Diesel Heater Build

I started this project last year and was delayed into the spring waiting for a 5L fuel tank to ship from China. The tank arrived in the spring and I didn’t need heat in the truck for warm season truck camping trips.

I just had a few remaining thing to complete, including solving how to connect the fuel line to the tank so that I could remove the fuel tank to fill it. I’ve never been able to cleanly fill any fuel tank without spilling some gas or diesel on the sides of the tank. The newer (required) spouts make it difficult because you have to depress the spout lock and pour at the same time. As the heater is portable and would go into the back of the truck, I didn’t want to to get any spilled fuel in the box – plus the exhaust is contained within the box – another reason not to have any fuel anywhere hear that hot exhaust that could potentially combust.

I ended up using a hole saw and opening up the fuel cap on the tank, then putting the stand pipe (and fuel line) through a small hole in a plastic disc from an old water jug. It’s the same configuration on any larger water jug with a spout, there is an inner seal and the outer ring that threads to the top of the container.

Set up this way, I can unscrew the lid and remove it, pull out the stand pipe, pull the 5L fuel tank out of the box, fill it up and put it back in. After the first use – I realized I should have a spare fuel tank (with an intact lid) that I can keep as spare and if I need any more fuel while using the heater, I can just swap out the tank and put the sealed cap on the empty tank.

So some numbers first. I’m using a Jackery 500 to power the heater. When the glow plug is primed and fuel is combusting in the chamber, the heater is using about 14 watts of power. It takes less than 2 minutes for the heater to ignite and start blowing warm air. Running the heater for about 12 hours, I used about 4 1/2 Liters of fuel. I’m not using the thermostat on the controller to set a temperature, but controlling the fuel pump using the hertz settings, so that I can reduce the fuel (and therefore the heat output). I’m also not recycling the inside air back through the heater, but I’m pulling cold air from outside. This probably reduces the efficiency somewhat. If it were used in an enclosed van for example, the air would be recycled and the heater would operate more efficiently. Using it with the truck, that would be yet another duct to a system that I would prefer be as simple as possible.

The particular case I’m trying to solve for is to sleep 3 people inside the truck. 1 adult and 2 kids, with heat for winter ski trips. An adult and kid can sleep moderately comfortable in the back – impossible to sleep 2 adults, or to sleep 3. I’ll write up my cab bed solution in a future post, but I was comfortable all night with a 73” platform “loft” over the passenger side of the front + rear seat. Both kids were comfortable in the bed on the sleeping platform, with heat. There was still plenty of room for skis, boots and poles in the roof box, and any duffles and clothes in the cab or in the back of the truck in cubbies or on the side shelf.

I wanted to keep a heat shield between any plastic and heated components of the build, so I built a mount for the heater within the box. The base is a piece of sheet metal and the threaded rod allowed me to raise or lower the height of the heater in the box. When mounted, I maximized the space below (the intake and exhaust ports) and raised the body of the heater to the point where latching the lid puts slight pressure to keep everything snug within the box. The aluminum angle is also bolted to the back of the box. The 5L fuel tank sits inside the box with a sheet metal heat shield around it that I fabricated with some flashing and pop rivets. The exhaust line is wrapped in motorcycle exhaust wrap attached to a double walled marine port. The heater itself is a Chinese copy of a Webasto, but I upgraded the exhaust line with a better Webasto (better materials, slightly thicker).

The hot air duct outlet is split and I have one hose running to the side sliding window of the SmartCap, the other is running to a port through the rear passenger window. Both have 1 1/2 holes to fit the detachable controller wires. I cut and re-soldered all the controller wires so that I can unplug the 6? pin connector from the box and store it separately.

So how does it work!?

It got down to 17 degrees and we were all snug and warm. I should note that I have carbon monoxide detectors in both the truck bed and cab. I woke up around 4am worried that we were going to run out of fuel and I was going to burn out the motor if the pump was running and it wasn’t getting any fuel. I have no idea if the heater has a fuel sensor that will shut off if it runs out of fuel. When turning the heater off, there is about a 3 minute cool down period. This cool down first warms up the combustion chamber to burn out any remaining residue and then spins up the fan with no combustion to cool things off before final shut off. If the heater were to lose power, I think bad things would happen – residue wouldn’t burn out, and it would just turn off hot – possibly damaging components. Running out of fuel is probably better than running out of power.

Test setup at home. I used metal ducting adhesive tape to attached the dual exhaust port. This was sufficient over a hose clamp.
Heating both the cap and the cab. Power is going into the cab (where I have the controller).
20 degrees and making a pancake breakfast.

Happy to answer any questions about the setup. This is my solution to winter trips until I can build a proper camper. I think the ideal solution is to be able to stand up, and change in out of ski clothes, and to cook meals inside a warm space.

I’m in the design stages of building a slide in pop-up for the spring. Design is to scale in Shapr3D. Design inspiration is coming SuperTramp and Enduro and Hiatus Campers. In future I see the advantages of mounting the heater in an interior space with the fuel tank on the exterior for easy filling. Until then.

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