[TowerTalk] Schedule 40 or 80 PVC Conduit Underground

[Gene Smar]

Allen:
 
     To add to the "rules of thumb" on this subject, when I designed power substations for my local electric utility, we spec'ed conduit large enough so that the ultimate fill occupied only 40% of the area of the conduit.  Two inches seems ok for the initial pull but that pull will be a PITA.  I concur with others' recommendations to use larger diameter conduit (3" or even 4").  Laboris the same for either vs 2" and material cost is only slightly greater.  Also, use sweeps and not elbows at bends.  Sweeps have larger radius curves than simple elbows and make pulling easier.  
 
     As for Sch 40 vs 80 ( your original question), it depends. Sch 80 will be more rugged but considerably more expensive than Sch 40.  Your plan to bury the conduit tells me 40 will be fine.
 
 
73 de
Gene Smar  AD3F
 



On 11/12/14, 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 at 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 at 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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