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Protection


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Posted

its the first thing that the nacoss inspector would be looking for.

No earth,x on the sheet :yes:

Posted

But many units dont have earth connections!

Posted

Back to phone systems:- I know that the old LG GSX systems had no mains earth as they relied on the telecoms earth but now there is not really a telecoms earth the systems rarely get earthed (yes they are in a metal case too! :o ) but all new LG phone systems are earthed to the mains earth and have a stud if you require an additional one.

David Avery.

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Guest Peter James
Posted

The digi will always blow on a lightning strike on the bt line but if you dont earth it so will everything else.

If you look closely at or close to the a an b terminals you will see two glass looking components, in the event of high voltage these components will leak (kamikazi) to the earth terminal thus preventing further damage to the main cpu.

The reason for the size of earth wire used is becouse electricity will always take the shortest route if the cable is not man enough it will choose the route through the cpu.

There are lots of suppressors available if you suffer from lightning Bowthorpe emp used to manufacture most of them.

(I like the ones with the live bullet inside that explode when hit by hi v (not for home use on your digis though :w00t: ) )

Pete :)

Guest Adrian
Posted

B) I had an install last year that got hit by lightning 4 hours befor it was due to be handed over and paid for. What a bugger.

Needless to say the replacement panel was filtered to the hilt.

Adrian :(

  • 9 months later...
Posted

I went out to a Redcare STU in comms fail this afternoon. Before I even opened the panel I could smell the aroma of fried silicon and plastic. I have never seen a piece of equipment so badly damaged through lightning - melted plastic, PCB with HOLES in it, the works.

Turns out it wasn't lightning at all - some monkey was playing with the mains wiring over the weekend, and when I checked the earth, I got 241V across L and N, 241V across N and E, and 480 across L and E. So Earth was in fact live - and I think it must have zapped its way across th the BT line. Whoops...

Posted

i always earth comms , got told by a BT engineer to use stranded 1.5 mm earth cable opposed to solid because after the panel has been opened a couple of times and the cables rived round solid can break easier than stranded , leaving you with no earth protection

personnaly i think if its gunna get hit, its gunna fry :whistle:

the reason he recomended 1.5mm to 1.0mm is because the pins for the plug on are about 1.0mm so either way it has a 50/50 chance of the cpu or the mains connection :blink:

just what i was told

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