thermostatic mixing valve, how \"off\" is \"off\"?

Greg_50

For occasionally dumping extra heat from a solar collector, I have in mind a radiator mounted behind the solar collector and a thermostatic mixing valve. Plumbed so that the mixing valve can choose either to draw from the panel directly (normal operation) or draw from the panel through the radiator to dump the extra heat, so max leaving the mixing valve is, say, 170 deg F.

My question: What fraction of the flow will go through the radiator and the "cold" inlet to the mixing valve when I don't want any of it going that way? Suppose the solar panel is putting out 150 deg F and the valve is set at 170. I'd like more than 99% of the flow to go straight through the mix valve, less than 1% diverting through the radiator where it would be unnecessarily cooled to ambient. Are mixing valves that selective? (e.g. Honeywell AM series)

hot_rod

a contractor in the Chicago area

installs a strip of commercial fin tube along side his evac tube arrays for heat dumping. He uses the 3 way thermostatic as you describe. i'll see if i can find his info. He showed me a number of pictures of his installations at a seminar last fall.

You could "mock up" the valve on your bench and see what happens?

Another solar contractor/ importer I visited with is having an evac tube header build with the dump fins built right into it, everything is on the roof top, thermostatically controlled.

It's a shame to need to dump excess heat that way, be nice to be able to put it to some use like cooling

hr

1bourbon

good use...

My closed-loop SDHW system has a thermostatically controlled Taco valve that opens when the tank gets to about 160-165F. The loop flow is then diverted through 12 ft of Slant/Fin MP-80 mounted along a wall in the basement.

In the shoulder seasons, it makes the unfinished, unheated basement workshop a bit warmer and more comfortable.

In the summer, it serves a minor to moderate role in raising the space temp and thus dehumidifying. Fortunately, we live in a climate that does not require A/C, so there is no impact on the cooling load.

In a climate that requires A/C, an outdoor/rooftop dump sounds cool. As it were.

Greg_35

taco valve

I am working on a system and am considering incorporating a thermostatically controlled valve for a dump zone much like the one you have described. Could you tell me what model Taco valve you used?

Thanks, Greg