Very good advice, guys. I'll add that if you are burying conduit
underground consider going significantly larger than the minimum to pull
your current needs through. The cost difference is not a big deal so I
standardized on 4 inch and find that eventually I need the extra space. If
you bury deeply enough such that any traffic driving over the finished job
will not crush the thin wall S&D then that is easier to work with and less
expensive. I'm currently (except for hiatus for weather) burying a pair of
4 inch PVC S&D pipes in the same trench, a 280 ft run to service three
towers with 140 ft spacing.
A minor caveat RE not worrying about moisture or water in the conduit. If
the coax or other wires or whatever are essentially moisture or water proof
then no worries but some "stuff" will let water get in over time. I use
buried PVC conduit to protect from critters chewing up the unprotected wires
and it is very convenient to be able to add cables without having to trench
again.
If you are concerned about water vs some particular lines you are running
and they are small enough you can pull them through the low pressure drip
irrigation roll tubing rated for 100 PSI that comes in 100 ft rolls for
about $12 at the big box stores and then pull that through your conduit.
Irrespective of naysayers comments to the contrary I have done that easily
single handed several times.
Best of luck with your project.
73,
Patrick NJ5G
-----Original Message-----
From: Roger (K8RI) on TT
Sent: Wednesday, November 12, 2014 12:53 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Schedule 40 or 80 PVC Conduit Underground
On 11/11/2014 9:45 PM, Larry wrote:
2" will work fine with a snake and wire pulling soap. Check on how the
electricians do it. I've seen them pull so many wires through conduit
(steel and not EMT) that there was an electrician every 6 feet or so,
pounding on the conduit with hammers (in time) You couldn't pull them
out. If you were lucky, you could pull out a few, one-at-a-time until
they were no longer compressed, but we're talking real world, "I'm gonna
reuse this--I hope"
"For me", I'd use conduit that would easily hold at least twice as many
cables as I planned on using. I'd need convincing to use something as
small as 2".
I make it a practice, not to have splices or connectors in the conduit.
I usually have them within about a foot of each end. I end the conduit
in a junction box large enough for a grounding plate for all coax
jackets, whether I plan on grounding in there or not. I try to allow
for the unseen future even if it does cost a little more. A little more
now, can save a LOT of work and money later on. If the run is flat and
no more than a 100-200 feet, I don't even glue the sections together. I
make the run slightly long so the junctions are under pressure and wipe
the inside coupling surfaces with a light coat of silicone grease. Never
had a sealing problem and after years in the ground, they come right
apart. Easy to put in and easy to take out.
Typically the conduit is to protect the cables and little else, but they
sure can make additions a lot easier later on.. I used to install a "Y"
at the low points with a cap on the unused side. I'd add a few small
holes for drains. I don't bother any more.
Conduit can be schedule 40, 80, thin wall plastic sewer pipe, plastic
water pipe. IOW, A slippery tube of sufficient size to handle the
cables, plus possible future expansion. Unless in a very dry
environment, I'd avoid thin wall/EMT as it will rust and the price goes
up rapidly with size. Any more, I don't worry about water in the
conduit. If the coax is unbroken it shouldn't be a problem.
Leave a messenger cable in the conduit plus a length a bit longer than
the run coiled in a junction box at one end or the other. It can easily
be pulled back so you can pull in additional runs from either end. Just
make sure the ends are hooked to something solid to prevent pulling an
end into the conduit, out of reach. I use 1/4" braided nylon. Cheap and
slippery, but don't pull it around sharp corners. It will eventually
cut into PVC conduit.
73 and good luck,
Roger (K8RI)
I used 3 inch sch 40. I had a electrical pull snake for pulling coax and
control lines down 150 feet of conduit without any trouble - not even pull
soap was required.
73, Larry W6NWS
-----Original Message----- From: Drax Felton
Sent: Tuesday, November 11, 2014 9:29 PM
To: Allen Brier N5XZ
Cc: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Schedule 40 or 80 PVC Conduit Underground
I use 4" French drain line surrounded by gravel to let the moisture out.
I cannot imagine being able to slide coax 160 feet in 2 inch conduit.
That would be tough. I've built 5 towers all in excess of 180 feet from
the house and always used 4" and it's hard enough.
Sent from my iPhone
On Nov 11, 2014, at 7:16 PM, Allen Brier N5XZ <n5xz@earthlink.net> wrote:
I am running about 160 ft of 2" conduit underground for cabling. Is Sch.
80
required or will Sch. 40 do?
Allen R. Brier N5XZ
1515 Windloch Lane
Richmond, Texas 77406-2553
(281) 342-1882 (Home)
(713) 705-4801 (Cell)
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73
Roger (K8RI)
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