Low-BTU Heat Options for a Small Foamie Camper

[dt400]

I am building a small (5x8x4) foamie with 2" XPS foam with an R-10 rating.
Based on some calculations I would need about 1k BTU to maintain a 50 deg F differential temp.
Most small heaters (diesel/propane) are in the 5k-6.5k range. Something like this will put out so much heat so fast it will overrun the thermostat (temp rises faster than the thermostat has a chance to respond) before it comes up to temp so I would end up with some pretty wide temperature swings.
Since a diesel heater will carbon up if run for short durations it needs to run for longer cycles than propane. I can turn the pump down but it'll still be too much, I could just open a window a bit to bleed off excess heat and try to modulate that way.
Propane can be run in short cycles and uses less electrical power, but a Propex is 6500 btu. and would overrun the thermostat even quicker than a diesel heater would.
I understand there isn't much of a market for such a small heater but does anyone have any ideas on how to accomplish this with either a premade device or a homemade option?
My water system is in my truck so I have thought about doing a bleed air set-up to have some heat go into the truck which would help with my problem.

Ideas? Thoughts?

Thanks

Darrell

 

[Pmullen503]

A teardrop requires a lot of ventilation because of it's small volume. So calculations based on R values alone dramatically underestimate the amount of heat required.

Likewise, you rapidly get to diminishing returns on insulation for the same reason.

If you search for "diesel heater" or "Propex" you'll find users with practical experience with these systems.

 

[dt400]

A teardrop requires a lot of ventilation because of it's small volume. So calculations based on R values alone dramatically underestimate the amount of heat required.

Likewise, you rapidly get to diminishing returns on insulation for the same reason.

If you search for "diesel heater" or "Propex" you'll find users with practical experience with these systems.

You are correct, and I forgot to allow for the permanent small cross ventilation I have to control humidity and supply fresh air.

Darrell

 

[Brumasterm01]

According to google AI, you will need 6.7 Air Exchanges per hour (about 18 CFM) to keep CO2 levels at 800 and 1000 PPM in a 5x8x4 trailer with one resting adult. Above 800 to 1000 PPM the trailer will start stuffy. Not unhealthful, but that's when it starts to feel stuffy.

I've tested Google's AI calculations with a CO2 meter in my 4x8 trailer and the predicted values were spot on.

Safe/uncomfortable CO2 levels are somewhat debatable.

What about a 2K diesel heater?

 

[reaver]

I run a 2k diesel heater in my 5x9 trailer, with only R5 insulation in the walls, and have camped in single digit temps. Even that is too much if not running in thermostat mode.

Even with cross ventilation, and the fan going, on low, the heater will cook me out of the trailer.

For a low amount of heat, I would recommend a 12v electric blanket underneath you. Or maybe a small 300w or 12v heater that you can turn on as needed. I'd still outfit the trailer with a diesel heater, but you may find that there are times where you need a it of heat, but can't justify turning the big heater on.

 

[dt400]

According to google AI, you will need 6.7 Air Exchanges per hour (about 18 CFM) to keep CO2 levels at 800 and 1000 PPM in a 5x8x4 trailer with one resting adult. Above 800 to 1000 PPM the trailer will start stuffy. Not unhealthful, but that's when it starts to feel stuffy.

I've tested Google's AI calculations with a CO2 meter in my 4x8 trailer and the predicted values were spot on.

Safe/uncomfortable CO2 levels are somewhat debatable.

What about a 2K diesel heater?

Not sure I trust that. IIRC hosiptals have 3 air exchanges per hour and according to the EPA a house needs a minimum of 0.35 exchanges per hour. Not that 6.7 is bad for you but a bit excessive if your just heating (or cooling) the great outdoors....but either way I agree a tiny space needs air exchanges and I do have a couple 3" permanently open wall vents with filters (one high and one low) to allow for a constant supply of fresh air/ cross ventilation. slow? Yes but constant...

I like the cost of the diesel heaters but they are designed to run constantly( the pump speed can be adjusted so on the lowest setting I can prolong the run time but not sure if they fire up on full speed then throttle the pump back once up to full operating temp, if you short cycle them they will carbon up and fail. Plus they use a lot of energy running the glow plug during start-up. I could also do some sort of bleed air set up but that seems wasteful.....BUT for as cheap as they are the smaller of the diesel heaters might be worth a test if nothing better is available.

Darrell

 

[dt400]

I run a 2k diesel heater in my 5x9 trailer, with only R5 insulation in the walls, and have camped in single digit temps. Even that is too much if not running in thermostat mode.

Even with cross ventilation, and the fan going, on low, the heater will cook me out of the trailer.

For a low amount of heat, I would recommend a 12v electric blanket underneath you. Or maybe a small 300w or 12v heater that you can turn on as needed. I'd still outfit the trailer with a diesel heater, but you may find that there are times where you need a it of heat, but can't justify turning the big heater on.

That's my worry, just too much heat too fast. I have used a couple different BTU calculators and come up with about 1,000- 1,200 BTU for a 50 degree temp differential. Basically the heat of 4 or 5 candles. I don't need heat while sleeping, but want it while awake inside and it's nice to have getting up in the morning.
My calcs don't include ceiling, window or door insulation plug/curtains which if used would require even less BTU.
The use of a 300W electric heater would be right about the heat I need but put a deplete a small (100 ah) battery in short order.

