Domestic Hot Water Recirculation with a mixing valve

Bob Gagnon plumbing and heating

Does anyone have a diagram of how to pipe a recirc line with a thermostatic Honeywell mixing valve? It in New Hampshire and I can run 140 degree water to the system, maybe I don't need the mixing valve? I can't put mixing valves at point of use.

Thanks, Bob Gagnon

hot_rod

Hmmm, I'd be surprised if the plumbing code allows 140F to the faucet, but I don't know the exact application. In some commercial jobs high temperature is allowed, maybe required for some dishwashing or sanitizing applications.

A point of use valve at every HW connection may be and acceptable option?

Here is a drawing for the correct way to pipe record thru a mixing valve. The crossover balance valve is crucial to prevent temperature droop or creep in the recirc loop.

Idronics11 is an issue dedicated to DHW production and recirculation.

Bob Gagnon plumbing and heating

Thanks for the quick response Hot Rod, I'll go with the mixing valve, I like that diagram. Should I put an aquastat in there, or just run it continuous?

hot_rod

Sure, an aqua stat and or timer, or one of the Smart recirc pumps that learn usage trends.

The very best thing for recirc is insulating the entire loop. Then you have the most efficient system.

I've heard California requires recirc on any system longer that 100' and they also require 1" insulation!

Bob Gagnon plumbing and heating

Thanks for all the good info Hot Rod, one last thing. They are boxing I the hot, cold and recirc line, is there any reason why they couldn't insulate around the pipes with fiberglass, rather than insulating the individual pipes?

hot_rod

If the insulated box enclosure has both H&C running along side one another, will the cold line sweat? The hot may heat up that space and cause condensation? Don't know for sure.

At DHW temperatures, even the less expensive foam pipe insulation is fine, doesn't need to be Armaflex like refrigeration lines use.

I don't know how much tube you have to insulate, but it may be money well spent.