NeverDie
Senior Member
There's another possible tweak here, which is: are you sure she really wants 120F? Maybe she does, but for most people that's pretty hot. If 105F is what she really wants, then you can recirc at a slower speed to achieve that, and your standby losses are considerably less. In my case, the thermo-siphoning pretty much does that. i.e. there's no point delivering 120F if it's going to be mixed with cold water at the tap to deliver 105F. Instead, simply recirc 105F to the sink and use just the hot water tap (assuming your particular installation provides adequate flow from just the hot water line. If it doesn't, then you may be stuck delivering the higher temp water, which is perhaps your situation).
It's actually difficult to get 120F all the time from tank heaters without setting them a lot higher and using a thermal mixing valve. There can be a 20F degree difference between the cut-out and the kick-on temperatures, so if you set your tank for 120F, you might be getting only 100F if the tank has cooled but hasn't actually kicked on yet. In practical terms, that can be the difference between a hot bath and a bath that's doesn't feel hot enough, all from the same tank, but on different occasions.
Regardless, I really like BSR's solution. It's a platform you can do a lot more with than just trigger a recirc pump. For example, you could use the same thing to turn on the HVAC or the exterior lights if it's dark out but your wife is coming home to an empty house...
It's actually difficult to get 120F all the time from tank heaters without setting them a lot higher and using a thermal mixing valve. There can be a 20F degree difference between the cut-out and the kick-on temperatures, so if you set your tank for 120F, you might be getting only 100F if the tank has cooled but hasn't actually kicked on yet. In practical terms, that can be the difference between a hot bath and a bath that's doesn't feel hot enough, all from the same tank, but on different occasions.
Regardless, I really like BSR's solution. It's a platform you can do a lot more with than just trigger a recirc pump. For example, you could use the same thing to turn on the HVAC or the exterior lights if it's dark out but your wife is coming home to an empty house...