[randen]

Jeff5may

I'm suprised you have asked the question; "I have a question about this plan: what size and length of copper tubing is enough to make the thing operate at high efficiency?"

You had posted Oct 10 2013

Acquarioe,

"I believe 10 meters is a magic number. The airtap hpwh unit uses this length of tubing for its hwt snake condenser. Many, many hobbyists have used this length for their water side exchangers. As long as the tubing is large enough for the refrigerant to flow, I believe one could heat or cool a skyscraper with a 10 meter exchanger!"

I'm for certain you're looking for some corroboration.

It's true for a small pump the 30' of copper 5/16 dia.works well (5000 BTU) as this is what I had found. However for 24,000 BTU this would be different.

Case in Point:

In my solar hot water tank I have 50' of 7/8 dia. copper tubing. It works but not the best.

If you consider the heated copper tube immersed in water there would be a film of heated water surrounding the tube, slowly rising via convection presenting cooler water to the surface of the heated tube. I you have an abundance of heat inside the tube the convection action may not be enough. This is what I have in my case.

It would be best for this amount of heat be mechanically moved. I would humbly suggest for a system capable of a 2 ton output be part of a heat-exchanger with a circulation pump. The movement of water over the heated surfaces via a pump would greatly enhance the efficiency instead of relying on convection.

This is what I had found working with the HP hot water tank and solar hot water tank as well as the 5T GeoThermal heat pump.

Randen