In article ,
Huge writes:
On 2017-02-10, Dave Liquorice wrote:
On Fri, 10 Feb 2017 10:37:02 +0000, Bob Minchin wrote:

An outside container is very difficult to fully seal as thermal
expansion/contraction will act as a pump admitting small amounts of
water vapour laden air. The water condenses and stays inside and on the
next heating cycle the air gets pushed out but the water does not and so
it slowly builds up as the cycle repeats.

Double plus 1. Not many people realise/know that.

So although holes seem bodgy it's the only way. Only need one at the
lowest point and it doesn't need to be very big 1mm is ample. Much
bigger and a decent blow will manage to force water in, not to
mention letting in spiders or other wild life.

The spiders get in anyway. I have no idea how.

(Over the last few weeks I have dismantled all the outside electrics
in the so-far fruitless search for the nuisance RCD trips, and they
all had spiders in them. Even the IP44 junction boxes.)

Spiders can generate RCD trips.

My parents have a desk fan (class 2 - double insulated) which
has a 2-core cable and a plastic body. I was initially rather
surprised that it caused an RCD trip. The culprit was found in
the plug - a spider's web/nest between the live and earth.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]