Forum Discussion

adamis's avatar
adamis
Nomad II
May 02, 2019

Build your own Water Heater / Furnace Unit?

I know there are newer campers that have combined water heater / furnace units but they are pricey and not necessarily an easy drop in unit. It got me to thinking that it would be an interesting experiment to see if a standard RV water heater and add furnace capability.

Pros:

1. Elimination of one large and complex component

2. Opening up space for additional storage

3. Possibly less heating hot/cold "cycles" at night because heated water in the tank would act as a stored reservoir of heat for the furnace.

4. Possibly quieter overall (my furnace is very noisy while my water heater is nearly silent).

Cons:

1. May take longer to heat interior

The idea I was thinking about is cutting access into the stainless water tank, running some stainless tubing channel inside with inlet connection and one outlet connection. Weld it all back together. Then running a line to a radiator / fan combination that ties into the existing ducting. Cycle the fluid with a water pump and use some sort of relay to activate the water pump with the fan when the thermostat calls for heat.

Aside from the welding, I don't see this as something too difficult. I know there are some very skilled people on this forum and so I am wondering if others have toyed around with the idea themselves.

This post is about whether the idea is feasible and could be done readily enough by a moderately skilled person. I'm not actually considering actually doing it (too many irons in the fire as it is) but might keep it in mind for a future project.

24 Replies

  • Not totally a bad idea,
    That system works great in homes and very fuel efficient.
    I’m not sure the RV hot water heater is capable of a hot water cycle and then a cabin heat cycle too often without it ending its life cycle prematurely.
    To manufacture one yourself would be dangerous as a hot water tank is a pressure vessel and requires some engineering to ensure you don’t blow your camper off of the truck.
    Pressure safety devices would also be required.
    Very good idea though, maybe something to run by the hot water heater manufacturers.
    Good Luck
    Wes
  • A 12gal rv water heater produces approximately 12000 btu,some of that is exhaust . It is doubtful it would provide enough for cabin heat plus hot water in anything more than mild weather.
  • I think your proposed solution will not transfer enough heat. You would probably need a heat exchanger to transfer enough energy from the water tank to your heating circuit.
    Also, how much energy (BTUs) does the water heater deliver? Will that be enough heat for the camper?
    Someone with more engineering knowledge than myself should be able to do some calculations on the energy needed to be transferred and the necessary surface areas.
    I would also consider moving away from a hot air heater towards a water filled radiator system like Alde.
  • I have considered installing a recirculating pump like what's used in residential homes to reduce the wait time and wasted water at the shower. I suppose one could run the recirculating water through some baseboard heaters and heat the cabin that way. Might even be able to install a radiator in the space where the original forced air furnace is along with a much quieter fan.