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  1. #1
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    Default Unprotected NM, how high?

    Does anybody know offhand the minimum height that NM is allowed to be unprotected?
    How about how far out of level a condenser / compressor can be?

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  2. #2
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    Default Re: Unprotected NM, how high?

    On the NM-B, no hard rule. It depends on the location. It's pretty common to see a garbage disposer wired with NM-B. This is most often a common sense call, or one by the AHJ.


  3. #3
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    Default Re: Unprotected NM, how high?

    Actually, there is a hard and fast rule. It is Article 334 in the National Electrical Code.

    As the AHJ of my municipality it is my opinion that exposed NM cable is not allowed to be "unprotected" anywhere.

    The code says: If NM wire is exposed it shall closely follow the surface of the building finish or running boards. 334.15(A). So, NM should not be allowed to connect the garbage disposal. Flexible metal conduit or armored cable would be the code compliant wiring methods for that.

    So, NM cable, as I understand the code, must always be protected by either following the building structure or by being installed in conduit where it doesn't follow the structure. Also, running through bored holes in floor joists in an unfinished basement is considered protected.


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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Ray Norton View Post
    Actually, there is a hard and fast rule. It is Article 334 in the National Electrical Code.

    As the AHJ of my municipality it is my opinion that exposed NM cable is not allowed to be "unprotected" anywhere.

    The code says: If NM wire is exposed it shall closely follow the surface of the building finish or running boards. 334.15(A). So, NM should not be allowed to connect the garbage disposal. Flexible metal conduit or armored cable would be the code compliant wiring methods for that.

    So, NM cable, as I understand the code, must always be protected by either following the building structure or by being installed in conduit where it doesn't follow the structure. Also, running through bored holes in floor joists in an unfinished basement is considered protected.
    While your AHJ may define NM usage conditions in that manner I would in no way say that it was a universal definition.

    You should also note that neither FMC or armored cable is suitable where subject to physical damage either.

    All answers based on unamended National Electrical codes.

  5. #5
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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Jim Port View Post
    While your AHJ may define NM usage conditions in that manner I would in no way say that it was a universal definition.

    You should also note that neither FMC or armored cable is suitable where subject to physical damage either.
    Yep. Jurisdictions vary on interpretation.


  6. #6
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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Ray Norton View Post
    Actually, there is a hard and fast rule. It is Article 334 in the National Electrical Code.

    As the AHJ of my municipality it is my opinion that exposed NM cable is not allowed to be "unprotected" anywhere.

    The code says: If NM wire is exposed it shall closely follow the surface of the building finish or running boards. 334.15(A). So, NM should not be allowed to connect the garbage disposal. Flexible metal conduit or armored cable would be the code compliant wiring methods for that.

    So, NM cable, as I understand the code, must always be protected by either following the building structure or by being installed in conduit where it doesn't follow the structure. Also, running through bored holes in floor joists in an unfinished basement is considered protected.
    That opinion would probably get you a blanket party around here. Actually, there is NOT a hard and fast rule.

    You are aware, I suppose, that there are surface mount devices available intended to straddle surface mounted NM-B?

    I work in about 55 jurisdictions and none I'm aware of flat out ban exposed and/or surface run NM-B. On the other hand I probably wouldn't disagree with you around 90% of the time on where it's appropriate - in MY opinion


  7. #7
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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Jim Port View Post
    You should also note that neither FMC or armored cable is suitable where subject to physical damage either.
    Schedule 40 RNC (Schedule 40 PVC for most) is not allowed for subject to protection from physical damage either, Schedule 80 RNC *IS* listed for protection from physical damage.

    On the other note, no place I have ever been would allow NM cable to be run from the cabinet to the garbage disposer, not unless it was in FMC.

    The only hard and fast rule is that there is no hard and fast rule.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Unprotected NM, how high?

    I was just commenting on what some areas appear to allow that have the same restrictions as NM but are "approved". I was not going to the whole list of approved methods of physical protection.

    This is one area where I feel that greater leeway could be used. I doubt that anyone could damage Sch 40 PVC under a sink, but it is not mentioned except by the "or other approved methods".

    I can count on one hand the number of disposals I have seen that were not wired with NM. I have never wired one with a cordset.

    Last edited by Jim Port; 10-20-2011 at 07:28 PM. Reason: spelling
    All answers based on unamended National Electrical codes.

  9. #9
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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Jim Port View Post
    I was just commenting on what some areas appear to allow that have the same restrictions as NM but are "approved".
    That is why I mentioned Sch 40 PVC - many places allow it to be used for protection from physical damage even though it is not rated for such.

    The reason is likely perception, i.e., NM cable is quite easily damaged while Sch 40 PVC is not ... under the condition which are 'most likely' to be encountered.

    I can count on one hand the number of disposals I have seen that were not wired with NM. I have never wired one with a cordset.
    Completely the opposite here - virtually all are wired with a cordset. When I was in the Florida Panhandle, it was about a 50/50 mix, but South Florida was almost all cordset too.

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    Default Re: Unprotected NM, how high?

    For what it's worth, most cabinet space under a kitchen sink is filled with things like cleaners and such that have a tendency to be spilled, squirted, and otherwise splattered around. Some of this stuff is corrosive and will do a number on FMC and MC/AC type cable. NM-B, on the other hand, has a jacket that is impervious to most of this stuff and is often in good shape after 35-40+ years. I don't know how many times I've had an old flexible metal covering deteriorate in my hands when it was under the kitchen sink but it way outnumbers the damaged NM-B cables, and I've seen more of those.

