Dealing with lightening induced voltage on Cat5...

[frowertr]

Curious on techniques to protect my home network from lightning induced voltages forming on my Cat5 wiring inside my house from near (not direct hit) lightning strikes. I live in the Florida panhandle and we get horrible thunderstorms nearly on a daily basis during the summer time.

Just yesterday a bolt hit extremely near my house during a storm. I was on the computer at the time and noticed my network connection drop as soon as the lightning flashed. Shortly after that, my fiance complained her computer was no longer connected to the internet. After some investigation I found that I lost the NIC on my HTPC server, two ports on my 8-port Gigabit switch and another two ports on a smaller 5-port switch.

I have done some reading and a lot of people suggest using fiber to combat induced voltage, but that really isn't much of an option as I would have to re-pull everything. Others suggest using shielded Cat5 cable, but again, I would have to re-pull all my wiring which isn't something I look forward to doing in my attic during the summer. There are "lightning arresters" for Cat5 but those damn things are expensive and one would have to clamp both ends of every Cat5 run in order to work. Considering I have 8 runs I would need 16 of those things so that is out...

I know the phone company/cable company/power company all have their equipment on the outside of my house tied to a single ground rod at my service entrance. Is there any way I can do the same with my nework. Perhaps by grounding my main 8-port Gigabit switch to that rod? There must be some way to dissapate overvoltages...

Thanks!

 

[JackMDS]

http://www.nextag.com/cat5-surge-protector/products-html

 

[frowertr]

http://www.nextag.com/cat5-surge-protector/products-html

As I mentioned, I have considered arresters and clamps but I would need too many of them to make it cost effective. I'd rather re-pull the copper Cat5 and replace with fiber if I had to spend the money to buy the clamps...

 

[ScottMac]

You don't have many options; most often a "line protection device" or "entrance protection" is used on the cable just after entry to your house. The phone company should already have one in teh NID, if your data connection id via CableTV coax, you should also have a protector on that as well.

You should verify that the grounds to all of the protectors are clean and well-secured.

As far as using fiber, you can have a segment of fiber in-between the outside and your internal equipment ... that link can be two transceivers (copper<->fiber) with a ~one meter or longer chunk of fiber between them. That breaks the direct electrical path. You should still have entrance line protection on all copper entering your premises.

Near hits can still be bad, even with data entrance protection, because the pulse can also exist in your power system. Those surges may be handled by a good surge protection system (power strip w/ protection apparatus).

Again, it might be worth also having your power system (Circuit box, neutral, and facilities ground) checked out by a professional.

 

[frowertr]

You don't have many options; most often a "line protection device" or "entrance protection" is used on the cable just after entry to your house. The phone company should already have one in teh NID, if your data connection id via CableTV coax, you should also have a protector on that as well.

I do use cable for my data but I don't don't think there is any kind of clamp or arrestor on the incoming coax from the street. I'll have to look at it today. I do know that it is bonded to the ground rod (all incoming connections are by law).

You should verify that the grounds to all of the protectors are clean and well-secured.

As far as using fiber, you can have a segment of fiber in-between the outside and your internal equipment ... that link can be two transceivers (copper<->fiber) with a ~one meter or longer chunk of fiber between them. That breaks the direct electrical path. You should still have entrance line protection on all copper entering your premises.

Since I am using cable modem for data, how would this work? You are talking about a segment of fiber between the incoming coax and the cable co splitter on the outside of the house?

Near hits can still be bad, even with data entrance protection, because the pulse can also exist in your power system. Those surges may be handled by a good surge protection system (power strip w/ protection apparatus).

Again, it might be worth also having your power system (Circuit box, neutral, and facilities ground) checked out by a professional.

I appreciate your response. I do have a small segment of Cat5 that runs outside and down my house for about 5 feet before it re-enters. This could also be a problem as the house isn't able to "shield" this small piece.

 

[netsysadmin]

The cat5 cable run outside and/or the coax from your ISP is causing the issue. If I had to guess is is the outside cat5 cable is the one causing you your problems. Just setup surge arresters on both ends of the cat5 run that goes outside. One near the computer and one at the router/switch. This will protect both devices from any issues.

John

 

[imagoon]

Odds are you took damage from the outside. You do not need to add isolators inside the house / in the house runs. You use the protection from the circuits outside and verify the house ground is still intact. A small 5ft section outside is unlikely to be the cause even in a near miss. After the (cable/dsl/whatever) modem put a suppressor between it and the router. The rest of the houses grounds should already be tied together at the premise rod. You do have the third "pin" in the plug on your gear right?

A near miss recently came in through my cable line, fried the modem and the router and few nics. Sadly my attester didn't save me that time so I replaced it.

 

[ScottMac]

I do use cable for my data but I don't don't think there is any kind of clamp or arrestor on the incoming coax from the street. I'll have to look at it today. I do know that it is bonded to the ground rod (all incoming connections are by law).



Since I am using cable modem for data, how would this work? You are talking about a segment of fiber between the incoming coax and the cable co splitter on the outside of the house?



I appreciate your response. I do have a small segment of Cat5 that runs outside and down my house for about 5 feet before it re-enters. This could also be a problem as the house isn't able to "shield" this small piece.

There are coax entrance protectors ... I prefer Polyphaser ( http://www.protectiongroup.com/Home ) again, make sure they tie (clean and tight) to the facilities ground ... it's very important. IF possible, ALL grounding should occur to the facilities ground. Multiple grounding paths can cause a variety of issues.

The fiber segment would be from the inside Ethernet connection to the rest of your house (i.e., the cable modem remains at risk).

A short copper segment outside shouldn't be too much of an issue, unless it's hit directly.

DO NOT use more than one protection device on a single span ... it doesn't double your protection, it cuts it in half.

 

[frowertr]

Wow. This is great info guys. I'll check my coax today and make sure to get an arrestor on that ASAP. I don't have land line service (but I do have the connections at my house). I think I'll just disconnect the incoming phone line from the NID since I don't use them anyway. I'll also check on a whole home protection AC suppressor. My power company will install one for me for $10/month, but I am "electrically savvy" and should be able to do it myself.

One thing though, if I put an arrestor on the on the coax coming into the house I wouldn't then need a small segment of fiber coming out of the cable modem to my main switch would I? Wouldn't that be double protection?

 

[ScottMac]

IF the coax protector is done right, it greatly reduces the need for the fiber segment. However, only a chunk of non-conductive glass (fiber) can absolutely prevent an electrical surge on that line.

As a matter of routine maintenance, check those connections periodically to make sure the connections are still clean & tight. Also note that suppressors, ALL suppressors, get weaker with every surge they save you from and need replacement every so often ... how often depends on how often you figure you're getting hit.