Hot Water Heat for camper

[redbarron55]

Has anyone else thought about using the hot water system and a pump with an accumulator for cabin heat?
I have a thermostatically controlled demand tankless water heater and I am well pleased with it.
My thinking is that if I installed a hot water circulating pump and a small insulated tank with a radiator for a fan to blow through and recirculated through the heater this would allow just the one high efficiency burner to provide heating for water and cabin.
I don't really need it since I have a heat pump, bit it is an interesting project.
One thing I like about the tankless is that I am not carrying six gallons of water around all the time or 48 pounds,
If you alrwady had a tank type heater all you would need is a pump and radiator and a fan to blow air through the radiator.
The thermostat would control the fan and pump.


A radiator like a transmission cooler with no lead solder might work for the system and PEX tubing for the plumbing.




Just a thought.

[David B.]

Norm (Honda03842) and I spoke of trying that very thing years ago, but I never persued it (don't know if he ever did). I believe that Truma Combi is making just such a combination of hot water and furnace. I still think it's a great idea.
Dave & Paula

[Raspy]

It's a perfectly sound idea and would work very well if set up right. It's really the same system cars use and there are aftermarket fan/coil systems available for truck cabs and boats too.

The tankless (propane) is not perfectly suitable, but will work. It should work very well with a buffer tank in the circuit to keep the heater from short cycling and to deliver a relatively constant temperature to the room. The problem is, by the time you install the buffer tank, expansion tank, all the plumbing, pump and the fan coil, you might just as well put in a conventional propane RV heater. But if you start with a tank style water heater it makes a bit more sense. Especially since the tank style water only monitors the tank temp to decide when to fire up, whereas, the tankless monitors flow to start and it is not used to warm water coming into it (return from the fan/coil will be just 20 degrees or so cooler than the hot side).

If you really wanted to be fancy, you could lay coils of 3/8" PEX (1/2" OD) between the subfloor and the finish floor (in routed grooves in a plywood layer) and have a radiant heating system that required no fan or visible parts in the room. Extremely quiet and the best comfort of all. Then just use the tank water heater as the heat source and connect a thermostat to the pump to make it go on or off. Very simple. Quiet. Minimal parts. The pump would be a centrifugal pump, not a diaphragm style pressure pump, so it would be very efficient and silent. The hot supply and cool return would simply TEE into the hot and cold connections at the water heater. It would require a small expansion tank, but that's it.

[Wayne Collins]

My vague recollection from school, is that with each exchange of energy from one form to another, you lose some. So, you burn gas (LP) to heat water, then run water through a coil, and air over the coil, to heat the air.
It would be most efficient to burn LP to heat the air. ... but then you have the problem of using up the oxygen and making CO2 and H2O.

A small cube electric heater works just fine for us

[Raspy]

Wayne,

Well, your not exactly losing energy while changing it from one form to another.
In a heating system for houses or trailers, you're giving up all the energy to the surroundings and enjoying the benefits of the process. Your electric cube heater is giving up 100% of the energy you put into it, to the outside surroundings. You are just making an inefficient delivery system to the surroundings by delivering it to the interior of your trailer instead of just running the electric heater outside.

All heating systems lose all of their energy to the outside, eventually.

Your cube heater is fine as long as you have a power source for it. It's not really comparable with a propane system that will run while off the grid. Propane allows us to camp in cold areas, without shore tie and without running a generator.

There are many ways to deliver the heat from a propane source to the interior of a trailer or a house. Most of us have a forced air system that blows hot air into the interior. That requires a loud and power hungry fan in addition to a propane burner. Another delivery system is to do what I described in my earlier post. Circulate warm water through tubing in the floor, from the water heater. Radiant heating. The advantages are: one less propane appliance, less noise, better comfort and lower power draw.

But if you are connected to shore power and it's just a bit chilly some morning, the cube heater can take care of it simply and quickly too.

[Darwin Maring]

Way up North in Nacoma North Dakota at our only Anti Ballistic Missile site, I had a popcorn heater on by truck. It had a tank with an electric heating element and a check valves and was placed in series with the heater hoses. It boiled the water and the hot water was forced out the bottom connection and that forced return water in the top connection and the cycle started all over again. It made a popping sound, therefor the name popcorn heater.