Grundfos595444-3/4" Clip-on Aquastat Kit for UP Series Circulators, 85-105F

Easy instructions and straightforward setup. Runs as it should.

I can't believe I used my recirculation pump for years without this! Why run the pump when you already have hot water throughout the system? Adding this has reduced pump run-time by probably 90% for us. We do have the hot water and return lines fully insulated, which helps, and live in CA so temps aren't extreme, so your experience may vary. What a huge savings in pump run time and electricity usage. I calculate that this pays for itself in well under a year. It would be nice if you could tune the temperature, but this is really a minor point, perhaps for a future improvement.

The thermostat works perfectly. However..... It's low setting of 85 deg is not high enough to ever let my pump turn on due to gravity flow on my return line. I have just enough gravity flow to keep the hot water lines warm, but not enough to keep HOT water in them. I unhooked this thermo switch and put a timer on and that works fine. Actually, I'm OK with immediate warm water, with a 15 second delay for hot, so am leaving the pump off most of the time too, LOL. I guess you could say that I over engineered my system since I'm not even using the pump now, but am very happy with the performance of the gravity return.

Given its advertised as the companion to a hot water circulator pump I expected its control temp would be close to one size fits all.NOT SO.No matter where I placed it in the loop, on-time For the pump was 20+x longer than needed for hot water to flow at the faucet.My choice in system control is a user initiated button. The aquastat was to limit pump on if the pipes were already warm and shut-down the pump once it got hot enough.Required on time for my pump was only 10sec. for water to be hot at the faucet. At normal flow it would take 60 sec + 1/2 gal of water wasted before it was useably hot. The aquastat would allow for a 4 min. run time.A count-down control timer relay is the solution for my system. (Maybe your system too)HTH! :)

Solved my problem. Hot water faster to Bath opposite side of home from water heater. I turn on shower and sink at same time to get hot water faster for I only have single lever faucets. Before, I was wasting gallons of water. Now it is hot before I can brush my teeth.

I purchased the Grundfos 595444 3/4-Inch Clip-On Aquastat Control with a listed heat range of 85 - 105 degrees F. to turn a hot water heater circulating pump on and off. The pipe that the sensor is clipped to is copper, and the temperature at the attachment point is 116 degrees. The control does not open at this temperature. I added heat transfer paste to the fitting, and it still doesn't open and shut off the pump. Finally, I insulated the control, and still no luck. I have not yet tested the open/close span of the controller, but I am positive that it is not what is advertised. I bought a timer and installed it instead.

This add on sensor is great if you purchase the Grundfos basic models. The model I purchase did not require this temp sensor. Be sure to look at the model your buying.

This works to keep the recirculation temperature about right with the water heater at 125 degrees. The higher temp unit I had required me to up the water heater to 135 degrees since it wouldn't turn off until the recirculation water was at about 130 degrees. That was too hot.