Geothermal Add-On for Cooling

hawkjm73 · 10-30-2007, 12:57 PM

Hello all!

I have a half-baked idea I would like to get some input on. I live in the Phoenix, Arizona area, where the summers are vicious and the winters believe they are mini-summers. Needless to say, the electrical usage for my heat-pump air conditioner is horrid.

I have been reading about the efficiency of geothermal heat pumps, and find the idea very attractive. Financially, though, I wouldn't be able to retrofit my system all at once. So, I would like to go in stages, but I also want the stages to be profitable in and of themselves. First off, I want to put in a ground-loop, of the horizontal "slinky" arrangement, around five or six feet deep. I could do this myself with a rented digger. The vertical arrangement would require major permits and a very expensive drilling rig. I have almost two acres to play with, and am outside of any city.

At first, the ground-loop would just serve as a heat sink only. It would be a closed loop with a water/anti-freeze mix (we don't usually get freezes, but better safe then sorry) and a simple circulating pump. The underground pipe would be cross-linked polyetheline (PEX), for ease of use and flexibility.

The above-ground part is where I need some advice. My goal at this stage is to improve the efficiency of the existing heat-pump. The condenser coils have to dump the heat from inside into air that easily reaches 115 F or above. If I bring coils from the ground-loop in physical contact with the radiator fins from the condenser, then the condenser should be able to dump its heat (at least partially) into the cool fluid in the ground-loop, to be dissipated into the earth.

I'm tempted to use flexible copper that comes in a spool for the above-ground section, but copper gets stolen readily around here for the scrap value. It really seems like the easiest to use here, though, and I ought to be able to hide or disguise it.

So, am I totally insane, or does this have a chance of being beneficial? This setup would, of course, be temporary, just until I can get the actual heat-pump upgraded to a geo-therm unit to make proper use of the ground-loop.

Jenny

#CARRIERMAN · 10-30-2007, 11:03 PM

Hi hawkjm73

I was thumbing through and saw that no one had answered your question. I am a advocate for the geothermal equipment. Your idea is not necessarily half backed, but more trouble than it will be worth. The loops that you put in the ground are considered to be a condensor in the summer and an evaporator in the winter. Do yourself a favor if you are going to do a Geotherm. Put a BIG X through the picture of the slinky system or tear it completely out of the book and burn it. this was an early space saving idea that is only practical in about 1 in 5000 applications. The best way to do what you are wanting to do with a loop are individual trenches set about two feet apart. You will need two trenches at 300 feet each per ton. The first thing you will need to have is a geological survey of the area that you live in to determine the proper burial depth. The unfortunate thing is, you cannot guess at this. If you are going to do all of that, you will be money ahead to install a Quality manufactured geothermal heat pump system. By the time you install a water condensor on the current equipment with all the needed mods. You will have bought one. Hope this helps, good luck.

Rusty