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-   -   automatic heat source selector (https://ecorenovator.org/forum/showthread.php?t=4398)

nexsuperne 04-15-15 01:40 PM

automatic heat source selector
 
Hi All,

I have a 300 litre 30 tube solar water heater on my roof, which circulates the water through the indirect coil on my 200 litre thermal store.
Do they make a mixer valve that will work out whether the solar water heater water is hot enough and use this directly, or if it isn't quite hot enough, then use some heat from the internal thermal store?


This way I don't need to circulate the water from the solar, as I can use it directly.

Thanks :)

AC_Hacker 04-15-15 09:25 PM

Quote:

Originally Posted by nexsuperne (Post 44657)
...I have a 300 litre 30 tube solar water heater on my roof, which circulates the water through the indirect coil on my 200 litre thermal store.
Do they make a mixer valve that will work out whether the solar water heater water is hot enough and use this directly, or if it isn't quite hot enough, then use some heat from the internal thermal store?

This way I don't need to circulate the water from the solar, as I can use it directly...

It sounds to me that you are looking for a "Differential Thermostat" that can control a valve.

There are commercial versions HERE.

And if you search HERE you will see DIY projects that were done here on EcoRenovator.

Best,

-AC

Mikesolar 05-19-15 05:28 PM

Im not sure I understand what you are trying to do but it's not a good idea to try to use the solar directly because, if you don't use the tank, you will get just a small amount of heat and will have to use it only when it is available. The thermostat in the tank knows when to turn on or not and you can adjust it to not come on at any time if you want.

jeff5may 05-19-15 07:41 PM

I see a few unknowns in your post. Without knowing your targets, goals or main purpose of your solar thermal collector, it is difficult to lead you in the right direction. Rather than try to read between the lines, make assumptions, and take potshots at an answer, i'm going to ask more questions.

Sure, the collector is made to gather heat and store it, but for what purpose? Are you circulating potable water through it, to use for dhw? Or is it filled with brine or glycol with a separate heat exchange component? Are you also using it for space heating?

Another unknown facet is the interaction with the external store. How warm is the store getting while the sun is shining? Does it discharge quickly when drawn from? How is the circulation pump being operated now? How will the indirect hot water loop heat your potable water quickly enough to meet demand?

Feel free to provide as much or as little information as you are comfortable to divulge. The better you can describe your system and intents, the more spot-on your replies will be. There are as many ways to configure these systems as one can imagine.

nexsuperne 05-25-15 02:26 PM

I have managed to sort this out by using a couple of 2 port valves a relay and a cylinder stat. When the solar tank is above 50C, then the 2 port valve from the thermal store closes, the valve on the solar water heater opens and lets the solar heated hot water run to the showers and taps directly.

Thank you for your ideas. :)


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