# "Shallow rock" affects vertical loop's capacity to heat?

Discussion in 'Vertical and Horizontal Loops' started by Tamar, Dec 12, 2013.

1. ### Mark CustisNot soon.Industry ProfessionalForum Leader

Eric:

Tamar is with the lawyers.

Mark

2. ### docjenserWell-Known MemberIndustry ProfessionalForum Leader

This is the formation conductivity, not the total heat exchanger conductivity.
No formula, but an algorithm .

Factor in:
1) Borehole spacing
2) Grout type
3) ground water flow
4) pipe size and volume
5) borehole diameter
7) whether the design is to cover the whole load (water-water) or with means of supplement heat
8) Turbulent flow

plus a few more things to affect heat exchanger size and performance.

Last edited: Dec 24, 2013
3. ### urthbuoyWell-Known MemberIndustry ProfessionalForum Leader

Doc,

I've had mechanical engineers ask me to spec btu's/ft. "It doesn't work that way" - is all we can say.

4. ### DavidCraigMember

Doc,

Thank you, lol. But really ... I googled the topic and got some really intesting formulas:

L = (qhRb + qyR10y + qmRlm + qhR6h) / (Tm - (Tg + Tp))

Length = (Hc (COP-1)/COP) (Rb +RgRh) / (Tg - (EWT - LWT) / 2)

[ http://s3.amazonaws.com/suncam/npdocs/091.pdf ]

Not exactly for the faint at heart. For example, how does one really calculate R10y, R1m, and R6h with accuracy? It would seem in the end you would get what specs you could and then make a judgement call based on experience. Then, during drilling, you would have to adapt based on findings or problems that showed up then - a dynamic process.

Last edited: Dec 25, 2013
waterpirate likes this.
5. ### docjenserWell-Known MemberIndustry ProfessionalForum Leader

David, you seem to start to realize that there goes a bit more into things then ft/ton. But once you understand what affects the performance of a geo system, and its loop, you can design some crazy and ultra efficient systems. Yes, ultimately there is a dynamic process, and I make the last decision about the design of the loopfield when the first borehole is in, it is always my test bore. I also see a huge difference in pipe diameter and more so the increased volume of fluid in the pipes. Keep in mind, the step up from 3/4" to 1.25" for example puts 3 times as much fluid in there, which acts now as a buffer tank, which no formula or software accounts for. Now add in the not accounted effect of variable speed pumps, which changes the Reynolds number continuously.

For smaller residential applications, lets say less then 12-15 tons, we are down to 133ft/ton, plus-minus a couple feet.
http://welserver.com/WEL0662/ vertical 400ft bore, 1.25" pipe
http://welserver.com/WEL0712/ horizontal slinky 2400', 0.75" pipe

For larger applications we are down to less than 100'/ton (http://welserver.com/WEL0714/), for example we have a 38 ton system on 3600' of bore.

I am to the point were I don't use design software or formulas anymore, because it does not account for the things I need it to account for, but exclusively rely on the feedback from the monitoring from other systems in the area.

Tamar likes this.

For smaller residential applications, lets say less then 12-15 tons, we are down to 133ft/ton, plus-minus a couple feet.
http://welserver.com/WEL0662/ vertical 400ft bore, 1.25" pipe
http://welserver.com/WEL0712/ horizontal slinky 2400', 0.75" pipe

For larger applications we are down to less than 100'/ton (http://welserver.com/WEL0714/), for example we have a 38 ton system on 3600' of bore.

I am to the point were I don't use design software or formulas anymore, because it does not account for the things I need it to account for, but exclusively rely on the feedback from the monitoring from other systems in the area.

They are very impressive numbers...

Is there anyone else who is coming up with a different number for soil conductivity? One of the things I may do is ask the installer to recalculate their assumptions based on this information. It would be good to have at least 2 experts here supporting the conductivity number of 1.13......thanks!

