[TowerTalk] Need Help For Cable Runs To Tower

[Patrick Greenlee]

How high is up?, how long is a roll of string? These are two easy questions 
compared to the knock down drag out fights we have had over conduit, holes 
for drainage or no holes...

I have successfully glued PVC pipe that survived 100 plus PSI keeping water 
in and believe a good job on plastic conduit will keep water out. It is 
possible that if you don't seal the conduit well at the ends (I like GE 
Silicone rubber, the 50 year kind with no vinegar smell when curing) that 
over time condensation will potentially build up (maybe in Biloxi, 
Mississippi) but less likely in dry parts of California.  I have a strong 
cord run through all of my conduits and can tie it into a continuous loop 
whenever I want.  This is good for pulling a dry rag through the conduit to 
test for water. So far no water after a few years.

If I had a recurring condensation problem I could arrange for a periodic 
leak of dry air to be injected into the conduit as I have a refrigeration 
unit type air dryer on my shop air system.  There are commercially available 
dehumidifier chemicals that could be used to absorb moisture.  The 
silica-gel type can be recycled by heating in the oven over and over and 
don't "wear out."

My advice (risking being flamed...) is to do a good glue job plus seal the 
openings.  If you opt for a desiccant, install "T" fittings so you don't 
have to reseal the ends with  RTV every time you change the gel pak(s). Long 
run? Consider a "T" with a "riser" at intermediate distance(s.)

Note: Two conduits does not imply two failures to get a short since the 
wires will be insulated.  You would need both wires to lose their insulation 
plus both conduits to fail and then a miracle migration of the wires so they 
could touch.  Of course if you are a member of the drain hole camp and 
insist that bugs will sneeze into the conduit with sufficient force to get 
past the RTV  then wire migration say during an earthquake could be a 
problem if the tower is still standing.

Disclaimer:  I acknowledge that some folks have had water ingress into their 
conduit, that it is not a laughing matter, and that minor misinterpretations 
of the laws of physics are the likely root of the mistaken ideas propagated 
post water incident/disaster.  ;)  ;)

Patrick AF5CK

P.S.  I am still working on taking down the 40 ft tower made of 4 1/2 inch 
tubing with 14 ft between the triangular legs at ground level.  For those of 
you who have heard about some of our "interesting" weather you can 
understand a certain lack of alacrity in finishing that project. (I'm about 
25 miles from ground zero of the latest Oklahoma tornados and the tower is 
closer.  I was dong some prepping Sunday the day of the Shawnee twister and 
drove through the devastated area a couple hours before the devastation took 
place totally unaware of what was to come.



-----Original Message----- 
From: Jim Lux
Sent: Saturday, May 25, 2013 3:57 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Need Help For Cable Runs To Tower

On 5/25/13 1:02 PM, Eugene Jensen wrote:
> Drilling holes in conduit for drainage is not a good ideal. It going to be 
> full of water in time. As long as your trench is 18 " or deeper you could 
> use  UF #6-2 with ground  to keep the voltage drop under 3%. And the run 
> your control/Rf cables in the same conduit, It you using hard line just 
> bury it in the trench. 73 and good luck with your tower project. Gene 
> AA4VX
>

CHeck your local codes, if you're concerned. around here (Thousand
Oaks), UF is not allowed for direct burial.  Underground has to be in a
raceway (code speak for conduit).  There's various burial depths
depending on the kind of conduit (plastic, thinwall metal (EMT), or
thick wall metal) and whether it's under a concrete slab or similar.
The depth is all about damage to the wires (since frost is a non issue).



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