I need advice. My last post was the Retro Geothermal Project. I am very concerned about the discharge from an open loop system. Our home is built on a glacial moraine. For the geologically challanged, thats where the glacier stopped, melted and deposited all the crap it picked up along it's 4,000 mile journey. Most of it is rock - lots of rock - from basketball size to Volkswagons. It took 7 attempts just to sink a mailbox post. Soil type is Heinz 57 - sand, loam, clay, grave, rock, loon shit and everything else. Needless to say, it does not drain well. We had to go with a mound septic and the house foundation could only go down 4' below grade (they hit clay and moist soil). The 20 acres we are on are beautiful, all wooded, mature oaks & maples.

We really want to retro geothermal. LP was at $2.12/gal on our last full up and won't get any cheaper. I conducted a heat loss calc using a calculator recommended on another post and my total heat gain is 34,055 & the total heat loss is 73,678. The contractor quoted a Geocomfort 3 ton unit that uses 6 gpm.

As far as discharge goes, drilling a return well will run about $5-$7,000 (domestic well ran $7,000). Considering poor drainage, would I be better off considering a closed loop? If so, a conventional horizontal or DX? Also, any guesses as to how many, how large the loops are needed? Finally, based on the loop specs, how large and deep do the trenches need to be? I know a contractor who likes cash and is in to playing with his excavator on weekends - may be able to get a little break, considering this area is "excavation from hell".

BTW, this is an awsome site. I knew absolutely nothing about geothermal before reading the posts and now I know enough to be dangerous. Keep up the good work everyone! Thanks.

fhunt

I forget where you're located.

What you need is a sonic drill to come drill for DX geothermal for you. I own a sonic drill. We are in CO with it right now drilling gravel/cobbles/boulders. The boulders are all granite. It's not the easiest drilling, but a sonic gets it done.

For your load calc, it seems pretty high. If your load calc is accurate, then a 3 ton system is grossly undersized. You'd need at least a 6 ton system with that load.

6 tons of drilling for DX would be 6 holes, 100' deep each. If not drilling, it can be excavated, but just like with poly loops, digging would be hard, it sounds.

How big is your home?

I'm located in central Wisconsin (Bancroft, Portage County). Home size is 2100 sq ft. We have  a lot of windows and radiant heat in the basement floor which I plan on leaving the propane boiler. The second problem is finding an installer that can handle DX in my area. Been surfing the web with no luck.

It's frustrating because geothermal sounds so promising.

I stand corrected. Went and recalculated heat loss and heat gain twice and took the average (both results were very close). My revised Total Heat Gain is 22,784 btuh and Total Heat Loss is 51,219 btuh. If one ton equals 12,000 btu's, then  (without a buffer) I should need a 4.5 ton unit. If I add 20% for good measure, I should need a 5 ton unit.

Please let me know if I'm off track in my calcs. Boy, I wish I had this software program BEFORE we built. I would have made some definite changes to the blueprints.

Also, it sounds like an open loop system under my circumstances is out of the question. Figuring at -25F (it does get that cold here), using 9 gpm and at that temp the unit should run about 51 minutes out of every hour. That will pump a whopping 11,016 gals of water per day. If it stays cold for several days or weeks, at that rate I will recreate the glacier that caused the problem in the first place.

It appears to be closed loop, but I want to go DX or to hell with it.

I am a little lost regarding the need to drill a return well, but then again, this is all still very new to me. I thought one of the great savings of open loop systems is that they use the same well for geothermal as for domestice water. Do you have to drill two wells? Or is the issue that the orignal well was drilled with only domestice water in mind?

Are there open loop systems that just discharge onto the ground? That seems problematic in a numer of ways. As for discharging back into an aquifer, that seems problematic too. What if some contamination got inside?

NickB:

Aparently domestic well can be used as a souce of water for an open loop system. That was the premise to my system design. However, the discharge is a problem for me. It is my understanding that open loops were designed to discharge into streams, ponds, or lakes. However, they can also be discharged into a return well (drilled 70-100ft away from source well) or in some instances, directly on the ground. Discharging back into the sourse well is discourage because of water temperature homogenization from mixing warmer source water with cooler return water.

