The setup makes a lot of sense.... The reason why Ground Bars are isolated from the tower is because if there is a direct strike to the tower, the tower should ground that strike. and the Ground Bar should not provide a better path for lighting to go down bus bars... however if there is any kind of static buildup, that should drain via the Copper Bus bars and the higher quality (lower resistance) ground (bus bars with the welded connections).
The Bus bars are providing a 'high quality' low resistance ground for the equipment / cables etc. One should keep in mind that in this setup the actual radios (considering the long coax runs) are installed below, and the Coax cables are most likely to have gas tube protectors on them.. Regards. Faisal Imtiaz Snappy Internet & Telecom 7266 SW 48 Street Miami, FL 33155 Tel: 305 663 5518 x 232 Help-desk: (305)663-5518 Option 2 or Email: [email protected] > From: "Paul McCall" <[email protected]> > To: [email protected] > Sent: Monday, July 24, 2017 4:56:06 PM > Subject: Re: [AFMUG] Tower Top Grounding discussion > I was told they are isolated by the climber, using the red rubber isolators. > However, not ALL of the carriers do that. The subcontract from the cellular > company we are using said that also some of the tennis have harden plastic (or > similar material) at the bracket attachment point, thus isolating also. > For what its worth… > From: Af [mailto:[email protected]] On Behalf Of Gino A. Villarini > Sent: Monday, July 24, 2017 4:39 PM > To: [email protected] > Subject: Re: [AFMUG] Tower Top Grounding discussion > The grounding bus bars are isolated but I doubt the gear at the top is, the > antennas and RRUs are bracketed to the tower… > From: Af < [email protected] > on behalf of Paul McCall < [email protected] > > > Reply-To: " [email protected] " < [email protected] > > Date: Monday, July 24, 2017 at 2:29 PM > To: " [email protected] " < [email protected] > > Subject: Re: [AFMUG] Tower Top Grounding discussion > Well, somehow this cellular guys survive these direct tower hits. Tower # 1 > from > the weekend is a 500’ tower that we are at 410 feet on. Two cellular providers > right below us and a FM station and Lojack above us, and we were the only ones > hit. Cellular guys have isolated ground bars at the top that are connected to > the outside shield on their large coax cables, with a “wrap kit”. At the > bottom > of the tower, they have another isolated ground bar and attached the same kits > to get the ground to the ground bar, then have their own grounds. MOST are > doing it that way. I will send pictures of 2 different carriers on the same > tower doing it differently. > Tower #2, is a 130ft water tower with Verizon. They are at the top of the > tower, > have the same exact type setup. > This picture is from a 3 rd tower (bottom) that I took pictures … same thing. > We do have fiber and 48vdc to the top and 48vd protectors (Polyphaser) at the > top at both these towers. Everything blew, including the polyphaser that is > grounded to the tower itself (on both towers). Obviously, that isn’t working > :) > From: Af [ mailto:[email protected] ] On Behalf Of [email protected] > Sent: Monday, July 24, 2017 1:42 PM > To: [email protected] > Subject: Re: [AFMUG] Tower Top Grounding discussion > Nothing stops a direct hit. It will blow up everything that gets in its way. > You are probably seeing induced surges from nearby strikes. > Fiber to the top. Surge suppressors on the DC conductors. > Gino A. Villarini > President > Metro Office Park #18 Suite 304 Guaynabo, Puerto Rico 00968 > From: Paul McCall > Sent: Monday, July 24, 2017 11:20 AM > To: [email protected] > Subject: [AFMUG] Tower Top Grounding discussion > We have two 500ft towers that get hit a bunch, and a water tank that gets the > same treatment from mother nature. > Anybody doing full isolation of all their antennas, equipment etc. at the top > of > the tower and then running your own ground down the tower? > 1. Wondering what materials people are using to isolate their mounts? What > is > sufficient? Would the rubber from a thick radiator hose be enough to keep > the > lightning from coming through? Double thicknesses? > One consultant recommended starboard, but I am not sure how I will craft that > into a work piece that would mold around a tower leg and be able to grip it. > 1. What size wire should be going down the tower to bond to my tower / > electrical ground? > I am assuming it should be insulated but is normal THHN jacketing enough to > have > it truly isolate from something jumping over or does it have be in conduit. > Paul > Paul McCall, President > PDMNet, Inc. / Florida Broadband, Inc. > 658 Old Dixie Highway > Vero Beach, FL 32962 > 772-564-6800 > [email protected] > www.pdmnet.com > www.floridabroadband.com
