Can I splice wire together in a junction box in my attic?

Answer 1

IF you are picking up power for another light somewhere, yes is the short answer! Just follow normal code, be careful not to splice to a switched circuit (light) or your power will be off when the light is off!  

Answer 2

Yes, so long as the box isn't covered up by construction. It must be accessible and it must have a s***w on cover.

Answer 3

Yes. So long as your code and the box fall into the size category. Some boxes are 6 wires @ 10 GA. and some are 6 wires @ 12 ga. and so on. You are only allowed so many splices per, run, box,switch, outlet, breaker, etc. you get the idea.

I am sure you probably can add just the one and be ok. So long as the box and circuit and wire are not overloaded.

That is what a junction box is technically for. Wire Junctions, aka (splices).

Make sure you go, black to black, white to white, bare to bare.

Some codes do not allow you to make a spice in a run. Well except for a light.  But, the bottom line is that as long as you have the proper sized wire nuts for the amount of wires and the gauge of wires, you should be ok.

Answer 4

Yes, if.....

All splices are required by the NEC to be in listed junction boxes or conduit bodies with a marked volume. The "if" part of the answer is "if it won't cause the box to become overfilled".

All boxes have a maximum wire & device volume either assigned to them by the NEC (so-called "standard" boxes), or marked on them at the factory. This volume is generally listed in cubic inches. The reason it is important not to exceed the allowed conductor-fill volume is to allow for the dissipation of the heat the current generates as it travels through the conductors. A "standard'" 1900 box (4" x 4" x1-1/2") has an assigned volume of 21 cubic inches (some are marked at the factory as 20 or 22 cubic inches, you should always check the inside of the box). If you have a Type NM cable system, there may also be clamps built into the box, this is important because the clamps count as 1 conductor of the largest AWG size in the box.

Conductor volumes, as assigned by the NEC are 2 C.I. for a #14, 2.25 C.I. for a #12, and 2.50 for a #10. Wire nuts do not count, but each wire being spliced with the wire nut counts 1 time, as do any conductors passing through the box without a splice (if you have a raceway system installed, this is very common). What is more, after the 2002 NEC, any conductor passing through the box that is more than 12" long counts as 2 conductors.

Since you are asking about a splice in the attic, I won't say much about the volume of a "device ring", since you probably will be installing a flat "blank" cover. If a device ring is installed (such as for an attic light, the volume of the device ring can be added to the volume of the box ONLY if the ring has a volume marked clearly & legibly on it by the factory (stamped or formed into the box).

To check your conductor fill, simply open the box and count the conductors, one size at a time. (The grounding conductors all count as only one conductor based on the largest size in the box.)

If, for example, you have 3 #14-2 cables, 1 #14-3 cable, and 2 #12-2 cables, all with a grounding conductor, with a "Romex" box using integral clamps; the volume is calculated like this:

You have 9 # 14 AWG conductors x 2 C.I. each = 18 C.I.

4 #12 AWG conductors x 2.25 C.I. each = 9 C.I.

1 equipment grounding conductor (#12) = 2.25 C.I.

1 clamp volume (based on a #12 conductor) = 2.25 C.I.

Your total conductor volume is 30.5 C.I., so you would need to install a new box. Using a standard sized metallic square box 4” x 4” x 2-1/8“ (a 1900 deep box) only provides 30.3 C.I. of space (NEC Table 314.16); so you would have to go to the next largest “standard size” box, (an “11-B, deep”), which is 4-11/16 inches square x 2-1/8” deep. This provides a volume of 42 Cubic inches.

While I will generally pass a box that IS marginally over-filled, THAT is a judgment call that the Inspector in the field has to make. The Code does not give any plus/minus figures. Remember, the whole purpose of these calculations is to keep excessive temperatures from damaging the conductor insulation. In an attic, the ambient temperature of the conductors may have already been a factor in determining what their sizes where allowed to be; so don’t push the fill limit too far. Adding devices like switches or receptacles also count towards the fill count. Consult NEC Article 314 before adding to box fill (2005 NEC).

As for the other part of your question, can you do this in the attic? YES, just remember that the NEC requires all boxes to be “accessible”. This means they can be opened without removing any of the building’s finished surfaces. I have also taken to interpreting this as allowing the boxes to be located under the insulation. Either mount the box up high, above the insulation, or identify its location. I have always done this myself by using the small marking flags used by surveyors. They can be attached to the outside of the box with cable ties, or stapled to the building framing directly alongside or above the box.

Be sure you cover the box with a listed cover; I have lost count of the number of times that I have been “tickled” in the leg or arm by a box buried beneath the insulation that was not covered, and had not had the splices wirenutted securely together.

When in doubt, or in trouble (hopefully before), call a qualified, licensed Electrical Contractor. “Swallow your pride before burning down your house” is the best advice I can give. ALWAYS check for any local amendments, and to see what edition of the NEC (or ICC Electrical Code [IRC Chapters 33 -39, plus the Administrative Provisions]) your jurisdiction has adopted.

My apologies for the long-winded answer, I just want you to do it safely if you do it.

Answer 5

Any splice should be in a grounded junction box.

Answer 6

That is the place to do it.  Wire nuts and make sure you fasten the cover back when you are done.