[TowerTalk] Fwd: where the condensation comes from

[Hans Hammarquist]

So, what Jim is stating is:"Avoid ventilation of the duct as much as possible regardless openings up or down."


Hans - N2JFS



-----Original Message-----
From: Roger (K8RI) on TT <K8RI-on-TowerTalk at tm.net>
To: towertalk <towertalk at contesting.com>
Sent: Sun, Jan 31, 2016 12:43 am
Subject: Re: [TowerTalk] where the condensation comes from

In the summer here 85%, or more at 80 to over 90F is not uncommon.  So 
that's a lot more water, but the outside ends of the conduit are inside 
sealed NEMA boxes. The coax comes out at the tower, either through 
bulkhead connector or fittings that seal against the coax jackets or 
control cables. The same at the house and shop ends.
Depending on open conduit ends (assuming they point down) and wind 
direction, the wind can cause pressure or suction from blowing across 
the open end.

73

Roger (K8RI)

On 1/30/2016 Saturday 8:35 PM, jimlux wrote:
> I did a bit of calculating about what might push damp air into a conduit.
>
> I assumed that I had 30 meters (100ft) of a 2" diameter tube where 
> there was a pressure difference corresponding to a 10 mi/hr wind (it's 
> about 1/4 lb/sq ft)
>
> You'd get a flow of about 2 liters/second (which is surprisingly high)
>
> In an hour, then you'd have 7200 liters.  If you had 100% humidity air 
> at 68F (20C) going in, and the soil was at 50F (10C), you'd be 
> condensing out about 50 grams/hour.
>
> In reality, you probably don't have 100% humidity at 68F. But you 
> might have 50% humidity at 85F, and that's about the same amount of 
> water.
>
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-- 

73

Roger (K8RI)


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