Date: Fri, 22 Oct 2010 10:47:42 +0100 > From: Alan Pope <a...@popey.com> > Subject: Re: [ubuntu-uk] Powerline Recommendations > To: bdr...@crosswire.org, UK Ubuntu Talk <ubuntu-uk@lists.ubuntu.com> > Message-ID: > <aanlkti=eeef3pwvvg3r2bdtmafvjzaq8nun6b5gp7...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > On 22 October 2010 10:44, Barry Drake <bdr...@crosswire.org> wrote: > > I drilled throught the outside wall and have CAT5 all around the > > outside. ?Quick, easy, fast, secure .... > > > > ...almost certainly against building regs.. :) > > If it gets struck by lightning (a very real possibility given it's > grounded via your PC/switch at each end, it could blow your entire > network up. > > Armouring the cable may help though. > > Al. >
I've been active in the Home Automation market, both as a hobby and then professionally, since 1997, and have never encountered a lightning strike on external cable. External CAT on WALLS is very unlikely to be against building regs. Indeed, building regs are far more likely to frown on INTERNAL risers, because of the need to fire-break them every couple of storeys. As far as I'm aware, it poses no more risk than, say, a satellite dish. The way that lightning groundpaths work, the best thing you can do if you have external ethernet is to have an external TV aerial mounted higher :-) If you assume that any grounded point basically causes a "cone" below, that extends out about 1m for each 1m in height, and that anything inside the cone will broadly be safe (because lightning will have an easier path via the higher grounded item), that's a good rule of thumb. Actually, the biggest problem I've come across is the fact that ethernet cable sheathing doesn't have great U/V stability - it will degrade over about 7-10 years if it's left in direct sunlight. Hence, what we did (based on electrician's recommendation) was to put it in some external trunking. The sort that B&Q (other DIY sheds are available) sell for air extract is good. Leave a vertical run with the bottom open, so that any water that gets in will run down the insides and drip out without puddling, but use a decent sealant where the cable goes back into the house. If anyone needs pictures, contact me (Mark AT Ascentium DOT co DOT -the-country-code-for-this-list ) and I'll mail some JPGs over. If you are very paranoid, then of course you need to be aware that ethernet is tappable, so if you have reason to believe that the security services are interested in your data, then you may want to keep those runs internal :-) Mark
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