opnspaces wrote:
I've always found this intriguing and want to build one some day. I'm curious though if it could be made without the water pump. I seem to remember that back in the late 70's or early 80's when the water cooled motocross bikes came out that the Kawasaki KX bikes did not use a pump. I don't know what it's called, convection, thermal dynamics, whatever, but the concept was that hot water would rise to the radiator and the cold water would sink back to the motor.
I don't know how well this system worked for a high revving motocross bike, but for what we're talking it might be perfect.
I believe a pump is necessary for this application. Of course, it all depends on room size, ambient temp, and insulation values. Using a smallish exchanger and assuming typical RV construction, one would like the hottest temperature possible at the exchanger. That would mean a pump is necessary.
IIRC, Forum member smkettner uses an non-impeller pump (magnetic drive) for recirculating water through his system to abate plumbing freeze-up. Maybe he'll chime in with the name of the pump.
Besides the lack of noise while using hot water heat, it's also very efficient because you have the mass of the water working for you.
FWIW, I have a fanless furnace in my rig, an older Sportsman propane fired heater. The 20K BTU Sportsman will cook me out of the rig if left on High for any extended time. Even at Winter deer hunting camp, we turn it down to just idle through the night. It isn't as efficient as a hydronic system but probably burns less propane than a forced air unit.
For those wishing to use hydronic as an adjunct to a forced air system (eliminate some of the run time), I would bet recirculating water from the water heater would be all that is needed. Unfortunately the water heater has some noise involved, also.
