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Thread: 517.13 (A) Can I beat a dead horse?

  1. #1
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    517.13 (A) Can I beat a dead horse?

    So I have a question about the requirements of 517.13(A). Yes, I read it. Yes, I own the Mike Holt illustrated guide to 500-820 and read that.

    Now, I understand that all wiring in or serving patient care areas must comply with 517.13(A). But what I have a question about is this, someone is telling me that I cannot change from HFC to MC between the patient care area and the panel. For instance, I would think it would be fine to run regular mc from a panel to a box in a nearby space that is not designated as a patient care space and then break out of that box with HFC to actually serve the patient care areas. I really don't see how this is a problem. They are telling me that I have to run HFC all the way back to the panel. To me, this just doesn't make sense because that redundant ground that is the jacket, is terminating inside a connector in a box that will be grounded to the insulated grounding conductor and will be a better ground to the panel than the jacket ground having to go through snap in connectors.

    I am having a really hard time believing that the intent of the redundant ground is to actually increase the fault current capability of the circuit as this person is alleging. I think it more likely that in the unlikely case a wall and the mc inside it become damaged and accessible, the intent is to ensure that if the hot shorts to the jacket, it will ground out and trip the breaker or at the very least, keep the jacket from becoming a hot conductor. Both of which would still be the case if I switch to regular mc outside of the patient care area.

  2. #2
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    The redundant grounded system will need to originate at the branch circuit panel.

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    Think of it as parallel EGC's required. With regular MC, the jacket is not a qualifying EGC.


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    Quote Originally Posted by david View Post
    The redundant grounded system will need to originate at the branch circuit panel.
    Why? It doesn't make any sense to me. Really. I want someone to prove to me that this is the case. I really can't see why it needs to be HFC all the way to the panel. For starters, the jacket acting as an egc terminates in every box, so if you had a box between the panel and the patient area, the jacket egc is going to be electrically the same as the insulated ground wire. I'm asking for an honest to god explanation of this. Because if it "just is" the way you say, the only reason in my mind for it would be to drive up sales of HFC, and I'm not one to do things just because.

  5. #5
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    Quote Originally Posted by Smart $ View Post
    Think of it as parallel EGC's required. With regular MC, the jacket is not a qualifying EGC.


    Welcome.
    Really? Parallel egc's all the way to the panel? Can you provide a single instance where parallel ground conductors is a required thing in any other section of the code? I'm not aware of it. I totally get that doctors and hospitals are worried that the jacket of the conductors may become energized, but if you have a box anywhere between the panel and the end of the line, that jacket is bonded to the box, and to the insulated egc. Adding another conductor won't improve the ability of the circuit to do it's job or impede the grounding of the jacket at the patient care area. I'm not trying to say I don't want to use hfc where the code applies, but I really don't see how it improves safety by any factor to use hfc outside of the patient care areas, nor do I see where the code requires it. If that were the case, wouldn't we just get rid of all mc and have a nema standard requiring all metallic jacket to be approved egc?

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    Quote Originally Posted by OkieElectrician View Post
    Really? Parallel egc's all the way to the panel? Can you provide a single instance where parallel ground conductors is a required thing in any other section of the code?
    I"m not sure i understand your point. i also don:t understand what difference it would make

    Quote Originally Posted by OkieElectrician View Post
    So I have a question about the requirements of 517.13(A).
    are you asking if it is required or are you wanting to make the point you feel it is not necessary

  7. #7
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    The jacket EGC connects to every box along the way. True.
    Standard wire EGCs bond to the boxes along the way (if there is a splice or junction in the box). True.
    But an isolated ground EGC does not bond to boxes along the way. That, in addition to being electrically separate from the jacket EGC between boxes, makes the isolated ground unique.

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    Quote Originally Posted by OkieElectrician View Post
    Adding another conductor won't improve the ability of the circuit to do it's job or impede the grounding of the jacket at the patient care area.
    Well actually providing a parallel conductor would lower the impedance of the fault clearing path but more importantly, it provides redundancy in case the continuity of the wire conductor was lost.
    Quote Originally Posted by OkieElectrician View Post
    I'm not trying to say I don't want to use hfc where the code applies, but I really don't see how it improves safety by any factor to use hfc outside of the patient care areas, nor do I see where the code requires it.
    You wouldn't be required to use it for circuits completely outside of the patient care areas but as already stated, if it serves the patent care area it has to start at the branch circuit panel. Unless the sheath is considered and EGC per 250.118 you don't have an EGC and without the EGC making it back to the source it won't clear a fault. Note, the metallic conduit or recognized metallic sheath is the primary EGC in this case, not the wire conductor.

    From NFPA 99
    NFPA 99 A 6.3.3.1.3


    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 grounding path of less than 10 milliohms at the receptacle, including plug to receptacle impedance. The green grounding wire becomes a backup, not a primary path performer


    Quote Originally Posted by OkieElectrician View Post
    If that were the case, wouldn't we just get rid of all mc and have a nema standard requiring all metallic jacket to be approved egc?
    We might would like that to be the case but it isn't at this time.

    Roger
    Moderator

  9. #9
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    Quote Originally Posted by OkieElectrician View Post
    Why? It doesn't make any sense to me. Really. I want someone to prove to me that this is the case. I really can't see why it needs to be HFC all the way to the panel.
    The code section states "Branch Circuits SERVING patient care areas....." That means the entire branch circuit.

    If HFC were only required once the branch circuit reaches the patient care area, it would says something like "Branch circuits IN patient care areas....."

    As Roger mentioned, its a redundancy thing.

    Is HFC really that much more expensive than regular cable?

  10. #10
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    Quote Originally Posted by OkieElectrician View Post
    So I have a question about the requirements of 517.13(A). Yes, I read it. Yes, I own the Mike Holt illustrated guide to 500-820 and read that.

    Now, I understand that all wiring in or serving patient care areas must comply with 517.13(A). But what I have a question about is this, someone is telling me that I cannot change from HFC to MC between the patient care area and the panel. For instance, I would think it would be fine to run regular mc from a panel to a box in a nearby space that is not designated as a patient care space and then break out of that box with HFC to actually serve the patient care areas. I really don't see how this is a problem. They are telling me that I have to run HFC all the way back to the panel. To me, this just doesn't make sense because that redundant ground that is the jacket, is terminating inside a connector in a box that will be grounded to the insulated grounding conductor and will be a better ground to the panel than the jacket ground having to go through snap in connectors.

    I am having a really hard time believing that the intent of the redundant ground is to actually increase the fault current capability of the circuit as this person is alleging. I think it more likely that in the unlikely case a wall and the mc inside it become damaged and accessible, the intent is to ensure that if the hot shorts to the jacket, it will ground out and trip the breaker or at the very least, keep the jacket from becoming a hot conductor. Both of which would still be the case if I switch to regular mc outside of the patient care area.
    As others have stated, it really doesn't need to "make sense" because this is about the entire circuit as stated in this quote "(A) Wiring Methods. All branch circuits serving patient carespaces shall be provided with an effective ground-fault current path by installation in a metal raceway system or a cable having a metallic armor or sheath assembly." It is about the "branch circuit" that is serving that patient care space.

    Now as a member of CMP 5 and manufacturer of such a cable assembly I can promise you that when we evaluate it and give it the recognition to being in compliance with 250.118(10)(a) and (b) for use with compliance to section 517.13(A) we intend for it to be based on the entire branch circuit from the origination of that branch circuit.
    *All code responses are based on the 2017 National Electrical Code[NEC]

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