plenum ceiings

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copper chopper

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wisconsin
is it true that any octagon or 4 inch square that has mounting holes already in it from the manufacture, and is installed in a plenum ceiling is not rated for use in that zone??? has anyone heard of this??
 
There is no such thing as a metallic "plenum" box unless you are in Chicago. There is a requirement for boxes without holes in return air ceilings in Chicago.
 
capybara said:
300.22C3 requires metal boxes or NM boxes listed for use within an AH space......
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But, there is no special requirement for a metal box in a "other space used for envriomental air", only the non-metallic box has to be listed for use in that space.
 
I was just wondering, the other day I was looking thru a raco catalog and wondered what the astrik was for next to some of there boxes and it said listed for plenum use. so i noticed that all of them had no holes in them.. thanks for your input...
 
I heared but i can't adress now, the code requires solid bottom+solid cover for boxes that located in plenum ceiling.

Actually, i would think there is a solid reason, during the fire case where cable burns and emitts the smoke, the smoke will flow in HVAC ducts.
 
m sleem said:
I heared but i can't adress now, the code requires solid bottom+solid cover for boxes that located in plenum ceiling.

Actually, i would think there is a solid reason, during the fire case where cable burns and emitts the smoke, the smoke will flow in HVAC ducts.
Click to expand...

Well in that case you wouldn't be able to use Flex either since the smoke would escape from it as well.
 
m sleem said:
I heared but i can't adress now, the code requires solid bottom+solid cover for boxes that located in plenum ceiling.

Actually, i would think there is a solid reason, during the fire case where cable burns and emitts the smoke, the smoke will flow in HVAC ducts.
Click to expand...
Please cite the code section that says this.
 
cowboyjwc said:
Well in that case you wouldn't be able to use Flex either since the smoke would escape from it as well.
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I'm not sure what do you mean by flex. but if you mean the flex non-metallic conduit, i would think this type of conduit is not permitted to be used in plenum ceiling....!!!!
 
iwire said:
Flex, as in Flexible Metal Conduit.
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Well, please see 300.22(b).
.......The connectors used with flexible metal conduit
shall effectively close any openings in
the connection. Equipment and devices shall be permitted
within such ducts only if necessary for the direct action
upon, or sensing of, the contained air. Where equipment or
devices are installed and illumination is necessary to facilitate
maintenance and repair, enclosed gasketed-type luminaires
shall be permitted.
Click to expand...
 
m sleem said:
See 300.22(c)(1) & 300.22(c)(2)(b).

I'm not 100% sure, perhaps it is near to my opinion.
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There is nothing in those sections that say you have to use a metallic box without holes. 300.22(C)(2)(b) applies to cable tray only. It does not apply to boxes used with cables or raceways.
 
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don_resqcapt19 said:
There is nothing in those sections that say you have to use a metallic box without holes. 300.22(C)(2)(b) applies to cable tray only. It does not apply to boxes used with cables or raceways.
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Yes,you are right.

May be i'm not familiar with cable box. Initially i was thinking there is no difference between cable tray and cable box.
 
don_resqcapt19 said:
A "plenum" ceiling is a 300.22(C) space, not a 300.22(B) space.
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I'm confused, if the flex shall effectively closed where located in non-plenum ceiling, i would think it should be in plenum as well.

From the beginning, i mean the cables that laid directly in cable tray without any tube (I'M NOT SURE THIS APPLICATION IS PERMITTED OR NOT AS PER NEC).

If permitted, don't you think this tray or box has to be non-ventilated where located in plenum?
 
Enclosed cable tray

cable_way_2_large.jpg


Open cable tray

Ladder_Type_Cable_Tray.jpg



Boxes like we are talking about

51ByQysJY3L._SL500_SS500_.jpg
 
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