atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Outside Plant OSP Construction Need some help burying a 25-pair cable ...

Hi everyone:

I really need some help with a burial project. I'm in a bit over my head. I'm the programmer, and can do basic cross-connecting and terminating, but I think this job requires more. Here's the scenario:

-I need to run a 25-pair cable from building a to building b. The run will be about 75 feet.

-I have new conduit that the cable will go in.

-A good friend of mine who is a phone vendor gave me 175ft. of 25-pair cable to use for the project.

-The phone system I'm using is an Avaya Partner ACS (v6).

-Building A has the KSU. Building B will have three phone extensions (2 pairs for each extension).

-The CO/POTS line will come over from Building A to Building B.

-I need to hook a cable from the outside line at Building B to an elevator phone and an alarm panel.

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Do I need lightening protection if I'm going below ground? One side, both sides, and what would I use? I'm in southwest Wisconsin; we do get storms and lightening occasionally, but not real often.

Will I need anything specific for the phone sets to work? I thought I remembered something about Partner phone sets needing some in-building/out-of-building thing, but I'm not sure.

I want to use 66 blocks because I just prefer them, and they're easier for me to work with. In Buildings A&B, can I wire my phone sets directly to the block that has the cable coming across, or do I need to have the phone sets on a different 66-block, and then cross-connect them to the other one?

Any help that you guys could provide would be gratefully accepted and most appreciated. Thanks again!

What kind of 25 pair cable were you given? Is it black-jacketed, shielded and filled with goo? That is probably the best place to start. You will need protected entrance terminals at each end that incorporate gas tube protector modules. Behind those at each end, the IROB secondary protectors should be used. These items aren't cheap.

None of this is required from a legal perspective (as in NEC regulations), but from a professional and practical point of view, it is. If the buildings are contained within the confines of a legal city block, then you really don't have to do anything. I hope that you will consider going above and beyond this loophole to protect the equipment.

Whether the cable is above- or below-ground is insignificant. It's not a matter of lightning actually striking the cable or either building. It is more a matter of difference in ground potential when lightning strikes in the immediate area. Several million volts of energy may hit the ground a few thousand feet away and it will continue to dissipate in the soil for a very large radius. By the time this hits the grounding system of building A, it may have dropped down to say, 5,000 volts and by the time it reaches the grounding system of building B, it could be down to 100 volts. That's a 4,900 volt differential that needs to be addressed by your cable that is actually tying the buildings together. Granted, this all occurs in a split-second, if it's not installed correctly, that split-second can cause big mess in grand fashion.

Granted, this example is a bit of an extreme, but it can happen. The building entrance terminals will provide the base-level personnel/property damage protection and the secondary (IROB) protectors will do what they can to protect the connected equipment.

The true key is to bond the cable sheath to the building entrance terminals at both ends using the factory-equipped bonding harness within the terminal. Then, these terminals must be bonded to each building's main electric service grounding conductor using a #6AWG solid copper conductor. This places both buildings at a common potential.

WOW! Thanks for the great post, Ed - I really appreciate it.

At this time, I'm not sure exactly what kind of cable it is as I haven't had a chance to pick it up yet. My friend assures me that it will provide for my needs.

I did a bit of research on the building entrance terminals ... I'm seeing prices in the $500-$800 range per box; is that about right? We're a very small, rural Catholic church. I completely agree about proper protection, and if I were in a well-funded church, I wouldn't think of sparing the cost, but $1,600 is a cost that we can't afford right now.

I would, however, think that we could do the IROBs to provide at least a bit of protection to the phone sets and the KSU. I'm not exactly sure how they work, though. Do you need one IROB device per pair, or is it one device per set?

Thanks again for the help, Ed.

That pricing is a bit high, but I'll do a little bit of shopping for you tomorrow. As for the IROBs, they are good for four pairs each, so you would need two at each end for your application. I might have some used stuff around if that would help soften the blow.

IROBs date back to the Merlin days. They have an 8 pin/8 pos jack and will protect 4 pair and they were always designed for use as one pair (one at each end) per extension. If you were to use them you would need 6 for your three extensions. But that's not really the way to go anyway because you need to protect all 25 pair at both ends. You ARE going to need protection in Wisconson.

If you can't afford to do this properly consider the cost of replacing a processor or a 308 or 206 mod and some phones every time you have a storm. I'm here to tell you that that is what's going to happen. Been there, done that for lots of customers.

I agree with one thing and that is you are in over your head. You can't tell us what kind of cable you have, you have no idea where and how to ground everything, and even if you get the proper protectors the grounds are the most important thing. This could wind up costing you lots of money for repairs if you don't get it right.

Nope, I'm going to tell you to get somebody who knows what they are doing to do this for you. Unfortunately Wisconsin is a bit far for Ed or myself.

-Hal

I was thinking of the newer IROBs that were made by Panamax, not the really older ones made by TII.

Hal, you and Ed could meet in say, Pensylvania and drive on over to Wisconsin in an easy 2 days, Do the job in a couple or three days and at least one of you would probably be home in 3 weeks. I'm figuring you guys would work together for about 12 hours before one of you killed the other and I'm betting Ed will be the deceased. The reason it'll take 3 weeks to get home is that you'll have to convince the law that it was justifiable homicide, then you'll have to make arrangements for Ed's body, and of course the job that was so rudely interrupted will have to be completed! John C. (Not Garand)

I was thinking of the newer IROBs that were made by Panamax, not the really older ones made by TII.

Never saw the Panamax ones. But if you were going to go the Panamax route they make protectors for 25 pair like the IROBs. Only problem is they are secondary protectors like the IROBs AFIK. That means you are still going to need primary protectors at the point of entrance.

-Hal

The newer ones looked exactly like the other Panamax Towermax modules, just with Lucent or Avaya's logo on them and a comcode. I'm sure that they are secondary only.

I checked some of the older Tii IROBS today and sure enough, all four pairs were protected. Honestly, I've never looked inside one before until today, but sure enough it has four 1-pair gas tube protectors, grounding means and solid-state secondary protection all in one outdoor protector enclosure. Kind of nice.

Thank you, gentlemen, for all of the helpful posts. I do appreciate it very much. Hal, it may very well come to getting an Avaya tech. out here to help with the rest of the project, but I'm doing all that I can to try and keep from having to pass the plate around one too many times!

I understand all of the concepts, and it seems that I really need to make sure that I have good ground protection at both ends. One phone technician advised me to purchase a TowerMax surge protector base unit. That would do the job of securing the KSU and providing proper ground to it. But what about the 66-block in the other building? We've got a ton of steam pipes and other piping in the basement - can I ground the block using this?

Now, about the IROB's - it seems to me that these devices seem a bit cumbersome. I'm assuming that the wires "pass through" these devices as they are wired to the blocks? Could I get something that would plug into the clips on the block - something like this: https://www.qualitymatters.com/ProductDetails.asp?ProductCode=QMT-ITWUP3B100&click=21247

I'm much more familiar with these, as we used them to protect our Norstar system. When I think back to the programming and support on it, I remember there being a rod in the block, and then a wire that went to one of the pipes in the basement from that rod. Hal - A+ in meterology school! We do get lots of storms here, and through all the storms I endured with the Norstar, I never once had any set fail due to lightening - even when lightening struck the ground RIGHT next to the building where all of our buried cables left.

Hal, I was advised that I need only protect the pairs that I will be using. I expect to use 7 pairs on the cable - 1 pair for the CO line, and three extensions @ 2-pair per set is six pairs, for a total of seven. Was I misinformed?

Thanks again everyone for your continued assistance.