[Greenbuilding] stealing heat from a woodstove for water heating

[Reuben Deumling]

On Tue, Dec 31, 2013 at 2:54 PM, Erin Rasmussen <erin at trmiles.com> wrote:

> Hi Rueben,
>
> There is some good math hidden in online conventional water heater
> calculations, including some great averages for how much water typical
> tasks like dish washing etc takes. You may want to download one of those
> and see if the setup you're thinking of hits the right sorts of numbers.
>

I've got that part covered. I've been submetering end uses for many years.
Our average total household indoor water use (hot + cold) is right around
19 gallons per day. When the incoming water temperature isn't in the low
forties we can heat our domestic hot water with the pilot light in our
20-gallon water heater.

The other part of this is the heat transfer. I'm guessing that that's a
> coil around the flue transfer system, there are other heat exchangers out
> there.
>

The axeman system is a stainless steel sleeve that is installed in place of
the first section of stove pipe immediately above the stove.

> The pricey ones are pancake style and do a beautiful job of transferring
> heat, but are not usually used residentially.
>

pancake style? Where are these located relative to the stove/firebox?

> The other part of this is making sure that you don't have too much heat
> loss between the firebox and the point of use.
>
Short runs, small pipe diameter, well insulated. The current system
(natural gas fired) has all three. The revised version, relying on a
combination of wood and solar, is, unfortunately, going to have
considerably longer runs due to the N-S orientation of the house.
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