Thermostatic Mixing Valve and Recirculation System

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SAS

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I would like to add a Therm. Mixing Valve to my hot water heater, but I am somewhat confused about doing it in conjunction with my recirculation system. I have read about problems that arise when there is no demand but the recirculation pump is running. Since I have an aquastat on the recirculation line right next to the pump, do I need to be concerned about any temperature fluctuations due to the recirculation system? Also, I noticed that this product has a separate recirculation port
https://www.cashacme.com/resources/tank-booster-pro-spec-sheet/

Should I be using something like that?

cash-acme-tempering-valve-1.jpg
 

Terry

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With a tempering valve and a recirc pump, you also use an aquastat which turns the pump off when the return line is at a preset temperature.
Without a means of turning the pump off, the water continues to cycle through and gets as hot as the highest setting on the water heater.

You can't run the pump continuously when you have a tempering valve. It defeats the purpose.
 

SAS

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With a tempering valve and a recirc pump, you also use an aquastat which turns the pump off when the return line is at a preset temperature.
Without a means of turning the pump off, the water continues to cycle through and gets as hot as the highest setting on the water heater.

You can't run the pump continuously when you have a tempering valve. It defeats the purpose.
I already have the aquastat in the system, so does that mean that I do not need a mixing valve that has a designated recirculation port? Is there one that you would recommend?
 

Terry

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I already have the aquastat in the system, so does that mean that I do not need a mixing valve that has a designated recirculation port? Is there one that you would recommend?

My experience has been that the temperature starts to climb without a way to turn off the pump when the return gets too hot.
Let us know how it works though.
 

SAS

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My experience has been that the temperature starts to climb without a way to turn off the pump when the return gets too hot.
Let us know how it works though.
Sorry, I wasn’t clear. I have an aqua stat that turns the recirculating pump off at 120 degrees (or something close to that). So can I just connect a valve the same way as if I didn’t have a recirculating pump? Do I connect the mixed recirculated and cold water that feeds into the heater or cold water before it mixes with the recirculated water?
 

Reach4

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This is their drawing. It looks like you bring the return to the port on the hot side.
It looks like they should have shown the thermal expansion tank connection too.
 

Jadnashua

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Some tempering valves have dedicated ports for recirculation. Using the return line for the cool water is generally the solution, otherwise the full output temperature of the tank can get into the line and defeat the operation as potentially super hot water could be in the lines prior to where you're monitoring it with the aquastat.
 

SAS

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So here's the challenge. My water heater does not have the connections on the top, and the current installation is a bit complicated. The vertical copper pipe running down the front of the heater is the return with a mix of cold and recirculated water. The horizontal copper pipe in the front is the hot water output. The horizontal CPVC running off to the right of the picture is the recirculating line - the pump is just out of the picture to the right. If I were to use the valve shown above, that has a port for the recirculation line, where and how would you recommend installing it?

My first guess would be to cut off the elbow from the copper pipe on the output from the water heater and screw the mixing valve directly onto the water heater (as it is intended to do). I could then put a tee in the return line with a male threaded adapter that could attach to the hose that would normally run to the water heater input. Finally, I would have to put a tee with a check valve after it in the CPVC recirculation line and run a pipe (probably more CPVC) down to the mixing valve. Does that sound right? Any other ideas? What if I didn't use a valve with the recirculation port? In that case could I just install it on the hot water output, put in that tee on the return line and be done? I do have an aquastat that will turn off the pump.


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