Mixing valve recommendations??

[tinkerer]

Hello everyone! I need some advice on a mixing valve in a domestic water system. Here is how my system is set up. I have a wood/coal furnace with a hot water coil that thermosiphons into a 50 gallon storage tank. This usually supplies enough hot water when its cold, but on a warmer day it gets behind. We then have a tankless hot water heater we can switch over too on the warmer days or when the stove is not going. What I was thinking of doing is installing a mixing thermostatic mixing valve between the storage tank heated by the stove and the tankless hot water heater. This way on a warmer day or a day when the stove is not going, I don't have to swich valves. I need to cool/temper the water that goes into the tankless as it can not have incoming water over 100 degrees. Do you think this will work? Anyone have any recommendations on what brand/model of mixing valve to buy?

Thanks!
Ben

[mike90045]

My plumber used some mixer valve, to select the warmer source feed water for my tankless, I'll look today to get a model #

[tinkerer]

Sounds good thanks!
Ben

[mike90045]

It's a "caleffi mixing valve"  - plumbed backwards, to select the warmest source of pre-heated water.  I have several of them installed to manage my hot water.  So far this season (my first season in the house) the masonry heater's water coil, gets my 80 gallon storage tank, up to about 100 - 110F.  In the summer, when the fireplace is not going, it will select the water from the rooftop solar heater, and send that to the tankless water heater.

http://www.houseneeds.com/shop/hydronicheating/mixing-valves-hydronic-plumbing-index.asp
&
http://www.caleffi.us/caleffi/en_US/Site/Products/Product_news/args/detail/~Details~News~news_detail_0000140/type/newshome/index.sdo

hope this helps.

[Tom Reed]

Never thought of using one that way. Good idea!

[BruceM]

Very interesting approach, Mike.  You say it's plumbed backwards-  does the hot inlet become the new outlet?

[oiler]

I would like to know too.....

[LowGear]

What about putting the demand unit after the tank so it's automatic?

Casey