Grundfos recirc tee

[Plumber69]

Can someone explain to me how this works. And how when it fails creates a cross connection.

 

[Reach4]

Picture is from https://api.ferguson.com/dar-step-service/Query?USE_TYPE=INSTALLATION&PRODUCT_ID=1661532

It seems to me there must be a check valve in the middle that has failed, presuming that the hot and cold are not hooked up backwards.

 

[Sponsor]

 

[Plumber69]

I still don't understand how water recircs through this gadget

 

[Reach4]

http://www.redytemp.com/hotwatercirculatorproblems.htm describes this system from the point of view of somebody selling a competing different way.

 

[Jadnashua]

There's a thermostatically controlled valve inside that thing. When the hot input is below temperature (like when things have cooled off from no use), the valve opens a path from the hot side to the cold side so that the pump can push water through. Once the hot water actually rises to the design point, the valve closes. Essentially, it is a temperature controlled crossover. It probably also has a check valve in there to prevent the cold water from reaching the hot side when you open the faucet.