Slinky loops are used in horizontal closed loop systems. The name “stealth loops” comes from the shape that is created when the tubing is tied into concentric coils. 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 down and back arrangement.
A slinky 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 to size the overlap (pitch) of the slinky as you build it. It will take three people to build a slink most effectively. One will do the tying, another will pass the coils to the one it is tied to, and the other will pull the slinky out the back of the jig as it is built. It will take three people approx. 20 min to tie a 800 ‘slinky once they are done and rolling.
The first step is to determine the length of a slinky you need to build based on the design of the loop field. Here you can find a graph showing the lengths of the skid coils based on the length of the tube, the pitch of the coils and the diameter of the coils. A section of pipe will be removed from the roll, which 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 it is removed from the coil, you can begin tying the tube into loops.
The first loop will be tied to the diameter your jig made (36 “is good). The second loop will fit over the first loop with the pitch needed for its full length to work. For example, if you have a 36” coil with a 18 “pitch, I would place each coil about half over the one in front of it. If your length required 36” loops with a 36 “pitch, you would not overlap them at all, just lay each loop end to end while tying the bobbin Cable ties are the preferred product for tying ties.
As you near the end, be sure to leave enough untied to return 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 returning 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 ends of the pipe to prevent dirt from getting in if they don’t already have caps.
The final step is to roll the slinky into a donut roll that 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 aligned as possible when you roll it up.
The slinky is now ready to be transported. It will take two people to carry it due to its weight and shape. It can be transported on a truck or trailer to the job site if you built it elsewhere. Once in place, take it to the ditch or well where it will spend its life and unroll it. If you are going to go into a trench, I would suggest unrolling it in addition to the trench at the top and then with multiple people throw it into the trench. 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 position the slinky as needed.
When placing the seat in the loop field, make sure that the backfill material is sufficient to provide good contact with the pipe without leaving any air gaps and make sure no large rocks fall onto the pipe. On rocky soils, it is recommended to sift the soil and cover the pipe with two feet of fines. After the pipe is properly positioned, the rest of the backfill can be done and the area compacted.