geo thermal well locations


  #1  
Old 11-24-08, 08:32 AM
K
Member
Thread Starter
Join Date: Aug 2007
Location: Virginia, USA
Posts: 226
Upvotes: 0
Received 0 Upvotes on 0 Posts
geo thermal well locations

I am meeting my contractor tomorrow. I'm concerned about where the proposed wells are to be drilled : 2 150 ft. deep wells alongside the house, 20 ft. apart, about 7 feet from the foundation each. One of them is about 4 feet from a tree (trunk is about 1 ft. in diameter). I'm on a small plot (slightly under 1/4 acre). There is more room to the back (pie shapped plot) but it tends to slope more downhill (about 1" per foot).
(1) Should I be worried about how close it is to the foundation? (2) Will the trees potentially damange the underground (vertical) pipes or is it more of a case where the drilling process will harm the trees? I can live with the later.
THANKS FOR ANY HELP!
 
  #2  
Old 11-24-08, 09:45 AM
N
New Member
Join Date: Feb 2006
Posts: 46
Upvotes: 0
Received 0 Upvotes on 0 Posts
Not a contractor here - but my neighbor had a geothermal system put in his new property. Told me it cost a small fortune, but it would pay for itself "in about 300 years!"

First off, is the contractor you're talking to a geo-thermal systems contractor? I'd sure hope he knows what he's doing; did he/she give you local references to contact about the work already done? What did he/she tell you about drilling near the house and the tree?

As a gardener, I'd be wary of anything putting anything down in the ground 4' from a 1' diameter tree trunk; as a rule of thumb, figure that the roots of the trunk are going sidewise from the center about as far as the limbs are stretching above ground. Drilling that hole won't hurt the tree much at all; but tree might get its "revenge" later. Not immediately - but roots don't grow smaller, they grow bigger.

Tom
 
  #3  
Old 11-24-08, 10:31 AM
dhamblet's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Oct 2008
Location: PAcific Northwest
Posts: 264
Upvotes: 0
Received 0 Upvotes on 0 Posts
We put a geothermal heat pump in when we rebuilt our home in 1999. It cost around $15,000 and has paid for the cost difference over a conventional system in the time we've owned it. I can't imagine how a tree could affect a well casing. I suspect it is steel pipe cased and should be impervious to tree roots. If it bothers you have him move the wells elsewhere on your property. Its just ditching, poly piping and wiring.
 
  #4  
Old 11-24-08, 10:54 AM
K
Member
Thread Starter
Join Date: Aug 2007
Location: Virginia, USA
Posts: 226
Upvotes: 0
Received 0 Upvotes on 0 Posts
geo thermal well locations

It's a retrofit. $20k (3 ton). 8 yr. payback. I think the casings are just cement / grout to keep the well pipe in contact with the ground where all the heat exchange happens.

The cant drill on a slopeside so if I move the well sites I have to put them pretty far away - it starts to become a pretty big decision.

BTW, these guys are indeed qualified and I definately checked references first hand before we started. He has been very proactive in coming back to me with any concners so I am sure we can work it out - I just wanted a steer going into tomorrows meeting.

Thanks!
 
  #5  
Old 11-29-08, 04:56 AM
F
Banned. Rule And/Or Policy Violation
Join Date: Nov 2008
Location: Cape Girardeau, MO
Posts: 17
Upvotes: 0
Received 0 Upvotes on 0 Posts
GSHP Preparation

GSHP are the heating cooling solution for reducing cost of energy, but one should do some preparatory work.

Contractors typically size the GSHP and loop field based upon the homes current HVAC size. So before you commit to the GSHP upgrade consider the value of insulation vs the cost of tons of GSHP and associated loop size.

If you have insulated your home to R-50 ceiling and R-24 walls and stopped air infiltration after your original HVAC was sized your old HVAC is over sized now so sizing GSHP based on that is wrong. If you haven't insulated your home to R-50 ceiling and R-24 walls and stopped air infiltration. do so as part of the GSHP upgrade and have the contractor size the GSHP based on the new heating and cooling load characteristics of your home.

Simply, if insulating your home to R-50 ceiling and R-24 walls and stopping air infiltration costs less than a bore hole insulate your home and eliminate the bore hole and you will be much happier with the investment in the GSHP.

I have found those people who install GSHP in a leaky 2X4 framed exterior walls with R-11 insulation are unhappy with the GSHP performance. The performance is not the fault of the GSHP but rather the changed behavior of the home owner turning the cool way down and the heat way up because now they own and 400% efficient GSHP. I have found those people who install GSHP in tight 2X6 framed exterior wall with R-16 insulation and R-50 ceiling are happy with their GSHP investment. But they would be extremely happy if they stopped air infiltration.

Typically, the size of GSHP can be reduced by one half by doubling the insulation and eliminating air infiltration of the home.

FYI Home Energy conservation DIY check list
1. Increase Insulation, and eliminate air infiltration
2. Other home thermal performance improvements, windows, attic venting, window shading.
3. Home energy audit data collection using blower door and infrared measurements and inspection
4. heating, ventilation, air condition (HVAC) reeneginnering to calculate new HVAC size.
5. Ground Source Heat Pumps (GSHP) with solar thermal assist. and/or
6. Active and passive Solar Thermal (ST) whole house heating,
7. Insulated Concrete Form (ICF) new home construction

Here is block diagram of a solar assisted ground source heat pump. With this you can possibly achieve up to 900% heating efficiency and 400% cooling efficiency. Note free hot water is provided. Hydronic and forced air models are available,


And possibly see your overall energy consumption reduced as in example below. Your results will very.
]

IGSHPA | What is geothermal?
Heat Pumps

If there are any questions I have started a thread
http://forum.doityourself.com/greeni...eparation.html
 
  #6  
Old 12-17-08, 05:33 PM
W
Member
Join Date: Mar 2008
Location: Cat Spring, Texas
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
Drilling a well is usually not that disruptive to the surrounding soil, so I doubt it would hurt the foundation. The proximity to the tree is another matter. True enough that it will probably not hurt the casing, but the wells are all connected together with a manifold (usually plastic) and a growing tree root could eventually cause problems with that.
Compared to the system I put in 22 years ago, two 150 foot wells does not sound like much (I had four 150 ft. wells for a 2 ton unit) so yours may already be scaled down to a minimum.
Conversely, I might have gotten screwed royally 22 years ago

My unit never paid for itself, but back then electricity was going for $.05 a Kwh. Payback gets a lot quicker when it gets up in the $.15 to $.18/Kwh range.

....and since I work for a utility, I can pretty much assure you it will get higher.....
 
  #7  
Old 12-18-08, 06:31 AM
K
Member
Thread Starter
Join Date: Aug 2007
Location: Virginia, USA
Posts: 226
Upvotes: 0
Received 0 Upvotes on 0 Posts
geo thermal well locations

Thanks for the frank feedback. The dirty deed is done - turning on new system for the first time today.

1) The most disruptive to root systems was trenching between boreholes. From inside the trench the stratification of earth was clear - a lot of rock at 2 and 3 feet so the roots all seemed to be within 1 or 2 feet of the surface. The trees are on the leeward side of the house so I'm not going to worry about it (what can I do now anyway?!).

2) I misstated well depths - they are 255 ft. each. There is also 2 loops per borehole for a total of 2,000+ feet of underground piping. I'm in Dominion territory (Virginia) and the $/Kwh is not much more than 0.07. However, we are also betting on a rise!
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: