Loop design gone wild

by **powerboatman1** » Mon Nov 02, 2009 9:04 pm

I've been playing with a loop design program (no names will be mentioned to protect the guilty), and the numbers seem a little wonky compared to some of the examples I've seen here.

The equipment: Trane Axiom 4 ton unitary, twin Grundfos 26-99 pumps configured in a push-pull, 3000 feet of 1 inch SIDR 9 HDPE tubing butt fusion welded every 300 feet.

The installation: Horizontal closed loop at 6 feet of depth in silty clay, southwest Ohio.

My program is calling for 2-1500 foot loops spaced 10 feet apart. (I have room for this and much more)

My question, is this in the ballpark or would breaking the length into additional shorter loops be more efficient ?

Thanks for the review.

-Dave S.

by **Mark Custis** » Tue Nov 03, 2009 6:23 am

You have the 3000 feet of 1" installed?

You want to know if the program is nuts?

I do not like to bury joints so I do not. I use manifolds. Infact we installed one in Greene County, Ohio, in July. Helped a great guy through a first job. Our plan called for 300' loops per ton which we ran to a storm water vault. We had six loops of 3/4' to the manifold then ran to the house with 1 1/4". The only down side to the projact was the pumps supplied by the Carrier dealer, as they where twice what we needed.

by **teetech** » Tue Nov 03, 2009 6:50 am

Playing with software will likely give you "wonky" results. As in any program there is a learning curve.
If you do not learn, it will not be useful

You are probably in the ball park but I have no idea what numbers you have entered or how.

by **palacegeo** » Tue Nov 03, 2009 7:03 am

We bury joints all of the time. It is a industry wide standard practice.

The size of your loop depends on the loop configuration, your location, the soil type, the heat load for the house, how balanced the heating and cooling loads are and several other variables.

Since we know none of these, there isn't much we can do to help you.

by **gabby** » Tue Nov 03, 2009 7:22 am

Most loop programs give you options to select the best fit for your soil, maintaining proper turbulence by pipe size and length, selecting the number of circuits comprising the loop, and selecting pump size based on total head for your earlier inputs. It is a balancing act to maintain turbulence and reducing pump size to lower operating cost.

by **geoconnections1** » Tue Nov 03, 2009 8:51 am

powerboatman1 wrote:I've been playing with a loop design program (no names will be mentioned to protect the guilty), and the numbers seem a little wonky compared to some of the examples I've seen here.

The equipment: Trane Axiom 4 ton unitary, twin Grundfos 26-99 pumps configured in a push-pull, 3000 feet of 1 inch SIDR 9 HDPE tubing butt fusion welded every 300 feet.

The installation: Horizontal closed loop at 6 feet of depth in silty clay, southwest Ohio.

My program is calling for 2-1500 foot loops spaced 10 feet apart. (I have room for this and much more)

My question, is this in the ballpark or would breaking the length into additional shorter loops be more efficient ?

Thanks for the review.

-Dave S.

The parameters that will affect ground loop design lengths the most are min/max EWTs and ground loop configuration. There are a lot of ways to skin the proverbial cat when it comes to horizontally-trenched GHEX design. What type of horizontal loop are you designing with? What values are you using for min EWT and max EWT?

by **powerboatman1** » Tue Nov 03, 2009 3:21 pm

Hello All, thanks for the quick response.

More information is obviously needed.

The pipe is not installed, merely welded together and pressure tested.

The current design is two parallel loops, one pipe per trench, ten foot minimum separation. The target depth is a minimum of 6 feet.

Target flow is 12 GPM, balanced across the two loops.

I'm a mile south of the Greene county line, so temps and soil conditions are likely similar.

EWT and LWT were not part of the software I used, average ground temps were calculated by geographic location.

As some of you may have guessed, this is a lashup of new salvaged components by a very experienced DIYer with no prior geoexchange experience. Not looking to rock the world with efficiency (the pump is not even Energy Star rated), just want to get as much as practical out of this setup, and provide a base for further refinement.

Thanks for your continued support.

-Dave S.