Building a new circuit

[Craig20]

I am refinishing my basement to be a home office. As part of this project I want to add some additional outlets and 8 recessed lights. The lights are to be separated in to 3 groups with each group controlled by a separate switch. All 3 switches will be mounted in a 3 gang switch box. The service panel is on the opposite side of the basement from the switch box location.

Given the number of lights and outlets I am adding I figure that it would be best to create a new circuit from the service panel. I have mapped this circuit out and feel pretty confident in my plan but this will be my most complicated electrical project to date. It would be great if some of you could review it and provide me with any feedback you have.

Here is the circuit diagram. Thanks!

[HayZee518]

New Project

Craig as per our discussion try this circuit for size.

[buckofdurham]

I agree with Hayzee.

You don't need 14-3. Just bring 14-2 staight to your 3- gang switch box.
Then go back out to your lights.

The only other thing don't forget your equipment grounds. Their probably the most important wires.

[pushkins]

Is a 15 amp circuit enough juice for 9 lights (max. 100 watt for calcs.) and 3 outlets ?

[Craig20]

As I understand it a 15 amp circuit can safely power up to 1440 watts.
Here is the expected load:

9 Lights @ 100 watt max = 900 w
26" color TV = 110 w
DVD Player = 25 w
PC & Monitor = 125 w
Radio Battery charger (x 2) = 35 w
------------------------------
TOTAL = 1195 watts

Assuming 100% load on the above there should be 245 watts spare on the circuit.

I could add another 480 watts for a total of 725 watts of spare by upgrading to a 20 amp circuit but I am not sure that is really necessary.

[pushkins]

Your calcs. are good, except I believe your supposed to work on a 80% of total load. that would bring you back down to 1152 watts, just under the wire in my book. If it were me I'd upgrade to 20 amp. never know when you need it and it's much easier to do now for very little extra cost.

[buckofdurham]

Yeas a 20 would be good but the wire in the boxes is harder to work with.
You could bring a 14-3 out of the main panel to the switch box. Have two circuits share a neutral. One for the outlets and one for the lights.
If your jurisdiction has adopted the 2008 NEC you would not be able to share a neutral. In 08 you have to use AFCI breakers.

[Craig20]

I am pretty sure that 1440 is the "safe load" (ie: 80&#37 of a 15 amp circuit.

15 amp * 120 Volts = 1800 watts
80% of 1800 watts is 1440 watts

At peak, a load of 1195 watts would be 66% of max and 82% of "safe load" of a 15 amp circuit.

20 amp * 120 volts = 2400 watts
80% of 2400 watts is 1920 watts

At peak, a load of 1195 watts would be 50% of max and 63% of "safe load" of a 20 amp circuit.


So, what is the "magic" number that I should be shooting for?
I don't want to over do it, but I definitely want to be safe.

[HayZee518]

9 bulbs at 100 watts equals 900. divide this by 120 and you get 7.5 amps.

[HayZee518]

buck of durham. using 12 would be ok, but you also have to consider "box fill" for conductors. 14s in a 3x2x21/2 inch box just about makes it, but the same amount of 12s in the same box is prohibited. he'd have to go with a 4x4x11/2 square with a plaster ring to stay within the box fill clause.