I've always wondered a few things about geo loops. If you used the slinky design, doesn't all the constant circling of fluid result in flow restriction, thus leading to high effort by the pumps? I know they are big loops, but if you had hundreds of loops, the small pressure drop/restriction would add up, right?

Also, other than space savings, is there an efficiency gain by doing wells, as opposed to horizontal loops?

Posted By jeepster on 29 Nov 2011 11:59 PM

Also, other than space savings, is there an efficiency gain by doing wells, as opposed to horizontal loops?

Again, vertical loops are more efficient collectors of btus due to higher mean surrounding earth temps. Because of that, twice as much loop is required in a horizontal system.
This mis conception is that efficient loops = savings. Quite the contrary in my AO. Vertical loops are about twice the cost/ton of horizontals while system operating cost remains about the same.

Posted By jeepster on 29 Nov 2011 11:59 PM
  If you used the slinky design, doesn't all the constant circling of fluid result in flow restriction, thus leading to high effort by the pumps? 

The pressure drop is no higher in a 500' slinky than a 500' straight pipe.

Posted By canadageo on 29 Nov 2011 01:11 PM
  they are NOT as efficient, as racetrack. For the most part the "older" guys are the problem.

I disagree

I guess I have the newer guy mentality, my guys prefer to install a racetrack and unless we don't have much room on the property and can only do a slinky with the space available. In our area my loop design program shows 3400 feet of pipe for a 6 pipe racetrack and 5480' of pipe for a 1000'/125ft trench compact slinky or 4350' of pipe for a 600'/100 trench normal slinky. Granted that is a 3' wide vs 5'+ wide trench but I like the wider trench for safety reasons and it is less pipe.

Posted By canadageo on 29 Nov 2011 01:11 PM
Depending on where you are.... slinky's may work for you... Go into frigid temperature areas, they don't work very good. You need at least 25-30% more pipe, and a lazy mans way of doing the install. Long term it's harder on the system, they are NOT as efficient, as racetrack. For the most part the "older" guys are the problem. They have learned to do it the way everyone said to do it 20-25 years ago.. Well that's what ruined most people's thoughts on geothermal... most didn't work properly. Most put in too small of systems, then undersized the loops for the undersized units... Now not all are still in this category some of the good old boys have adapted but I still run into it all the time.

Hello youngster. I would challenge your comments.
I would actually go as far as questioning your expertise and asking you to provide data to support your statements. We install slinkies in the Buffalo, NY area and monitor many of our systems. Our heating degree days are one of the highest in the US. Here are two systems with slinkies with annual EWT monitoring, and it shows that they perform as they were designed to, namely to bring the EWT into the operating range of the heatpump, and to drop not below 30F even at the peak or at the end of the heating season.
http://welserver.com/WEL0448/
http://welserver.com/WEL0267/
A slinky which does not perform is not a result of the slinky loop, but a flawed loop design in general. While it is true that they need more pipe length than straight pipe, they need significantly lesser excavation and speed up the install process. You call that the "lazy mans way of doing the install" I call that the more efficient way to do the install, which helps to save costs to both the customer and the installer. May be you can explain to us why they are harder on the system if designed properly, or why they don't work as well long term. If someone undersizes the system or the loop, that is not a slinky problem. While the industry has learned significantly to improve design material, the "older" guys who have the 20-25 years experience I rarely find problematic. The young guys, who have done a few installs, and then think they know it all are the trouble makers. Some even go on the internet and make misleading statements about design and performance.
One must understand that a greatly designed loop and a good performing loop is the one which brings the EWT within the operating range of the heatpump in the most cost effective way. If one does not understand that, he or she has not understood the geothermal concept.
If you have any data to substantiate your comments, I am the first to listen. Until then you have to be careful not to mislead people.

I install in much more frigid temperatures than buffalo... You do get alot of snow though ;) but with that it helps insulate the frost line. I've been at it for 22 years now. I have install loops as far north as the Yukon, in Canada. (Basically Alaska) None of the loops I've installed in the past 12 years (since I adopted racetrack or vertical only) drop below 36 degrees mid or end of winter. Thus, giving maximum efficiency to the customers. I don't have web servers to provide you with, but if I dug and pulled all our service records not 1 at any time of the year dropped below 36. Well that's not 100% true... Only 1 had but that was due to one of my installers putting in way too much antifreeze, once it was balanced back it went back up to 36 degrees.

I am sorry here, but I doubt that you can beat the physics.

Our deep ground temperature in Buffalo NY is around 49F. If I want to design a loop for min EWT of 35F rather than 30F, I need to increase the size of the loop by 2.5 times, no matter if slinky or racetrack. Not worth the increased upfront cost.

If you are in much more frigid climate as you indicate, and have a deep ground temp of lets say 43F in the Yukon, you will not be able to keep your horizontal loop at or above 35F EWT, due to the surface swing which is close to 35F. Now you start to pull some heat out of the ground, the warmest your loop can be at the end of the heating season, even with a minimal load on it, will be 31-32 degrees. BUt they have to be really, really big.

Tell us where you are so we can pull the climate data, how deep and how long your loops are per ton of HP capacity, and we can run the numbers.

Posted By docjenser on 30 Nov 2011 12:20 PM 
... Here are two systems with slinkies with annual EWT monitoring, and it shows that they perform as they were designed to, namely to bring the EWT into the operating range of the heatpump, and to drop not below 30F even at the peak or at the end of the heating season.
http://welserver.com/WEL0448/
http://welserver.com/WEL0267/
...

Nice job on implementation of your WEL monitoring systems.  And you 12 month charts for EWT are particularly informative.

Best regards,

Bill