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

I am being given the following information by the installer who put in our GSHP system (5 ton split and 3 ton hi temp W2W). After 3 years it is only in the past 2 months that they have started saying that the loop in the ground cannot support the load. Until today they did not divulge why they were claiming that. Here is the information I got from them (indirectly) today:

The homeowner desires to have a 98% coverage geothermal system, this is impossible giving the shallow rock that exists below their home, there just is not enough space within their property to install the number of wells required for 98% coverage. The highest level of coverage possible is the 67.6% estimated coverage that our engineer calculates in his design from 12/9/13.

I have to note that their initial proposal stated that 98% of the load would be carried by the geo, I did not pull that number out of thin air.

Attached is some detail from the well-driller's report. I'd really appreciate some expert opinions on the installer's reasoning (excuse?), and if someone can direct me to anything published that supports or refutes their claim, I'd be very thankful. As most of you know, this is not my first thread so I'm very aware that 6 bores x 200 feet would typically support 8 tons without a problem.

Many, many thanks in advance.

 

What a bunch of malarky!!!! I have been loosely following your trials and tribulations, but this is pure B.S. It sounds like to me that the contract was written with no knowledge of the local lithology. Not your fault. You can allways drill deeper, get a bigger machine, apply multiple stratrgies to achieve the amount of pipe in the ground to cover the design. In all of this remember that " money solves everything " since you have a signed contract it should not be your monies solving the problems.
Eric

 

"You can allways drill deeper, get a bigger machine, apply multiple stratrgies to achieve the amount of pipe in the ground to cover the design."

Exactly. The disturbing part is that they don't seem to know this, nor does their engineer. Further I'm not sure they understand what we mean by 98% of the heat. I think the engineer is thinking pct of load (which he butchered earlier).

 

I still think the issue is the near machine piping and not the loop field.

Mark

 

Thank you, Eric. I'm frankly a little shell-shocked, both that this issue (if it is an issue) is coming up after several years of being told by the installer that all was well, and that they are taking this stance that is so contrary to what all of the experts here are saying. I really appreciate your input!

Mark, the installer now seems to believe the right solution is to give up on geo, rather than fix the pipes and controls. This does not sit well for me, at all.

 

Oh gosh, I did not mean "all was well" as a pun, but I guess it is....

 

IMHO the best puns are the ones that happen on their own. Please do not let them off the hook. You deserve resolution of your problem, either a permanant agreed to fix, or a full and complete refund plus interest.
Eric

 

Today's weather will not allow a drive to St. Paul. With the bad guys bailing can you confirm the size of the pipe entering the home from the geo loops?

Mark

 

get a full report from driller, and installer as far as whats exactly in the ground.
Antifreeze type and mixture?
Pipe diameter and horizontal runs to house?
How was it tied together...Parallel or series?
Was was the loop field design and size of the loops?
What ground conductivity did they use for designing the loop field?
Where and how did they come up with the loop field design and finally come up with such a odd 67.6%?

Like WaterPirate already stated..... Drilling deeper would have been the simple solution to your issue. If you have room to drill 6 boreholes why did they stop at 200' if it would only handle 67.6% load? Your assumption of 6 bores easily handling 8 tons is not always correct. Your basing that on the internet search results of 150/ton. Which will work some places but not in others. It is all about the what your ground can transfer, which brings me back to the importance of getting drill logs and records of loops installed from your driller and installers.
Dan

 

Hi Dan, I think some of the info you are asking is in the attachment to my initial post. I've attached some additional info from the drilling permit and the initial geo-designer report we were given to show how much money we would save....

Thanks for your input! It is much appreciated!

 

We have been through all this. The latest false argument now is that the rock is "too shallow". The denser the material, the higher the conductivity, the better the heat transfer and performance. Our loopfield have the best performance the shallower the rock is, and the less casing you have to do.

