I have been working on finishing my basement and am starting my rough in electrical. I am learning as I go and have gotten most of the basics down.. calc load, box size, stapling, supports etc.

One thing I cant figure out is if you can have a junction within a live outlet or recessed light. Ideally I would like to run a Y from my last recessed light can with one line going right, to a receptecle and one going left, to the end switch. I am guessing this is against NEC code but have been unable to find out for sure, partly because I am unsure of the correct terminology for it.

Can someone point me in the right direction? Is this even called a junction? or is it called something else like a branch?

I am getting a pro to do some of the finish connections but I am doing all of the rough in.

  • ok thanks. From the responses below it appears the only limiting factor is box size and possibly accessibility. This will make doing the rough ins a lot easier. thanks Commented Nov 12, 2013 at 5:49

3 Answers 3


Modern recessed lights have junction boxes built in.

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Similarly on a new work recessed fixture

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You are free to daisy-chain other lights or receptacles, so long as you connect properly and do not exceed the number of wires for the size of the built in box. A chart to calculate this can be found here.

  • Hi, I know I can daisy chain. I am asking about splitting/junction/Y connect in a box, not daisy chaining. I am using the above H7ICT halo box Commented Oct 24, 2013 at 3:40
  • If by splitting/junction/Y connect you mean power in on one cable, and two (or more) fixture wires out, tying all the blacks together, all the whites together and all the grounds together, yes.
    – bib
    Commented Oct 24, 2013 at 11:38

According to the National Electrical Code (NEC), there are only two factors that limit you.

Conductor box fill

If you're working with standard sized boxes, you can use Table 314.16(A) to determine the number of conductors allowed in a box.

Table 314.16(A)

If you're using non-standard boxes, you'll have to make the calculations yourself. Basically, it works like this.

Conductor Fill

  • For each current carrying conductor (ungrounded (hot), or grounded (neutral)) that terminates or is spliced within the box, add 1.
  • For each conductor that passes through the box without splice or termination, add 1.

Clamp Fill

  • If there are any internal cable clamps, add 1 (not 1 per, just 1).

Support Fittings Fill

  • If there are any luminaire studs or hickeys, add 1 (not 1 per, just 1).

Device or Equipment Fill

  • For each yoke or strap containing one or more devices, add 2.

Equipment Grounding Conductor Fill

  • If equipment grounding conductors enter the box, add 1 (not 1 per, just 1).

Volume Allowance Calculation

Use this Table 314.16(B) to calculate the total box fill.

Table 314.16(B)

  • Sum up the count from the Conductor Fill section, and multiply by the value from the table. For example: If you had 4, 14 AWG conductors, you'd multiply 4 by 2.00.
  • Sum up the counts from the Clamp Fill, Support Fittings Fill, Device or Equipment Fill, and Equipment Grounding Conductor Fill sections, and multiply by the value from the table of the largest conductor in the box. For example: If this value was 4, and the largest conductor in the box was 12 AWG. You'd multiply 4 by 2.25.
  • Add the 2 totals together. For example: Using our values above (4 x 2.00 + 4 x 2.25 = 17), you'd need a box with a volume of 17 in. cubed.

Wire Connector Capacity

If you're using twist-on wire connectors, each connector can connect a specific number and size of conductors (Check manufacture documentation). This will limit the number of wires connected together. If you're using push-in wire connectors or terminal blocks, you'll be limited by the number of terminals.


If you want to supply multiple devices downstream; but the devices are in opposite directions, there should be no problem splicing multiple cables together to feed the devices.


Your question is not clear at all. Yes you can "split" inside a junction box, as long as you keep the connections within the limit allowed by the NEC per box volume. -Running a "y"- is not a term used by electricians, but by plumbers. Yes you can "run a Y" in a J box if I know what you may mean

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