We find that our kids seem to wiggle out of their sleeping bags all the time, so waking up every hour to tuck them back in is all too common. This got us thinking for ways to heat the tent on colder nights. Any quick searches seemed to pull up propane catalytic heaters such as the Mr. Heater, which may be OK for some, and I personally know people who use them… but they don’t have little kids that spin in their sleep like a tornado and will almost certainly kick it over (even with safety shutoffs etc, we don’t feel comfortable with the propane heaters). Some people use electric heated blankets, which once again is great for adults, but doesn’t solve the kid concerns of wiggling out.
This leads us to diesel heaters. There are some pricey ones that are used in big RV’s, and then there are cheap Chinese diesel heaters… which we will focus on here. These are basically heat exchangers, meaning that the the heating combustion exhaust does not enter the living space. These heaters use standard automotive diesel fuel, which gets pumped into a combustion chamber where it is burned with a glow plug, the exhaust then exists the unit to the outside air and does not enter the tent. This combustion heats up the metal combustion chamber, which has radiator fins on it, an electric fan then pulls in clean outside air, pushes it through the hot fins, which heats up the air, and then the clean hot air gets ducted into the tent.
This is really ideal for small quarters, the only caveat is that you need a 12V power source to power the fuel pump, glow plug, and the electric fan that blows the clean air air over the radiator fin surface. You could in theory power it from your car battery, but we didn’t want to risk it, so we built our own DIY 1300Wh battery pack. Overall the system is very efficient, it uses roughly 15% of the battery pack and 1/2gal of diesel per night.
Pick the right heater size
We selected the 2kW rating diesel heater, which are the lowest heat output we were able to find (the cheap ones seem to be available in 2kW/5kW/8kW, with 5kW being the most common). The tent is quite small, so this is plenty of heat output, on the coldest night, when it was ~33°F the heater ramped up 20% of the time, but then simply idled the other 80%. You don’t want to have a heater that is too powerful because they must maintain a constant minimum combustion, and if that is too powerful, you’ll be pumping in way too much heat even on the minimum setting.
Heater control panels
You’ll notice that there are some heaters that have a turn knob, and some have an LCD panel. We have the LCD version, and it is convenient that it has a thermostatic function, where you can set a desired temperature and it’ll maintain it all night. One downside is that the controller is very on/off, so when it needs to warm just a little bit, it turns the heater on full blast for for a short period of time, instead of slightly increasing the heat output to just keep a constant temp. This is why we sometimes just use the Hz (fuel pump frequency) function which makes the controller behave just like dial knob version, where you can gradually increase the constant heat output.
To switch between thermostat and fuel pump frequency mode just press the top two buttons at the same time (settings and up arrow). Here is a helpful video for other controls and setup of the LCD.
To make the heater Roof Top Tent friendly, we spliced in 16ft of extra wiring into the control panel harness. This allows us to have the panel inside the tent and use the thermostatic feature. We also replaced the duct that came with the heater with 3in dryer ducting to give us more distance between the truck and heater. Simply feed the control panel and ducting throuhg one of the windows and use the sipper to cinch down on it and secure it into place. TIP: aim the heater up, the moving warm air quickly dried out our lips when we had it pointed down at us, but not a problem if it is pointed away from your face.
There are ways to mount these heaters permanently, as it would be in a camper van, however we like to have it versatile and transferable between vehicles. They have a pretty convenient package and tucks in well with all our gear. We generally try to get it further away from the truck (as it does make some noise, a little ticking of the fuel pump, and some wind noise as the exhaust exits the combustion chamber), but when it is raining out we tuck the heater under the truck to shield it from getting soaked, seemed to work out just fine.
In summary, here is a quick pros and cons table:
|Simple||Emits Carbon Dioxide into living space|
|Compact||Creates condensation in side tent|
|Available in stores||Has a hot surface|
|Does not require electric power source||Can be tipped over|
|Does not work well at altitude|
|Compact||Consumes a lot of electricity|
|Does not heat the interior air directly|
|Safe||Requires 12V power source|
|Heats space with clean air||Requires automotive diesel|
|Fuel Efficient||Takes up a bit more space in gear storage|
|Consumes minimal electricity||generates some noise|
|Does not take up space inside tent|