|Subject:||Re: [TowerTalk] Weatherproof Sealant|
|From:||"K8RI on Tower Talk" <firstname.lastname@example.org>|
|Date:||Tue, 11 Jan 2005 16:23:49 -0500|
Where is it going to be located? Below ground? Above ground? on top of the
I need to weatherproof a relay box. Under test conditions it accumulated an
What were the test conditions?
What is a specific brand of silicone sealant recommended? I understand the kind with vinegar smell (acetic acid) will corrode electronics components in a sealed
It depends: In a small, sealed area with the sealant in contact with the components the answer is yes, but using it to seal the edges of a box should not be a problem.
environment. Also, is there a need to insert a desiccant in the box?Not normally.
In another life I worked in the chemical industry. We had to seal conduit and boxes to prevent gases and liquids from migrating through. This was very rugged equipment and it was not at all unusual to find condensation in conduit.
I can't think of a reason to seal any boxes that aren't under water, or underground in the real world. They need to breathe to prevent moisture accumulation, BUT in some conditions a vented box will cause water to condense on the relays. OTOH A sealed box can even force water into the cables through the connectors.
Typically, I try to use a box that is taller than the width which leaves a fair amount of space below the works.
Even a metal screen lower in the box will cause moisture to condense out, leaving the upper portion dryer.
I have one of the remote antenna switches mounted around 80 to 90 feet up on the tower. After a couple of years it shows no sign of condensation inside. OTOH the connectors on the outside (bottom) are looking pretty weather beaten. I'd say there has been a lot of corona up there.
The box is NEMA industrial type, made of plastic with neoprene o-ring seal on lid. However, there are many holes drilled for stainless hardware used
Mount the box upside down with the "dish" shaped part serving as a cover. Holes should be nowhre other than in the bottom. Sealing holes in sides and tops is a losing cause.
to mount the relay and connect wires to the exterior. The relay itself is the open contact variety with self-cleaning contacts (hot switch 20 watts RF), and supposedly impervious to damp conditions.
Put a plastic pail over it of a dark color.
I use a Hoffman box (TM) about 3 to 4 feet above ground at the bottom of the tower. The inlet (at the bottom) which is a foot long PVC conduit stub, where all the cables enter is sealed with the soft, expandable white building foam. The outlett (conduit to the basement) is not sealed. It is sealed in the basement. Even though the box is steel I've never seen any condensation inside. BTW, I should replace the photo of the box and cables as they have been rerouted are are much neater now.
Roger Halstead (K8RI, EN73 & ARRL Life Member) N833R, World's Oldest Debonair (S# CD-2) www.rogerhalstead.com
Thanks for any advice.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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