[mythtv-users] Uninterruptible Power Supply

Simon Hobson linux at thehobsons.co.uk
Tue Dec 22 19:53:30 UTC 2009

John Drescher wrote:

>For me the main problems are wind and lightning. I live on top of a
>mountain ...

As already stated, to deal with that is non-trivial but there are a 
few things you can do to make some budget protection effective.

The first is to realise that protecting just one part of the system 
won't help - for example, when dial-up modems were still common the 
biggest risk in thunderstorms would be common mode surges from the 
phone line. They don't affect a phone since a line powered 'bog 
standard' phone has no ground reference, but it will take out a modem 
(and possibly the computer) or a fax which are connected to other 
circuits and therefore have a ground reference.

So for example, to protect a fax you would need a half-decent surge 
protector that includes the phone line as well as the power - that 
way, even though the surge may well take the 'ground' of any attached 
equipment to some hundred or thousands of volts, all the downstream 
equipment and circuits see the SAME 'ground'.

To protect a whole property, you would need to route all incoming 
services via one point so that they (and therefore any equipment 
connected to them) can have surge protection that shares a common 

Back to the original topic, I have a UPS on my backend (well actually 
on the Xen host it's currently hosted on) - and it also runs the 
network switch and ADSL modem that are in the same place. I never got 
round to hooking up the data line, partly because we have reasonably 
good power here and momentary interruptions are the biggest things 
I'm worried about. That's not to say I'm not bothered about a clean 
shutdown - I just haven't got around to it yet, and it will run the 
box for at least half an hour. Oh yes, and it's a 'scrap' one I 
picked up from work and put new batteries in.

The rest of the network, and the TV/frontend, aren't protected. 
Should we have an extended power cut, then I do now have a portable 
generator and could therefore hook it up and run the essentials in 
the house - but I didn't buy it for that.

At work in the server room, we've an on-line double conversion system 
that will run our 7 to 8kW load for about an hour. It cost "somewhat 
more than my TV viewing is worth" and has about a 1/3 of ton of 
batteries attached !

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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