Though empirically I may not need more loop in the ground, if my installer says that I don't have enough loop and one of my units should be removed, what should I counter with? I think re-drilling my current wells deeper will be difficult due to this: on rock-bored applications, Minnesota law requires that a permanent well casing be applied to each borehole along any “unconsolidated” overburden (soil) between the bedrock and surface.

So, is one additional well with its own manifold an option? Maybe a horizontal well that goes under our garage or something? Or one/two wells in the front yard that tie back to the system?

9. ### AMI ContractingA nice Van Morrison songIndustry ProfessionalForum Leader

It is they that suggest you need more loop, it is up to them to figure out how to get it. A horizontal "loop" is possible, but again you are asking the people that said you have enough, how to get more this is a fools errand

I know I am doing their work for them. However, their contention is that "there just isn't enough space within their property to install the number of wells required for 98% coverage." I would like to be able to put that argument to rest forever, and to me it seems easier to give them one or more options for installing more wells, rather than say "I've heard you have options if you think this is a valid argument--figure it out". They think they've figured it out and their solution is fossil fuel.

And maybe this is a stupid question, but if I have 8 tons of equipment, what would be the downside of having enough loop to support it (as long as I'm not paying for the loop)?

11. ### AMI ContractingA nice Van Morrison songIndustry ProfessionalForum Leader

Ok. Vertical wells can be drilled deeper and they can be closer together than 10-15 feet. So if you have to go every 5 feet for instance, depending on the subsurface materials, you may derate the capacity of the loops say 20% or so, which can be compensated for by going deeper. Their latest load calc you offered me suggests your load is less than 7.5 tons, so whether you have 8 tons or 50 tons of equipment, you don't need more than 7.5 tons of loop. I think you have about 8 tons of loop (IMHO).
You will get honest answers from us. Amongst them is you appear to have enough loop. The incompetent boobs who installed your system simply don't know this. Just like they don't know what percent of load means in geo speak.

We are all assuming the ground loops were grouted correctly, and really drilled to the depth of 200' and didn't stop at 147' were the rock was hit.
I personally think the ground TC is near a 1.0 and have about 6 tons of loop installed IMHO.

If the original installer is saying there is not enough loop, what's wrong with allowing them to install 2 more loops to cover the load? If they are saying it's too short then it's their error and their problem to install enough loop to handle it.
Then if it does not work still, then they have no excuses about being short looped. It then is installation error and/or load calculated wrong.

Hi Dan,

The Vertical Heat Exchanger Record on file with the MN Dept of Health states that the grout used was Neat Cement from 91-200 ft and Bentonite from 0-91 ft. In the box labeled Depth (completed) it lists 4-3/4 in to 200 ft.

I think one of my next steps is going to be to get a statement from another local well driller that they feel they can install additional loops, and just take the "not enough room" argument out of the equation. Thanks.

Last edited: Dec 29, 2013
14. ### docjenserWell-Known MemberIndustry ProfessionalForum Leader

If you can go down and with 2 more loops in the front, they can drill down to 500ft each, using 1.25" pipe, and tie it in the system correctly (if they know how to do this). This would essentially double your capacity. It would only cost them money, and then they would have to address the inside, too. Or as Joe suggested, put more drills down between the existing boreholes. Yes they steal heat from each other, but that can be easily accounted for. This is not rocket science, this is geo designing 1O1.

15. ### waterpirateWell-Known MemberIndustry ProfessionalForum Leader

I can understand your pain, but do not understand your logic. I would " let slip the dogs of the courtroom battlefield " and wait for a check or 98% geo, whichever comes first. I told you once before that the last bastian of ignorant installers is " it is the loopers fault ". Untill they come to understand that regardless of the pipe in the ground it is a design by them that does not work. Makeing this whole salted cod sandwich their responsability. I agree with Joe that this loop thing is a fools errand. The documents the driller filled out are legal documents when filed with the state. He is going to swear on a stack of Bibles that the documents are correct, which I have to believe they are given all the banter. Soooooo it goes around for another six months and will land back in the installers lap, not the drillers.
Eric

They aren't blaming the driller, they're blaming the ground. And I need to prepare a response to that, hopefully one that leaves no room to NOT move forward.

