oversizing loops question

[sunnyflies]

Is there a downside to putting in extra loop footage?

I was originally told by the well driller that I needed about 1200' of vertical loops for six tons, but am being told 1050' would work by the installer. Obviously, I would save money, but would it be better to have the original 1200' ? Would having more do something bad to the efficiency of the system? I am guiess=ing it wouldn't, that having extra might be good. But, I'd like to know what you all think. Thanks.

I will be talking with both the well driller and installer shortly.

[down2earth geothermal]

It's a balancing act since putting in more loop results in a more stable EWT (and slightly higher efficiency) but also results in higher pumping costs related to more pipe-wall friction.

The designer should use loop-design software to ensure you are within turbidity specs for good heat transfer based on the pipe diameter, length and configuration. The specific subsurface geology--including any groundwater flow should also be taken into account in this design. A saturated sand can require only 1/2 the ground loop as a dry sand.

In your case, a 10% increase in loop length--provided you will still be within the same turbidity range, should only help efficiency.

-Adam
Hydrogeologist

[sunnyflies]

Than you so much! You have told me what I needed to know.

Our subsurface geology is sand and gravel - mostly coarse sand. It is saturated and the ground water moves at about a foot a day. The installer's proposal said the pipe diameter is to be an inch. I have not been told yet what configuration he wants, but back in March the driller recommended four loops at 150' for a total of 1200' in length for six tons of geo, while the installer said three loops at 200' each, though now he's recommending only 1050'. I don't know why he says less now, except that he says it should do the job.

I will be talking to both of them tomorrow and will try to see if they agree on the length and configuration. If they don't, then I think I should go toward the slightly longer loops, rather than risk going short. Both do a lot of geo installs and often work together.

Is there more turbulence in larger sized pipe? 1" vs 3/4" ?

[waterpirate]

Without a conductivity test we are all guessing. If you have a soils and water annalysis or a good idea from the driller, it is all about design ewt. Design ewt will be a function of the software. You pick a ewt and look at the capacity in both heating and cooling and adjust the ewt up or down with the amount of pipe you put in the ground untill you get output numbers for a given unit that you can live with.
For example in heating, the lower the ewt the lower the units output. In cooling the higher the ewt the lower the output.
No residential system is going to warrant a conductivity test... but you can ask the installer for ewt data on systems near your location in heating and cooling vs. amount of pipe in the ground and come up with something close that you are comfortable with.

[Mark Custis]

flyingmoose talks about.

I am about to crunch a loop field into a 1000 gallon concrete tank with a through-put of 35 GPM.

I am using a septic tank made of prestressed concrete as it is cheaper than plastic. I will toss four 50' rolls of refrigeration copper into the tank and tie them to a radiant floor manifold in a vault nearby. From the vault I will pipe to the house with HDPE.

My source of low value heat is unlimited with the spring running at 35 GPM. What I am doing is creating a wide spot in the plumbing so I can gather the BTUH. I will then pump this heat to a geo water to air system. The geo will do its magic and magnify the heat 400%.

At least that is the plan. We will dig next week.

[sunnyflies]

If our ground water is a constant 55º, would the EWT be the same? Or does it go up with friction on the pipes? If I have vertical loops would the frozen ground drop that temperature a lot as the water passed through it? I don't think our ground freezes much deeper than 4', but I could be wrong. If I have a choice, should I ask to have the loops brought in at 6' rather than 4' ? I would imagine that water traveling 50' or so through cold ground from the well field to the house would chill off some.

The driller definitely has a good grasp of the soil conditions and water temperature in my area as he works out here a good deal. He's putting in a huge loop field for an enormous house not far from me. 30 loops or so, I hear. I'd love to go see it.

[Mark Custis]

I would think that the wet of the isle of long would act like my spring.

THE REAL DEAL IS ON YOUR CHECKBOOK.

You have worked hard and long on your proposed system, at least as far as you have shared your quest with the folks on this BB.

My offer still stands.

Try Arzelzoning.com for ideas on your duct work.

Would it be good juju to add an extra loop per ton?

If you use a non island driller, Yes.

If you use a driller you do not trust, yes.

If you have found your true soul mate contractor, do what he tells you to do.

Call if you need me.

440.223.0840

Mark

ps. I want to know how this project works out for you and yours and for the geo community. We need all the help we can muster.

m

[sunnyflies]

I have definitely found the right installer. And, before meeting him, the right well driller. Actually, I had gotten a proposal from the well guy back in March for a closed loop geo install - before I realized the HVAC firms I had been talking with back then did not know all that much and that whatever they might give me would probably not work, no matter how good the loops were. So I held off and kept looking and trying to learn.

I think saw the drilling company's name mentioned on this forum, though it might have been GreenBuildingTalk, after someone asked for a firm that could put in closed loops for a commercial building in New Jersey. No one around here was doing closed loops, so I knew I had to look farther afield. It took me a while, but I tracked the guy down. Looking for him led me to several other large drilling firms who I discovered also do closed loops out here for some of the huge houses, but I liked him best.

Interestingly, one of those large firms invited me in to their impressive office to talk to them. I thought it was going to be about putting in loops for me - which they would do, but I realized partway through the meeting that they were actually trying to learn from me about what a residential customer for geo might want and need, as they were thinking of moving into the residential sector. It was a fascinating experience for both sides. They had their geologist show me maps of the soil layers in my area and told me what they would be capable of doing, engineering wise. I think they could be on the right track as they have a large staff of engineers and some geologists who could team up with residential HVAC firms all over the tri-state area (NY,NJ,Conn) to design geothermal systems which those firms could then install with some sense of confidence. Right now, a lot of the HVAC firms I've spoken to are flying blind. Blinder than some customers I think. And, that's scary.

[teetech]

Right now, a lot of the HVAC firms I've spoken to are flying blind. Blinder than some customers I think. And, that's scary.

Sad, but true.

[sunnyflies]

The driller just called! He's finishing a large job nearby on somebody's 27 ton system house and will be bringing his rigs over either tomorrow or Saturday with the plan to drill on Monday. He's not from around here and his next job is for a huge house on the north shore of Long Island (Great Gatsby area) which will take a long time. He and the installer decided it would make sense logistically to set up and put in my loops now, since he is already out here and because it's not a big job. The installer can't do the system yet, but that's OK. He'll get to it in due time.

I asked him about putting in 1200' rather than the 1050' the installer says will work. He said he's going to think about it and run some numbers tonight. He said it wouldn't hurt to be bit longer than specified, but shorter - never.