Box fill - surface mount LED???

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Old 04-14-17, 11:17 AM
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Box fill - surface mount LED???

I'm installing two surface mount LEDs in a stairwell and have to notch the ceiling joist to make them work. I chose a 1-1/2" deep 4" square metal box, as it's the shallowest yet biggest for that depth.

The fixture says it takes up 3 cu in. The box is 21 cu in. One box will have 5, 12 gauge wires using 13.5 cu in based on box fill, so I'm clear by 4.5 cu in.

But...

Does the fixture also count as a "device" in the box or is the 3 cu in the calculation for it's volume? In other words, do I count it for the 3 cu in I know it has, count it as a device in the calculation, or both?

Waiting to install...

Thanks guys!
 
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Old 04-14-17, 11:28 AM
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Before you go notching a joist you need to know that there are rules regarding where or if a notch is allowed. Can you post a picture ?
 
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Old 04-14-17, 11:32 AM
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I'll try and grab a photo, but am planning to add wood to resolve the notching impact.

What about the box fill question?
 
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Old 04-14-17, 12:17 PM
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I've used surface mount LED's in stairwells many times. I use the low voltage ones that don't require a junction box..... just a power supply. Consider that.

If you need to work with the 120v type LED's..... use #14 wiring. #12 is too heavy and un-needed to be used in most lighting circuits.

Five #12 cables will never fit in a shallow box.

I put all my lighting on #14 (15A) circuits.
 
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Old 04-14-17, 12:23 PM
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Too late, now, but using a saddle box over a joist will give you a good fill (16 cu in) and eliminate the need for cutting wood. It just fits over the joist and is fastened securely from below. Price is about $8

16 cu. in. Round Ceiling Fan Saddle Box (Case of 50)-CFB-16 - The Home Depot
 
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Old 04-14-17, 12:37 PM
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Ahhhh..... ready to install.

The 3 cu in is what the fixture takes up inside the box and gets added to the wire fill.
 
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Old 04-14-17, 12:49 PM
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Don't know how these lights would fit in a saddle box.

#12 because it's part of a 20A mixed circuit including outlets.

What kind of low voltage? Any examples? Enough lumens from 2 fixtures?

So if I continue this way, still not clear on box fill. Does the 3 cu in simply get added to the wire calculation or 3 cu in + a device (the fixture) allowance?

Thanks!
 
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Old 04-14-17, 01:36 PM
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The 3 cu.in. is the device..... just like a switch or receptacle.
Part of its power supply must protrude into the box.
 
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Old 04-14-17, 01:44 PM
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Sorry, the "surface mount" zoomed right over my head. Yeah, you will need a full size round box to mount them in. Too bad you couldn't have used a side mount fan rated box. It screws to the side of the joist.

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