MC cable in healthcare

Status
Not open for further replies.
M

mecojax01

Member
Are there any restrictions on the use of standard Type MC cable (not HCF) for lighting circuits on normal power in healthcare facilities?
 
As long as these lighting circuits are not serving Patient Care Areas (see 517.13) MC is fine.

Roger
 
Tshea, look again, it excludes an "Insulated Conductor" not a raceway or cable sheath from meeting the requirement of being a ground fault return path, and regular MC does not meet this requirement.



Exception No. 2: Luminaires (light fixtures) more than 2.3 m (7 1/ 2 ft) above the floor and switches located outside of the patient vicinity shall not be required to be grounded by an insulated equipment grounding conductor.
Click to expand...

Roger
 
shall not be required to be grounded by an insulated equipment grounding conductor

Roger look again. That doesn't say that you can't use MC, you can, and you can also use AC if it is otherwise permitted.

-Hal
 
Hal, sorry but you can't, you have to read the article for the requirement, the exception is just that, an exception.

BTW, AC is not being questioned.

517.13(A) mandates the metallic raceway or cable be recognized by 250.118

17.13 Grounding of Receptacles and Fixed Electric Equipment in Patient Care Areas

Wiring in patient care areas shall comply with 517.13(A) and 517.13(B).

(A) Wiring Methods
All branch circuits serving patient care areas shall be provided with a ground path for fault current by installation in a metal raceway system, or a cable having a metallic armor or sheath assembly. The metal raceway system, or metallic cable armor, or sheath assembly shall itself qualify as an equipment grounding return path in accordance with 250.118.
Click to expand...


Now, looking at (B), this requires an "insulated copper conductor" as a redundant ground fault path to the metallic raceway or sheath.

(B) Insulated Equipment Grounding Conductor
The grounding terminals of all receptacles and all non?current-carrying conductive surfaces of fixed electric equipment likely to become energized that are subject to personal contact, operating at over 100 volts, shall be grounded by an insulated copper conductor. The equipment grounding conductor shall be sized in accordance with Table 250.122 and installed in metal raceways or as a part of listed cables having a metallic armor or sheath assembly with the branch-circuit conductors supplying these receptacles or fixed equipment.
Click to expand...

Exception No 2: allows for excluding the insulated conductor required in 517.13(B), but does dot exclude any other part of article 517.13, so regular MC is not allowed in Patient Care Areas even above 7.5'

Roger
 
Good afternoon Pierre. That is why regular MC can not be used for this application. :)

Roger
 
Exception No 2: allows for excluding the insulated conductor required in 517.13(B), but does dot exclude any other part of article 517.13, so regular MC is not allowed in Patient Care Areas even above 7.5'

Roger
Click to expand...

Thanks for posting the explanation. At first glance it seemed as if you were saying that not requiring it meant that you can not use it.

Doesn't this seem a little strange. So you can use AC cable without an insulated EGC but not a MC cable with an insulated EGC.
 
Trevor, the explanation of why the metallic raceway or sheath takes priority over a copper conductor can be found in Annex A of NFPA 99, which is at home right now.

I will try to post it this weekend.

Roger
 
roger said:
Trevor, the explanation of why the metallic raceway or sheath takes priority over a copper conductor can be found in Annex A of NFPA 99, which is at home right now.

I will try to post it this weekend.

Roger
Click to expand...


Thanks Roger. :D
 
Roger

you have made me read this 10 times, and I agree with you, why does the NEC feel this is a concern with light fixtures or switches that patients will not be in contact with? and is a AC ground better than a MC ground?
 
MPD, I don't have an answer as to why this is a concern for fixtures outside the Patient Vicinity.

As far as the AC ground being better, here is an excerpt from Annex A 4.3.3.1.3 of NFPA 99 that I told Trevor I'd try to post this weekend.

The performance of the grounding system is made effective through the existence of the green grounding wire, the metal raceway, and all of the other building metal. Measurements have shown that it is the metal raceway and building steel that provide most of the effective ground path of less than 10 milliohms at the receptacle, including plug to receptacle impedance. The green grounding wire becomes a backup, not primary grounding path performer.
Click to expand...

The fixtures are allowed to be bonded without the redundancy required for the receptacles, but it must be done by the primary EGC, which is the metallic raceway or sheath.

Roger
 
Thanks for posting that Roger. I actually looked at NFPA 99 after you suggested it and was wondering if the exact thing you posted was what you were mentioning yesterday.

I guess that from the perspective of many on this forum, the insulated EGC is always better than the cable armor or metallic conduit. It seems that according to NFPA 99 the opposite is true.
 
Status
Not open for further replies.
Top