EES Lighting Wiring Methods

[Jelloshooter848]

So I have often been told that 517.31(C)(3)(3)(f) allows us to use 6' long flex whips for lights on the Life Safety and Critical Branches. I have two issues with the language and I'm curious if anyone has experience with AHJ's interpretations on this. Here is the language summed up:

517.31(C)(3) Mechanical Protection of the EES
"The wiring of the life safety and critical branches shall be mechanically protected by raceways...only the following wiring methods shall be permitted... (3) listed flexible metal raceways and listed metal sheathed cable assemblies in any of the following... (f) luminaires installed in ceiling structures.

Here are my two issues:

1. It specifically says "ceiling structures," which according to 110..26(E)(1)(d) a t-bar ceiling is not considered a structural ceiling. Does this mean in t-bar ceilings lights need to be 100% hard piped?

2. It makes no reference to a 6' limit. If we interpret the "structural ceiling" to indicate a hard lid only, as I read this we should be able to run flexible conduit or cable for 100% of the run as long as it is compliant with 517.13 when applicable. Is there another code section I'm missing that limits it to 6'? Is there something in 700 perhaps?

Thanks!

 

[Dennis Alwon]

I also read that as flex cable can be used

(3) Mechanical Protection of the Essential Electrical System.



The wiring of the life safety and critical branches shall be mechanically protected by raceways. Where installed as branch circuits in patient care spaces, the installation shall comply with the requirements of 517.13(A) and (B) and 250.118. Only the following wiring methods shall be permitted:

• (1)
  Nonflexible metal raceways, Type MI cable, RTRC marked with the suffix –XW, or Schedule 80 PVC conduit. Nonmetallic raceways shall not be used for branch circuits that supply patient care spaces.
• (2)
  Where encased in not less than 50 mm (2 in.) of concrete, Schedule 40 PVC conduit, flexible nonmetallic or jacketed metallic raceways, or jacketed metallic cable assemblies listed for installation in concrete. Nonmetallic raceways shall not be used for branch circuits that supply patient care spaces.
• (3)
  Listed flexible metal raceways and listed metal sheathed cable assemblies, as follows:
  • a.
    Where used in listed prefabricated medical headwalls
  • b.
    In listed office furnishings
  • c.
    Where fished into existing walls or ceilings, not otherwise accessible and not subject to physical damage
  • d.
    Where necessary for flexible connection to equipment
  • e.
    For equipment that requires a flexible connection due to movement, vibration, or operation
  • f.
    Luminaires installed in ceiling structures

 

[roger]

There are a lot of areas in a hospital so forget 517.13 for this. Per the IBC, CISCA (ceiling installation rules) an island (floating) grid system prohibits ridgid installations to fixtures

 

[d0nut]

It says "ceiling structures" not "structural ceilings". You can use a flexible raceway down to the lights in any ceiling.

The 6' limit comes from the grounding requirements. The circuits serving patient care areas are required to be installed in metallic conduit as the equipment grounding conductor. FMC only counts as an equipment grounding conductor in 6' or shorter lengths.

Run EMT or some other nonflexible metal raceway close to the lights and then use a flexible metal conduit or HCF cable into the lights.

 

[Jelloshooter848]

It says "ceiling structures" not "structural ceilings". You can use a flexible raceway down to the lights in any ceiling.

The 6' limit comes from the grounding requirements. The circuits serving patient care areas are required to be installed in metallic conduit as the equipment grounding conductor. FMC only counts as an equipment grounding conductor in 6' or shorter lengths.

Run EMT or some other nonflexible metal raceway close to the lights and then use a flexible metal conduit or HCF cable into the lights.

But what I'm wondering is based on this code couldn't we use HCF for the whole run? HCF does not have the 6' limitation that FMC has. So couldn't we run HFC for the whole run or am I missing something else?

 

[Jelloshooter848]

There are a lot of areas in a hospital so forget 517.13 for this. Per the IBC, CISCA (ceiling installation rules) an island (floating) grid system prohibits ridgid installations to fixtures

Do you have a reference to this in the code? I'm not familiar with it.

 

[roger]

It's been a few years but I think it's in chapter 7 of the IBC and now that I think about it, it has to do with the Seismic category of your area. In NC where I was we were under category (C)

As far as using a flexible wiring method for the whole circuit I would say no.

The link below might guide you to something helpful. Now that I'm retired I do not have access to the literature I used to have.

www.armstrongceilings.com/content/dam/armstrongceilings/commercial/north-america/brochures/seismic-design-what-you-need-to-know-brochure.pdf

 

[roger]

Note that all states have adopted the IBC even if they have amended it.

 

[Jelloshooter848]

It's been a few years but I think it's in chapter 7 of the IBC and now that I think about it, it has to do with the Seismic category of your area. In NC where I was we were under category (C)

As far as using a flexible wiring method for the whole circuit I would say no.

The link below might guide you to something helpful. Now that I'm retired I do not have access to the literature I used to have.

www.armstrongceilings.com/content/dam/armstrongceilings/commercial/north-america/brochures/seismic-design-what-you-need-to-know-brochure.pdf

I've always understood the limit to be 6' of flexible cable or conduit for this scenario. I'm just having a hard time finding anywhere in the code with that limitation.

 

[roger]

I've always understood the limit to be 6' of flexible cable or conduit for this scenario. I'm just having a hard time finding anywhere in the code with that limitation.

There is nothing in 517 that will help you. In NC we had the same problem with an overzealous local inspector but the state finally made an informal rulling allowing a flexible wiring whip