> problem I see is that all these programs assume an average and constant heating degree days or BIN days

Ie, a sustained cold spell near design temperature that starts to pull down loop temperatures? I'd put in enough aux heat to keep the customer happy for those cases and use the programs statistical weather values to get best ROI from the geo.

It happens in our neck of the woods. Sure there is aux heat, but as a third stage. The heatpump is still running at full capacity for a couple weeks. Again, I was glad I accounted for it. Surely an extreme case, but with fresh horizontal loops it happens more often then we think. Most systems are not monitored.

Posted By docjenser on 17 Sep 2010 03:40 PM
OK...after Joe brought up an interesting point I ran some scenarios with the software, 55KBTU/H, Buffalo (NY), 4 ton system with desuperheat, going from 600 ft total borehole lenght to 720 ft borehole (20% larger) changes COP from 3.69 to 3.80, and saves $62 per year (at 16 cents/KWH). Min EWT changes from 29 F to 31 F.

Going the other route (500ft borehole) drops min EWT to 26F and costs you $151 more per year.

Interestingly, making a horizontal loopfield bigger by 20% only increases COP from 3.71 to 3.77, and increased the min EWT from 29 to 30 F.

The main problem I see is that all these programs assume an average and constant heating degree days or BIN days. It is all great in theory. Then came winter. I had a monitor system on a fresh loop (new install), ground was not fully settled yet, old farm house, retrofit, pump was correctly sized by the book, loop was 20% oversized and buried at 8 ft (horizontal slinky), and at around 29 degrees at the middle of February, where it should be. Outside design temperature for Buffalo is 5 degrees. Then we had a cold front for 2 weeks, temperature sometimes at 10 below, with up to 40 mph winds. Heatpump was running at 2nd stage constantly, with supplement heat kicking in. After 11 days EWT was down at 25 degrees F......now what? System performed nicely, happy customer, happy me! But boy was I glad about the 1-2 degrees higher EWT thanks to the 20% oversize, and maybe another 2 degrees more thanks to the 8 ft versus 6 ft depth. Probably much better now that the soil is settled.

This is when you throw the software, ROI and COP out of the window and make sure the thing works.... no matter what.

Cost of KW definately changes the advantage of more loop and less aux. That is the whole purpose of sensible local design and the shortcoming of us regional guys on international sites such as this.


What's most important is that expectations are met. Customers must be educated in the equipment they are buying. Calculators that are taking a hit right now have proven their reliability to me. I tell folks at what temp they should expect aux. contribution and to call me if they do not find this reasonably accurate.
These systems work..... no matter what.
When they ask for extra loop or higher EWT's I quote them a price and tell them their calculated savings.
As most of our systems are horizontal, "a little extra" or even 20% more loop end up with paybacks in the half century range.

I suspect another reason for our design disparity is our thrust of business. Most of my jobs are retrofits paid for by folks in a ba ttered economy recognizing that their geo savings over propane out perform their current retirement vehicles.
These folks want the most bang for their buck. If paybacks weren't in the 5 year range I'd likely be in the custom home market only; which would make some of these other discussions more pertinant.

J

I agree with Joe, no matter what side of the more loop or not fence you are on the reality is that very few installers and even fewer consumers have the wealth of experiance available from this brain trust. A good tight design is exactly that when done by someone with a proven track record and tuned into regional costs.
Where advocation is for more loop or more machine is warranted is when you are still feeling your way through your initial designs. It is also a human nature trait. Some of us just over build everything rather than just building to design specs. It is only money and how you choose to spend yours is really in material to anyone else but you.
Eric

For some reason there seems to be the impression that we are charging the customer for this. Our systems usually run between $5-6K/ton, including 2 stage heatpumps, domestic hot water and buffer tanks. Since we started monitoring performance we increased loop size by about 20% for horizontal systems (not for vertical, drilling is expensive in our area). Because we did see added value. We also went from 8 ft to 6 feet and a couple years back to 8 ft. Once everything is on site and the crew is pounding away, how much more is 800ft of pipe and a few gallons of antifreeze for the material? Labour is pretty much the same, I still pay my crew for the day. We are doing this because of the experience and data we have gained over the years in our climate, in our soil conditions and with the logistics we run our operation. It works better for us, and the customer gets a system which runs $50-100 dollars more economical. Now, all of this is off when the customer would be charged $2000 more for this, but this is not the case. Our prices actually went down over the years, since we manage to run our operation more efficiently.

Posted By docjenser on 17 Sep 2010 02:48 PM
...a heatpump with a COP of 2 (30 years ago) of lets say 4 tons extracted 2 tons out of the ground and got 2 tons from the grid (mostly compressor heat). A new heatpump with a COP of lets say 4 now takes 3 tons from the ground and 1 ton from the grid. 50% more load on the ground loop than before.

That's a great argument for justifying extra loop on a new COP = 2 installation;
but today, we'd be starting with a COP in the 4-5 range -- so, even if efficiencies
were to double again in the next 20-30 years (ain't gonna happen!) it would only
increase loop load by 10% to 12%.