Thanks to everyone for the additional info and knowledge shared here!

Last edited: Dec 29, 2013
17. ### Mark CustisNot soon.Industry ProfessionalForum Leader

Tamar:
.......and if the loop field comes into the home in 1 1/4" pipe I can make it all work by changing the piping and maybe some pumping.

Keep the equipment you own.

Use Doc's idea of making the cast iron radiators and piping a gravity fed buffering tank the first stage of heat. The field as piped should support the 3 ton W 2 W high temp machine. So all the radiators are full of hot, but not as hot as boiler water, all the time based on outdoor reset.

With the changes I have in mind for the piping we would only need the poorly designed Unico system on design days. That would free up the w2w unit to do it's slow and steady heat pump work to the radiation. There is enough loop for the w2w to work without the air handler calling.

I agree with Eric and Dan that the driller, who produces documents of public record, is a good guy and reading the reports he covered the design day load on the home.

Do not waste time, energy and the HVAC contractor's money, on digging up the yard.

You have told us:

The high velocity work is not ducked correctly. So how will adding gas fired BTUH help the air flow. If you can work a battery powered drill motor you can install HV duct work given a good design.

The reason that the loop field can not support the equipment you bought is that it is improperly piped. That can be fixed.

You have gone to the lawyers and the state. What is up with the AHLJ inspectors.

Your contractor is unable to understand why your system does not work.

He is unable therefore to explain to you and yours why this system does not work.

The hired gun PE does not get it either.

So what do we want to do?

Go to court? Fix the system?

All I need to know to fix this is what size pipe comes into the home. It is more than likely covered with insulation.

The pipe is printed with all sorts of data as it comes out of the roll. A box cutter and some duct tape will let you get me the size of the pipe that enters the home. The Geothermal Police will not come and arrest you for gaining this information. If you are still afraid call the driller. He can look at his materials list in his file cabinet and give you a pipe size.

You have my email, and I believe my phone number, if not check lake-erie-indoor-air-services.net

I admire your brass ovaries, My wife is much the same, ask Joe Harden. I just feel bad that what we type for you goes unheard as we see it. Some of the best heads in our industry type here for a reason. We want to help you and promote what we have chosen to do for a living to mainstream thinking and planing. We know what we do works.

If anyone that types here thinks I am off base please feel free to point out any errors and spank me if needed..

I want what you have to work and will do what ever I can to make that happen.

warm regards,
Mark

18. ### docjenserWell-Known MemberIndustry ProfessionalForum Leader

The issue(s) here are many.

1) Yes, it can be salvaged, but is that an efficient solution.
2) Who salvages it? The current installer and the engineer appear to be lacking some fundamental knowledge!
3) Can the loop carry the load?
4) Can the loop carry the flow?
5) Who takes on the design liability that whatever changes are made will work well for Tamar?
6) who will pay for all of this?

If someone else touches the system before the legal questions are addressed and solved, then the installing company is not liable anymore for the mess, and Tamar has no means anymore to ask for them fixing it, or getting her money back.
They admit that indoor and outdoor design and installation is flawed and cannot work. Tamar paid a hefty sum of money to get of gas, not only for improved efficiency. Them putting a large portion back on gas just because that is the only way they know how to mask the design flaws should not be acceptable.

FWIW, I spoke to the VP of a large local well drilling company today, and when he heard that at 200 ft they were in St. Peter Sandstone, he said there is no reason they couldn't have kept going, that's one of the easiest materials to drill through. He also thought off the top of his head that our TC was/is probably 1.5 +.

Stay warm, everyone!!