 

Doc, that is assuming they drilled the rock. I could not open the attachment. Did they only drill the overburden, or is it just short looped period?
Eric

 

6x200'x3/4" loops in assumed .96 silt and sands. Rock was hit at 147'.
Was it grouted correctly from the bottom up, with the neat cement?
Your report is showing a bored length of 1085' not 1200' like your saying.
Unless I'm missing something obvious here.... Your short looped.

 

I'm re-attaching both docs as pdfs. The 1085 in the geodesigner report was the initial proposal design that showed how much we'd save....that was 5 months before actual dirlling; everything that is coming from the well driller (permit and report) says 200 ft. I expect the 200 ft x 6 is right.

Rock was expected at 147 feet, but the actual report shows the different materials hit and at what depth. I know this is discussed in other threads, but I really appreciate the new input from those who focus on drilling. Each new comment helps me understand better so that I can be ready for everything as negotiations continue and they throw new concepts at me like "shallow rock".

 

Your driller is showing and reporting he drilled enough bores to handle a 6 ton Heat Pump load.
Which in that formation looks to be correct for 6x200' bores.
Your saying you have 8 tons of equipment installed though, and your Geo design report is showing 10 tons.....either way there is NOT enough loop in the ground.
You are going to have to get your original design from the Heat Pump installer too. Do you really have 8 ton HP installed, and do they have desuperheaters installed too?
I am seeing a lot of inconsistency here and see all signs pointing to not enough loop to satisfy your HP.

 

I saw that "6" in the final report too for # of tons, and called the driller on that. He said it was a typo, and they drilled exactly what the installer requested. He was a bit hyper/skittish and seemed worried that something was going to come back to him as an issue with him being liable, but from all I can tell he did what he was asked to do.
We have 8 tons of equipment, a 3 ton hi-temp W2W and a 5 ton split with a hi-velocity air handler for our 1898 Victorian.
There is one desuperheater.
I don't believe there is any documentation of the original design. If there was, they might've piped and controlled the system correctly to begin with.

Dan, how far off do you think we are in having enough loop in the ground? The 3rd party engineer says we'd need 13 loops instead of 6, which of course there isn't room for on our city lot, but if it is one more loop, that's a different story...

 

"Your driller is showing and reporting he drilled enough bores to handle a 6 ton Heat Pump load."
With a variety of conversations over the last few months Doc and I are both reasonably convinced that the loop field is adequate as the house load appears to be in the neighborhood of 6 tons. So even though there is 8 tons of equipment, the loop field should not be overwhelmed as demand ultimately dictates field size.

 

Based on what your telling us here, the drillers report, and there assumption of it covering 67.6% i would agree that the loop is too small to handle a 8 ton system. I think with the drill records supplied 200'/ton is accurate. I think your 2 bores (400') short.
If you loops only need to satisfy a 6 ton load and the house is equipped with 8 tons then its no difference.
Maybe your original design for the loads were incorrect and loop design was also incorrect.... Who really knows what they designed for since you do not have anything else.
Alot of drillers only drill what they are told to do. I just think its a real coincidence the only typo was the "6 tons".

 

Agreed. The permit was for 6 wells/10 tons, but I guess I will never know the real story unless this gets to a place where participants are testifying under oath, and I certainly hope that isn't going to happen.

It's not clear from the "offer" if the 67.6% is based on the "real" load (somewhere between 70-90kbtuh) or the engineer's padded load (125kbtuh).

 

Couple things Dan,
Remember again demand matters more than equipment tonnage for loop sizing in this case where there appears to be about a 70ish MBH load based on consumption records, a 12 ton system still would only need a 6 ton loop field. Secondly Doc, who's worked in the area suggested he'd seen success with 150'/ton verticals which technically makes this an 8 ton field anyway.

The 67.6% number is due to ignorance first on actual load of home and second in ignorance to what we mean by percent of load (IMHO).

Your conclusions and suspicions would likely be different, Dan, if you new all the context.