GeorgeRa
2013 Sprinter DIY 144WB, Portland OR
A couple of years ago I had the factory winterized Canadian Bigfoot Trailer. The manufacturer sealed under the floor tanks and plumbing with a sheet of plastic from the outside air. The air furnace pumped hot air into that space. This is my plan as well except the heating will be done with Hydronic’s coolant (not engine coolant) flowing through sections of plastic supply tubes and copper tube inside the sealed air spaces.What is the best approach to using the Espar for heating the under-van plumbing? My GWV Legend has an Espar Hydronic that is used for cabin heating and on-demand hot water. How would I approach extending it to plumbing freeze-prevention? I know that the Advanced RV folk run the return line through a groove in the fresh tank, but I am picturing something more comprehensive than that. I am thinking of boxing in the plumbing area for starters. Should I install another heat exchanger down there, or what?
This http://www.foamboardsource.com/sintra-pvc-foam--sintra-pvc-board--sintra-pvc-6mm.html or alike material could be good choice for building a sealing structure or more durable material like this http://www.egilplastics.com/product-show.php?showlei=&Leiid=&n=1&id=215. In my case most of the plumbing tubes are within the under the floor left and right cavities so flat sheet attached with screws should be sufficient.
In your case a separate liquid to liquid heat exchanger could make sense in order to keep engine reliability high. I would be a little nervous having engine coolant going everywhere, just a higher potential for leaks. But this option could be complex, another coolant loop, another pump, expansion tank etc.
Another option for you, perhaps this is the one you were thinking about, could be to heat tanks and plumbing with hot air from an auxiliary heater heated by coolant. The small coolant to air heater could be installed right next to Hydronic heater minimizing risk involve with long coolant lines. Installing an air distribution manifold could be easier and more forgiving than running coolant. The 12V built heater fan should be controlled by a thermostat switch located in a coldest spot. To distribute hot air under the van from left to right you could use rectangular tubing to reduce the road clearance impact.
http://www.princessauto.com/en/detail/appareil-de-chauffage-d-appoint-3-425-btu-12-v/A-p4240007e
This is a very compact heater but from UK
http://www.demon-tweeks.co.uk/motorsport/cockpit-ventilation/demon-tweeks-micro-heater
Thermostat switch to control the fan, 25A resistive load should be OK.
http://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK
George.