Steve:
A few Conduit Rules of Thumb (based on my own experience; YMMV):
o Don't install elbows - use sweeps for turns. Sweeps are larger-radius bends
than elbows and permit easier pulling through these bends.
o Don't pull cable through as you assemble the conduit. This is way too messy.
o Use glue. Slip-fit conduit connections are neater but could become dislodged
if the ground heaves during freeze-thaw cycles. Then you'll have to pull future
cables through misaligned underground conduit ends.
o You may bury/cover the conduit system before pulling cables. After all, the
intent of a conduit system is to permit change in conduit contents - adding and
removing cable - over the life of the installation.
o Water WILL get into your conduit system. Therefore, you ought to permit it to
drain. I drilled holes in the underside of my conduit at the low points in the
run. Underneath these low points I dug a small pit and filled the pit with
crushed concrete; you also can use gravel. Conduit water will drain out of the
low points in the run and into the pit where it will percolate into the earth.
I sealed the drilled holes with ladscaping material - the kind of stuff that
permits water to flow through it in only one direction. I tied pieces of this
fabric onto the conduit with solid wire. (See
http://s83.beta.photobucket.com/user/ersmar/media/45degreeelbow.jpg.html?sort=2&o=4#/user/ersmar/media/45degreeelbow.jpg.html?sort=2&o=4&_suid=136189100743809135445073939117
.)
o Instead of a continuous conduit run you may also install pullboxes at
intervals. Pullboxes have no bottoms and are buried along the conduit route;
the tops are at grade level. Therefore, you should install pullboxes over
gravel pits as above and slope conduits so that they drain into the pullboxes.
You can use pullboxes to transition from one conduit run into another
underground, e.g., your Tower 1 and Tower 2 cables enter the pullbox from one
side and split into Tower 1 and Tower 2 conduits on the opposite side, etc.
o "Critter-proofing" is important, especially if you use pullboxes. I suggest
steel wool stuffed into the accessible ends of conduits. Fiberglass insulation
is too attractive for nesting material, plus it gets soggy when the
aforementioned conduit water tries to drain past it. Landscaping material is
adequate critter screening for drilled holes.
o Leave a pulling rope inside the conduit for (inevitable) future installs. You
can install this rope along with the last coax pull.
73 de
Gene Smar AD3F
On 02/25/13, Steve K7AWB<k7awbgoog@gmail.com> wrote:
This April, I will install my conduit and pull the cables to the existing
towers. From the shack
wall, its about 100 feet to Tower #1 and an additional 130 feet to Tower #2.
I live on 20 acres.
The cables to Tower #1 will terminate in a steel enclosure at the bottom of
that tower. Also, the cables to the far Tower #2 will terminate in a steel
enclosure at the base of Tower #1 and then continue to Tower #2 in their
conduit.
I probably will use three of the 4" PVC conduits for all the cables
to get to Tower #1. One will contain the cables for Tower #1 use; another
for Tower #2 use; and the third for future projects in the back field. Then
one additional conduit goes from Tower #1 to Tower #2. Ands one additional
goes in another
direction also from Tower #1 for future area in the back field.
I figure to glue and bury the conduit in the ground first and put sand,
dirt, & rock on top of it so pulling cables will not pull the conduit out of
the
ground rather that gluing each section, one at a time, around the cables.
Is burying the conduit before pulling a good idea like I suggest? After all,
once it is buried, it is impossible to remove it economically. I will use
sand to create a smooth bottom for the conduits to rest on and then cover
them with dirt. Its all fractured basalt out there, but the back hoe that
was used managed to make the trenches. The trenches are about 24" deep or
so.
I know this has been discussed before, but I still have not decided on
drilling or not a few water holes in the bottom every so often, or at least
at the lowest spots, to drain water from condensation. Holes bring bugs
which may or may not matter. I don't want a small hole to become an
enlarged entrance hole for a Vole which I have out there.
Any suggestions would be welcome.
Steve Sala
K7AWB
DN17es
Nine Mile Falls, WA
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