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Most of the recessed lighting fixtures I see in stores have a metal junction box separate from the can. There is an armored cable running from the junction box to the can already. You connect your NMD90 wire to the junction box. Makes sense.

However, I have two of these recessed lighting fixtures. They have a junction box attached to the top of the can itself.

The junction box itself says I have to use wire rated to 90C, which NMD90 wire would be. My question is, do I have to use metal clad (MC) wire from the power source to this light, or can I just use NMD90?

Edit

The back of the junction box says:

MAXIMUM OF 8 NO. 12 AWG
THROUGH BRANCH CIRCUIT
CONDUCTORS SUITABLE
FOR AT LEAST 90 C
PERMITTED IN A BOX (4 IN 4 OUT)
FOR FLEXIBLE CONDUIT ONLY

I'm not sure what that last line means: "for flexible conduit only".

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  • The last line means you can't use rigid conduit. – Tester101 Apr 16 '12 at 13:17
  • Does BX (MC) count as "rigid", or is that term reserved for truly inflexible conduit like PVC or metal pipe conduit? – KeithS Apr 16 '12 at 14:30
  • @KeithS Metal Clad Cable (type MC) is a cable assembly, not a raceway. It is not conduit at all. That would be like calling the jacket of NM cable, flexible plastic conduit. – Tester101 Apr 16 '12 at 16:17
  • @Tester101 - that is kind of what I assumed from other references. Thanks for the confirmation. – Scott Whitlock Apr 16 '12 at 22:58
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You are required to use whatever type of wiring your local code permits for this type of connection. If you are in a residential location then it is likely NMD90; if you are in a commercial location then it will likely require BX/AC. The shielding you are referring to between the can and the box isn't really BX/AC; its just flexible metal conduit. It looks similar to BX but it's not the same thing.

If you do use BX/AC, make sure to use plastic bushings at both ends of the cable so you don't nick the conductors with the sharp BX/AC.

Usually with cans, there is a friction cable clamp you just push the NMD90 through, however if you use BX/AC then you will need to use one of the punch-outs and a proper cable clamp to secure the cable.

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  • The junction box only has punch-outs on this model. I assume I have to buy the clamps that go in the punch-out holes. – Scott Whitlock Apr 16 '12 at 22:57
  • I didn't notice them first on some cans I worked with, but if they are not there, yes you will need to use the punch-out and a clamp. With NMD90 I believe you can use the plastic push-in clamps. With BX you need to use the screw-type. – Steven Apr 17 '12 at 2:19

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