We used a
Espar hydronic heater in a sprinter van. We did not buy the kit, just the heater with it's accessories. Primary 3 gallon glycol circuit heated to 195F with the diesel heater. This went through 3 heat exchangers. One was a radiator with a fan to heat the cabin controlled by a thermostat (set to 71F), second was a liquid to liquid heat exchange with a thermostatic valve set to 90F (so you can walk barefoot). The secondary circuit was 1.5 gallons of glycol with a pump controlled by a second thermostat set to 75F. This circuit ran to four 3/8" copper pipes on the floor of the van and covered with a 1/8" 4'x12' 6061T6 aluminum sheet. The fan warm initially in 5 minutes and then the floor keeps it at 75F. The third heat exchange was for instant hot water. I'm thinking of doing the troopy similar without the heated floors. It works amazingly good.
The van spent mid winter supporting 3 guys for 10 weeks in all the ski resorts in California, Oregon, Utah, Colorado and New Mexico. The heater would turn on at 2 PM. They would come in at 4PM to a toasty van, and be naked inside. There was 1 foot of snow on the roof.
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