J-boxes for fixtures

Alwayslearningelec · May 2, 2012

I know someone is going to slam me sooner or later... again:huh:

When installing 2x2's, 2x4's etc. in a suspended celing and you install all your 4" boxes whether it's one for every two fixtures or one for every four fixtures or however you do it are the j-boxes supported from the drop wire or what Caddy clip would you use?

THanks.

jumper · May 2, 2012

Are you referring to boxes in the grid that will support a fixture or junction boxes that are above the grid and have whips attached?

don_resqcapt19 · May 2, 2012

See 300.11(A)(2) and its exception and also look at 314.23(D).

jumper · May 2, 2012

horsegoer said:
I know someone is going to slam me sooner or later... again:huh:

Here is what you do.

Change your profile and say you are EC with 30 years experience, and then you get to ask all the first year apprentice questions you want without anybody saying a word.

Works for a lot of others.

jumper · May 2, 2012

jumper said:
Here is what you do.

Change your profile and say you are EC with 30 years experience, and then you get to ask all the first year apprentice questions you want without anybody saying a word.

Works for a lot of others.

The above is a sarcastic comment directed at others, not the OP.

Alwayslearningelec · May 2, 2012

don_resqcapt19 said:
See 300.11(A)(2) and its exception and also look at 314.23(D).

I did thanks. So you can attach as shown here
...although this is not for a box

http://www.erico.com/products/CADDYcfcCableConduit.asp

THe drop wire they show...isn't that part of the ceiling supports. That is not something the EC would need to install as part of the install. I only ask because I seen an assembly for estimating that included the drop wire and attaching it to the structure etc. When running MC above a suspended ceiling(in most cases) it should only be the caddy clip and cable....

Strathead · May 2, 2012

horsegoer said:
I know someone is going to slam me sooner or later... again:huh:

When installing 2x2's, 2x4's etc. in a suspended celing and you install all your 4" boxes whether it's one for every two fixtures or one for every four fixtures or however you do it are the j-boxes supported from the drop wire or what Caddy clip would you use?

THanks.

In CA, it has been illegal for years to secure a box to the T bar. Still allowed in some other States. That said, there are SOOOOOOOOOOOOO many ways to secure a box above the ceiling that the list could go on and on. There are Caddy clips to the grid, clips to to a ceiling wire, threaded rod, smooth rod. Given the restrictions for using grid wires, I got in the habit of buying smooth 1/4" rod, Caddy 708AB ( actually a similar sold by Lord and Sons that came with a powder actuated nail) and Caddy KX-K16 for conduit and Caddy 812MB18 for boxes and first strap. Had an apprentice cut the rod with bolt cutters, generally one length for all, and then you can assmble box clip and rod together and shoot from the floor. But this is just one of many ways.

jumper · May 2, 2012

horsegoer said:
I did thanks. So you can attach as shown here
...although this is not for a box

http://www.erico.com/products/CADDYcfcCableConduit.asp

Are you thinking about a j-box attached to a grid/support wire? Never seen that.

Alwayslearningelec · May 2, 2012

jumper said:
Are you thinking about a j-box attached to a grid/support wire? Never seen that.

Yes, so how would you support random 4" boxes for the fixture whips...or for MC branch above a suspended ceiling.

Alwayslearningelec · May 2, 2012

Below is an assembly for mc cable above a suspended ceiling(includes a box). All this is really needed?

#14/2C SOLID CABLE MC - STL ARMOR
3/8" CONN SADDLEGRIP DC FOR FLEX / AC-90 / MC
#3 BOOSTER 0.27 CALIBER - SHORT 10x MAG
CEILING CLIP W/ 27mm STD NAIL - STL/CONC
#12 CEILING WIRE
DROP WIRE TO T-BAR SECURING CLIP
3/8" CABLE SUPPORT FOR ROD OR FLNG
4x 1 1/2" SQ BOX COMB KO
4" SQ BLANK COVER
#3 BOOSTER 0.27 CALIBER - SHORT 10x MAG
CEILING CLIP W/ 27mm STD NAIL - STL/CONC
#12 CEILING WIRE
DROP WIRE TO T-BAR SECURING CLIP
SUPPORT HANGER FOR 1/4" ROD OR FLNG
WIRE CONN RED

jumper · May 2, 2012

horsegoer said:
Yes, so how would you support random 4" boxes for the fixture whips...or for MC branch above a suspended ceiling.

