2x4 Lay-in support in suspended ceilings

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jkim780

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Can suspended ceiling systems be used to support 2x4 lay-in fixtures as the sole support without an independant support per 410.16(C) (2005)?

Doesn't 314.23(D) come into play and prevent doing this?

Somehow I thought 2x4 lay-ins always need an independant support in suspended ceilings.

Thanks.
 
This is a common belief, but as far as the NEC is concerned, 410.16(C) is all that is required.

With that said, there are other codes and Architectural designs that may require more, for example, article 1621 of the IBC or SBC (seismic issues).


Roger
 
Triphase/Roger,

Thanks for the reply. It seems wierd that if it is an enclosure, it is restricted to 100 in^3 in size but not for a luminaire?
 
jkim780,

As Roger pointed out, there are other building codes to consider.

In the area I work we are in a seismic zone D1 and therefore use the CISCA design manual for seismic zones D1 and D2 for all acoustical ceilings. This standard requires 2 independent support wires at opposing corners of a 2X4 lay-in troffer fixture, in addition to being positively attached to the ceiling grid.

I would check with the local building department to see what the seismic issues and other building code requirements are.

JMHO, Chris
 
Re: 2x4 Lay-in support in suspended ceilings

jkim780 said:
Can suspended ceiling systems be used to support 2x4 lay-in fixtures as the sole support without an independant support per 410.16(C) (2005)?

Doesn't 314.23(D) come into play and prevent doing this?

Somehow I thought 2x4 lay-ins always need an independant support in suspended ceilings.

Thanks.
Click to expand...
314.23(D) doesn't apply. See 314.1

The Handbook commentary for 410.16(C) is very good. See the blue lettered commentary on page 499 & 500.

410.16(C) The end of the first sentence says "at appropriate intervals."
The grid manufacturer has specs, that are approved by a testing lab, that specify what the "appropriate intervals" are. The specs that I've seen specify only counting support wires that are within 6 inches of the fixture and require either 3 or 4 support wires for 2x4s.

If there's no local rule requiring more, you need to check grid specs for support of light fixtures. The grid can also support the whips if the "system manufacturers instructions" allow it [300.11(A)(2)X].

David
 
Look @ Art,410.16(C) & Art,300.11 - All of this would depend on what the rating of the ceiling is, if it is fire rated or not if you would need your own support wires but if your own support wires are used they need to be distinguishable by color, tagging if in a fire rated ceiling.
 
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