DIY well drilling / trench digging for GSHP
 

It seems to me that the #1 obstacle in building a geothermal system is the digging. Even the heat pump itself isn't too difficult as you can simply buy an pre built unit; albeit for a lot more money than one can make their own. There have been some valiant efforts on this front in the heat pump manifesto but most people there that have described their processes in any great depth have all run into various problems with getting down to great depths, such as 100 - 200 '. Let us here discuss the methods of drilling and digging at home without subbing out the work to a well driller or excavation contractor.

I will keep the first post of this thread updated as time passes with links to relevant posts and news.

Evolution Of Well Drilling
 

I wonder if DIY well diggers know they need a permit to drill??

Portable water well drilling rig, How to drill a water well

Looks like this is the place for this so here I go. If you are going to be drilling a well, by far your best choice to power your drilling platform would be a nice gas motor in the 4-8HP range which has its high RPM's geared down to produce high torque. For some people here though, having a nice reversible electric motor can bring with it some nice benefits such as noise level and reversibility which is a boon in attaching and removing drill pipe extensions. Also since this is EcoRenovator, why bring another gas engine into it :p

Before I get into electricity stuff, let me caution that my degree is in chemical engineering so my electrical engineering skills are a tad rusty, please feel free to correct anything that I don't get quite right here.

So after much research there are a few good sources for electric motors with similar power ratings to gas, electric vehicles and treadmills. Motors for vehicles tend to be rated for the 12-24Vdc range as they are going to be run off of lead acid batteries typically, this means that for high power loadings, they are going to require very high current. 1HP is ~=750W so a 1HP motor is probably drawing ~800W from the batteries which at 12V is almost 70A! If we're going to power this off the wall outlet the power supply becomes non-trivial at these kinds of loadings.

Treadmill duty motors on the other hand are normally designed to be run using ~130Vdc which makes it very easy to just run AC current out of the wall through some form of rectifier and power the motor directly. On top of that, treadmills and most other exercise equipment have the tendency to be used for a few months or so only to be forgotten and shoved into the corner when that good old American laziness sets in and there is normally a very nice selection in your local "for sale" section.

And now here's the one I recently picked up.
https://lh4.googleusercontent.com/_N...0/DSCN0136.JPG
As you can see, I've found a 130Vdc motor that has a full speed of 6700RPM at at that speed draws 18A and puts out 2.5HP. Below is the conversion of horsepower to torque
http://upload.wikimedia.org/math/4/9...bb30fd12da.png
From this we can see that at full speed, this motor is only putting out ~1.96 ft*lb of torque which is far too low for drilling. But if I were to gear this down at 60:1 we're now up to almost 120 ft*lb of torque at ~110RPM. That much torque will move some dirt and rocks.

Now for the other components of my haul
Power control board
https://lh3.googleusercontent.com/_N...0/DSCN0133.JPG

Toroidal AC choke
https://lh3.googleusercontent.com/_N...0/DSCN0137.JPG

sliding potentiometer
https://lh4.googleusercontent.com/_N...0/DSCN0135.JPG

Here's a schematic of the layout
http://www.instructables.com/files/o...NMFMEG9UME.pdf

Ok, so been reading up on types of controllers, and It looks like the control board is using some form of TRIAC (TRIode for Alternating Current) or SCR (Silicon Controlled Rectifier) to provide the pulse width modulated DC duty cycle to the motor. In effect, it's taking the 60Hz AC and rectifying it into 60Hz DC current pulses of a width varied by the sliding potentiometer.

Due to the fact that these controllers use relatively low frequency pulse modulation, a motor connected directly to the controller would end up with very jittery operation and thus it needs the inductor or choke to smooth this out. Inductors resist changes in current flow and will store the pulses in the form of a magnetic field. So the choke is also a must if I want smooth torque at low speeds and will help ease the strain on the motor.

Where I live we have an abundance of rock. In fact it some times seems like we don't really have any soil, just rock all the way down. I'm thinking that if you are either in a location such as I am or if you strike rock in you drilling you won't make it with 2.5 HP, with any torque. In the heat pump manifesto a fellow named Vlad I believe made some giant rig that was gas powered and he was using tri cone bits. As I recall he even had trouble getting down too deep and decided to only dig to 70'. He never explained why this is as far as I recall.

some do, but I bet many choose to ignore it. The regulations that surround well drilling are mostly in place for the purposes of preventing aquifer contamination which presents a risk to public health and safety. The regulations are somewhat more relaxed in most states for drilling holes that will not eventually exchange water with aquifers, such as closed loop geothermal wells. From my reading these types of wells only have the requirements that the wells are back-filled with some form of grout to prevent cross-aquifer or surface to aquifer contamination. Also as AC states in his other thread, closed loop geothermal wells must be done with fusion welded pressure tested HDPE piping so as to not leak.


In the state of Oregon, you need a permit and someone who is licensed as an Engineer or a well digger, but the permit costs are far less than costs for water wells. In my case I am currently an engineering intern as far as the state is concerned, and the requirements for being a state certified engineer is 4 years of working with others who are. But in my current job with Intel many are not, as certification is more for contractors who work on government contracts. My plan currently is to work with my friend who is.

I have been reading well reports for water wells in my area, and it looks like we are on clay to sand down to 100' on average, so I may be ok

What about down the hole hammer drills? Doesn't sound like something that you could DIY. I wonder how much such gear costs. The house I'm about to move into has a decent Buderus boiler (gas fired) and radiant baseboards so I'm not particularly itching ATM to start digging. But some day the boiler will buy the farm and I will have a huge PV array so geothermal will start looking pretty nice. When I install the HRV I will make sure to size the duct work for geo. But the obstacle is the digging. I may have to just bite the bullet and hire a well digger. I will be conducting an experiment this summer. I will be cooling the computers in the house geothermally. I want a 30' well. Once all of the renovations are done I'll start thinking more seriously about that. For now the giant bank of radiators I have for cooling will be sufficient.

BTW, if anyone thinks a certain post in particular should be listed in the OP let me know either via PM or by posting here. I'm toying with ideas of how to organize the index. I'm thinking about by topic and by poster.

So at 100' it goes to rock? How many well holes do you need to dig?

I have two donated treadmill motors and controllers and wonder if one could be for a clockwise rotation and the other for a counter clockwise? I am told too that my soil should be clay to sand also. Easy drilling I hope.