Box Fill Fun

[ivsenroute]

Alright, here we go!

You have a 4" square metal junction box 2-1/8" deep with NO integral clamps. An 1-1/2" extension ring is added to the box.

The box has 6 cable assemblies that terminate inside the box with the following wires:

2- 12/2 with ground MC cables
3- 12/2 with ground, 16/2 MC-LED cables
1- cable assembly from Emergency Light mini-inverter

The above is broken down as follows:

5- 12 awg equipment grounds
1- 18 awg equipment ground (from EL mini inverter)

5- 12 awg neutrals

5- 12 awg hots

6- 16 awg LED dimmer control wires

11- 18 awg emergency light inverter wires (12-1=11 equip gnd grouped above)


There are no devices in the box, just the wires, ground screw, extension ring and cover plate.

Is there adequate space in the setup as described for box fill?

 

[infinity]

Did you do the calculation?

 

[al hildenbrand]

Is the plaster ring round, single or double gang? And what is its rated cubic inches by it's manufacturer? Is the cover plate domed and is it rated with a cubic inch volume?

 

[infinity]

Is the plaster ring round, single or double gang? And what is its rated cubic inches by it's manufacturer? Is the cover plate domed and is it rated with a cubic inch volume?

His box has a standard 1.5" extension collar box not a plaster ring.

 

[al hildenbrand]

His box has a standard 1.5" extension collar box not a plaster ring.

:dunce: Ahh. Thank you. (And I even READ the words. . . :ashamed

I presume, then that the cover plate is a 4" square flat blank box cover, i.e., no dome?

 

[infinity]

:dunce: Ahh. Thank you. (And I even READ the words. . . :ashamed

I presume, then that the cover plate is a 4" square flat blank box cover, i.e., no dome?

Yes, I'm assuming that he has a flat blank cover which doesn't add to the box volume.

Unless otherwise marked for calculation purposes I come up with 30.3 cubic inches plus 21 cubic inches for the extension collar.

 

[Dennis Alwon]

I agree that there is 50.3 total cu. inch in the box, however, the wire fill is 51.75

 

[infinity]

I come up with a box volume of 30.3+21=51.3 but still too small if we use the calculated value that Dennis provided. Needs a 2 1/8" deep extension collar.

 

[ivsenroute]

:dunce: Ahh. Thank you. (And I even READ the words. . . :ashamed

I presume, then that the cover plate is a 4" square flat blank box cover, i.e., no dome?

Yeah, don't read into it. It is a 4" regular square metal cover. Nothing fancy or misleading.

 

[ivsenroute]

Did you do the calculation?

yes, I absolutely did.

 

[ivsenroute]

I agree that there is 50.3 total cu. inch in the box, however, the wire fill is 51.75

We both agree on this one. The allowable is off by 1.45 cu inches

 

[infinity]

yes, I absolutely did.

Ok let's see it.

 

[ivsenroute]

Ok let's see it.

Sure!

6 Gnds 5-12's plus 1 18 = 2.25
5 Neutrals 12 awg, 2.25 x 5= 11.25
5 Hots 12awg, 2.25 x 5= 11.25
6 16awg, 1.75 x 6= 10.5
11 18awg, 1.5 x 11= 16.5

Total= 51.75

I can't believe you made the inspector show you his work........

 

[al hildenbrand]

Unless otherwise marked for calculation purposes I come up with 30.3 cubic inches plus 21 cubic inches for the extension collar.

I agree that there is 50.3 total cu. inch in the box, however, the wire fill is 51.75

I disagree with the stated volume for the extension ring. I don't think the 21.0 cu in from Table 314.16(A) applies, as it is not a box, rather a "ring". Therefore a trip to the manufacturer's product description is in order. A Raco 201 4" square 1-1/2" deep extension ring, drawn, with 12 1/2" K.O.s has a specified 22.5 Cu. in. volume.

The total volume of the assembly is, therefore, 52.8 cubes.

 

[al hildenbrand]

I can't believe you made the inspector show you his work........

Always share the work.

 

[infinity]

I disagree with the stated volume for the extension ring. I don't think the 21.0 cu in from Table 314.16(A) applies, as it is not a box, rather a "ring". Therefore a trip to the manufacturer's product description is in order. A Raco 201 4" square 1-1/2" deep, drawn, with 12 1/2" K.O.s has a specified 22.5 Cu. in. volume.

