To be honest, I don’t think code requires this protection, but I believe that’s a technicality. Article 800.20 of the NEC requires lightning protection on both ends of an “interbuilding” circuit that’s exposed to lightning. I don’t think we’re referring to interbuilding circuits here. That said, I believe the interbuilding part is intended to make clear that both ends need protection when both ends terminate in a building, not that protection is only needed if the cable goes between buildings. I believe the intent is to require primary protection on these circuits. My reason for believing that is because it’s the only intellectually consistent way I can think of to interpret the entire article. I could be wrong. I often am.
There are three reasons for requiring primary protection on exposed cables. One is that before protection was common people on the phone at the time lightning or downed power lines contacted phone cables were getting injured. Another reason is fire protection. Cable sheaths/screens have modest ampacity and they get quite hot when struck by lightning. Screens in particular are typically grounded in the TR rather than where they enter the building, so the heat is conducted much farther into the building. Shunting to ground at the cable’s point of entry helps reduce the fire risk to the structure. Finally, we protect the signaling conductors and not just the sheath because lighting contact with the sheath can result in very large induced currents on the signaling conductors. Grounding the sheath does nothing to eliminate these. In my opinion, equipment protection is a side benefit, and above is the real reason for installing lightning protection on exposed circuits. That said, I would encourage you to investigate the definition of exposed, because many outdoor devices at our university are not exposed and don’t really benefit from the protection. Also, don’t be fooled into confusing the price of these devices, which I agree are very affordable, with the cost of using them. Installation of the device has an additional cost, and proper grounding of them can result in a considerable cost increase. I estimate that these cost anywhere from $200 to $400 installed, so I only use them where needed. I would be glad to post my understanding of exposure if anybody wants to hear it, but I’m not prepared to do that at the moment. Chuck From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU] On Behalf Of Jeffrey D. Sessler Sent: Friday, August 07, 2015 11:06 AM To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU Subject: Re: [WIRELESS-LAN] Outdoor PoE If one is following electrical codes/best practices, are these devices needed? That is, externally mounted ethernet devices such as cameras and access points as supposed to be using STP and not UTP cable (providing a solid path to ground). The camera/ap should be grounded at it’s mount point and on the PSE side (switch, injector, etc.), In the case of a switch, it should have a separate ground lug that’s tied into a ground bus-bar. I suspect If you follow the above, these additional devices may not be required. And if the above isn’t being followed, it may be a good idea to chat with an electrical engineer just to make sure your not installing a bunch of potentially deadly lightning rods. :) Jeff From: "wireless-lan@listserv.educause.edu <mailto:wireless-lan@listserv.educause.edu> " on behalf of Thomas Carter Reply-To: "wireless-lan@listserv.educause.edu <mailto:wireless-lan@listserv.educause.edu> " Date: Friday, August 7, 2015 at 6:23 AM To: "wireless-lan@listserv.educause.edu <mailto:wireless-lan@listserv.educause.edu> " Subject: Re: [WIRELESS-LAN] Outdoor PoE We haven’t had any problems, but we’ve used these: http://www.l-com.com/surge-protector-outdoor-10-100-1000-base-t-cat6-poe-compatible-lightning-protector-rj45-jacks with great success. They also have a punch down version as well if you want to mess with that. We have them mounted outside with the APs and a good copper ground wire. If you haven’t looked at them, l-com.com has a wide array of antennas, cabling, etc. No connection to them, just a happy customer. Thomas From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU] On Behalf Of Hector J Rios Sent: Thursday, August 6, 2015 8:24 AM To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU <mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU> Subject: [WIRELESS-LAN] Outdoor PoE For those doing outdoor wireless, here are two products we have purchased that we have found very useful: <https://www.amazon.com/gp/product/B00NMU85PM/ref=od_aui_detailpages00?ie=UTF8&psc=1>Microsemi Outdoor PoE Surge Protector PD-OUT/SP11http://www.newegg.com/Product/Product.aspx?Item=17B-00A5-00001<http://www.newegg.com/Product/Product.aspx?Item=17B-00A5-00001&nm_mc=KNC-GoogleAdwords-PC&cm_mmc=KNC-GoogleAdwords-PC-_-pla-_-Surveillance+Accessories-_-17B-00A5-00001&gclid=CIOKgobGlMcCFQmNaQodJ_0C0Q&gclsrc=aw.ds>&nm_mc=KNC-GoogleAdwords-PC&cm_mmc=KNC-GoogleAdwords-PC-_-pla-_-Surveillance+Accessories-_-17B-00A5-00001&gclid=CIOKgobGlMcCFQmNaQodJ_0C0Q&gclsrc=aw.dsMicrosemi PowerDsine 9001GO - PoE injector - 30 Watthttp://www.cdw.com/shop/products/Microsemi-PowerDsine-9001GO-PoE-injector-30-Watt/2578417.aspx?cm_cat=GoogleBase<http://www.cdw.com/shop/products/Microsemi-PowerDsine-9001GO-PoE-injector-30-Watt/2578417.aspx?cm_cat=GoogleBase&cm_ite=2578417&cm_pla=NA-NA-PWD_NE&cm_ven=ShoppingFeeds&ef_id=VLgjcQAABAHVQD8U:20150806132234:s&gclid=CKyxxczGlMcCFQgtaQodCO8PhQ>&cm_ite=2578417&cm_pla=NA-NA-PWD_NE&cm_ven=ShoppingFeeds&ef_id=VLgjcQAABAHVQD8U:20150806132234:s&gclid=CKyxxczGlMcCFQgtaQodCO8PhQRegards,Hector RiosLouisiana State University********** Participation and subscription information for this EDUCAUSEConstituent Group discussion list can be found athttp://www.educause.edu/groups/.********** Participation and subscription information for this EDUCAUSEConstituent Group discussion list can be found athttp://www.educause.edu/groups/.********** Participation and subscription information for this EDUCAUSEConstituent Group discussion list can be found athttp://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
