DIY well drilling / trench digging for GSHP

[Blauhung]

Originally Posted by braebyrn

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.

Most of the reports stoped after they hit the aquifer so I don't know about beyond that. But they don't mention an actual rock layer. As for the motor, it's DC so just put in a switch to swap the polarity to the motor and same motor spins both directions

[Blauhung]

Oh and for 1 ton of heat transfer in my area I will need 200' of pipe in place under 10' of ground so right now I will probably aim for 5 or so 50' holes

[AC_Hacker]

Originally Posted by Blauhung

Oh and for 1 ton of heat transfer in my area I will need 200' of pipe in place under 10' of ground so right now I will probably aim for 5 or so 50' holes

How well do you know the heating requirements for your house?

There are a couple of ways you can do this...

One way is to look at the amount of fuel you consumed over previous winters and average it on a per month basis. Then design for your worst month. If you don't have your bills, the company that sold you your fuel still has that info. I'm not so sure if the fuel company will give you that info for previous owners.

The other way is to do a "Manual-J" type of analysis. This method models the insulation type and window type and surface areas and your inside preferred temperature and the seasonal temperature for your particular location and comes up with an overall heat loss.

I don't currently have Excel installed on my computer, but I have found what appears to be Manual-J in a downloadable Excel form.

Additionally, I have found a Manual-J training video here.

And also, Watts Radiant has a free software tool called RadiantWorks that will do a heat loss calculation for you.

The heat load (AKA: heat loss) calculation is pretty important and I have used all of the approaches shown above, and in addition, I have done real time worst-case severe winter weather monitoring of my BTU requirements using electric heaters and Kill-a-Watt meters. I have then compared all of my approaches to get a good idea of how much heat I will actually need.

* * * * *

When you've got your drilling rig working, and have found how deep you can go, you'll probably want to do a heat transfer test (that test hole will become part of your loop field) to determine thermal transfer for your actual site . Your estimate of 200 ft/12,000 BTU is probably really close, but by going through the heat transfer test steps, you'll have the opportunity to familiarize yourself with HDPE welding, and hole grouting, and you'll be more assured that you're proceeding along the right path because your heat transfer test will give you the information you need to combine with your house heat loss information, to know exactly what the minimum loop size must be.

-AC_Hacker

[Geo NR Gee]

What is out there to calculate for your pump? In other words, if you have 10-50' wells or 5-100' wells which would be more economical?

[S-F]

I'm not sure that matters as the head pressure and GPM would be the same for both scenarios. But digging fewer and deeper wells would probably yield better results for garnishing heat as temperatures stabilize the deeper you go. The problem is, again, getting a well 100' deep. Hence loop fields like AC_Hacker's.

[Geo NR Gee]

Originally Posted by S-F

I'm not sure that matters as the head pressure and GPM would be the same for both scenarios. But digging fewer and deeper wells would probably yield better results for garnishing heat as temperatures stabilize the deeper you go. The problem is, again, getting a well 100' deep. Hence loop fields like AC_Hacker's.

I haven't done a test well yet. That should determine the depth. I don't want to find out after we dug a hole 200 feet and the pump won't work at that depth. This brochure shows that it doesn't go very deep..... http://www.bdmfginc.com/_GT_Brochure.pdf

There has to be some kind of pressure loss when you go up then down one then down and up another, and another, etc.

[S-F]

There is no difference is the total amount of vertical distance the water has to travel. It makes absolutely no difference as far as load on the pump is concerned. The only thing you have to loose with more shallow wells is efficiency of the loop, as I mentioned earlier.

[AC_Hacker]

Originally Posted by braebyrn

What is out there to calculate for your pump?

What there is out there is a set of manuals on this very subject. They may not be so cheap and they may not be a snap to read, but they are the very best source of information on this subject I know of.

If you are even thinking about a DIY GSHP installation, you at the very least should buy CLGS Installation Guide (#21020) - (The "original" Installation Guide). It is packed full of all the information you are interested in here.

So $100 is expensive for a book, huh? Just think about how much money you will save if you do your own GSHP... $100 is pretty small, especially compared to how much you will know going into this endeavor.

Regards,

-AC_Hacker

[Blauhung]

Originally Posted by AC_Hacker

How well do you know the heating requirements for your house?

Last January we used 95 therms according to the gas company. This is split between the 15 year old gas furnace and our very nice tankless water heater. 95 therms in January works out to be a bit over 12,000BTU/hr. This January was a bit warmer, but I've also dumped some extra insulation in the attic and sealed up some obvious leaks around doors and windows so we used 70 therms.

For the summer, my plan is to get something on the order of 200' of pipe under 10' of depth (where ground temp doesn't vary as much). 5X40' holes will give me exactly that and 50' sounds marginally doable from looking at well reports in the area, though this could quickly change. Once I get this pipe in, I want to setup a heat pump in a cooling config and just shove the air->refrig evap in our existing duct work so I can use the existing furnace blower to pump some cool air through the house. We currently have nothing in the way of AC so any cool air in the house for those 10 days Portland gets hot will be an improvement.

For the winter, we already have a tankless water heater that puts out far upwards of 12,000BTU/hr (don't have the exact #'s on me but its on the order of 2-4 tons I believe) and my goal is to setup a water-water heatpump as a pre-heater for the tankless. If I can get a continuous flow of 90F from the heatpump, the tankless can easily crank that up to 140F and run that through a radiant floor. And the furnace will still be functional in the event we need something to fall back on.

[Blauhung]

Originally Posted by S-F

There is no difference is the total amount of vertical distance the water has to travel. It makes absolutely no difference as far as load on the pump is concerned. The only thing you have to loose with more shallow wells is efficiency of the loop, as I mentioned earlier.

and yeah, what he said. You aren't pumping water up from the bottom a 200' hole, you are just circulating a close loop and the changes in potential energy all cancel each other out so your only head requirement is the resistance of the total length and all the fittings/valves/whatnot you have in the loop.

More holes means more pipe. I need 200' of hole under 10'. If I do one 210' hole I use 420' of pipe. If I do five 50' holes, i use 500' of pipe for about the same heat transfer ability.