I am installing a new geothermal system in a newly constructed house. The contractor says that the desuper plumbs directly into the bottom of the water heater and creates a recirc loop at the top of the water heater. It essentially acts as a maintenance water heater rather than a preheater and finishing water heater which I read about everywhere. I can not find any literature stating that this is the way it should be connected. I also do not see how this is saving anything significant as the electric water heater will engage as soon as the temps drop regardless. Any insight is appreciated. Geothermal system is Trane (WaterFurnace). House is 100% electric.

We have been around this bend a time or two- inexplicably all the major manufacturers continue to insist that the one tank configuration is fine, though data suggests that is only rarely true. I will not install a system without a buffer tank

You are correct. Desuper is virtually useless without its own dedicated preheat tank. Skip the cost of installing it if it won't have its own tank.

I don't understand what he / she means about "a recirc loop at the top of the water heater" That sounds like mumbo-jumbo. Desuper works best on coolest possible water. Pulling hot from top of tank has the potential to waste energy / increase cost.

And if the HWH is gas-fired, a DSH system installed directly to it, i.e. minus a staging tank, will not only not be effective, it actually causes reduced efficiency of the GSHP unit when in cooling mode.

A few years ago I put instrumentation on this, and showed that in many situations refrigerant was actually being heated, not cooled, when using the DSH function connected directly to a gas-fired HWH.

Best regards,

Bill

Posted By joe.ami on 26 Feb 2013 07:52 AM
We have been around this bend a time or two ...

Or three or four or five or six!