Towertalk
[Top] [All Lists]

Re: [TowerTalk] Pulling coax through PVC pipe

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Pulling coax through PVC pipe
From: Patrick Greenlee <patrick_g@windstream.net>
Date: Wed, 31 Jan 2018 20:32:52 -0600
List-post: <mailto:towertalk@contesting.com>
Just in case someone might be confused...  S&D (Sewer and Drain) pipe is  NOT corrugated.  By the way, I strongly agree with Grant S. in not recommending the corrugated.

S&D pipe is PVC, just a lighter schedule than water supply pipe and is not not good for as high of pressure as water delivery pipe such as Schedule 40 for instance.

It is, of course, highly unlikely that pipe used for electrical conduit will be subject to significant internal pressures so that is not a disqualifying attribute.

Patrick




On 1/31/2018 2:40 PM, Grant Saviers wrote:
John,

A bit of terminology confusion.  As shown with bell mouths and glued joints is the way to go IMO.  The wall thickness appears to be that of SDR35 and not sch 40 and both are great choices. SDR35 is not stocked at my HD store either.  I purchased  SDR35 at a construction supplier.

Here is the corrugated pipe also called "drain pipe" and think is a poor choice: https://www.homedepot.com/p/Advanced-Drainage-Systems-4-in-x-10-ft-Triple-Wall-Solid-Pipe-04560010/303020551

Grant KZ1W

On 1/31/2018 11:39 AM, john@kk9a.com wrote:
FWIW, when I suggested drain pipe I was referring to this:
https://www.homedepot.com/p/JM-eagle-4-in-x-10-ft-PVC-D2729-Sewer-and-Drain-Pipe-1610/202280933
There are no leaky fittings in my installation.

John KK9A


From:    Grant Saviers <grants2@pacbell.net>
Date:    Wed, 31 Jan 2018 10:49:21 -0800

Patrick,

I agree, "different strokes" but to understand the principles, the Carrier
Psychometric Chart was pretty helpful to me as it sorts out Rh from dew
point and shows "lbs of moisture per pound of dry air". It was developed
for HVAC uses.
http://www.handsdownsoftware.com/carrier-chart.pdf

The variables for conduit are its (ground) temperature and air flow water content. I think that occupied buildings almost always have lower Rh than outside - heated in winter, AC in summer. That doesn't mean the inside air dew point is lower than that inside the conduit, which determines if there
will be condensation. If temps inside the conduit are higher than dew
point, no condensation and evaporation of water that is present. When
reversed there is condensation, eg frozen ground and warm outside temps.
Venting to outside is another set of differential temperatures and water
content circumstances.

So IMO, with varying seasons, lagging ground temps and variable inside (or
vented) temps and moisture levels, it seems almost certain to get
condensation at times in the conduit (extreme desert climates excepted).
Sealing may help if done at the right time, but hermetic seals that
prevent in/out air flow are really hard. Broadcast stations sometimes
purge air dielectric coax with calibrated dry gases, bottled N2 or dry air from a refrigerated dryer or desiccant system or both. Then dew points are
known to be in well into negative F temps (eg -40). Possible, but a bit
over the top for hams.

So my approach, since in conduit condensation is highly likely, is to
always use direct burial cables in conduit with no connectors or breaks in cables. The polyethylene (PE) covered RG's or Heliax are my choice as are
PE sheathed control cables and UF rated power cables (which go in the
trench for AC, not inside the conduit for me). And water tight conduits
with glued joints. Generally schedule 40 PVC but SDR35 is a good and
cheaper choice for large diameters. Drain pipe IMO doesn't make water
tight seals with the gaskets. Why let in ground water and dirt? I've seen the water flowing out of conduit (and out of coax!) as you had when there
is a hole in the conduit.

This is an interesting topic, maybe a few hundred threads about it on TT,
but probably 97% of water in coax is due to poor connector sealing.

Grant KZ1W

_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk


_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk

_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
<Prev in Thread] Current Thread [Next in Thread>