I got a good lessen in this matter a few years ago when I purchased a new
weather-sealed Hoffman box in anticipation of a tower project. It took longer
than I anticipated to get the project underway, during which time (almost two
years) the Hoffman box sat outside through our four-season Ozarks weather. When
I finally opened it, I was shocked at the water (maybe a half-cup) that had
accumulated via condensation inside the tightly sealed box. I vowed after that
to always vent enclosures, with appropriate screening to thwart insect
intrusion through the vents.
Mike
--- On Tue, 2/26/13, Dick Green WC1M <wc1m73@gmail.com> wrote:
> From: Dick Green WC1M <wc1m73@gmail.com>
> Subject: Re: [TowerTalk] Water in buried conduit
> To: jcjacobsen@q.com, towertalk@contesting.com
> Date: Tuesday, February 26, 2013, 1:21 PM
> I guess it's possible. My conduit
> runs are terminated in weather-sealed Hoffmann metal boxes
> at both ends. The box at the shack end is mounted to the
> house and has holes drilled in the back just above the sill
> to run the cables to a patch panel in the basement. So the
> conduits are exposed to the air inside my house. At the
> tower end, cables run to the antennas through holes drilled
> in the bottom of the utility box. In some case I used coax
> feed-through bushings and in other cases I ran cables
> through fittings with rubber gaskets that tighten against
> the cable. I tried to plug any visible holes with coax seal.
> I don't get insects in the box, but I imagine it's not
> perfectly sealed against air coming in through the cable
> exit holes.
>
> So the long and the short of it (no pun intended) is that
> air probably can circulate through the conduit, though I'd
> say it would be a very restricted flow at the tower end. Our
> ambient humidity here in West Central NH tends to run
> 40%-100% most of the time, so there's almost always enough
> water in the air to condense.
>
> Any water condensing in my conduits would cling to the
> insides, but I would think eventually it could drip to the
> bottom and run downhill to pool at the low point of the
> 90-degree bend, which is where I know the water is. Could
> enough water condense in my conduits over a period of 16
> years to soak a few dozen feet of cable? I don't know. I'm
> certainly not worried about it.
>
> 73, Dick WC1M
>
> > -----Original Message-----
> > From: jcjacobsen@q.com
> [mailto:jcjacobsen@q.com]
> > Sent: Tuesday, February 26, 2013 10:45 AM
> > To: towertalk@contesting.com
> > Subject: Re: [TowerTalk] Water in buried conduit
> >
> > How do,
> >
> > Regarding water in buried conduit: Is it possible that
> the water is
> > actually condensation that has built up over time?? It
> would seem to me
> > that if the joints were well glued/connected there
> should be no water.
> > Years ago I watched as some electricians placed some
> buried
> > galvanized/rigid/threaded conduit between buildings at
> a commercial
> > site. After the sections were threaded together they
> wrapped each joint
> > with some 2" wide tape. Don't know if it was 33/88 type
> or some kind of
> > rubberized tape. I guess a belt and suspenders
> approach. YMMV.
> >
> > 73
> > K9WN
>
>
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