Since my last post I've been continuing in my research and design of my DIY RV. And while I'm still very much interested in making a hydronic heating system work in a small van RV, I've changed my method of attack a little. Well, actually probably a lot.
I'm still not sure whether this "new" idea will be "in addition to" or "instead of" the hydronic heater core idea I posted about earlier, but I'm seriously considering trying my hand at an in-floor radiant heating system for my RV. I'm sure you all know what I'm talking about
: Hot water being circulated through flexible tubing under a floor to provide radiant heat to the entire van. And not just to the "living area" but also inside the cabinets to help prevent the water tanks from freezing in colder weather. Yes, I'm planning on everything being inside the van, because I'd like to use the RV in cold weather, too. And here in Delaware, the winter can get really friggin cold!)
This system would include a water heater, circulator pump, PEX tubing, a reflective material (I'm thinking thin aluminum or maybe Reflectix), and a slightly-raised floor (to make room for the tubing). It's a bit more complex and involved than the simple heater core loop, but I'm hoping it will prove to be a better method of heating. I could still include another loop for the heater core idea as well in my design.
One thing I'm having trouble figuring out though (since I'm not a plumber or a HVAC technician): I don't understand how the basic water heater, on-demand water pump, and piping system works in a simple sink-only RV setup, so I have no idea how you would add a closed loop (or two) to your water heater for the hydronic system(s). And could the hydronic closed loop be antifreeze based or would it have to be water, since it's attached to a potable hot water source?