How far is too far for a pond loop? I'm installing a Geocomfort 4 ton system and am considering a pump/dump installation but I have two adequate ponds 500-800 feet away. Trenching costs aren't an issue. Since I'd need 2000'+ of loop anyway why not go to the ponds and weight the difference in the deep end? Will two Grundfoss 26-99 pumps handle this? Should such a long loop be oversized in diameter so friction losses will be less of an issue? I'm not sure I'm reading the tables right, for say 10 GPM will it take 20 psi to get 0psi at the the other end of 2000' of 1.25" HDPE? Thanks...

"too far" is a relative term.
the thing about pond loops is an expectation of savings that isn't really there as it is the loops themselves and labor that are the significant part of the "loop cost" not the excavation.
therefore you could run pipe to the ponds, tear up just as much of your lawn (or more) and spend more on pipe and pumping power.
joe

Few things to ponder:

1. Any ecological restrictions on water dumping (including various fish at the bottom)?
2. How deep are your ponds and whether they'll be able to divert water @10-15 per minute w/o substantially increasing water table around you.
3. Did you consider diverting water for irrigation lawn during summer months, relatively expensive idea but still "very green" and appealing, at least, to me. I hate waste anything....
4. How deep are you planning your water well, what is the projected capacity / maximum capacity? Any idea where it is being fed from?
5. What is the water temperature? Anybody (neighbors, etc) will be sharing the same aquifer with you?

I should add that the a discharge drain of that length will only save you a thousand or 2 over the closed loop install cost which may be small consolation with higher pumping cost and maintenace.
J

Wow!! Tthat is a shocker. Why even bother????

Solenoids and flow raters as well as lots of ball valves, sediment filter, flow gauge, extra large well tank and trench with drain cost thousands that can be applied towards closed loop.
j

Joe, I am done with that method...  thanks....Actually I was never a proponent of pump / dump variety, even injection well. Too many unforseen issues

Open loop holds more appeal to the DIY and newbies in our field as they avoid thousands in fusion equipment et al.
New shift in geo buyers from engineers and gadget guys has closed loop out pacing it 10 to 1 in MI.
j

Dear Joe, to tell u the truth, I am not really in favor of U-bend either. I am seriously looking in all kind of other alternatives, i.e concentric loop design methods (Helix, Rygan, Austrians / Germans..etc) with substantially improved grouting material compared to currently used fusion method. I do not believe that even properly and highly professionally installed traditional u-bend can deliver the best performance for the money, mediocre, maybe. However I am not about mediocrity..sorry

 

In response to points to ponder:
1) 3 & 10 acre ponds in Alabama, I can do what I like basically... The ponds never freeze and the fish will take care of themselves.
2) Deep end of smaller pond is closest, probably 12' deep on average but shallower at the other end, a typical hillside type farm pond.
3) I'd rather not encourage the Pensacola Bahia in my yard with irrigation, it's enough work as it is! ;~)
4) Existing well as designed for 4.5 acre orchard drip system but I don't have the actual data on the well as drilled, 300'+ deep into North Floridian Aquifer actually hitting a cavity which the driller liked.
5) Nearest neighbor is 1/2 mile, not a concern. I've been told well water temp here is usually around 65 degrees.

Joe.ami: What I'm thinking about is a closed loop going to the pond so there'd be maybe 1200' buried and another 800' in coil in the deep end, all in one loop of 1.25" or 1.5" to reduce frictional losses. My concern is the pumping power you mention. It looks like 1.25" HDPE looses 2.4 ft and 1.5" looses 1.0 ft of head per 100' at 10GPM, that's 48 and 20 foot head loss respectively if I understand the tables. The flow center has 52 foot of head at 10gpm so in a perfect world I'd have about 2psi or 13psi respectively. I've read on various forums that pressure isn't the issue in loops, it's about flow, so I don't know if the low return pressure of the 1.25" will work or not. Then there is the question of cost, one 2000' 1.5" loop is a lot more expensive than four 500' 3/4" loops...

