Shielded 25 pair cable for machine shop

[pccsipoffice]

Shielded 25 pair cable for machine shop
Scenario:
Two buildings with one buried 25 pair between.
building A has a KSU
building B has phones.
Storms come through, KSU damaged.
Buried 25 pair is lighting protected and secondary protection is also used.
Building B has a 25 pair (NOT SHIELDED)cable that is inside and is installed up to the
a high point of the office which is a 3 story tower. The tower is made of
steel and sheet metal. Thinking of replacing inside cables with shielded but can find anyone who sells it.
Thoughts?
......
.B | .
. | .
..... . | .
A --.---------------------.--- .
..... ......

 

[Wanebo]

If the KSU is in building A (which has lightning protection from anything coming from building B) and is getting blown out I would have to say the installed lightning protection is ineffective and should be addressed first. Do you have a ground loop? Is the grounding adequate and measured? Do you have the correct type of lightning protetction (solid/gas tube/low trigger)?

Sheilded 25 pair cable is typically known as armored cable. Graybar or Anixter should be able to steer you in the right direction. Remember that simply having sheilding doesn't mean you can skip having a proper drain for the sheild.

 

[pccsipoffice]

I believe the lightning protection is adequate it is gas-filled and looks typical.
I will look closely at it.
Both ends of the cable are grounded Bld A is grounded to the same point as the Att feeder. Bld b is grounded to an electrical conduit.
I set a ground to the shield in bld A yesterday.
I am going to increase the wire size to #6 soon.
How do I measure ground? Should I have an electrician do it?
It is a real issue as cards are blown regularly when stormes arrive.

 

[libellis]

Assuming it's the station cards that get damaged (is that the case?), are the phones analog or digital? Do phones get damaged as well as the cards? If they're digital, you might want to look at the limiting voltage (clamping level) of the protection modules. If the clamping level is, for example, 240 volts, then a lower level would be more suited to digital station cards. From what manufacturer is the phone system?

 

[pccsipoffice]

The phones are digital ATT spirit. Two pairs, They are not damaged.
The cards are station and yes they are blown.
The secondary protection is the device that were made for the Spirit.
I will look at the fuses I am sure they are for trunks and not stations.
If the grounding is the problem, and assuming all grounds are bonded together,
there is an expensive repair coming down the pike.
I dont know what the spirit system required for primary but I will bet it is hard to
find now. This is 80s stuff.
There may be a ground issue in the building as I know other equipment in the same closet
have died prematurely.
All equipment is on surge and UPS

 

[libellis]

Certainly confirming proper system bonding/grounding is very important, especially for the protectors (if possible, short connection to ground with no sharp bends). Is this a relatively new problem, or is it long standing? If it's new, then of course something has changed.

I'm still wondering though about the clamping levels. I'm guessing that the KSU is relatively close (in cable length terms) to the entrance location of the 25-pair cable. I'm also guessing that the phones at the other end (in the other building) aren't nearly as close (again in cable length terms) to the entrance location of the 25-pair cable. Trying to find an explanation for why the phones survive, and attenuation over distance of any fast pulses remaining after the protectors have done their job is one explanation - or maybe the phones just have sufficient built-in protection - or maybe I'm way off base with this (likely), so this is the last I'll mention it.

 

[Dexman]

Is the 25-pair running between the buildings direct burial, or, is it through a conduit? If direct burial, is installing conduit a viable option?

I "FEATURE 00"

http://dexman.webs.com/

 

[pccsipoffice]

I will look into the clamping level Libelles. That may be key. A storm came through over the weekend and there
was no damage. The shield grounding may have helped with it. I also added a #6 cable to replace a #10 for ground.
Dexman it is directly buried. Any conduit added would be plastic. I doubt that would improve the situation.
If the clamp level is correct the electrician may be called to do a ground measurement.

 

[libellis]

In case you don't have a copy, attached is the installation manual for the In Range-Out of Building (IROB) protectors that it seems are installed in your Spirit system. From another source (the manual doesn't give details like voltage clamping levels) I see that the secondary protector does have a low clamping level (obviously - it's intended to protect this system) so if the the protection modules are still in working order (including primary), then the problem is elsewhere. (The primary protector does have a high clamp level of 265V - 600V).

Seems like the IROB was installed by the book - manual shows #10AWG for the primary protector, but heavier gauge like the #6 you added never hurts.