Hi.  Buidling a house this summer with a geothermal closed loop system with infloor heat throughout.  Some of the geo guys go with a coil system with the pipe in the loop filed and some do a racetrack system where they just stretch the pipe out so the pipe isnt in contact with each other.  What are some of the pros and cons to either system??

Thanks

If this is your only worry, you are doing fine.
The short answer is any loop system is good as long as it is properly sized.
After doing a thousand or so loop designs I have noticed that slinkies remarkably seem to require a little less feet of trench. Comparing a 6foot/foot slinky buried at 6 feet, to a 6foot/foot racetrack, the slinky is buried at an average depth of 6' while the racetrack with the bottom pipes at 6' and the top at 4 or 5 has a slightly shallower average depth.
I found that often times more mature companies/installers prefer slinkies which allow more prep off site and less time in the trench. This is not always true however.

That said, if you are doing a geo radiant, the pitfalls are numerous and your installer must be truly expert. talking about the loops is far from due diligence.

we prefer slinkies for the reasons Joe stated

A racetrack loop has only 1 pipe laid out in a horseshoe design buried to a certain depth. They are there is no second pipe buried in the same trench.

Slinkies!

Posted By Calladrilling on 28 Mar 2013 09:09 PM
A racetrack loop has only 1 pipe laid out in a horseshoe design buried to a certain depth. They are there is no second pipe buried in the same trench.

To clarify, there can be 2 pipes in a '4 pipe layout', and 3 pipes in a '6 pipe layout', however the pipes may be at different depths.

Just to reiterate, worry about how many successful geo radiant projects your installer has, not his ground loop preference.

I have to disagree. If you can get a slinky in, you can get a racetrack in. A slinky is pipe laid on top of pipe, which is not as good as pipe laid on dirt. Over time you get expansion and contraction, even if its just millimeters your loop will create ever so slight air pockets as your loop goes from 35 degrees winter to 90 degrees summer. A racetrack should not create these air pockets except where there are tight corners.
When we do our racetrack we also do it different, rather than going out 125' and then adding 2' of dirt then coming back 125' for an average depth of 5' vs the 6' that you install a slinky at(we install ours at 5' for safety/shoring regulations since we use a 5' wide by 5' deep trench) and since most excavators have a 5' wide bucket it will give us a perfect trench for a 6 pipe(6 pipes wide) racetrack so we can put as much pipe as a slinky in but without looping pipe over the top of it self. This gives us more even contact with the soil unlike a slinky where some spots of the soil have 2 pipes over the top and others have no pipe over it.
Would you install a radiant floor system with a slinky? NO! So why would you isntall a ground loop like that?

Anything that expands and contracts can create air pockets. Worry about the installer enough loop is fine regardless of how it's laid out.

We have been doing slinkys for 6 years. We have never had a slinky system not perform well. You can say that you like to install 6 pipe more than slinkys and get no argument from me. However, I will always disagree that slinkys do not work as well as any other kind of loop.

I have nothing against slinkies and I think they can work well just as a racetrack can work poorly. I just think that per foot of pipe a racetrack is an ideal layout for the reasons listed above, but as we all know, as long as enough pipe is in the ground the configuration does not matter.

as long as enough pipe is in the ground the configuration does not matter.

I'll add "and spread over a great enough area". Jamming lots of pipe into a small area/volume doesn't provide enough soil/thermal mass to draw from.

Posted By jonr on 21 Apr 2013 09:04 AM

as long as enough pipe is in the ground the configuration does not matter.

I'll add "and spread over a great enough area". Jamming lots of pipe into a small area/volume doesn't provide enough soil/thermal mass to draw from.

Posted By SkyHeating on 21 Apr 2013 12:08 AM
I have nothing against slinkies and I think they can work well just as a racetrack can work poorly. I just think that per foot of pipe a racetrack is an ideal layout for the reasons listed above, but as we all know, as long as enough pipe is in the ground the configuration does not matter.

Both those comments are misleading. Of course the configuration matters, for example because of pressure drop. It matters if you run 2 or 3 or 4 or 5 circuits with the same amount of pipe. It matters if you put it at 5 ft depth or 8 ft depth. And it matters if you are using 1" pipe or 0.75" pipe. So the comment to just put enough pipe in the ground is wrong, also the comment that as long as being spread over a large enough area.
You can certainly put them closer together, and in smaller areas, as long as you are aware of the impact and compensate for it. The design is key to make those installs work efficient. In terms of loopfields, no design is good or bad as long as it brings the entering water temperature within the operating range of the heatpump. Many different designs can get you there.
The last 10 main complains here with lack of performance or no performance at all were were flow or pressure drop issues, so please don't say that the configuration does not matter, or as long as you have enough pipe in the ground, everything will be fine!

By configuration I should have said loop type, IE Slinky, Racetrack etc. but yes number of circuits and length of pipe matter in the overall design, i just meant with enough pipe there will be the required amount of heat extraction. With a racetrack if you can put in less pipe and keep it around 6 circuits like we normally due, there is a very low pressure drop and most systems we install work just fine with a single pump flow center(UP26-99) while most manufacturers recommend 2 pump flow centers for 4 ton and larger we do all of our 4 tons with 1 pump.

You are on the right track now, but I don't see much difference for the racetrack versus the slinky, just in installation speed, thus my preference for the slinky. All of our 2-5 tons in the last 2 years are on a single 26-99 with slinky loopfields. 6 tons is tougher, although my own 6 ton synergy runs on a single 26-99. Again, once you understand pressure drop and heat extraction, there is really not much difference between slinky and racetrack.

no design is good or bad as long as it brings the entering water temperature within the operating range of the heatpump.

Misleading too. Just because it's somewhere within the operating range doesn't mean it isn't inefficient (ie, not a good design in my book). COP matters.

Posted By jonr on 21 Apr 2013 08:14 PM

no design is good or bad as long as it brings the entering water temperature within the operating range of the heatpump.

Misleading too. Just because it's within the operating range doesn't mean it isn't inefficient (ie, not a good design). COP matters.

Are we talking about loopfield design or are we talking about heatpumps? Loopfields discussed here don't have a COP!

Are we talking about loopfield design or are we talking about heatpumps? Loopfields discussed here don't have a COP!

Complete systems and conditions (not heatpumps!) determine COPs and conditions change with the loopfield. But I'm sure some installers have a "it's working, so there is no problem" attitude.

So what are you suggesting here. Doubling the size of the loopfield to get the COP up? It is very well established that designing a loop for EWT between 30F and 90F gives the best balance between upfront costs and operational costs. If you have any better idea or design suggestions, I'll be the first to listen!

"Jamming lots of pipe into a small area/volume" can work very well if you compensate for the smaller area with more pipe.

Here is a good example: http://welserver.com/WEL0602/


The footprint of the loopfield is smaller than the footprint of the church. Sometimes you have to play with the cards you got. The slinkies are 1-2' apart and stacked above each other at 8' and 5' as you can see in the picture. EWT is at 31-32F at the end of the heating season, as indicated by the monitoring. Performing right on target. So "it's working, so there is no problem".


I was trying to point out that one should not generalize, jamming a lot of pipe in a small area can work well. The art is to make it work.

I'll generalize.
Get a good installer and the loops will not be an issue.
I've said before, if the only question we get from a geo buyer is loop design, then we probably haven't done a good enough job about stressing priorities to geo shoppers.