General electrical questions

[cppoly]

Just a few questions:

- Are low voltage cabling above the ceiling permitted to be supported by ceiling tile supports?

- Are junction boxes above a hung ceiling allowed to be there without a cover if not used?

- Are lighting fixture whips from fixture to to fixture permitted to be larger than 6' or is 6' rule only for junction boxes to lighting fixtures?

 

[Smart $]

- Are low voltage cabling above the ceiling permitted to be supported by ceiling tile supports?

Don't know of any restriction.​

- Are junction boxes above a hung ceiling allowed to be there without a cover if not used?

Not really a junction box if not used. No cover required.​

- Are lighting fixture whips from fixture to to fixture permitted to be larger than 6' or is 6' rule only for junction boxes to lighting fixtures?

Can be longer than 6'... but not unsupported.​

 

[cppoly]

Just to add:

- The junction box has wires spliced in it without a cover

- Are pullboxes required to have 3' clearance above hung ceilings?

- Are disconnect switches above hung ceilings required to have 3' clearance and be accessible?

 

[Smart $]

- The junction box has wires spliced in it without a cover

Covered, yes, if wires capable of being energized. Wires abandoned and no portion within an energizeable enclosure, no.​

- Are pullboxes required to have 3' clearance above hung ceilings?

Debatable (IMO no)​

- Are disconnect switches above hung ceilings required to have 3' clearance and be accessible?

Same as above re' clearance. Accessible, yes..​

 

[realolman]

The 6' whip thing might be because of a ground being required.

 

[Gregg Harris]

- Are low voltage cabling above the ceiling permitted to be supported by ceiling tile supports?

My opinion is it is required to have independent support wires and marked 300.11(A)(2)
Here is where the quandary may be

725.21 added in 1993

along with 725.143 Support of conductors and clarified in 2011

 

[Smart $]

- Are low voltage cabling above the ceiling permitted to be supported by ceiling tile supports?

My opinion is it is required to have independent support wires and marked 300.11(A)(2)
Here is where the quandary may be

725.21 added in 1993

along with 725.143 Support of conductors and clarified in 2011

Here is where there is no quandary re' 300.11(A)(2)...

725.3 Other Articles. Circuits and equipment shall comply
with the articles or sections listed in 725.3(A) through
(L). Only those sections of Article 300 referenced in this
article shall apply to Class 1, Class 2, and Class 3 circuits.

 

[infinity]

A fixture whip made of standard 3/8" FMC cannot be longer than 6'.

In NYC, LV cable can be supported by attachment to the pencil rod.

 

[cppoly]

Did some digging in Mike Holt's 2011 NEC book, in the communications section & fire alarm section (class 2 or class 3 cabling) it says raceways and cables can't be supported by the ceiling support wires or the ceiling grid.

This section reference 310.11

 

[cppoly]

Also the 6' rule for lighting fixture connections is for tap conductors only as in section 410.117. This limits the fixture taps to a minimum of 18" and a maximum of 6'.

 

[Smart $]

Did some digging in Mike Holt's 2011 NEC book, in the communications section & fire alarm section (class 2 or class 3 cabling) it says raceways and cables can't be supported by the ceiling support wires or the ceiling grid.

This section reference 310.11

That is not true. See posts #6 and #7. I only quoted 725.3 in post #7, but you can find similar sections regarding any of the others.

 

[Smart $]

Also the 6' rule for lighting fixture connections is for tap conductors only as in section 410.117. This limits the fixture taps to a minimum of 18" and a maximum of 6'.

That's only for tap conductors. Under that and the branch circuit tap conductors "rules" [see 210.19(A)(4) exceptions] a fixture-to-fixture "whip" of 6' or greater cannot consist of a tap conductors... but it can consist of branch circuit conductors.

 

[infinity]

Tap or branch, 3/8" FMC cannot exceed 6' regardless.

 

[Smart $]

Tap or branch, 3/8" FMC cannot exceed 6' regardless.

Agree... but nothing prohibits 1/2" or larger FMC, AC , or MC... yes?

 

[cppoly]

Smart $, should I post the sections from Mike Holt's book showing fire alarm cable and communications cable above hung ceiling is not to be supported by ceiling grid supports?

 

[Smart $]

Smart $, should I post the sections from Mike Holt's book showing fire alarm cable and communications cable above hung ceiling is not to be supported by ceiling grid supports?

Not on my account.

I think you meant 300.11 in post #9. There is no 310.11.

Anyway, you (and Mike) are correct regarding FA and com. 760.46, 760.130(B), 800.24 all specifically reference 300.11.

725.143 references 300.11(B)(2), and is the only reference to 300.11 in Article 725.

 

[cppoly]

Thanks Smart $.

For PLFA circuits, section 760.130(B), it just says devices shall be installed in accordance with 110.3(B), 300.11(A), and 300.15. Is this interpreted as devices and wiring?


Here's 760.130(B):

PLFA Wiring Methods and Materials. Power-limited fire alarm conductors and cables described in 760.179 shall be installed as detailed in 760.130(B)(1), (B)(2), or (B)(3) of this section and 300.7. Devices shall be installed in accordance with 110.3(B), 300.11(A), and 300.15.

 

[acrwc10]

Nothing is allowed to "hang" from grid support wires, the Tee Bar system is a Pre-engineered system that is calculated to only hold the grid and tiles. When you want to hang electrical boxes or conduit from the ceiling you need to add additional wires for the added support.

 

[cppoly]

Nothing is allowed to "hang" from grid support wires, the Tee Bar system is a Pre-engineered system that is calculated to only hold the grid and tiles. When you want to hang electrical boxes or conduit from the ceiling you need to add additional wires for the added support.

I agree and this is mentioned in chapter 3 section 300.11. But what I think is the challenge here is that article 760 for fire alarm systems doesn't follow chapters 1 - 4 unless referenced. Wiring for fire alarm needs to have a reference back to section 300.11 which prohibits attaching cables to the ceiling grid support wires.

 

[Smart $]

Thanks Smart $.

For PLFA circuits, section 760.130(B), it just says devices shall be installed in accordance with 110.3(B), 300.11(A), and 300.15. Is this interpreted as devices and wiring?


Here's 760.130(B):

PLFA Wiring Methods and Materials. Power-limited fire alarm conductors and cables described in 760.179 shall be installed as detailed in 760.130(B)(1), (B)(2), or (B)(3) of this section and 300.7. Devices shall be installed in accordance with 110.3(B), 300.11(A), and 300.15.

That is the "gray" area of interpretation... and the reason I said Mike's stipulation was not true. The term "devices" does not include the wiring method.

Note 760.46 does not say the same regarding NPLFA circuit wiring.