Pre heating hot water with wood stove advice needed

[agz124]

Hi,

I am considering building a tempering tank to warm up the hot water before it enters my electric hot water heater. The wood stove in on the first floor and the water heater is almost directly below in the basement. I have about 2" of space between the stove and brick hearth wall behind it. The temperature of that air space is usually around 120F.

I also thought about taking 50' of 1/2" copper(coil) and mounting on the brick behind the stove and using it instead of tank. I don't want to cut down on the rate of flow too much.... I am well aware of the dangers of steam and pressure and I am not interested in using the woodstove to completely heat the water I just want to warm it up a little bit before it enters the hot water heater. The water entering my hot water tank is about 51F and I figure if I can raise it to 70F that will help save a significant amount of electricity.

Any advice is greatly appreciated.

Thanks

 

[walasse]

I would use a thin copper sheet with the 1/2" copper pipe brazed to it in a loop.
Instead of copper you can buy the Aluminum floor heating plates that accept the 1/2" copper pipe. Aluminum has only 60% of the conductivity of Copper but these plates you can buy on Ebay for $1.5 for 24"
This copper sheet or the aluminum plates you attache to the brick and in this way you can cover a large area what is key to capture the heat.
There are some German and Austrian companies that apply this concept

 

[walasse]

I don't know the specifics of your setup but be sure to build in some safety accesories just to make absolutely sure it's safe !!

 

[bigburner]

did this in the 80's. used an old water tank next to my stove and it was heated by convection with a coil in the stove and then when there was a call for hot water, the water from the upstairs tank refilled the downstairs water heater. We had more hot water then we needed and dumped a lot of it. The idea of it being a little more indirect might work better.