Grounding of New/Existing Telecomm Systems

[mikeybmdb32]

I recently installed a new telecommunications system in an existing building. The new system is installed per ANSI/TIA/EIA J-STD-607-A, meaning that there is a Telecommunications Main Ground Bus (TGB) at the service and in each equipment room , aTelecommunications Backbone (TBB) which branches off to each TGB, and bonding between the TGB’s and the telecommunications equipment/panelboards. However, the existing equipment in the building in not grounded per this standard, rather the equipment is only grounded back to the service. My contractor is suggesting that we upgrade the existing equipment to match the new, but I’m not sure if it’s worth the added cost. Neither ANSI/TIA/EIA J-STD-607-A nor IEEE 1100 address the interface of existing and new systems … they just recommend installing new systems per ANSI/TIA/EIA J-STD-607-A. Could anyone offer some guidance?
Also, is there any testing that can be performed to determine if the additional grounding is needed? Resistance or voltage tests?

 

[dereckbc]

Mickey I wil ltry to help you out here as I know a bit about the standard because I had a little input to IEEE 1100 and know the floks at BICSI who wrote the J standard.

I assume you know anything in the BICSI standard is not required by the NEC. It is supplemental grounding which is allowed, but not required.

If the equipment was powered by a 24 or 48 volt DC plant, I would say yes it would be necessary, especially if it were configured as an Isolated Ground Plane. I know it is not because that is out of the scope of BICSI. However I suspect all of it is powered by commercial AC? I also suspect much of the equipment is passive that uses no power like equipment racks with cross-connect panels and RJ-45 patch panels.

Here is where I am going; in the equipment racks with AC power, each of those racks have at least one EGC installed with the circuit conductors. In many cases the equipment racks have more than 1 AC circuit which means more than 1 EGC. In addition the racks many times are in a line up and bolted together, so you have a huge amount of EGC's all forming one large surface ground. Adding a supplemental ground is a waist of time and money as it does absolutely nothing except make the contractor installing it money.

Now for the equipment line ups that only have passive equipment, the supplemental grounds do serve a purpose. It satisfies the NEC requirement that all equipment containing electrical wires must be bonded of sufficient size to operate any OCPD likely to be imposed on it. For example a installers drill motor cord getting pinched. Having it bonded would provide a fault clearing path. However do not let anyone bambozzle you into thinking it has anything to do with noise because they are surely mistaken. The only way to do that is to electrically isolate the equipment racks from the building structure, and then use a Single Point Isolated Ground Plane which includes the power source.

Hope that helps. Fell free to ask anymore question you might have.

Edit I got a follow up questions. Where are the building entrance cable protectors for Telco, CATV, optics, etc??

 

[mikeybmdb32]

All of the protectors are located in the entrance facility.

Also, the racks contain both patch panels and servers, but I'm not sure of the nature of the power source; will have to investigate.

I believe we are meeting all of the requirements of the NEC, but the job spec also calls for satisfying the ANSI requirement. Just so I have this straight ... it comes down to whether or not we're feeding the equipment with DC or AC power?

 

[dereckbc]

Also, the racks contain both patch panels and servers, but I'm not sure of the nature of the power source; will have to investigate.

Well I would bet they are AC power. Real easy to determine just by looking. If that is the case adding a supplemental ground will do nothing because the racks are already grounded by the EGC.