NEC 517.13 Existing Construction

[solarEI]

We have a renovation project in a doctor's office. The scope of work is to add an additional receptacle to the existing exam rooms.

The electrical contractor used healthcare rated MC cable (HCF-MC) for the new devices but the existing installation has regular MC cable (not health care rated). Both the existing and new MC cable have an insulated equipment grounding conductor so i don't think there is an issue with NEC 517.13(B) since this is continuous back to the panel. However, the existing MC cable armor is not listed as an equipment grounding conductor so the electrical contractor connected the new MC cable armor to the existing MC cable equipment grounding conductor. While this would provide an effective ground-fault current path per NEC 517.13(A) I don't think it complies with the intent of a redundant ground path. Is this a code violation?

Can the contractor connect the new MC cable armor to a new (separate) equipment grounding conductor back to the panel ran outside of the existing MC cable? They are trying not to replace all the existing wiring with new HCF-MC.

Thanks!

 

[LIM]

The simple answer is in order to bring the existing non HCF MC cable up to code, it would have to be replaced with a cable/raceway that has a sheath/conduit complying with 250.118.

 

[roger]

The simple answer is in order to bring the existing non HCF MC cable up to code, it would have to be replaced with a cable/raceway that has a sheath/conduit complying with 250.118.

Agreed.

Roger

 

[solarEI]

So everything I stated above is a code violation? Do you have code references? It will cost a lot of money replace all the existing wiring.

 

[roger]

So everything I stated above is a code violation? Do you have code references? It will cost a lot of money replace all the existing wiring.

You already stated it, 517.13(A).

Connecting an acceptable EGC to the sheath of plain jane MC does not make the sheath a continuous EGC itself. Unless the sheath is listed and identified as an EGC per 250.118(10) b & c you can not meet the requirement of 517.13(A).

Roger

 

[solarEI]

You already stated it, 517.13(A).

Connecting an acceptable EGC to the sheath of plain jane MC does not make the sheath a continuous EGC itself. Unless the sheath is listed and identified as an EGC per 250.118(10) b & c you can not meet the requirement of 517.13(A).

Roger

I think you are misunderstanding the situation. They did not connect anything to the sheath of the regular MC, the connected the sheath of the new HCF-MC to the green insulated ground conductor of the existing MC. So the new HCF-MC has both the insulated equipment grounding conductor and the metal sheath connected to the existing MC insulated grounding conductor.

Thanks!

 

[GoldDigger]

It comes down, IMO, to the question of whether extending a circuit by properly connecting the wire and sheath of a compliant MC to the not-currently compliant single EGC of older MC (which may have been allowed at the time it was installed) is acceptable or whether the existing installation needs to be replaced.

It may turn out that the cheapest way to comply is to install the new outlet (receptacle?) as a home run back to a panel.

 

[solarEI]

It comes down, IMO, to the question of whether extending a circuit by properly connecting the wire and sheath of a compliant MC to the not-currently compliant single EGC of older MC (which may have been allowed at the time it was installed) is acceptable or whether the existing installation needs to be replaced.

That's what I'm trying to determine. So far I haven't found any codes that point to this being a violation.

It's not directly applicable but 2012 NFPA 99 6.3.2.2.2.3 - Separate Grounding Conductor states "When existing construction does not have a separate grounding conductor, the continued use of the system shall be permitted, provided that it meets the performance requirements in 6.3.3.1." (ground system performance testing). It seems logical that if the existing construction does not have a separate grounding conductor and you are permitted to use the metal conduit/cable sheath for an effective ground fault current path (assuming it meets the performance requirements) why wouldn't the opposite be true and it be permitted to use the existing separate ground conductor as the effective ground fault current path of the new HCF-MC sheath). It appears the intent of this code section is just to make sure there is an appropriate effective ground fault current path.

 

[roger]

I think you are misunderstanding the situation. They did not connect anything to the sheath of the regular MC, the connected the sheath of the new HCF-MC to the green insulated ground conductor of the existing MC. So the new HCF-MC has both the insulated equipment grounding conductor and the metal sheath connected to the existing MC insulated grounding conductor.

Thanks!

Whether or not I'm misunderstanding the problem or your proposed solution is not the real problem, your problem (or the contractors) is that 517.13(A) is not met unless the existing installation is left alone (2012 NFPA 99 6.3.2.2.2.3) and given the fact that you are upgrading (IMO) takes that argument out of the equation, of course the AHJ would be the real judge and jury here.

Roger

 

[JFletcher]

We have a renovation project in a doctor's office. The scope of work is to add an additional receptacle to the existing exam rooms.

The electrical contractor used healthcare rated MC cable (HCF-MC) for the new devices but the existing installation has regular MC cable (not health care rated). Both the existing and new MC cable have an insulated equipment grounding conductor so i don't think there is an issue with NEC 517.13(B) since this is continuous back to the panel. However, the existing MC cable armor is not listed as an equipment grounding conductor so the electrical contractor connected the new MC cable armor to the existing MC cable equipment grounding conductor. While this would provide an effective ground-fault current path per NEC 517.13(A) I don't think it complies with the intent of a redundant ground path. Is this a code violation?

Can the contractor connect the new MC cable armor to a new (separate) equipment grounding conductor back to the panel ran outside of the existing MC cable? They are trying not to replace all the existing wiring with new HCF-MC.

Thanks!

Would have run HC MC from panel to new receps, left the existing cable alone. Existing install can probably stay old MC, I dont see any AHJ requiring you gut it all to upgrade it just by adding a receptacle to each room.

You cannot connect the new HC MC to old MC and use the latter's EGC to ground both the new cable's cover and EGC; no redundant ground. and yes it's a code violation.

As to your second question, I dunno, tho if he can get a new EGC from exam rooms to panel, he could get HC MC there too.