The total volume of the assembly is, therefore, 52.8 cubes.

I agree that's if he uses a Raco extension box and it is marked on the extension otherwise you use the dimensions in the table as I stated.

314.16(A) Box Volume Calculations. The volume of a wiring
enclosure (box) shall be the total volume of the assembled
sections and, where used, the space provided by plaster
rings, domed covers, extension rings, and so forth, that are
marked with their volume or are made from boxes the di-
mensions of which are listed in Table 314.16(A).

 

[ivsenroute]

I disagree with the stated volume for the extension ring. I don't think the 21.0 cu in from Table 314.16(A) applies, as it is not a box, rather a "ring". Therefore a trip to the manufacturer's product description is in order. A Raco 201 4" square 1-1/2" deep extension ring, drawn, with 12 1/2" K.O.s has a specified 22.5 Cu. in. volume.

The total volume of the assembly is, therefore, 52.8 cubes.

You are correct Sir! The extension ring is 22.5 cu.in.

Therefore we are good by .05 cu.in,

Talk about cutting it close!

 

[al hildenbrand]

I agree that's if he uses a Raco extension box and it is marked on the extension otherwise you use the dimensions in the table as I stated.

314.16(A) Box Volume Calculations. The volume of a wiring enclosure (box) shall be the total volume of the assembled sections and, where used, the space provided by plaster rings, domed covers, extension rings, and so forth, that are marked with their volume or are made from boxes the dimensions of which are listed in Table 314.16(A).

It would be an odd manufacturer that didn't mark their extension rings, in my opinion. But, you got me looking at some of the other extension rings. It appears to have been my dumb luck that I looked at Raco first. Raco appears to be the exception to a more common sizing shown below.

A Garvin #53151-1/2 1-1/2" deep extension ring, welded, with 12-1/2" K.O.s, as seen in this linked Garvin PDF is marked "21.0 Cu. In."

A Cooper Crouse Hinds #TP4xx line of 1-1/2" rings are all 21.0 Cu. In. as shown in this link to a catalog PDf.

Thomas and Betts #53151 line also shows 21.0 Cu. In.

 

[ivsenroute]

It would be an odd manufacturer that didn't mark their extension rings, in my opinion. But, you got me looking at some of the other extension rings. It appears to have been my dumb luck that I looked at Raco first. Raco appears to be the exception to a more common sizing shown below.

A Garvin #53151-1/2 1-1/2" deep extension ring, welded, with 12-1/2" K.O.s, as seen in this linked Garvin PDF is marked "21.0 Cu. In."

A Cooper Crouse Hinds #TP4xx line of 1-1/2" rings are all 21.0 Cu. In. as shown in this link to a catalog PDf.

Thomas and Betts #53151 line also shows 21.0 Cu. In.

Uh Oh, I just looked at a Raco 4x4 1-1/2" deep extension ring and although the manufacturer says it has 22.5, the ring has no markings or stamps indicating its cubic inches, therefore..................drumroll please............we have to go by the chart of 21.

Bad installation.

 

[al hildenbrand]

Uh Oh, I just looked at a Raco 4x4 1-1/2" deep extension ring and although the manufacturer says it has 22.5, the ring has no markings or stamps indicating its cubic inches, therefore..................drumroll please............we have to go by the chart of 21.

But can we go by Table 314.16(A)? Look at 314.16(A) again.

314.16(A) Box Volume Calculations. The volume of a wiring enclosure (box) shall be the total volume of the assembled sections and, where used, the space provided by plaster rings, domed covers, extension rings, and so forth, that are marked with their volume or are made from boxes the dimensions of which are listed in Table 314.16(A).

The rule says where the extension rings are "made from boxes". . . In my opinion, there is no way to determine if an unmarked Raco 201 is made from a box. To my mind, the extension ring is more likely to be made from a sheet of steel with a hole punched in it.

I would submit that, for the absence of the marking, the Raco 201 you have examined has zero cubic inches.

It also would be interesting to hear what Raco / Hubbell's tech support has to say about the cubic inch size and "marking" of the 201.