I mean the EGC of the AHU if bonded to chilled water pipes and acts as GEC, i know the EGC of water pipes shall be extended from the electrical source e.g. MCC panel, but i am trying to understand the exception and use it.I don't think so. Are you dealing with an equipment grounding conductor or grounding electrode conductor? 250.121 is about the equipment grounding conductor being used as a grounding electrode conductor.
GEC per NEC definition is "a conductor used to connect the system grounded conductor" (neutral) "or the equipment" (if supplemental grounding) "to a grounding electrode or to a point on the grounding electrode system."Hi Dennis,
I thought GEC could be any location as long as it bonds different electrodes not only at service.
Per NEC definition of EGC: "the conductive path(s) that provides a ground-fault current path and connects normally non-current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both."How do you call the supplemental bonding wire from AHU body to nearest grounding bar?
I dont think your chiller pipe would fit definition of GEC, metal water pipes must be bonded to to the GE (Gounding Electrode) eventually, but it's not acting as an EGC or a GEC, it simply is an attempt to limit objectionable current from presenting on the metal part. Metal conduit can serve as an EGC if installed in a manner to allow continuous bond, but not the GEC. The metal water pipes can be used as the GE under specific criteria none of which you have mentioned. Thus your attempt to use the exception in 250.121 for this seems to be not applicable.I mean the EGC of the AHU if bonded to chilled water pipes and acts as GEC, i know the EGC of water pipes shall be extended from the electrical source e.g. MCC panel, but i am trying to understand the exception and use it.
Due to ground fault or another reason?it simply is an attempt to limit objectionable current from presenting on the metal part.