Under ground piping. [RE-wrenches]

Tue Jun 25 10:24:08 PDT 2002

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Wrenches -- While at the Midwest RE Fair I showed this to my friend 
Bob Ramlow. I have seen two of his installations with underground 
pipe. Here is his reply.

Windy

-------------------------

Dear folks,

I have installed many underground pipes for solar energy projects over the
last 25 years. Here are some of my experiences:

I suggest using urethane foam insulation to insulate at least the hot supply
pipe, if not both pipes, which should be type L hard(medium wall) or type K
soft (heavy wall)copper. This type of insulation is closed cell so it will
not absorb moisture. It can also withstand the high temperatures that can be
experienced by solar energy systems. This is especially true for evacuated
tube collectors or concentrating collectors.

The urethane foam insulation must be protected. It is brittle. I use a UV
stabilized PVC pipe insulation jacketing. This jacket easily wraps the
insulated pipe and can be glued and taped. I use Proto covers for the
elbows.

These products are available from most plumbing supply houses. I also stock
it.

Once inside a building, I switch to high density fiberglass pipe insulation.
This is also available from your plumbing supplier.

Rubatex pipe insulation can be used on the return pipe, as an option. I
never use it on the supply pipe. The supply pipe from a solar collector
array will exceed the rated temperature of Rubatex. It will quickly turn
brittle and will be very delicate and be easily damaged. Evacuated tube and
concentrating collectors get much hotter than flat plate collectors, so
insulation types become even more critical.

Styrofoam will also melt on the hot supply pipe.

Do not use Wirsbo or any other pex tubing for the hot supply pipe. It 
can not stand the high temperatures that can be generated by a solar 
array. Again, this is especially true when using evacuated tube 
collectors or concentrating collectors. Just this spring I was shown 
a piece of melted and blown-out Wirsbo pipe that was used too close 
to the collector array. Use copper!

Another consideration to keep in mind when burring pipe from a remote solar
array:
As the pipes heat and cool daily, they will expand and contract. This
expansion when heated is magnified over the length of a copper pipe. When
pipes are buried, stress can build up in the pipe because the ground can
prohibit the expansion because it is tight around the pipes, especially
where pipes make bends. This can lead to pipes breaking underground. I can
tell you from experience that this is not a fun deal.

I now always make an expansion joint at every 90 degree bend in buried
pipes. This includes the 90 where the pipe enters and exits the ground (if
any). I make this expansion joint by making a tight 360+ degree coil of type
K soft copper pipe and use that as the elbow. For insulation, I make a
sandwich with sheet urethane foam insulation (Thermax or Tuff-R) on top and
bottom with the pipe coil inside. Make the foam pieces large enough so that
when backfilling, the dirt does not pack tight against the pipe around the
edges of the sandwich. This coil can then move between the foam and take up
the expansion and contraction of the ridged copper pipe.

For the Earth,
Bob Ramlow
Artha Renewable Energy
WI Focus on Energy
715-824-3463
artha at wi-net.com
Amherst, WI 54406-9355

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