Finally made it into a CO.. Our C15’s cages are isolated and bonded separately back to an EGB.
It amazes me how accurate guys could troubleshoot those switches just by the sound it was making. He tells stories of watching the switch during lightning storms and being able to watch the arcs across the frame. There is a story of a farmer hooking the ‘drop wire’ into his electric fence, the eskimo’s that shot holes into the switch they delivered to Deadhorse Alaska.. I mentioned going to Animal Farm and Beehive Teleco and two of them recalled the one time president? of Beehive writing a comments section for a trade magazine that they all read. Unfortunately two of the three OG’s “Old Guys” that started BPS, Falcon Communications, and Diversified Communications have passed recently, a lot of early telecom history is disappearing with them. From: Af [mailto:af-boun...@afmug.com] On Behalf Of ch...@wbmfg.com Sent: Friday, April 10, 2015 10:49 AM To: af@afmug.com Subject: Re: [AFMUG] APC PRM-24 Our C15 might be in an isolated rack inside the cage. That is a funny story. I started on AE Step switches. In time not only could I hear problems, but I could tell when someone was calling the office and answer the phone before it would ring. That would freak folks out. From: Robert Haas <mailto:rob-li...@bpsnetworks.com> Sent: Thursday, April 9, 2015 8:42 PM To: af@afmug.com <mailto:af@afmug.com> Subject: Re: [AFMUG] APC PRM-24 I'll have to take a look at our C15 installs and see what they did. To be honest I haven't paid too much attention to them. Our offices were converted to DMS10's in 97 or 98 from step switches when the company bought the exchanges from GTE :p *Funny story, when our owner (who cut his teeth as an X-Y switch installer for Stromberg Carlson) when inspecting one of the CO's prior to purchase he heard something wrong in the switch room (A stepper motor?) mentioned it to one of the OSP guys as he was leaving - something along the lines of 'Sounds like you have a bad motor back there'. Said OSP guy filed a union grievance against him for troubleshooting the problem. Surprisingly the same OSP guy retired from the company just a few years ago after 40+ years of being in the same CO under Contel, GTE and then BPS. On 2015-04-09 20:59, Chuck McCown wrote: The original digital switches were so touchy that they started doing the isolated ground zones for static sensitive equipment. But now-a-days we bolt them to the concrete floor and bond them all together. Same with cable racks now. Back to the old days of non isolation in all the new installations I have been involved with. And this is with RUS financing. I haven’t seen a new isolated rack for some time. From: Robert Haas <mailto:rob-li...@bpsnetworks.com> Sent: Thursday, April 09, 2015 7:33 PM To: af@afmug.com <mailto:af@afmug.com> Subject: Re: [AFMUG] APC PRM-24 All the superstructure within the buildings are isolated & bonded. A lineup of racks may be bonded together and then bonded back to the I/MGB, the racks themselves are isolated from the floor, walls and the cable rack. Same for cable rack - it is all bonded together and then bonded to the I/MGB but isolated from the walls, celling and racks etc. We've gone through RUS inspections in the past and have not failed any of our grounding/bonding portions. Since the chassis is obviously metal there is a risk that the surge could energize the rack, which given our past experiences gives me the heebie-jeebies. By isolating the chassis from the rack the only path would be to the EGB and avoid the rack (and potentially other equipment) absorbing the surge. At least that is my thinking anyway. I guess that is where my question lies - am I worried about nothing? On 2015-04-09 19:14, Lewis Bergman wrote: If you look at the relevant docs on the subject like the Telco standard or R56 you'll see the rack itself is part of the ground bus. This really is forced by equipment designers. I can't think of many pieces of equipment that chassis ground isn't equivalent to ground reference in the circuit. You should ground the rack as if it is an integral part of the IGB. On Apr 9, 2015 4:56 PM, "Robert Haas" <rob-li...@bpsnetworks.com <mailto:rob-li...@bpsnetworks.com> > wrote: We’ve been deploying the WB suppressors using the prm24 chassis for over a year now and have ~30 or so in the field. I’ve had an uneasy feeling since day one about mounting the PRM’s in the rack with other equipment – to the extent of when I have the option I buy a 1u wall mount bracket and mount the chassis on the wall next to the cable entrance (bonding to the EGB). I’ve even isolated the chassis off the rack using poly washers and poly screws (again bonding to the EGB or MGB in a cabinet). My line of thinking is that I do not want to risk shedding the surge into the rack and potentially into another piece of equipment. I do not trust that the surge will follow the bond/ground wire to the EGB or MGB and not go into the rack/superstructure. We’ve had this happen in the past where a redline AN50-E was struck and the surge was brought inside into the superstructure and took out $20k+ of cards in one of our DMS10s. In that case there was a polyphaser IF SS at the cable entrance that was bonded to the ring – the polyphaser popped but not before damage was done. The case of the IDU showed arc marks around the ovals where the screws to the rack pass through, the screws in the rack welded themselves along with the bond screw in the chassis (it was bonded to the EGB using the screw in the back of the chassis). Anyone else have the same feeling that bringing the surge into the rack is bad juju or is thatoneguysteve sitting there looking at me shaking his head saying that guy is f*ing nuts?
