Temporary fix!
 

I have a new build with pex pipe in the slab and manifold etc plumbed for a GSHP. Unfortunately I have been caught out by weather/contractor so have been unable to dig trenches for the loop before our wet weather starts-making trenching difficult. My wife is not really happy that we don't have underfloor heat yet! For a temporary fix (until I can get the trenches dug) I am thinking that I could either:
1/Connect the GSHP to the floor and plumb a heat exchanger where the ground loop would normally be and on the other side of the heat exchanger connect that (with a circulating pump) to the house hot water cylinder (which obviously has hot water). The GSHP should then extract heat from the hot water cylinder (which is large and also solar heated as well as electrically)
and heat the floor. This would require the least replumbing when I get around to putting the loop in.
2/Connect the heat exchanger with pump to the hot water cylinder and on the other side of the heat exchanger connect the floor (with an additional pump). This maybe more efficient? But would require an additional pump that I am not sure that I would reuse.
:rolleyes:

Are you in New Zealand? If you are, you're heading into winter.

I think your wife might be right on this one.

I'd say to NOT connect the GSHP until you have a real loop field to feed it.

I vote for choice #2. Maybe you can find a used circulation pump of about the right size.

Listen to your wife.

Get it done.

Best,

-AC_Hacker

Hey you seem to be very perceptive about women! You think I would have learned by now. Yes we are in NZ so autumn for us now and weather just starting to turn. I think I already knew that the second scenario was the best option... We have a very well insulated slab and house so should be ok. Eventually I am intending to use additional solar thermal panels to dump heat into the ground. I am thinking a combination of putting an additional loop buried in the ground and also I have a large insulated tank that I intend to use coils of pex as a heat exchanger to take solar heat into the ground loop or floor loop. Not figured that one out yet... Thanks again for your advice.

If your property is such that there is little or no water migration through the soil, you could store heat in the soil. But if there is water migration, the water will carry the heat away.

If, on the other hand, that is not the case (your rainfall is not torrential and you are situated high on a hill) you could use your loop field as a giant heat battery, and all heat surplusses could be directed into it, for future withdrawal.

Best,

-AC_Hacker