Number of wires per junction box


Old 01-14-06, 12:06 AM
Thread Starter
Join Date: Jan 2006
Posts: 4
Number of wires per junction box

We have a game room that's on a 15 amp circuit that currently has a total of 350 watts of ceiling lighting and outlets on it. I wanted to add a ceiling fan, recessed lights and a couple more outlets. If I put a junction box in the ceiling, is there a maximum number of 14 guage wires that can be connected together with wire connectors because there would be 6 wires connected together (and is there a maximum number of wires per box). Coming into the juntion box would be:
- one 14-2 wire used for a switch and 3 recessed lights(65 w each)
- one 14-2 wire used for a ceiling fan/light and 3 outlets
- one 14-2 wire used for a switch and 3 lights (60w each)
- one 14-2 wire used for 3 outlets
- one 14-2 wire used for a switch and 4 recessed lights (65w each)
- one 14-2 wire that's hot

Sponsored Links
Old 01-14-06, 06:05 AM
Join Date: Jan 2006
Posts: 78
Their shouldn't be a limit to how many you can connect so long as you dont go over the amperage limit for the wires. to figure out your amperage usage from the watts use Ohm's Law ( google it).
Old 01-14-06, 06:55 AM
itsunclebill's Avatar
Join Date: Jan 2006
Location: Denver, CO area
Posts: 221
The number of wires allowed in a box is determined by the size of the box and the size of the wire. Plastic boxes are marked with the maximum number of each size wire. Metal and other material boxs fill is based on the box size in cubic inches and the required space for each conductor size.

#14 wire require 2 cubic inches each. All the grounds together count as 1 wire. In your case, 6 cables with 2 wires each plus a ground requires a box that is big enough for 13 #14 wires. This winds up being a 4 X 4 X 2-1/8 (or deeper) metal box, or a plastic box rated for 13 or more #14 wires.

Generally, the number of connections in a box doesn't matter as the required space in a box for a given size wire takes connections into account. I generally like to limit the number of wires in a wire nut to 4 as more makes getting a good connection with all the wires a bit tough. I would also encourage you to run different circuits for receptacles and lights so plugging in something with a problem doesn't leave you in the dark

Old 01-14-06, 10:17 AM
Join Date: Nov 2004
Location: USA
Posts: 973
As itsunclebill stated, the box must be large enough (in terms of cubic inches, or "cu in") for the number of wires, and size of the wires. This is termed "box fill".

To calculate this, you add the number of wires (not counting grounds), plus one for any grounds, and plus two for every device in the box (receptical, switch, etc). In your case, you have 12 wires, plus 1 for grounds, , no devices, so you count it as 13 wires. The fill is then based on the size of the wires. For #14 wires, each counts as 2 cu in. So 13 * 2 is 26 cu in. You need at least a 26 cu in box. If you think you may ever add additional cables, you will want a bigger box.

Keep in mind, this junction box must be PERMANATELY ACCESSABLE. You CANNOT close it up behind drywall. If you install a drop ceiling, it can be accessable by moving a ceiling tile.

If you use a metal box, you will need to be sure to ground the box as well.

I would strongly urge you to try to reduce the number of cables coming into this box. Securing six wires into a wirenut is going to be VERY hard. Also, the advice to put the lights on a separate circuit is good (though certainly not required).
Old 01-14-06, 11:55 PM
Thread Starter
Join Date: Jan 2006
Posts: 4

Thanks for all of your replies. Once I started, I realized there were some other wires that needed to also go into a junction box so I divided them into 2 boxes and I bought the 6x6x4 size boxes, just to be on the safe side (plus have extra room to work). I did connect 6 wires together...... and it was a bit of a pain. Thanks again for all of your help and the box calculation.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes