Cat5e Lightning Protection

[andygee]

I'm looking for something to keep the surge from running in from outdoor cameras back into my switches. I've been using APC PNET5r units and they blow but the surge continues and usually shorts the switch out. I'm looking for any other suggestions that would help me cut down on some of the risk. I found these http://www.l-com.com/content/Data_Line_Protector_Comparison.html and am curious if anyone has had any experience with them or has any suggestions.

Thanks,

Andy

 

[gatchel]

Could you stick in a cheapie 5 port switch of hub as a sacrificial device before you main switch?

Otherwise a Ditek DTK-MRJPOE might be what you are looking for. Or for more ports use a DTK-RM16C5 or a DTK-RM12C5

 

[JimS]

The L-Com devices look interesting but I looked at the data sheet for the first device - no energy ratings! I normally deal with surge suppressors for other than ethernet so it is a bit different but for the things I deal with the energy rating is very important and I don't see how this is any different. This is typically rated in Joules (or millijoules). Having a voltage clamp like stated is what you need but without an energy rating you don't know how much current it can handle while clamping the voltage. I expect the energy rating needed is fairly low - much lower than the power line protection I normally deal with. I would do some comparisons and see if other devices carry energy ratings. For example, here is an APC unit - I found it though google and amazon.com.

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=PNET1GB&tab=models
I don't have any connection with APC and can't say if this is better or worse than typical but it looks to have more complete specs than the L-com device. Specifically it has current ratings and references a UL spec.

 

[andygee]

Thanks, I'm looking at the Ditek units now.

The problem with the APC units is they don't work. That's what I have in place now and yes they blow, but the surge still continues down the line at least initially. I've got several of these as well as their PNETR6 units in a chassis but they keep allowing it through and then I have to replace those modules.

Thank you for the suggestions.

Andy

 

[fwd03]

If lightining hit your cat5 cable, the surge protection will not do it. Most network IC will not be able to take more than 7V DC on its input pins for even really short time. You may build some little fuse block yourself to let lighting fry that fuse block in front of your switch.

 

[drozwood90]

If lightining hit your cat5 cable, the surge protection will not do it. Most network IC will not be able to take more than 7V DC on its input pins for even really short time. You may build some little fuse block yourself to let lighting fry that fuse block in front of your switch.

This is the beauty of cat5. There are magnetics in front of the IC. They blow first. The circuits for ethernet are inherently protected. It's part of the standard that they can take a hit without hurting stuff down stream.

Not to say you should not try to stop it BEFORE it hits the cat5...but if the lightening is already on the cat5...at least you are only blowing out ethernet cards and switches (until the first one that can...shorts the power to ground).

--Dan

P.S. this is also why the "TRUE" POE circuits are complex, costly and ineffcient. They are optically (and other) isolated to ensure they do not bridge the power from a surge.