There's also a disused 8" PVC irrigation line from the ponds going right by the location, I wish there were a way to use that for a supply in an open loop system w/ raw pond water, maybe through a separate heat exchanger...

Posted By GBT_energy_freak on 07 Mar 2011 09:27 AM

Dear Joe, to tell u the truth, I am not really in favor of U-bend either. I am seriously looking in all kind of other alternatives, i.e concentric loop design methods (Helix, Rygan, Austrians / Germans..etc) with substantially improved grouting material compared to currently used fusion method. I do not believe that even properly and highly professionally installed traditional u-bend can deliver the best performance for the money, mediocre, maybe. However I am not about mediocrity..sorry

 

While all of this has been discussed here before, it always lacks the supporting data to substantiate claims of performance and the cost of the actual product seems to allways send us screaming in horror as the roi even if taken at face value on performance leaves us wondering who really buys and installs these systems.
Eric

Eric, with all due respect..data are there... scattered all over the Internet, not well organised, not neatly arranged but they are there.. I'll attempt to collect them as soon as I can and bring them to this forum so we can all have intelligent discussion w/o waving our hands in total despair so to speak

Fair enough, respect given.  We will patiently await your offering to the collective data repository.
Eric

The Floridan is an ideal open-loop aquifer in Southern Alabama in many cases. The water quality is reasonably high and water quantity is generally not a problem at all--especially when you hit some subsurface dissolution conduits as your driller mentioned. However, what is really nice is that the aquifer is often found pressurized under artesian and flowing artesian conditions. Many installs don't even require a pump to get the 1.5 gpm per ton needed through your heat pump. Of course you do have to put the water in one of your ponds or a horizontal leach bed etc. for the water. -Adam Hydrogeologist

Open loop it is. I'm also interested in supplying the HP with a low pressure pump and a large underground tank instead of directly from the potable pressurized supply. With the right float switch and a timed relay the well would run continuously to refill the large tank as needed, thus avoiding repeated inefficient starts/stops when the HP is running. The large tank might also allow rainwater collection to supplement the well water though proper filtration would be paramount. This has to have been done somewhere, any thoughts?

I would size the well pump such that it runs continuously (and at low pressure) when supplying the geo. Then add a booster pump to get the higher pressure needed for household water.

Pressuring water to 50 psi and then using it for geothermal wastes energy.

What is the problem with using existing 8" pipes?

Posted By abh3 on 08 Mar 2011 08:42 AM
Open loop it is. I'm also interested in supplying the HP with a low pressure pump and a large underground tank instead of directly from the potable pressurized supply. With the right float switch and a timed relay the well would run continuously to refill the large tank as needed, thus avoiding repeated inefficient starts/stops when the HP is running. The large tank might also allow rainwater collection to supplement the well water though proper filtration would be paramount. This has to have been done somewhere, any thoughts?

Why not just get a variable sppeed pump?
(That is if you need a pump at all)
j

If you want to use a large tank for something, consider using it to stored heated/cooled water (ie, on the geo output side) and then using mostly off-peak or interruptible power to get a better rate.

The deep well pump was replaced not that long ago so I'm reluctant to replace it again. At the time, what I could gather from well people suggested that variable speed pumps were problematic, more vulnerable to lightning and three times as expensive (the only actual quote was $4k+ and that was to just replace the old pump!), now I wish I'd have talked to more companies about that... The other issue is that the VSP will still be high pressure, a waste of energy. My thinking is it would be better to use a low volume/pressure pump & tank to provides what the HP needs and use the well pump to fill the tank when it runs low without inefficient stops/starts... A float switch in the bottom of the tank with a timed relay controlling the solenoid valve would work, it could probably be designed to fill at times when there is less water demand as well and that might be a real plus from time to time. I've got a LOT of room to work with so burying a used 2,4,6k gal tank is not a big deal. The catch is to not spend a fortune doing this, I missed a basically FREE probably 2k gal fiberglass tank not long ago so it can be done... I can't really use a booster pump as there are a number of farm buildings on my 'system', some RV hookups and distant livestock troughs...

What is the HP of your existing deep well pump? How far from the surface to the water level in your well?