Adding a new switch to a branch

Hello all,

I want to add a new switched circuit to one of my branches. Can I just tap off the live wire and add a two way (SPST) switch to control some lights? What is the general best practice? Do I use a junction box, or do I use a switch box which breaks the live wire into 2 (one for my new switch and one for the current circuit)?

I live in Washington State, if that makes any difference due to electrical codes etc.

Thanks

 

Hello all,

I want to add a new switched circuit to one of my branches. Can I just tap off the live wire and add a two way (SPST) switch to control some lights? What is the general best practice? Do I use a junction box, or do I use a switch box which breaks the live wire into 2 (one for my new switch and one for the current circuit)?

I live in Washington State, if that makes any difference due to electrical codes etc.

Thanks

So you want to splice into a romex cable to add a branch (like a T-junction)?

Switch box = junction box.

Metal or Plastic? Plastic boxes are cheaper but they are awkward because the boxes are designed for use in walls and to cover it you use a blank wallplate like you would use on a wall, which makes it awkward but apparently it is correct.
Metal boxes look more proper. You can use an octagon box with romex clamps and a metal cover and it would look like a proper junction box, and also it would be easier to work with.

If you want to use plastic, get a box like this and a cover like this.
Cut the existing cable where you want to mount the box. Then punch the knockouts out of the box. Mount the box and staple the cables close nearby the box. Then insert the third cable that goes to your new devices and staple it. Then strip and do your connections. Finally, cover it up with the blank plate.

If you want to use metal, get an octagon box (or a square box) and a matching metal lid. (couldn't find the octagon box on HD website) You'll also need some cable clamps that fit the knockouts (unless the box has its own NM clamps). Then do your connections the same way with the plastic box.

There are many other boxes out there that you can use. But plastic wall boxes or metal octagon boxes are the most common for junctions (I think).

 

The standard is still 60w per bulb for the calculation of max for a 15 amp & 20 amp. Nothing will overload the Circuit Breaker, unless you install too many light fixtures on the branch circuit.

The only way that they would have access to 100 watt bulbs in the future, is if either they come across some hidden cache of them, or invent a Time Machine.

All can fixtures have a sensor that will trip when the unit gets too hot.

 

Greg is incorrect. The standard is not 60 watts per bulb. Recessed lights need to be figured at the maximum bulb size that can be installed with the trim. It does not matter the bulb size installed.

Branching or a second switch can be installed in a switch box. The power feed is spliced to both switches.

 

Merged your threads.

 

The trim should have a sticker on it with the maximum wattage allowed.

 

This has been discussed over and over on this site. http://www.diychatroom.com/f18/how-many-lights-15-amp-circuit-38486/

See NEC Table 210.24 and section 210.23(A)

 

I read section 210.24, and they seem brief, but I don't get a lot of information from it. Nowhere can I see it saying it there is a maximum number of the amount of things I can attached to the branch, except that it mustn't overload the branch. I also can't see the calculation I'm meant to use to see if I'm overloading the circuit.

If I read the forum post you linked, I see they write

As stated it doesn't matter what bulb you are using
It depends upon the Max wattage bulb that could be installed according to the fixture. IE my cans usually have a rating of 100w, but I only use the 23w CFL's

OK, so I'm using the Halo H99TAT, http://www.cooperindustries.com/con.../dam/public/lighting/products/documents/halo/spec_sheets/110469_h99tat_spec.pdf, I cannot see from the spec sheet what the maximum power the device can handle? I see popular models for lights, and the highest wattage I can see is 60W, but where can I find out the maximum power handling of the unit?

I also have trouble understanding the table (210.24). It's meant to be the minimum requirements, but it mentions tap and then a number 14. Taps? Does each light on the circuit form a tap, or is a tap just off the original branch cable (e.g. different switched circuits on same branch)

Unfortunately when i went to the NEC I could only find it when I signed up to nfpa and then I have to use their terrible, advert embedded online reader.

 

I'm not an electrician however, the trim dictates the maximum bulb wattage that can be used. Look at the spec sheet under the trim section. Each trim lists bulb type and watts. That's the max for that particular trim.

 

http://ecmweb.com/code-basics/branch-circuits-part-1
http://ecmweb.com/code-basics/branch-circuits-part-2

 

http://ecmweb.com/code-basics/dwelling-unit-calculations
http://iaeimagazine.org/magazine/20...ne/2013/05/16/residential-service-calculations-in-the-national-electrical-code/

 

poiihy there is no such thing as a "T" junction. What the OP is doing, is feeding another branch circuit from the incoming power from the panel. Only problem is that all branches that feed off of that single power feed, cannot exceed the max wattage as stated by the NEC for the circuit.

Without any drawings of what the OP is planning, along with a breakdown of details of max wattage of the cans, regardless of the bulbs that they place in them. There is no way of telling them if only one branch will work, or that they need multiple branches from multiple breakers (ie MWBC on 2 15 amp breakers or MWBC on 2 20 amp breakers).

 

poiihy there is no such thing as a "T" junction. ).

Would you like to explain why you think this does not exist? It iis possible for a T to occur in a branch circuit.