I use NEMA boxes with gasketed doors. Cables leaving the box now go
through either bulkhead connectors, or plastic fittings with compression
glands (I forget the name of them) The conduit into the basement goes
into a similar, but much smaller box with the same size conduit out the
back and through the end plate under the floor and into the basement.
The basement end is left open. The run from the tower goes through a
sweep 90 and into another NEMA box. The conduit stub through the wall
is sealed with expandable foam. I had been getting a surprisingly
strong flow from the basement, through that sealed junction box and
finally into the shop summer or winter. Even with that strong flow,
condensation was never a problem. Nor was it a problem.
From that, I concluded in my installation that worry about condensation
was not worth it, but as I said before, even were there water in the
conduit I don't see a problem. Direct burial coax has a gel fill
between the jacket and internal insulation, but that is there to stop
water migration from damage caused from stones, or other causes, none of
which are present inside conduit. A coax with a good jacket that stands
up well in weather should have no problem with water in conduit. Gel
filled coax is OK, but expensive overkill.
The run into the basement used to be 5" plastic sewer pipe in through
the basement wall and open at both ends with a "Y" pointed down at the
low end as a moisture trap and drain. The down stub was capped with tiny
drain holes in the low spot in the cap. When the contractor replacing
the septic tank caught a ground cable and pulled out a bunch of blocks
in the basement wall, I went to the present system where the underground
conduit is about 3 feet below the ends and has a vertical run into the
boxes on both ends. Our "current" contractor then poured and dodder the
entire basement wall as well as resealing the outside, adding 1"
Styrofoam to the outside of those walls and installing new weep tile.
The basement wall work, old conduit, "Y", and new conduit installation
are shown in http://www.rogerhalstead.com/ham_files/cablebox.htm as well
as the messenger cable in the box at the house. The installation of the
run to the shop as well as the NEMA box at the tower are also shown.
73,
Roger (K8RI)
On 2/1/2016 Monday 9:34 AM, Russ Dearmore via TowerTalk wrote:
John, You are correct in that few pipes are sealed by anything other than the
junction box. When sealing is called for a foam sealer is usually specified.
The only exception I can think of off-hand is in rigid pipe in explosive
locations such as gas stations where a product called Chico is used. Don't
quote me on the name as it's been 30 years since I wired a gas station. Hi I
used the foam sealer in a highly methane location which was an amphitheater
built over an old city dump in Mountain View Ca. Maybe Canada has different
code requirements but I seriously doubt it. Besides, duct seal would make a
poor pipe seal. Russ K5ZZR My Heroes Wear Combat Boots!
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