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Conduit system under slabs in patient care areas

Posted By Eugene Morgan, Tuesday, July 01, 2008
Updated: Monday, February 04, 2013

Question

This question is about patient care areas, and I am referencing Sections 517.13(A) and (B) and 517.19(D). We are installing a conduit system under the slab and our branch circuits from the panel in the area are in PVC-coated galvanized rigid conduit to patient care devices. It is our understanding that the feeder from the MDP to this panel can be in PVC (rigid polyvinyl chloride conduit type PVC) conduit. We are installing a properly sized equipment-grounding conductor per Table 250.122 in the PVC conduit. Please advise. — R. V.

Answer

NEC Sections 517.13(A) and (B) require the installation of branch circuits to receptacles and fixed equipment in a patient care area to have two separate and different grounding paths. One grounding path is a metal raceway system, or a cable having a metallic armor or sheath assembly that "shall itself qualify as an equipment grounding conductor in accordance with 250.118.” The other grounding path is, of course, the insulated copper grounding conductor.

The intent of Panel 15 to require two separate and different grounding paths for branch circuits was emphasized during consideration of proposals for the 2008 National Electrical Code. There were two proposals that would allow a branch circuit to be run in a nonmetallic raceway with two equipment grounding conductors. Both proposals were rejected by a unanimous vote of the panel.

Section 517.19 gives additional requirements for critical care areas. Section 517.19(D) details grounding requirements "Where a grounded electrical distribution system is used and metal feeder raceway or Type MC or MI cable that qualifies as an equipment grounding conductor in accordance with 250.118 is installed…” This does not require the use of metal raceways, Type MC or MI cables for feeders to panelboards in other areas.

Section 517.12 allows the use of wiring methods in chapters 1 through 4 of the Code to be used, "Except as modified in this article.” However, one must always be aware of the project design specifications, and of locally adopted codes that may affect the wiring methods that can be used. — Eugene Morgan, CMP-15

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Tags:  Focus on the Code  July-August 2008 

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