Hospital Grade MC (Critical Branch Circuits)

[Pasquale1966]

We recently completed an in-wall inspection for a project where MC-HCF cable was installed for circuits associated with the essential electrical system. The installation passed the in-wall inspection.

Several weeks later, the electrical inspector informed us that he had reversed his decision, citing the requirements of 2020 NFPA 70 (NEC) Article 517.31(C)(3) – Mechanical Protection of the Essential Electrical System, which states that wiring of the life safety and critical branches shall be mechanically protected by raceways.

Based on this interpretation, the inspector indicated that MC-HCF cable would not be permitted for the installation in question.

However, the branch circuits serve patient care spaces, and the installation was performed in accordance with NEC 517.13(A) and 517.13(B), which specifically address wiring methods and grounding requirements for patient care areas.

Therefore, clarification is requested on the following point:

Is Type MC cable listed for healthcare facilities (MC-HCF or MC-AP-HCF) permitted as a wiring method for a Critical Branch circuit serving a patient care space when installed in accordance with NEC 517.13(A) and 517.13(B)?

Any clarification regarding the interaction between NEC 517.31(C)(3) and NEC 517.13(A) and (B) as it applies to MC-HCF cable installations would be greatly appreciated.

 

[roger]

If you do not meet one of the 6 conditions of 517.31(C)(3) then you would need a non-flexible metallic wiring method. This has been the case for many code cycles so the inspector is correct.

 

[Pasquale1966]

Grey area since flex metallic is acceptable and I realize that MC-HCF. is a cable assembly but it’s also flexible. Also the submittals state it’s approved for use in article 517. It wouldn’t have been a big deal if it was caught on the rough wall inspection not after walls lead lined Sheetrock and painted. Ty

 

[roger]

The wording could be better but it's not a grey area, 517.31(C)(3)(3) states

1. Listed flexible metal raceways and listed metal sheathed cable assemblies in any of the following:
   1. Where used in listed prefabricated medical headwalls
   2. In listed office furnishings
   3. Where fished into existing walls or ceilings, not otherwise accessible and not subject to physical damage
   4. Where necessary for flexible connection to equipment
   5. For equipment that requires a flexible connection due to movement, vibration, or operation
   6. Luminaires installed in ceiling structures

Those are the conditions where flexible wiring methods can be used. For Normal Branch wiring flexible HG wiring methods are fine