Geothermal Heat And AC

quickfix

Guys what do you know about geothermal heat? Has anyone installed it and how does it work? I think I understand the basics of the system when used for heat in that the energy from the ground is used to heat water or some other liquid in a tube and that is pumped to the building, however, how can this be reversed to cool a house? Does this work? is it efficient? and Why doesn't anybody I know have it?

thanks guys

HVAC Doc

Why doesn't anybody you know have it? COST. An average buried loop ground source heat pump system can easily start in the 15K range. If you have to have vertical wells drills instead and live in an area with rocky soil, cost goes up. Efficient? Very much so. Some systems can be as high as 27 EER. EER (energy efficiency ratio) is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level (usually 95° F). A higher EER means the system is more efficient. Another rating that may be used instead of or with the EER is the COP rating(Coefficient of Performance):
The ratio of heating or cooling provided by a heat pump (or other refrigeration machine) to the energy consumed by the system under designated operating conditions. The higher the COP, the more efficient the system.

While these are great systems and fairly reliable, you have to look at your payback. If you drop 15K down for one of these, you are probably looking to spend 10 or more years in your home.

quickfix

HVAC Doc, thanks for the response.

OK, i understand that if the soil is sandy or rocky then it might be harder to dig a deep hole. but 15k for a deep hole and some pipes??? what if i just rented some equipment and did it myself? The problem would be figuring out exactly how deep and how many feet of pipe, but i wouldn't mind the reserach and experiment for nearly free heat energy. Does anyone know how deep a verticle drill would need to be for an approximately 4,000 sq.ft. home? Also, what material would be best used for the pipe. Copper, polyethy, or something else?

Bestheating

I will relate to you a customer of mine, with thoughts similar to yours. He and his partner wanted to give their customer a really sweet system. But being Building Contractors, they were thinking with their checkbooks and not thinking their project through. They brought in the less expensive contractor and put in a bad system. It didn't work out. This however was not discovered until the house was occupied and the proud owner was about to go rabid. I bid on the installation of a forced air system in a home which was already finished for geothermal. Oh my... you can take it from there.
My suggestion is that in this business, you are often paid for what you know and not what you do. Geothermal is a good concept. Proper engineering is everything. My suggestion, get a good contractor and be glad you did.

HVAC Doc

Bestheating nailed it. It is more than just the holes. It is critical to have the system sized correctly to size the piping requirements correctly. How many holes are needed for a 4K sq ft home?? Don't know. Have to do a load calc which takes into consideration insulation values, windows, roofing materials, composition of structure, design temps, even house direction. Also, depending on how close you are or where your land plot is, it is ALWAYS a good idea to have it surveyed and all utilities marked as you don't want to hit buried power/gas/sewer/water lines. The pipe is high density polyethelyne. Is is connection by being heat fused. There is not a manufacture one that will warranty a loop system that isn't installed by a licensed contractor. Average hole depth depending on soil and tonnage of system is 200 ft. So yup, 15K for just holes in the ground.

quickfix

bestheating,

i was just wondering why this customer's geothermal heat system did not work out. was it undersized? did the pipes leak? were the holes not dug to the correct depth? do you even know? if the system was just undersized but did provide some heat would the owner still use the geothermal system to provide approximately half the energy heating needs of his home and then use the forced air to bring the temp up to hospitable status? sure if it didn't work out someone would get mad. that is what the reserach and planning is supposed to prevent. Once you know what needs to be done and how it should be done then often times the decision who should do it is obvious and not something anyone would have to decide.

quickfix

what equipment would be used to excavate a 200ft or more well type hole? As i see it , i would think that it would need to be more of an area dug than just a "hole" b/c the pipes would need to run horizontally at the specific calculated depth in order to pick up the necessay heat energy.


just b/c i think diagrams are fun and i want to be creative :

______________________________ <-- represents correct mimum lenght of area needed to be excavated for proper pipe laying. (covers both the horizontal and verticle pipe)

________ <--- represents what one might incorrectly think the minimum lenght of the area of the hole one would need to dig. (covers just the verticle pipe)
_______
...|...Hot..|
__|Building|___ ground surface
|| || . . . . .
|| || . . . . . . . . ........ .. . . . . . . . . O <--- marked sewer #1
|| || . ..... O <-- marked sewer #2
|| || <--- verticle pipe
|| || . 200ft or calculated depth
||_||_ _ _ _ _ _ _ _ _ ___ _.
| _ __ __ _ _ _ _ _ _ _ _ _ _ |
| |_ _ _warm earth_ _ _ _ _| | <--underground horizontal closed loop
|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ |
. . .

some of the spacing might be off, i couldn't help that.

notes: In this diagram the area dug would encompass sewer #2 and hence would either have to dig around and under orr not be dug in this location. marked sewer number 1 would be far enough away from the area dug so as not to be a problem.

jmic

A buddy of mine has a Geothermal System and swears by it. He has 2 wells ( not sure of depth, but around here usually 200 - 500 feet, gotta get to da water) Anyways his domestic household water and heat system water are taken from one well, the water goes in the house then goes through a heat exchanger then is recycled back into the 2nd well. I think the wells are about 30 feet apart from one another. Just thought I'de pass this on.

__________________
___"Remember You Never Get A Second Chance To Make A First Impression"______________________
Joe

HVAC Doc

Here, this link will show you the types and terminology of loop systems: http://www.waterfurnace.com/content....tial&page=loop

And to answer your question as to what kind of machine digs a 200ft. hole, it is a vertical well driller.