Some additional thoughts -
Once you are considering 4" or larger conduit, check out SDR 35 pipe.
HD doesn't have it, although I've seen it at Lowes. Check with
commercial suppliers, they usually stock lots of it. It has a wall
slightly less than schedule 40 at a lower price. It comes in "sanitary"
and "drain" grades, the sanitary has rubber gaskets and costs more, the
drain glues together with PVC cement. While new my primary line (12kv?)
to a new service transformer is in 2" sch 80, that was the directional
drillers choice, only sch 40 is required by PSE. So, it is hard for me
to see why sch 80 is needed for any amateur radio conduit. I installed
400' of 4" and 6" SDR35 drain down 24" and medium size tractors and
pickups run around on this field without problems.
For conduit loading I use "UGLYS" little yellow book, usually in the
electrical section at HD. While the rules are based on temperature rise
in the conduit, they give a good idea of how many conductors will fit,
including mixed gauges. This book is invaluable to me for doing any
serious electrical work. I use liberal amounts TFE loaded cable pulling
lubricant. On the web I found the flat cable pulling polyester braid
which has less tendency to cut into the conduit edge and won't introduce
twist in the wires. When buying my last 350' of 3" sch 40 conduit, I
found exit collars that glue on to the od so there is no sharp edge.
Large radius 90 deg sweeps (36" minimum) also help ease the pulling.
Electrical code does require a bushing for larger than 1/2" adapter
threads, it's just a good idea for coax etc.
Grant KZ1W
On 11/11/2014 10:53 PM, Roger (K8RI) on TT wrote:
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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