Change Summary

• Revisions to 517.16 were divided into two subdivisions for prohibition of isolated ground receptacles inside a patient care vicinity and allowance of isolated ground receptacles installed outside a patient care vicinity.

Expert Analysis

Isolated ground receptacles are permitted to have their grounding terminal purposely insulated from the receptacle mounting means for the reduction of electrical noise (electromagnetic interference) on the grounding circuit [see 250.146(D)]. The isolated ground receptacle grounding terminal is to be connected to an insulated equipment grounding conductor run with the circuit conductors. This isolated ground equipment grounding conductor is permitted to pass through one or more panelboards without a connection to the panelboard grounding terminal bar as well as pass through boxes, wireways, or other enclosures without being connected to such enclosures. The requirements of 406.3(D) calls for isolated ground receptacles to be identified by an orange triangle located on the face of the receptacle.

Changes were made to 517.16 for the 2014 NEC to make it clear that isolated ground receptacles were not permitted to be installed within a patient care vicinity of a health care facility. The concern is the assurance of the equipment grounding conductor redundancy requirement of 517.13(A) and (B) for wiring methods at a patient care vicinity. This redundant grounding provision in a patient care space requires two equipment grounding paths to always ensure one is functioning at all times. This redundant grounding provision cannot and should not be accomplished with an isolated ground receptacle equipment grounding conductor as this conductor should not be connected to the metal enclosure. Therefore, such a connection would negate the isolated grounding of an isolated ground receptacle established by 250.146(D).

Apparently, confusion still existed regarding the number of equipment grounding conductors that must be installed for isolated ground receptacles installed outside the patient care vicinity. To meet the requirements of 517.13(A) and (B) for redundant grounding provisions, it is not uncommon to find a wiring method of electrical metallic tubing (EMT) with a separate 12 AWG copper insulated equipment grounding conductor in spaces outside of a patient care vicinity. The problem comes in when this redundant grounding equipment grounding conductor is incorrectly utilized to serve double-duty as the isolated ground equipment grounding conductor where isolated ground receptacles are installed outside of a patient care vicinity. This type of installation is in violation of 250.146(D) and 517.13.

The new provisions of 517.16(B) will clearly identify the requirement of three grounding paths when isolated ground receptacles are required [metal raceway or cable armor equipment grounding path, green wire type equipment grounding conductor for the 517.13 redundant grounding requirements, and a separate isolated ground equipment grounding conductor to comply with 250.146(D)]. The new provisions of 517.16(B)(1) will demand a color designation of green with one of more yellow stripes for the isolated ground equipment grounding conductor. This color designation was chosen to provide a color pattern typically used as an industry standard for isolated ground equipment grounding conductors.

Leviton offers Isolated Ground Receptacles in Industrial Grade and Hospital Grade with standard Duplex and Decora® styling. Offered with back and side wiring terminals as well as with 6” wire leads. Modular Lev-Lock® wiring system also available. Several colors available.