...Mr. Diminishing Returns strikes again,

Looby

I was thinking along the same lines as Looby, but didn't want to do the math. Thanks Looby.
Maybe in 50 years we may have cheap power from fusion, perhaps courtesy of the National Ignition Facility.

Posted By Looby on 18 Sep 2010 10:25 AM

Posted By docjenser on 17 Sep 2010 02:48 PM
...a heatpump with a COP of 2 (30 years ago) of lets say 4 tons extracted 2 tons out of the ground and got 2 tons from the grid (mostly compressor heat). A new heatpump with a COP of lets say 4 now takes 3 tons from the ground and 1 ton from the grid. 50% more load on the ground loop than before.

That's a great argument for justifying extra loop on a new COP = 2 installation;
but today, we'd be starting with a COP in the 4-5 range -- so, even if efficiencies
were to double again in the next 20-30 years (ain't gonna happen!) it would only
increase loop load by 10% to 12%.

...Mr. Diminishing Returns strikes again,

Looby

Guys, this was hypothetical.... You were asking the question why efficiency has anything to do with increased loop load. I am not saying anyone should do this....

Posted By docjenser on 18 Sep 2010 08:02 AM
For some reason there seems to be the impression that we are charging the customer for this.


Now, all of this is off when the customer would be charged $2000 more for this, but this is not the case. Our prices actually went down over the years, since we manage to run our operation more efficiently.

You are (or you are headed for bankruptcy).
That you have lowered prices due to business efficiency suggests you are well in tune with job cost. To suggest that you are taking the added expense of extra loop, antifreeze sometimes larger flow centers and additional labor (regardless of how modest) out of the your desired margin is naive at best.
That you consider it good business to have more loop and have included it in your pricing still makes it the customers expense not yours. If you used less loop and maintained the same desired margin, systems would cost your customer less.

You appear to provide good product at reasonable prices to your customers. I simply would suggest that extra anything is not free. Our insistance on micro managing loop design on this and like forums is one thing, but to suggest extra loop should cost nothing.....
j

I'd be content with "the incremental cost of some extra loop is often small". On the other hand, if it leads to another day for crew and equipment, then it could be expensive. Depends on the situation.

.
You are (or you are headed for bankruptcy).
...out of the your desired margin is naive at best.
Our insistance on micro managing loop design on this and like forums is one thing, but to suggest extra loop should cost nothing.....
j

Joe, I would argue differently. To standardize loop-design for our area which covers all variable such as different soil conditions has allowed us to run our loop install much more sufficient, where we do not have to worry about ground conductivity and other things. We were wondering how we can install loops more efficiently without sacrificing performance. So it turned out that the loop looses 20% of performance the 1st winter if we do not water it down and ensure compaction. However you can compensate for it if you add one more loop of pipe. So it was cheaper for us to add one loop of pipe since the crew is on site, and after year one the customer has a better performing system. While our competitors are taking an average of 3 days to install a 6 ton loop, we are done in one day and can move on to the next job. The install costs in our area was about $1700 per ton, we have decreased this to $1400. What you call naive has added a $1000 per job to our bottom line, but also allowed us to lower install costs for a customer buy an average of $1000. As a result we won many more bids, doubling the number of installs compared to last year, but using the same amount of people for labour. Heatpumps are unlikely to change in price significantly, so the costs for loop installment have the largest potential to decrease the costs for a geosystem. What you call micro management has had the biggest positive effect on our business in the past years. My intent was to share this with everyone here, it does not mean that what worked for us will work for you. But to try something new and find out if that works better or not is how we progress, the last thing I expected is to be called naive for communicating this to everyone....

Doc,
You insist extra loop is free, but support that statement by pointing out that you found a cheaper way to accomplish your goals. There is a difference. You argue that your practices before cost your customers money they no longer have to pay (and that's great). They still pay for all you do. Would you charge the same if they needed less loop?....Insist they buy more than they need?.......

The "extra loop" discussion began in the context of ROI/benefit. As you describe your situation there it sounds like a winner. But still not free.
We don't have many compaction issues here (mostly damp or saturated sand and gravel). So yeah, extra loop just costs extra.....

I'm sorry if you are insulted (honestly not my intent).
Please do not continue to insult us by suggesting you are giving work away.

j

Joe, No insult here.... I never suggested that I give work away or that extra loop is free to us, I certainly admitted that there are extra costs in material. I made the argument that for us slightly over-sizing the loopfield turned out to be more efficient/cost effective for all parties, since it standardized and simplified the horizontal loopfield install, and gave us additional safety margins for extreme weather conditions or hard to calculate load conditions (older houses). This allowed us to work much more efficient, which then comes back to the original ROI/benefit question. You can put a negative touch on it by saying that we had practices before that cost our customers money they no longer have to pay; or you can be positive and state that you found a better, more efficient way of doing things which benefits each and every party. Same thing! Would I charge the same of they needed less loop? No of course not, I would put less loop in and charge them less. Insist they buy more than they need? Are you kidding me? Never! I never suggested anything like that. No idea why you come up with that. May be the word over-sized is not correct and be better worded "correctly sized for that application".