Attach to ceiling or bar joists and MC whip down. I believe you are allowed 6' unsupported or secured for cable to fixtures.

330.30(D)(2) Is not more than 1.8 m (6 ft) in length from the last
point of cable support to the point of connection to
luminaires or other electrical equipment and the cable
and point of connection are within an accessible ceiling.
For the purpose of this section, Type MC cable
fittings shall be permitted as a means of cable support.

Sierrasparky · May 2, 2012

jumper said:
Attach to ceiling or bar joists and MC whip down. I believe you are allowed 6' unsupported or secured for cable to fixtures.

330.30(D)(2) Is not more than 1.8 m (6 ft) in length from the last
point of cable support to the point of connection to
luminaires or other electrical equipment and the cable
and point of connection are within an accessible ceiling.
For the purpose of this section, Type MC cable
fittings shall be permitted as a means of cable support.

your method works fine as long as your ceiling is not more than 4 or 5 feet from the ceiling above.

Strathead · May 2, 2012

horsegoer said:
THe drop wire they show...isn't that part of the ceiling supports. That is not something the EC would need to install as part of the install. I only ask because I seen an assembly for estimating that included the drop wire and attaching it to the structure etc. When running MC above a suspended ceiling(in most cases) it should only be the caddy clip and cable....

When I take them off, I use less drop wires than supports, because I can clip more than one MC/conduit to a wire, but your assembly is correct, because you have to install independent ceiling wires attached to the grid and the structure. The ceiling wires provided by the installer are not to be used. You can use the wires that tie to the fixture (called seismic wires in California, hurricane wires here in Florida) if they are required and installed, but not the 4 wires tied to the grid around the fixture which are part of the "ceiling system" Again, it is likely you don't have to provide 1 for every 6 feet of MC so you can provide an assembly with 1 KX for every 6 feet and .5 wires fore every 6 feet. You should be covered. Be careful not to put too much labor in.

infinity · May 2, 2012

horsegoer said:
Yes, so how would you support random 4" boxes for the fixture whips...or for MC branch above a suspended ceiling.

Where are you using drop wires to support stuff above the ceiling?

Alwayslearningelec · May 2, 2012

infinity said:
Where are you using drop wires to support stuff above the ceiling?

Huh? Drop wire mist be installed by the electrician when running mc above a suspended grid ceiling....as Strat indicated correct?

Alwayslearningelec · May 2, 2012

Strathead said:
When I take them off, I use less drop wires than supports, because I can clip more than one MC/conduit to a wire, but your assembly is correct, because you have to install independent ceiling wires attached to the grid and the structure. The ceiling wires provided by the installer are not to be used. You can use the wires that tie to the fixture (called seismic wires in California, hurricane wires here in Florida) if they are required and installed, but not the 4 wires tied to the grid around the fixture which are part of the "ceiling system" Again, it is likely you don't have to provide 1 for every 6 feet of MC so you can provide an assembly with 1 KX for every 6 feet and .5 wires fore every 6 feet. You should be covered. Be careful not to put too much labor in.

Thanks Strat. Is that the most common method of securing mc above a ceiling... Drop wire & supports?

Alwayslearningelec · May 2, 2012

Well actually in NYC it is usually pencil rod down to black iron and I'm told they use a candy clip attached to that. Strat you don't do that down there?

infinity · May 2, 2012

horsegoer said:
Huh? Drop wire mist be installed by the electrician when running mc above a suspended grid ceiling....as Strat indicated correct?

That depends on what is holding up the ceiling. A typical pencil rod and "black" iron support system doesn't use drop wires. Here's a photo setup for Cat6 and a 120 volt junction box.

Alwayslearningelec · May 2, 2012

infinity said:
That depends on what is holding up the ceiling. A typical pencil rod and "black" iron support system doesn't use drop wires. Here's a photo setup for Cat6 and a 120 volt junction box.

Thanks.... Great pics. Yes I do know that. Are most of the suspended ceilings you have come across supported with pencil rod to the black iron?

infinity · May 2, 2012

horsegoer said:
Thanks.... Great pics. Yes I do know that. Are most of the suspended ceilings you have come across supported with pencil rod to the black iron?

Yes. I believe that it has something to do with the building code.

J-boxes for fixtures

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