thermostatic mix valve and recirc pump

don_205

Sounds like you need a spring check some where in that circuit.

Could be the sensor itself.I had a sensor off by 10 degree on a chiller last week.Drove me nuts untill i finally caught it.

I would think there would be a chart some where that converts ohms or dc volts to temps.That a big help when you start adding sensor to a system.

Ed_32

thermostatic mix valve and recirc pump

I have installed a TT prestige excellence with the built in 14 gallon domestic tank. It comes with a thermostatic mixing valve for the domestic hot outlet, and I installed it with a clip on sensor as the mix valve manufacturer recomends when installed with recirc. The problem I am running across is that the sensor does not shut off the pump soon enough, and as the water became hotter returning to the water heater and cold water inlet of the mixing valve it confuses the mixing valve, and it allows water to exit the mixing valve higher than its setting. I tried a new mixing valve thinking it might be defective, I tried the lower temperature range of the Grundfos sensors, they do not react fast enough, and finally I tried moving the sensor to the outlet of the mixing valve. This did shutoff the pump before it gets too hot, but now the customer complains the water is barely lukewarm. Has anybody else ran into this problem and have any suggestions?

Uni R_2

I think it is the nature of the beast.

If you have a mixing valve and a recirculation pump, you will get mixed temps when the water is flowing but when you recirculate the hot water is going to be at full tank temperature. The mixing valve cannot draw from the cold side when you are recirculating since the domestic hot water recirculation loop is mostly closed (unless you open a tap).

I observed this on my own system and was doing the same **** analysis as you are... ;-)

This may be a really good reason to mix at points of use instead of at the tank when you are doing recirc.

EJ hoffman

Honeywell makes a mixing valve with a bypass for a recirc

or look on the honeywell pages/specs they also show you how to build a bypass for the recicr so you don't over run the mixer.