hospital grade mc

[teufelhounden91]

hospital grade mc

Did some digging in the NEC.

Need to go back and specify both areas Im talking about are dentist patient care areas. Not patient bed locations or critical care areas.

517.13(A) says branch circuits shall be provided with an effective ground fault current path...a cable having a metallic armor or sheath. the metal cable armor or sheath shall itself qualify as an EGC in concordance with 250.118. Doesn't say it has to be HGMC or say it has to have a second redundant equipment ground for the entire branch ckt. Just says it must have AN effective ground fault path for the branch ckt.

250.118(10) says MC is an effective ground fault path of it contains and insulated or uninsulated egc. (Doesn't say both are required) Most normal mc qualifies here in my opinion. If it has an insulated or uninsulated EGC inside the sheath/armor may be used as an EGC. (For redundancy I suppose)

250.122(A) says if cable armor or sheath IS USED as the EGC (as achieved by 250.118 it is considered an effective ground fault other per 250.4(A)(5) or (B)(4)

Lastly 330.108 lists MC sheath as an approved EGC as long as it passes 250.118(10)


The takeaway...in patient care areas regular mc can be used. It doesn't say HGMC is required in such areas in 517.13. Also all of these articles point to MC sheath/armor being acceptable as an EGC so it seems you can change over to regular mc in a hallway as long as you keep the branch ckt having AN effective ground fault path...not two.

Even 517.19 mentions while you must use HG plugs, MC sheath/armor is allowed to be used as an EGC.

So why did we say EMT was ok in the halls but MC was not?


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[roger]

Did some digging in the NEC.

Need to go back and specify both areas Im talking about are dentist patient care areas. Not patient bed locations or critical care areas.

Doesn't matter, see 517.10(A), the wiring methods of 517.13 must be used.

Ground fault current path...a cable having a metallic armor or sheath. the metal cable armor or sheath shall itself qualify as an EGC in concordance with 250.118. Doesn't say it has to be HGMC

Correct, it can be any of the metallic raceways recognized as EGC's.

or say it has to have a second redundant equipment ground for the entire branch ckt. Just says it must have AN effective ground fault path for the branch ckt.

Correct again, the requirements of 517 are stand alone.

250.118(10) says MC is an effective ground fault path of it contains and insulated or uninsulated egc.

Yes it does but only specific types of MC

(Doesn't say both are required)

517.13 does.

Most normal mc qualifies here in my opinion.

No it doesn't

If it has an insulated or uninsulated EGC inside the sheath/armor may be used as an EGC.

This where things become a little muddy, MCAP that has both an insulated conductor and a bare shunt wire would qualify but plane jane MC does not.

250.122(A) says if cable armor or sheath IS USED as the EGC (as achieved by 250.118 it is considered an effective ground fault other per 250.4(A)(5) or (B)(4)

Yes it does but once again, it doesn't cover all of the requirements of 517.13

Lastly 330.108 lists MC sheath as an approved EGC as long as it passes 250.118(10)

And unless you are using a MCAP type of MC it does not recognized in 250.118

The takeaway...in patient care areas regular mc can be used.

Nope, it can not.

It doesn't say HGMC is required in such areas in 517.13. Also all of these articles point to MC sheath/armor being acceptable as an EGC

No, this is a common misconception, you have to do some study on the different types of MC.

so it seems you can change over to regular mc in a hallway as long as you keep the branch ckt having AN effective ground fault path...not two.

Short answer here, Nope.

Even 517.19 mentions while you must use HG plugs, MC sheath/armor is allowed to be used as an EGC.

517.18 and 19 are separate issues and does not change 517.13

So why did we say EMT was ok in the halls but MC was not?

See above and take the time to read THIS ARTICLE

Roger

 

[teufelhounden91]

hospital grade mc

Great article but what confuses me is the uninsulated bonding wire. Is that just to bond the sheathing? I can't find any refer ce to this bonding wire, what to do with it, etc.

They specifically talk about an insulated equipment ground but for instance outside of a patient care area it says receptacles do not have to be grounded by the insulated equipment grounding conductor. What??


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[roger]

Great article but what confuses me is the uninsulated bonding wire. Is that just to bond the sheathing?

Yes, that is exactly what it is for, it shunts the coils of the cable sheath.

I can't find any refer ce to this bonding wire, what to do with it, etc.

You simply cut it off at the connector although some people will fold it back under the connector.

They specifically talk about an insulated equipment ground but for instance outside of a patient care area it says receptacles do not have to be grounded by the insulated equipment grounding conductor. What??

See article 90.3, Chapter 5 modifies earlier articles and has it's own rules.

Roger


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[kwired]

Great article but what confuses me is the uninsulated bonding wire. Is that just to bond the sheathing? I can't find any refer ce to this bonding wire, what to do with it, etc.

They specifically talk about an insulated equipment ground but for instance outside of a patient care area it says receptacles do not have to be grounded by the insulated equipment grounding conductor. What??


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Roger said it - it shunts the coils of the cable sheath. It is outside any nylon fillers commonly found wrapped around the conductors and in intimate contact with the cable sheath. Without it the resistance of the sheath potentially increases as current has to follow a spiral type conductor, though it does have ability to jump from turn to turn nothing assures a good low resistance short cut between turns and this is why they add said bonding wire. Standard MC cables are not rated for equipment grounding and contain an EGC. More recent MCAP or other equivalents are rated for use as an EGC, add a green conductor inside and they meet 517.13 requirements.