View Full Version : New Recessed lights-existing switched outlet, options?

May 17th, 2003, 12:31 AM
I am installing new 4 new recessed lights in a bedroom that currently has a switch that controls 1/2 of a duplex outlet. I have a spare circuit (unused 120V) in the attic and accessible. I have 2 questions.

First, can I change the switch box into a 2 gang box and add a second circuit that will feed a separate dimmer switch for the recessed lights, and not touch the switched outlet?

Second, if I wanted to use the feed from the switched outlet as the feed to the recessed lights, how do I figure out if the circuit (by code) can handle the additional 4-65W R-30 bulbs? The circuit currently feeds the bedroom outlets, as well as the bathroom light bar and exhaust fan, and may feed other things that I haven't tracked down yet.

May 17th, 2003, 07:50 AM
You can convert the switch box to a double gang. Run the available circuit down to the new dimmer then to the lights.

To use the existing switch, you need to trace every electrical outlet to verify that you will not overload it. A 15A circuit can handle 1440 watts.

May 20th, 2003, 08:47 AM
Please confirm my understanding of the 1st option is correct. I understand that I may have two 120V circuits in a 2 gang box feeding different switched load, with no special requirement about the circuits. I had previously heard from friends that there may be a requirement to have both circuits fed from the same polarity, or another version was that the circuit breaker handles needed to be "clipped / ganged" together so that with one motion all the electric in the box would be dead.

I am also looking for a more in-depth understanding of the second part, the circuit loading question. Consider the following situation. The circuit that I am going to tap into for these 4 new 65watt (total 260 watts) recessed lights already feeds a switched outlet in a bedroom, a bathroom exhaust fan (approx 40 watts), a bathroom ceiling light / light bar (200 watts), and a number of other general purpose outlets in 2 bedrooms and a hallway. The direct connected load will be 500 watts (260+40+200). How do I calculate the amount of load for the intermittently used outlets. Is there a factor that is used for each outlet? Also what about diversity, do I assume that all of the direct connected load is on at the same time? Lastly, do I use the full 1440watts for a 15amp circuit, or due to the diversity issue, is there a rule about loading a circuit up to something like 120% of the rated load?

May 21st, 2003, 10:44 PM
If you want the light and receptacle on the same switch [not dimmer] then you can use the following link. If power is in the receptacle as suspected. You may also use that as an idea how to make the receptacle always hot and switching the new lights using the same switch. Doing this you would fish a 12/2wGrnd from that switched receptacle to the first light then daisy chain from light to light with 12/2wGrnd romex and you are done.


I am suspecting your power is in the receptacle. If true then I suggest it would be easier to separate two single boxes installing the second dimmer switch in its own box using a remodel switch box and picking up a new power. Converting a single gang box to a double gang box usually means patching drywall. Not hard to do if that is what you wish.

It is not a code violation to have more than one branch circuit in the same box as you discribe. You are fine with two power sources in the same box.

You are adding general lighting for that same room the new load you are installing replaces the load on the receptacle to create the required lighting for that room You would not be considered as adding load to that branch circuit.

However if you wish to calculate load the 15 amp branch circuit is allowed to be loaded to 100% loading 1800 watts per 15 amp circuit for general lighting. The convenience outlets you have are unknown loads and are considered as general lighting branch circuits allowing to be loaded 100%. As Ron mentioned the 1440 watts on a 14 awg wire loads to 80% giving you some growing room or extra load during a party and such if you like. Not bad advice.

The NEC does not set watts per receptacle for dwelling convenience receptacles. If you want to use a number the NEC sets 180 watts per receptacle if used commercially. You may use this number multiplied by the number of receptacles for an easy calculation but not really that accurate in an intermittent general lighting convenience outlet design.

I do not beleive you have a concern to install general lighting in a bedroom. To me you are not increasing load but creating an option. You are either going to light that room by the new lights or the switched receptacle but not commonly both.

Just my opinion