I've done all kinds of construction, including lots of electrical. But I've been deferring learning about the finer parts for...ever. Whoops!

I bought a device that detects hot water flowing in our house. The water opens a valve that creates a closed switch/circuit to a 110v pump that circulates the hot water. So, turn on faucet, turn it off, wait a minute, and the water is hot at the faucet. Very green. But the electronics died. I want to build my own replacement, so I don't rely on this product existing later.

Ideas for how I can connect the two valve wires (low volt) to switch on power to the pump, and after 2 mins, have it switch off again? Thanks in advance.

 

off the shelf delay off timer?

 

off the shelf delay off timer?

How how would it turn the power to the pump on?

 

How how would it turn the power to the pump on?

http://ecmweb.com/training/basics-time-delay-relays

 

Build or Buy?

I have a similar situation. The county requires a hot-water recirc pump so that you do not waste water by running it down the drain while waiting for it to get hot. They do this to save water on one end, and so they do not have to treat the waste water at the other end.

I live rural; no city services; my own well, and my own septic. Every gallon I pump out of the ground goes right back into the ground. The net result is that I have to pay for gas (expensive) to keep the water in the house recirc loop hot all of the time, 24/7. So the county's requirement just costs me money for no benefit...