a rubber mallet fix the problem? Maybe the valve gets stuck on new tanks but loosens over time? Maybe this project will never end . . .

I got the problem before on a 5lbs can, but in my case, I beleive it was form bouncing around. The bottle was 2 years old, but had only be used a few time. A new valve was the fix.

 

[MattJ]

Some explanation and tips here:
https://www.bournesenergy.com/news/propane-in-cold-weather-800937483
I wonder if you could circulate the warm return air around the propane tank via a small enclosure?

If you look back at the very first page of this post you can see that I was worried about the tank losing pressure in very cold temperatures. I bought a tank heating blanket but decided it was crazy . . . run the engine to charge the battery to heat the blanket to warm up the propane to fuel the Propex heater which also draws 12v power from the battery . . .

Propane has a boiling point of -45F, so I am hoping that the 1-gallon tanks have sufficient pressure at any temperature above 0F. I have had trouble with the smaller 1-pound tanks in cold weather.

I'll have to try my 1-gallon tanks again with the Propex heater, now that "rubber mallet fix" has been applied.

 

[MattJ]

Now that the weather is 80F, I finally found time to build the last hose for the Propex heating system. I purchased additional 60mm ducting and 2.5-inch thermoplastic tubing, and THIS time I sliced the ducting from end-to-end. It took some work, but finally I was able to get the entire tube threaded with the ducting. Now I just need to drive 3,000 miles north or south to find some cold temperatures for testing it. Or just wait six months . . .

 

[lchavez]

With my hobbies, I am usually out 2-3 weekends a month during the winter season in Arizona. I typically only need the heater for 4 months of our AZ winter. I have great sleeping gear that keeps me warm once I am in bed, but i like to run the heater before I get in bed and when I wake up in the morning. I camp with a oz-tent ground tent.

I had been using a Mr. Heater Big Buddy for over ten years. Has a fan built in, dual tanks, and lots of heat settings.
Pros
- never froze up, dual tanks must help with this
- built in fan, ran for a whole season on d-batteries with my use
- lots of heat settings
Cons
- igniter is useless, had to keep a wand lighter handy
- ignition is finicky, until i figured out the sweet spot

I also invested in refillable propane bottles. These have worked very well and have saved me hundreds of dollars and reduced waste.

Last year, while I was storing my gear, the Mr. Heater bounced of my dolly and landed in the pool. I decided to try the smaller Mr. Heater single can/burner model. I have been very disappointed in the smaller model. For some reason it burns through the fuel much faster than the Big Buddy. Heat settings are not as flexible, probably the reason it burns so much fuel. Froze up when I needed it most. does not have the built in fan. I really missed the fan.

I am adding a off road trailer to the mix for next season, which will have a roof top tent with annex. I will more than likely go back to the Big Buddy.

PS: significant other loves Mr. Heater. Mr. Heater and Luggable Loo are mandatory when we camp together.

 

[Scoutn79]

Heating a tent, or a tent camper long term while sleeping always seemed like a huge waste of resources to me. Thin fabric just isn't going to keep the heat in.
While sleeping I just make sure I have the appropriate clothing/sleeping bag. Long Johns help a lot to ward off the cold if you have to get out for a quick relief during the night.
In the morning, if it is cold, I will just fire up the stoves burners in the pop up camper then get back under the covers for a few minutes to take the chill off, same could be done with a buddy heater in a tent.
When I am in my 3 person true 4 season tent the interior stays about 15 degrees warmer than the outside air when it's just me and my 70lb pup.
The dead air space between the tent body and the fly that goes all the way to the ground does a great job of insulating us. Something similar might be able to be worked out in cold climates with a tarp to help single layer tent bodies.
My $.02
Darrell

 

[MattJ]

The dead air space between the tent body and the fly that goes all the way to the ground does a great job of insulating us. Something similar might be able to be worked out in cold climates with a tarp to help ingle layer tent bodies.

Thanks for your input! Yes - I bought some extra reflective tarps that should really boost the effectiveness of the Propex system. I am hoping it traps more of the very hot, dry air that the Propex system circulates inside the tent. Now I just have to wait six months for more cold weather. Heading back out into the woods this weekend and the forecast is for 90F temperatures, so I'll be leaving the Propex system in the garage . . .

 

[MattJ]

Well, now that the temperatures are dropping it is time to bring this project back to the front burner for more work! Two updates:

1) I coated the case with Sharkhide, which should provide durable protection against the elements.

2) After more research and close inspection, I have FINALLY figured out how to make a very tight and removable exhaust system. Since I sleep in the tent with my kids, it's very important to me that I give the carbon monoxide someplace to go. My previous fix with a reducer and stove tube felt loose at the joints, and I was worried that it would leak or fall off in the middle of the night. The breakthrough was when I realized the exhaust port on the case was a 1-inch electric conduit connector. I plan to cut an 8-foot section and use it to dump the carbon monoxide away from the tent.

It's cost me hundreds of dollars and dozen of hours to figure this out, and it's frustrating that the company that sold me a $2,000 portable Propex system offered no help, hints or suggestions. But I guess that's what Expedition Portal is for! Hopefully this thread helps someone else, someday . . .

I'll post more pictures next week of the full system in action with the tent.

 

[Heavyopp]

Curious if you tested the conduit itself for leaks? Not sure if that stuff is “ watertight”.