Patient Care Redundant Ground

[georgeswe]

I would first like to thank everyone that may post on this thread...

We have been doing more and more of Doctor and Patient care facilities in the past few years. I have some questions about why and if we are installing the redundant ground correctly.

Recently we have had a few new out of state emplyees that have raised some questions of why we are installing a redundant ground MC cable and that they have never used such a thing when they worked on similar installations. (this is something that I look at closely but dont put too much weight to as to they could have been doing it wrong)

The 2 NEC sections that I am looking at is 517.113 (A) & (B) and 250.118. Also, I am utilizing a NEC 2005 hard cover handbook which has more info then a standard NEC code book.

We are currently intalling EMT brach circuits runs to Junction boxes then roping the walls in any patient care area i.e. examination rooms, rest rooms, waiting areas, therapy rooms with a 12-2, 12-3 green MC cable it has #12 conductors #12 grounded conductor #12 Equipment grounding conductor (green) and a aluminum wire which looks to be smaller than #14 as a redundant ground. This aluminum that is running thru the cable we take and turn back on itself at least 3 turns on the outside of the MC, per instruction from the manufaturer.

So now starting at

517.3 (A) Wiring Methods All branch circuits serving patient care areas shall be provided a with a ground path for fault current by the installation in a metal raceway system, or a cable having a metallic cable armor, or sheith assembly shall itself quallify as an equipment grounding return path in accordance with 250.118

(B) Insulated Equipment Grounding Conductor the ground 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 250.122 and installed in a metal raceway or as part of listed cables having a metallic armor or sheith assembly with the branch circuit conductors supplying these receptacles or fixed equipment.

In a standard code book there is no use of the word REDUNDANT. So a person may think that a standard MC having a green equipment conductor in both instance (A) and (B) would be sufficent. But looking at the wording under the header of 517.13 it states "Wiring in patient care areas shall comply with 517.13(A) AND 517.13(B)." The "AND" being the key word there. That is where it should be understood the redudency comes from.

So under the (A) section if you were to comply with all 250.118 (5) a-d you could infact utilize a MC cable. I however am not sure if the MC connectors are listed for grounding and most of the installations we do the MC runs are longer than 6ft. so this blows that exception out of the water for us.

I would like some input to make sure we are doing correct install or if anyone is doing anthing diffrent that I have not looked at. I have never had an inspector call me on any portion of our istallation in Patient care areas. (bummer is that some have asked why we were installing the green MC.)

 

[Buck Parrish]

We use it in patient care areas. Not the waiting rooms, halls, etc...

 

[augie47]

sounds as if you have a good handle on the subject.
If you are using MC cable as health-care it does have the alumimum ground to allow such use and the connectors need to be ones designed to be used with MCap cable.
There is also an AC cable, often referred to to HCF, that is permissible.
One slight correction. The Exception in 517.13(B) for fixtures does not remove the requiremt for the outer sheath of cable to be a eq. grounding means, so standard MC is not permissible. Flex (less than 6ft) or AC would be

You might want to read this thread: http://forums.mikeholt.com/showthread.php?t=107495&highlight=517.13&page=2 as well as "search" the Forums under 517.13 for more info.

 

[djd]

djd

djd

We came into a situation with the green MC and the argument was what to do with the Al ground, some guys terminated it with the ground others terminated it with its own ground screw, I felt that was ok but time consuming, but ultimatley the best way since the al was no.12

 

[raider1]

We came into a situation with the green MC and the argument was what to do with the Al ground, some guys terminated it with the ground others terminated it with its own ground screw, I felt that was ok but time consuming, but ultimatley the best way since the al was no.12

The aluminum bond strip in the AC or MCAP cable does not need to be terminated at all. All you need to do is cut it off where you strip off the cable sheath and install the MCAP or AC connector.

Chris

 

[KevinVost]

When you get to the 2008 NEC, read the exception to 517.13 (B). A change in the wording for the exception to lighting above 7' 6" reads that you are still required to have the raceway comply with 517.13 (A) [as augie47 mentioned]. So if you are under the 2008 code the exception for lighting means you don't need an insulated ground but you do need the raceway to comply with 250.118.