1. Think I got screwed.

I put a Geo unit in my house. Started it last winter but not living in the house, it was always warm running on 1st stg heat pump only. Moved in in April and noticed the loop hoses going into the unit were sweating so I checked the lop temp, it was 37°. I did not figure that was to bad so I didn't think any more of it as the bills seemed reasonable also. Fast forward a few months and we are having 100° weather with some high humidity for here anyway. I was just doing a quick check on the system and noticed the brass fittings on the non pressurized pump were hot. I checked loop temps again and had 105 in and 111 out. This seems way to high to me. I called the guy that did the loop, he had me try some things as he is about 1.5 hours away. It ended up and took him over a month to come down. He ended up opening up the manifold and found where the grout was no longer filling the bore holes (horizontal boring). He pumped the holes with grout and covered it back up after about a week. The outdoor temps have cooled down but I am still having 85°+ loop temps.

The system is a 2 stg Bosch 2T on what is suppose to be a 3T loop. The most it has run any month was in July with the 100° temps and that was only at 66% total run time with most of that being 1st stg. Shouldn't my loop be removing more than the 2ish ton that is going in to it? How can you measure what the loop is transferring?

2. 129 views and no suggestions

{crickets chirping}

Anyone!!

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The actual loop heat rejection energy (summer) is determined by measuring the loop flow rate in gallons per minute and the differential temperature between the supply and return:

500 x gpm x (return deg F - supply deg F) = BTU/hr, BTUs / 12,000 = tons.

Because the loop also carries away the energy used by the system, the energy (BTUs) removed from the house (summer) will be less by that consumed by the compressor and water pump. Your measured BTU/hr reflects the actual energy removed from the house, not the system capacity (e.g. how fast you're driving vs how fast you can go).

High summer loop temperatures and differential temperature (return deg F - supply deg F) is a tattle tale of problems with heat transfer from the loop to the ground.

A search on the internet will reveal loop requirement calculations (e.g. required length of pipe, area of field, etc.) based on climate and soil conditions.

The energy advantages of geothermal heat pumps is created from condensing temperatures (water loop vs outside air conditions) being lower (summer) than conventional air cooled units.

The above applies to the heat pumped out of the ground in winter, but in reverse.

If I understand what you are saying the loop will only reject what the WSHP capacity is since you are using the same measurements when you calculate heat of rejection.

My thought was that with more loop than needed the loop should remove more heat than the unit puts into it so the loop temperatures would stay cooler.

Since I have been monitoring it there has not been much difference between outdoor temp and loop temp and on many days the loop was warmer than ODA. Since they re grouted the loop the temp has gone down but it is still not much difference than ODA. Also the ODA has went down by over 10° since this came to my attention and we have had some lows in the upper 40's to low 50's. I wish there was a good way to tell if the loop was performing properly.

Is there a formula that would take into consideration time? What I am thinking is a properly performing loop should warm very slowly while an under performing loop will raise quickly. I guess what I am thinking is if a system runs constant for an hour putting 30k BTU into the loop then the loop temp should raise accordingly, in essence raise by the temp rise across the coax in that hour. So if you start with an 80° loop it would raise 8°, under performing would be more, over sized would be less.

Does that make sense or am I missing something?

5. You need a copy of IGSHPA's design manual. Loop design is like any other design, you look at equipment specs and design a system around it. The temperature data that your looking for should be in the technical guide for your heat pump and will plot the relationship of loop temp/efficiency/capacity.

You have to figure out what your looking for to supply that heat pump with correct flow and temperature, then look into ground transfer as mentioned above.

What length of loops do you have?
How deep are your loops buried?
What is the loop configuration, how close are they to each other?
Buried manifold or in your basement?
What is your current GPM and delta T?

Just trying to point you towards the important parameters....

6. Joab, I started to answer this last night on my iPad and lost it so rather than hassle with it again I decided to wait till this AM. I have a copy of the manual from when I took the course years ago.

The loops were installed using a horizontal boring machine. There are 6 loops that are 100' long. The loops are paired to equal 3-200' rather than the 6-100'.

The loops are about 1'-18" apart and about 4' deep at the manifold pit and go apart and down from there, kinda like when you spread your fingers apart. The opposite end of the loops are staggered with one being at 33' the next at 28' alternating.

The GPM was at 6 with the non pressurized pump on low speed then the loop guy changed it to high for better turbulence through the loops. Last night running on low I had 85.6 in and 90.3 out so 4.7. It seems like the last time the loop guy was down it was running about 6° on 2nd stg.

Here is the issue. When the loop was put in they were suppose to go down about 75-100' which is about what I figured as the depth of a limestone shelf is at. There is a creek at that level that is within 3 blocks or about 1000' so I figure there is a good chance of water being there. This is the reason why I didn't go vertical as they can't get through the limestone formation as I had a vertical loop put in about a mile away and they could only get down 135'. That place is higher than my place. When they started to put the loops in the first 2 I was told by the operator that they could only get 60' in. The boss told me that they were going to try and get 140' in on the third and tie that together with one of the 60's. So they got 1 60 in on Monday, the second 60 in on Tuesday, all of a sudden on Friday they were done and I supposedly had 6-100's and I found a bunch of loop tube in the trash which makes me question just what I have there. Add to that we didn't start cooling until the end of May and they just after the 4th of July we were running 104 in and 111 out. I am trying to figure out if I got the loop I should have gotten, if we just have bad contact, or if it is just a matter of some adjustments. Part of the problem is we went from 100° ODA's in July to upper 80's to low 90's in August.

7. Where are you located, what's your zip?

At first blush that's not sounding good at all...

8. Location is listed.

I think it is way past the blushing stage.

Ok, today it got up to about 95. I was home because of having some other workers in. The thermostat was set for 78 and the unit was not running. About 3:30 the unit started so after it ran for a short time I checked the loop temp. It was 84.5. At 4:30 the stat came it of set back to 76. I left before 5 and got back around 6:30 and checked the loop temp. It was 91.1. A 6 degree rise in the loop in 3 hours seems like a lot to me. I checked it again close to 9:00 and it was down to 87. I just don't think alp should change that fast or that much.

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