Sneaky loops are used in the horizontal closed loop system. The name “sneaky loops” comes from the shape that is created when tubing is tied in concentric spirals. The purpose of this procedure is to make long pipe runs more manageable during installation and to be able to build a consistent heat exchanger in a given amount of space. Not all horizontal closed loop systems are built using the stealth method, some simply lay the pipe in a downward and backward layout.
A sneak is most easily constructed using a jig made of edged plywood to contain the pipe. Measured marks can be drawn on the template to give you a reference point for sizing the overlap (step) of the slinky as you build it. It will take three people to most effectively build a slink. One will do the tying, another will feed the coils to the tyer, and another will pull the slinky out the back of the jig as it is being built. Approximately three people are needed. 20 minutes to tie up an 800′ slinky once they’re up and rolling.
The first step is to determine how much slinky time you need to build based on your loop field layout. A graph can be found here showing the lengths of the slinky coils as a function of tube length, coil pitch, and coil diameter. A length of tubing will be taken from the coil that is the length necessary to be the return from the end of the coil to where the collector will be; this portion will be straight. Once this is removed from the coil you can start tying the tube into loops.
The first loop will be tied on whatever diameter the template has made (36″ is good). The second loop will be placed over the first loop by whatever step is needed to make its overall length work. For example, if you have a 36″ . coil with 18″ pitch, I would place each coil about halfway over the one in front of it. If your length called for 36″ loops with 36″ pitch, I would not overlap them at all, but simply place each loop of end to end just like you Zip ties are the product of choice for tying loops.
As you near the end, make sure you leave enough untied to head back to the collector location. The first part of the coil that was left unwound can now be tied along the length of the coil while coming back to the “front” of the coil. Both ends should now be close to the same distance from the loops and both at the front of the coil where you will build the collector. Tape the pipe ends to keep out dirt if they don’t already have caps.
The final step is to roll the slinky into a donut roll which will actually look more like a giant bird’s nest, but will actually be quite manageable and transportable. Just start at the “end” (not the “front” where the lines are) and roll the thing up. Try to keep it as straight as possible when rolling it up.
The slinky is now ready for transport. Two people will be needed to transport it due to both weight and shape. It can be transported on a truck or trailer to the job site if built elsewhere. Once in place, take it to the ditch or pit where it will spend its life and unroll it. If it’s going to go into a ditch I would suggest unrolling it in addition to the ditch at the top and then with several people throwing it into the ditch. Make sure the coil lies flat on the bottom of the trench, but be careful if you enter trenches that could collapse. The safest way would be to use a long stick to locate the slinky as needed.
When laying the loop field bedding, make sure the backfill material is sufficient to provide good contact with the pipe without leaving air gaps and make sure no large rocks fall on the pipe. In rocky soil, it is recommended to filter the soil and place the pipe in two feet of fines. After the pipe is correctly placed, the rest of the backfill can be done and the area compacted.
