Common electrode system and detached garage

[hurk27]

I'm just wondering about these two requirements in the NEC and if they are a requirement for even bonding the GC at a detach garage? and if not what were they put into the code for?

250.94 Bonding for Other Systems.
An accessible means external to enclosures for connecting intersystem bonding and grounding conductors shall be provided at the service equipment and at the disconnecting means for any additional buildings or structures by at least one of the following means:

250.50 Grounding Electrode System.
If available on the premises at each building or structure served , each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used.

 

[rick5280]

Re: Common electrode system and detached garage

Hurk, I'm not sure what you are asking.

The 1st quoted section is for the "other" utilities, like cable tv, telephone etc to attach their grounding conductor to, in order to have all systems grounded to the same grounding electrode system.

An example of this has been done for years, where the phone company attached a clamp that looks alot like a hose clamp, to the mast or riser of the service, to which they attach their wire.

There rule spells out what is acceptable to attach to. If, for some reason you cannot apply them, then you can always attach a 6" piece of ground wire (bare copper) sticking out, which they can connect to. I ran into this situation where the contractor installed a remote meter, fed underground to the home, up an exteerior wall in pvc, turned in using a short elbow, also pvc, which attached to an interior panel. The grounding electrode system was a "ufer" ground, so no point along that system was accessible from the outside of the home, for the "other" utilities. I required a piece of bare copper, connected to the equipment grounding buss in the panel, which was stubbed out through the wall, leaving about 6" available to the "other" utility to connect to.

The 2nd quoted section is the basic rule for installing a grounding electrode, telling where it is required.

Rick Miell