Telecommunication Main Bonding Conductor

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vinchenzo

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If the Telecommunications Main Bonding Conductor is installed in EMT, the EMT needs to be bonded at both ends does it not? I have an engineer telling me that it doesn't.

The EMT is connected to the enclosure for the Main Service Disconnect but ends short of the TMGB

It's my understanding that the Telecommunications Main Bonding Conductor is essentially an extension of the Grounding Electrode System of which this engineer claims it is not. In his words Article 250-64 E "relates specifically to ?Grounding Electrode Conductors? which only occur at the service entrance" thereby imlplying that the requirement to bond both ends of the conduit doesn't apply in this case.
 
vinchenzo said:
If the Telecommunications Main Bonding Conductor is installed in EMT, the EMT needs to be bonded at both ends does it not? I have an engineer telling me that it doesn't.

The EMT is connected to the enclosure for the Main Service Disconnect but ends short of the TMGB

It's my understanding that the Telecommunications Main Bonding Conductor is essentially an extension of the Grounding Electrode System of which this engineer claims it is not. In his words Article 250-64 E "relates specifically to ?Grounding Electrode Conductors? which only occur at the service entrance" thereby imlplying that the requirement to bond both ends of the conduit doesn't apply in this case.
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I personally don't believe the NEC says the GEC occurs only at the service.
The defintion of Grounding Electrode Conductor is "A conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system."

It does specifically call out any system. It just says system. To me this includes telecom...
 
vinchenzo said:
I agree. As far as not grounding both ends of the conduit though...that just defies common sense in my opinion
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Yeah IMO, since there doesn't seem to be a difference betweens systems af far as EGC is concerned than 250.64 (e) applies.

250.64 (e) " Enclosures for Grounding Electrode Conductors. Ferrous metal enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting."

Out of curiousity what exactly do you mean grounding at both ends? Is the conduit not one (electrically continous) piece?
 
Yes, it is, but it must be bonded (usually through a bond bushing) on the end that is 'floating' before being connected to the TMGB as well as the end that is electrically conected (in this case - to the service enclosure).

The reason for this is hard for me to explain but it has to do with overheating of the conduit in the case of a ground fault.

Maybe someone with engineering experience can give you a technical explaination to help you understand it better.
 
well, your going to have to tell us what kind of voltage your are dealing with on the equipment.

Is the telecom gear AC driven or DC drivin.

If it is DC,, it is a totally different ball game. Telecom gear follow the rules of "PANI" on a DC platform.

there are reasons grounding is different with telecom gear, if you were able to get away with emt as your raceway to path the ground, it would be pysically connected to the metal chassis of of an infrustructure that is subject to the problems with AC. This is why Telecom gear has its own grounding path and isolated ground bar. Your TMGB is a new one to me but people can stenciel thier bars with whatever they feel like.

Typically you would never under any circumstance run a telecom ground inside EMT ***if it were a ground for DC***. The reasons are obvious to include unistrut clamps,, clamp backs and other metal objects that create chokes.
let us know,
 
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vinchenzo said:
Yes, it is, but it must be bonded (usually through a bond bushing) on the end that is 'floating' before being connected to the TMGB as well as the end that is electrically conected (in this case - to the service enclosure).

The reason for this is hard for me to explain but it has to do with overheating of the conduit in the case of a ground fault.

Maybe someone with engineering experience can give you a technical explaination to help you understand it better.
Click to expand...

Well I don't see 250.64 (e) requiring that.
 
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