    Quite honestly, if it was up to me I'd ban metal flex under a sink. 'Course if it was up to me, all the stuff would be cord connected to receptacles in the cabinet back (or side) and there wouldn't be an issue.


  11. #11
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    Default Re: Unprotected NM, how high?

    I stand behind my original post. The code is very clear. Way too often the code leaves gray areas that make enforcement difficult. When there is no gray are, don't create one.

    NM should not be allowed to connect a garbage disposal. The code specifies the 3 ways to install EXPOSED NM. Follow surface closely/ running boards, in conduit or through floor joists.


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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Bill Kriegh View Post
    For what it's worth, most cabinet space under a kitchen sink is filled with things like cleaners and such that have a tendency to be spilled, squirted, and otherwise splattered around. Some of this stuff is corrosive and will do a number on FMC and MC/AC type cable. NM-B, on the other hand, has a jacket that is impervious to most of this stuff and is often in good shape after 35-40+ years. I don't know how many times I've had an old flexible metal covering deteriorate in my hands when it was under the kitchen sink but it way outnumbers the damaged NM-B cables, and I've seen more of those.

    Quite honestly, if it was up to me I'd ban metal flex under a sink. 'Course if it was up to me, all the stuff would be cord connected to receptacles in the cabinet back (or side) and there wouldn't be an issue.
    Bill,

    All of the above are excellent reasons for using nonmetallic liquidtight conduit there.

    Even though it, too, is not rated to provide protection from physical damage.

    Jerry Peck, Construction / Litigation Consultant
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  13. #13
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    Default Re: Unprotected NM, how high?

    well, the actual situation was NM installed under a patio cover, up about 7.5 feet under the eaves of the cover, stapled around the perimeter.
    The AC was an estimated 2 degrees out of plumb.
    I didn't recommend any repairs on these items, was I wrong?


  14. #14
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    Default Re: Unprotected NM, how high?

    Per CEC 20th edition as amended by BC Regulations:

    Where loomex cable is run on the surface of the wall and within 1.5 m from the floor, ....the cable must be protected with wood or similar moulding. (Our local electrical inspector also applies the 1.5m height rule to cables running through studs in an unfinished wall.)

    But from the perspective of the home inspector, instead of being concerned about the the code that was applicable in that city/state/province in whatever year the cable was installed, would it not be better to recommend a change or not depending on one's judgement as to whether the cable as installed is vulnerable to mechanical damage, or damage from other things like rain, ice, sun etc.

    Quote Originally Posted by Benjamin Thompson View Post
    well, the actual situation was NM installed under a patio cover, up about 7.5 feet under the eaves of the cover, stapled around the perimeter.
    The AC was an estimated 2 degrees out of plumb.
    I didn't recommend any repairs on these items, was I wrong?



  15. #15
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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Frank Norman View Post
    Per CEC 20th edition as amended by BC Regulations:

    ....
    But from the perspective of the home inspector, instead of being concerned about the the code that was applicable in that city/state/province in whatever year the cable was installed, would it not be better to recommend a change or not depending on one's judgement as to whether the cable as installed is vulnerable to mechanical damage, or damage from other things like rain, ice, sun etc.
    Yes! I agree totally. For the standard home inspection stay way from code quotes. Use a common sense approach that makes sense to the client.

    The above statements are expressed solely as my opinion and in all probability will conflict with someone else's.
    Stu, Fredericksburg VA

  16. #16
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    Default Re: Unprotected NM, how high?

    Now that we know the wiring was outdoors, Yes, you should have called it out for repair.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  17. #17
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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Benjamin Thompson View Post
    well, the actual situation was NM installed under a patio cover, up about 7.5 feet under the eaves of the cover, stapled around the perimeter.
    The AC was an estimated 2 degrees out of plumb.
    I didn't recommend any repairs on these items, was I wrong?
    With NM cable outside, protection from physical damage is not required at any height.

    is what most of you are doing right about now.

    That is because NM cable is NOT ALLOWED to be used or installed outdoors (unless it is being used as a clothesline and is not connected to anything electrical at either end).

    If you see something like NM cable outside, it should be UF cable, which looks a lot like NM cable and is allowed to be used outside, and is required to be protected from physical damage as has been discussed.

    I.e., if you think it is NM cable outside, or call it NM cable outside, then it should be written up as not being allowed to be used outside. Make sure it is what you are calling it before calling it NM cable.

    Jerry Peck, Construction / Litigation Consultant
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  18. #18
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    Default Re: Unprotected NM, how high?

    Quote Originally Posted by Jim Port View Post
    While your AHJ may define NM usage conditions in that manner I would in no way say that it was a universal definition.

    You should also note that neither FMC or armored cable is suitable where subject to physical damage either.
    Romex as I understand should be protected below 7 feet and garbage disposals should have appliance cords many of which are supplied with the disposals not to exceed 18 inches

    - - - Updated - - -

    Quote Originally Posted by Jim Port View Post
    While your AHJ may define NM usage conditions in that manner I would in no way say that it was a universal definition.

    You should also note that neither FMC or armored cable is suitable where subject to physical damage either.
    Romex as I understand should be protected below 7 feet and garbage disposals should have appliance cords many of which are supplied with the disposals not to exceed 18 inches

    - - - Updated - - -

    Quote Originally Posted by Jim Port View Post
    While your AHJ may define NM usage conditions in that manner I would in no way say that it was a universal definition.

    You should also note that neither FMC or armored cable is suitable where subject to physical damage either.
    Romex as I understand should be protected below 7 feet and garbage disposals should have appliance cords many of which are supplied with the disposals not to exceed 18 inches


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