Box sizes

[600SL]

First a sanity check here. I believe I need a 22.5 CU for my reversible fan based on"

Fan has 4 18 ga wires - which dont count.

4 12 gage wires coming into the box
4 12 gage wires leaving the box going to another fan
1 ground
1 hanging hook that passes through the box

Total = 10x2.25 = 22.5

The hook just passes through the box. The box does not bear the weight of the fan.

12 ga wire is required because of the CB power is coming off.

OK so I go to look for an octagon box and I come up with HD which has them in stock but you have to buy a case of 25 or Platt who doesn't have them in stock and they are really expensive if they ever get them.

But HD and pretty much everywhere else has 4" octagon boxes of the same 2.125" depth but for some reason only rated at 20 cu.

https://www.platt.com/platt-electri...el-City/54171-1-2-3-4/product.aspx?zpid=57694

I know I can use an extension ring but I kind of don't like them.

 

[matt_i]

Can you use a 4" square box? it would drive a different coverplate but its not structural so its just getting it covered in the end.

 

[600SL]

Can you use a 4" square box? it would drive a different coverplate but its not structural so its just getting it covered in the end.

I could but I would have to make a new cover. Not a difficult task. Just a cover plate with a hole in it. Might be the way to go.

 

[mm08822]

What makes up the four conductors each into and out of the box?

 

[600SL]

What makes up the four conductors each into and out of the box?

In is 4 wires from the switch required to reverse the fan. Out is 4 wires to the next fan.

 

[mm08822]

Raco 294 / Raco 299

22.4 cu in, fan rated, 70# each

 

[matt_i]

In is 4 wires from the switch required to reverse the fan. Out is 4 wires to the next fan.

You know, based on this, the reverse-wiring only carries the fan-motor-current (iow not even close to the potential downstream current of the circuit fed by #12 awg). I feel that one could potentially wire that part to the switch and back with #14awg.

Does that change your box volume requirement enough to make a difference?

 

[zmaxmotorsports]

If you're using it as switch box why not just use a single gang box like an allied 1098?
Or if you're really worried about it I'd use a fg 4sq box with a single gang plaster ring?

 

[600SL]

I went with the first suggestion 2 1/8" deep 4 in square. Got a blank cover an drilled a 1 1/2" hole in it. Actually a very nice solution.

But I would still like to know why steel city gets to rate there 2 1/8" deep octagons at 22.5 cu only for the ones that seem to be available in quantities of 25 and the Steel City 2 1/8" deep boxes available individually are not rated in CU they get the standard NEC rating which I believe is 20CU.

 

[600SL]

Pictures

4" box with drilled cover plate.

Just waiting for the wires to come in.

 

[600SL]

You know, based on this, the reverse-wiring only carries the fan-motor-current (iow not even close to the potential downstream current of the circuit fed by #12 awg). I feel that one could potentially wire that part to the switch and back with #14awg.

Does that change your box volume requirement enough to make a difference?

Its kind of strange. I'm carrying 2 whole amps between two fans but they are ultimately connected to a 20 amp circuit. That dictates the wire size and it does make sense. And in this case 2 wires share the 1 amp of current to each fan. They are only required to reverse the fan direction.

Code is code.

But I must admit I still have 4 12 ga wires in 1 conduit. Not sure if I'm to code with derating involved.

 

[mm08822]

That works. I thought the fan was supported by the box until I just re-read the OP.

Website shows same volume for all 2-1/8" deep.