[TowerTalk] Condensation Inside Tower Cable Box

[Gene Smar]

 Shawn:
     If you're willing to plug up the conduit leading into this box as Jim W7RY writes below, I can suggest you look into using Hoffman (yes, the steel box makers) corrosion inhibitors in the space, rather than ventilating the box.  Here's a link:  https://tinyurl.com/4nvhryhz .  The inhibitor sponges exude a substance that coats the surfaces of electronic and electrical components in an enclosed volume which protects from corrosion.  Kind of like desiccants in reverse.

BACK STORY:
     Forty years ago, when I was an engineer for the local electric utility company (PP&L, for Shawn's benefit), I assigned an engineering student to investigate these Hoffman things.  Our objective was to try to quantify their effectiveness using various metallic substances, temperatures, humidity and salinity conditions (we had a salt fog chamber at our disposal.)  We wanted to see if using these things inside our substation outdoor equipment boxes (containing relays, contactors, etc.) would permit us to turn off the electric space heater strips that most of these equipment boxes had, and save bunches of energy and $ in the process.
     IIRC, these little sponges seemed to work.  We even recommended that a trial be undertaken to install a few dozen of these out in the field and turn off the corresponding heater strips to check for subsequent corrosion.  Of course, nothing ever came of this project; I soon left the company to work in telecomms here in the DC area.

73 deGene Smar  AD3F, LU 73


    On Monday, October 16, 2023 at 04:04:44 PM EDT, Jim W7RY <jimw7ry at gmail.com> wrote:  
 
 Agreed with heating the box...

Shove a rag (a long one to provide lots of area to keep the moisture 
out)  into the conduit that comes from the underground.

Ventilate the box on the bottom with a screened opening at least an inch 
in diameter. (Larger would be better).

73, Jim W7RY


On 10/16/2023 2:51 PM, Lux, Jim wrote:
> On 10/16/23 11:56 AM, Shawn Donley wrote:
>> Hello fellow TowerTalkers,
>>   I have an aluminum outdoor electrical enclosure at the base of my 
>> tower.  My underground runs of hardline enter the box through a PVC 
>> conduit elbow entering at the bottom of the enclosure. The tower coax 
>> and rotor cables exit the bottom as well.    In humid weather, 
>> especially this time of year when the temperature goes down at night, 
>> I get a significant amount of condensation inside the enclosure, not 
>> only on the enclosure but on the outside of the cables within it.  
>> Enough water to make one think there's no environmental protection 
>> provided by the enclosure in the first place.  I suspect the moist 
>> air from the conduit is the source since the underground run uses 
>> slotted corrugated drain pipe covered with a soil sock rather than 
>> solid wall PVC.   Why ... concerns of long term condensation inside 
>> solid conduit...another subject thoroughly discussed elsewhere and 
>> hopefully not again on this thread.
>>   Has anyone experienced something similar and has a proven fix?   I 
>> considered a small 12v box fan to circulate some outside air through 
>> the enclosure but I think the cold box walls would just condense that 
>> moist air as well.  Perhaps a low wattage 12v light bulb inside the 
>> enclosure to provide some heat to keep the walls warmer?  Some water 
>> pipe heat tape on the outside of the box (but I would like to avoid 
>> any 125vac solution)?  Sealing the entry conduit is problematic with 
>> the several cables of different diameters.  I would not want to 
>> "foam" the conduit with expanding foam or something like that which 
>> would make pulling a new cable much more difficult.
>>   tnx
>> N3AE
>
> I'd think it's the usual problem of cooling in the evening, pulling in 
> humid air from outside, which then condenses. It might be from the 
> conduit, but probably more likely the air around the box.   The only 
> solution is to provide a source of dry air. Heating the box *might* help.
>
>
>
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-- 
Thanks and 73, Jim W7RY
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