Wood Burning & Mixing Valve

Eric Johnson

That's a great thread on wood burning going on down below. I had a few related questions and since that one's getting a little cramped, I thought I'd start a new one.

Some time ago I heard something about installing a mixing valve on a wood-fired boiler that (as I understand it), allows you to use water in the system for heat storage. My house, for example, has about 15 cast iron radiators in addition to the boiler's water storage. Am I correct in thinking that you can somehow (safely) mix return return with supply from the boiler and essentially store heat in the radiators?

What happens when a zone calls for heat? Does a pump simply kick on and supply that zone with hotter water?

Do you need convection for a mixing valve arrangement to work?

Is this a realistic alternative to a heat storage tank?

And finally, my understanding of reverse circulation schemes is that they tend to void boiler warranties. But the mixing valve I heard about sounds like a legitimate deal. Are there any downsides?

hr

You may be thinking

about a 3 way thermostatic mix valve at the boiler to assure it sees a return temperature of 140 or more.

With high mass or large volume systems you can send a cold slug back to the boiler. The mix valve blends supply temperature from the boiler into the return water stream to keep that return temperature up.

The Tarm folks have some nice piping diagrams at their site that shows a 3 way valve placement.

http://www.woodboilers.com/piping-layouts.asp

hot rod

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Sun Energy , Mora MN

I would not plan on "much" storage in your radiators, they are designed to give off heat not store it. They will "store" some heat for a certian amount of time.