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Standard User mbdcs
(newbie) Wed 11-Mar-15 12:39:26
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Lightning/surge protection


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On a client's site, their ADSL modems keep dying (last one was less than 6 months old). It's starting to seem like more than just bad luck. At least one was due to a lightning strike (guessing on the overhead line somewhere, rather than the building). Apparently there was a large flash from the wall socket area and dead modem. This time they recall a recent thunderstorm, so it could be that again.

Could there be a fault with the incoming line (earthing)? Is there a plug in surge/lightning protector device available that is compatible with ADSL? Or is it just a case of replacing the modem every time one dies?
Administrator MrSaffron
(staff) Wed 11-Mar-15 13:04:15
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Re: Lightning/surge protection


[re: mbdcs] [link to this post]
 
There are a few 'protectors' that say they work, but its a case of trying them out and most will not stop a direct hit on a line stopping the modem being killed. A lightning bolt that has travelled through the air for 100's of metres will think nothing of jumping a foot or two of air gap when leaving a wire.

In short not a lot you can do, your master socket should already have protection built into it, but ADSL modems are very sensitive RF devices so even a near strike and induced voltages can kill them. The modems themselves usually have a safety device internally to help reduce the risk of fire and onward problems e.g. propagating onto Ethernet network.

Most lightning protector devices you can buy are really insurance products where the insurer will try and work the clauses to not pay when you do claim.

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User 961a
(learned) Wed 11-Mar-15 14:34:30
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Re: Lightning/surge protection


[re: mbdcs] [link to this post]
 
Living in an area where electrical storms happen we had trouble with modems being fried quite regularly. Eventually we came to the conclusion that the surge as often as not came from the telephone wire rather than the power supply

We installed one of these
http://www.apc.com/products/family/?id=29
and have had no trouble since but I would add that if we know there is electrical disturbance likely in the area we still are inclined to disconnect modem from both the power supply and the phone system


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Administrator MrSaffron
(staff) Wed 11-Mar-15 15:49:16
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Re: Lightning/surge protection


[re: 961a] [link to this post]
 
On the disconnection - if lighting is in the vicinity DO NOT unplug stuff because of the risk that a strike may hit wiring and earth via your body.

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User 961a
(learned) Wed 11-Mar-15 16:53:17
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Re: Lightning/surge protection


[re: MrSaffron] [link to this post]
 
Yes, agree with that but weather forecasts do give advance warning and several fairly accurate predictors available on line such as http://www.netweather.tv/index.cgi?action=lightning;...
Standard User andygegg
(regular) Wed 11-Mar-15 18:12:26
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Re: Lightning/surge protection


[re: mbdcs] [link to this post]
 
I lost a motherboard to a lightning strike once but the modem survived!

As an aside, being on FTTP doesn't completely remove the risk. After a recent storm I got some very odd results from the TBB meter
http://www.thinkbroadband.com/speedtest/button/14226...

which were resolved by switching the HH5 off and on
http://www.thinkbroadband.com/speedtest/button/14226...
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