Heat Pump Water Heater - Coil in Tube

[AC_Hacker]

vwhead77,

I admire your project, and the ingenuity with which you are solving the problems involved.

Great photos, by the way. I wish everyone was as generous with their photos as you are with yours.

It will be interesting to see how your approach compares with other approaches, where the condenser HX tubes are actually placed inside of the water heater.

Did you mention if you will be using a small circulation pump in your approach? If you do plan on having a pump, your approach could have better heat transfer because of improved fluid flow (maybe even turbulent) around the heat transfer surface. However, since your HX will be external to the water that is being heated, you will have heat loss. Insulation of your HX will reduce that.

The DIY heat pump water heaters that have internal coils, don't have the HX heat loss issue, on the other hand, they are relying on the slow movement of thermal water currents in the water tank to help with heat transfer. A pump that forces circulation could make a big, advantageous difference.

In any case, you will eventually need a Heat Pump Controller for your project...

The Homemade Heat Pump concept has had some notable success.

However, one link in the chain that is missing is an open-source general-purpose heat pump controller.

If such a controller existed, it could increase the success of people who undertake a homemade heat pump project.

It would be most excellent for you if the rest of us could complete and contribute at least a rudimentary, open source, controller for your project. The General Purpose Controller thread has made some progress, but as yet, we don't have anything, even rudimentary, that is tested that we could offer you.

Good luck,

-AC