geothermal drilling concerns
We're considering putting in a geothermal system, which would require two closed vertical loops in our backyard. Our concern is that we'd be retrofitting an existing house, so we're nervous about the disturbances that could be caused by drilling two 300+ ft holes near our house and water well. Due to the shape of our property, the holes would probably be at best only about 20-30ft from our well and 15-20 ft from our foundation. We also live near several stone quarries so we assume that there's a good chance that the drillers may require especially invasive machinery to get down 300 ft.
Has anyone heard of any permanent damage done by nearby drilling (house foundation cracking, well refill rate dropping, etc)?
Thanks in advance.
It's rather easy to drill through solid rock. They usually charge per foot and then extra for casing and so the sooner you hit rock the less it will cost. My holes were put in along side my home and you can only hear the loud noise of the engine and air compressor. It should have no impact on your well or your foundation. When you think about it, it's just a 4 inch hole in your back yard. The depth doesn't matter much except that it's warmer the deeper you go. In my yard they lauged because they never hit dirt and so didn't use any casing.
They do make a mess and a good driller can make the difference when it comes to established yards.
PA-Licensed water operator
Thanks, jongig, that makes me feel a lot better. I keep picturing all of this ground shaking equipment, sounds like it's not nearly that bad.
By the way, I really liked reading your thread about your experiences. I'm glad everything worked out for you, and it was good to read that you still seem to be a fan of geothermal even after all you went through.
How far apart are the loop being spaced.
They'll probably end up being spaced 15 ft apart from one another.
The distances mentioned are too close for proper operation. What is the tonnage , I am assuming 2 tons at the moment.
There is nothing wrong with 15' spacing of bore holes. We do it all the time.
The spacing is a parameter to be set in the design program.
As long as proper design methods are used, the loop will perform great.
I am not as concerned about being that close to the house, but we use a air rig a less avasive method than conventional well drillers. The distance from the well I can,t say for sure, in MO we are governed by dnr they require 100' away from a well. The rock is no problem,unless there are caverns How deep is your well and how much is cased?
acwizard:This will be for a 4 ton system (with two loops each 340-380 ft deep, so I guess 1360-1520 ft of total looping). We're also in central Maryland so it doesn't get super cold in the winter, perhaps that's why they suggested only 15 ft apart for loops.
mo geo man: Our well is only 200 ft deep. I'm not sure about the casing, but that's a good question. We just bought the house two years ago, I only know the depth from the county records but unfortunately they didn't mention anything about how much is cased. The house and well were built in 1994, if that helps too.
I'll have to check around to see who uses an air rig, that does sound like a better option given my concerns.
Since I have training on subsurface drilling and wells I'm going to tell you that this is at best complicated and I'm only going to give some basics here.
Originally Posted by pennstater
One of the problems I see in Geothermal is that many have a "rule of thumb" and I really see this as a copout to doing actual work. No one can make a general statement of how your wells should be installed without data and we don’t have this. Some parts to this are what are you drilling through. A local geologist can tell you exactly what is beneath your yard. The well driller will also keep a log as he drills. Second is when do they hit water and how much. Since you already have a well your driller can get at least some idea. It can change however over distances apart as little as 20 feet or so, maybe less.
In my wells I have two that were solid rock most of the way. I think and know that dry wells are less efficient when it comes to heat exchange. My third well had water at 50 feet and in reading my thread you can see that my system was not good and then became great. It was the third well which may be as efficient as the other two combined. After dealing with a geologist the light bulb went on and it really made sense. You are trying to keep your exchange temperature from static within 18 degrees and I just don’t see room for guessing that something may or may not work. I’m giving a rule of thumb here, which may be good for the ground exchanger but may not be the best for the geothermal system. Here’s why. My system goes down in efficiency around 32 degrees EWT. My static is 48. That’s a window of 16 degrees unless I don’t mind getting less heat than I need. After the third well I barely hit 34 degrees on a below zero day and my unit keeps up. That’s what you’re looking for, not just energy savings but comfort also.
rule of thumb
jongig, I can appreciate your feelings on rule of thumb but this is not exact science. IGSHPA tought me all about soil types, water levels and so on but at the end of the day it is what works, and what works within the specific loopfield. Water levels fluctuate, house loads are seasonal. We were tought that in most cases it is faster, cheaper and better to just add another loop when there are any doubts about the soil. I would like to have the luxury of nowing every soil type for all our jobs but it is just not practical. We are seeing problems more with the flow rate (renolds number) not giving us decent numbers seting to factory standards, using there recommended pump packages. (there rule of thumb pump sizing- up to 3 ton 1 pump, over 2 pumps)
Originally Posted by mo geo man
I do aggree with you for the most part and to utilize a IGSHPA trained installer is the way to go.
It's a good idea to remove at least as much of the guesswork as possible within a reasonble amount of work on the part of the installer. If you don't use a geologist you an at least look up the informatin of the formations below ground where the install is. Again using me, my rock was sandstone which exists only in a small area near my home.
I would opine that most geothermal installers are not nearly as educated in geothermal as some on this board like yourself or Geodean.
My diller seemed very good when talking to him and he had information on his website that he was IGSHPA trained but in the end I found out he was not.
You really do have to be careful.
Well here in Texas wells have to be mim of 20'
and can not be less than 50' from water well