Lots of options...

Darrell

 

[featherliteCT1]

If you do not plan on using shore power, I suspect that the most practical solution based upon your needs is to buy a cheap Chinese diesel heater for about $120, and let it run on low for as many hours as needed, with the windows/vents open as wide as required to keep temperatures reasonably comfortable.

I do not use a self contained unit because I want the fuel and the fuel pump mounted outside the living quarters.

I burn kerosene rather than diesel, because the kerosene runs cleaner. Also, my shutdown procedure is to run the heater on high for 10 minutes to burn out carbons, every time I turn the heater off. Whenever I have read about someone having a problem with a diesel heater carboning up, it’s because of user error (failure to read the manual resulting in not having programmed the unit properly, improper installation, and or using alternative fuels like vegetable or used motor oil and the like).

I have been running my diesel heater for six years, mostly on low, without ever having been cleaned. However, I do carry a spare diesel heater in case my first diesel heater ever carbons up or otherwise fails. For me, it was cheaper to buy a whole new spare unit rather than a repair kit.

If it turns out you don’t like the diesel heater, throw it away.

On the other hand, there are several members on this forum who are very happy with their $1,000, Propex heaters. Of course, the Propex has its own advantages and disadvantages.

Keep us posted and let us know how things work out for you!

 

[Brumasterm01]

Not sure I trust that. IIRC hosiptals have 3 air exchanges per hour and according to the EPA a house needs a minimum of 0.35 exchanges per hour. Not that 6.7 is bad for you but a bit excessive if your just heating (or cooling) the great outdoors....but either way I agree a tiny space needs air exchanges and I do have a couple 3" permanently open wall vents with filters (one high and one low) to allow for a constant supply of fresh air/ cross ventilation. slow? Yes but constant...

The math is correct. There is just 100s times more air volume in a house than a tiny trailer. Hence, why you don't need as many air exchanges.

I even tested this myself with my tiny trailer, a CO2 sensor and my two 3" side vents. One high and one low. I closed my doors and the closed top maxxair top vent. Then C02 levels rised just as google had charted out for me. The part I don't trust is what is considered unhealthy levels. That's the subjective part. OSHA puts that level at 5000 ppm. As others have posted here before, there's no history of anyone suffocating or dieing of CO2 poisoning in homebuilt trailers.

The only reason I started looking at it was because I was frustrated that I spent so much time insulting my trailer only to lose the heat through the side vents. Never had any condensation issues, so I thought I could further restrict air from my lower vent and use low wattage electric heaters and my electric blanket to keep the heat in.

My point in all this is that a smaller diesel pumping air from the outside might have some positive benefits like air exchanges.

I have a 5k diesel heater. Its definitely too big, but have been considering a 2k. As others have recently posted that too may be overkill.

 

[dt400]

The math is correct. There is just 100s times more air volume in a house than a tiny trailer. Hence, why you don't need as many air exchanges.

I even tested this myself with my tiny trailer, a CO2 sensor and my two 3" side vents. One high and one low. I closed my doors and the closed top maxxair top vent. Then C02 levels rised just as google had charted out for me. The part I don't trust is what is considered unhealthy levels. That's the subjective part. OSHA puts that level at 5000 ppm. As others have posted here before, there's no history of anyone suffocating or dieing of CO2 poisoning in homebuilt trailers.

The only reason I started looking at it was because I was frustrated that I spent so much time insulting my trailer only to lose the heat through the side vents. Never had any condensation issues, so I thought I could further restrict air from my lower vent and use low wattage electric heaters and my electric blanket to keep the heat in.

My point in all this is that a smaller diesel pumping air from the outside might have some positive benefits like air exchanges.

I have a 5k diesel heater. Its definitely too big, but have been considering a 2k. As others have recently posted that too may be overkill.

I see your points. And agree fresh air input from the heater vs recirculating air for the heater is the way to go.
I'm thinking what I'll look into is splitting the air hose with part into the camper and another leg into the truck somehow. Since the water system is mounted in there.

Darrell

 

[Brumasterm01]

splitting the air hose with part into the camper and another leg into the truck somehow. Since the water system is mounted in there.

I hadn't thought of that. My lithium batteries are mounted outside the trailer on the tongue. Even with a 2K heater you still have a surplus of heat and air, why not put it to good use when the temperature drops below freezing.

 

[NeilYoung]

i thought about trying one of these in my foam camper. not all night. just for a bit before bed and then when i wake up.

Candlelier Candle Lantern

Triple candle lantern for real candles. Includes 3 long-burning emergency candles. Trusted outdoor lighting for camping, power outages, prepping, and storms.

ucogear.com

 

[iamroot]

A hydronic system would be easy to modulate. Propane water tank. Probably would have to DIY the fan coil unit, but that's a fan and a pump and a small radiator and a thermostat.

 

[TwilaR]

In my really crappy rental house that leaks air like a sieve, when it's super cold out I close off the bedroom and use this to heat the space

VESTA Self-Powered Indoor Space Heater and Stove (Compact, Off-Grid, Emergency)

Cook your food and heat a whole room with the VESTA Self-Powered Indoor Space Heater and Stove. Runs on canned heat—no power needed! Stay prepared with the VESTA today.

www.instafire.com

I buy things with the thought of what I can use in the trailer later

Edit: Two 6-hour cans keeps it warm