Terrible conditions to drill in, poor surface drainage, and severe cold temps in winter will not allow me to discharge on the surface. According to my calcs, under extreme conditions in the winter, my heat pump could be running 45 - 50 minutes out of every hour, therefore discharging greater tham 11,000 gallons of water a day. At -20, for an extended period of time, that would probably start the second Ice Age by forming a huge glacier, then I would have Al Gore all over my ass for scewing up his agenda - don't want that.

But, if you lived in an area with excellent drainage, I don't see why one could'nt discharge directly on the surface provided you aren't committing any code violations.

 

Aspen:

http://www.hvaccalc.com/main.asp

The link above is where you can pay $49.00 and use their software for two months and calculate your heat loss & gain. Definitely read the directions and spend 10 minutes with the video. I didn't know didly about heat loss calcs, but learned a hell osf a lot about it from using this program. Really wished I knew about it PRIOR to building  -  could have done a calc on the blueprints and maybe made some alterations to improve efficiency. Anyway, it's a great program - good luck.

I had simular concerns with my open loop system. The water discharges into the back yard, I was concerned that the frozen ground wouldn't allow the water to absorb into the ground and it would form a good sized lake over time. However when I checked it on one of the coldest days this winter (around 20 degree F), I couldn't find wet ground even 2 feet from the discharge pipe. You have to remember the water coming out of the pipe is around 40 degrees, which is warm enough to heat up the frozen ground and allow it to be absorbed into it. If your system running 50 minutes out of every hour, I would think that would be enough volume to keep the area of ground where the water is discharging from becoming frozen. I don't think you'll have a problem. 

But if your still concerned, insulate. Where my discharge pipe is it's usually covered with leaves from the trees, I'm sure that adds some insulation and helps reduce the heat loss of the ground. Why not cover a larger area with some kind of foam installation, with discharge pipe under it pumping out 40 degree heat 50 minutes out of ever hour would be enough to keep the ground from becoming frozen. 
      

Please tell me if anyone has heard of this. While I am waiting for my five proposals, I can already see that open loop is in the lead as far as popularity. I got my first well drilling estimate, based on a 6 ton open loop system: $16,000. Wow.....

It includes drilling to a depth of 660'. Wow.....

When I asked why do deep, here is what I was told. Since the water will be discharged back into the same hole, it needs to drop 600+ feet to heat up/cool off before landing in the same aquifer space. There will be some "bleed off" of water on the surface, but my understaning was that this would only occur occasionally (my impression was that it would occur during the most extreme conditions).

So this plan does not call for drililng a dedicated return well, nor does it call for discharging everything onto the surface. Right back down the hole it goes, with the drop presumably acclimating it roughly back to earth temperature, and the most extreme water being pulled off and pumped onto the ground.

So, has anyone heard of this? Is this a sound plan? Thank you.

Nick B

Thanks so much for the link.  Having the first contractor do a site visit next week.  This will give me some info to start.  I am a total newbie at HVAC anything.

660 feet sounds awfully deep to me, how far down beofre you hit enough water to run your 6 ton system.

I would wager much less than 660, TG.  What do you think?

I brought up what I think your talking about in a prior thread on this forum (scroll to the bottom).  It is called a Standing Column Well and sees to have a decent amount of research behind it.  I got a few comments about it here.  I may try to use this system to upgrade a propane based hydronics system because we already have a pretty deep well with a good static water level.  It'll be a while, but I'll let you know how it goes.

B

One of the issues you need to address is the cost of pumping water up 600'.   There will be considerable expense involved.  If your water level is at 300'  you might be better off to drill two 300' wells, take water out of one and dump it back in the other.

Be careful about just dumping water on the ground.  I know one poster here has not had any problems,   but most soils will not absorb that amount of water.  If I tried that in my area,  I would have a big frozen muddy mess.