Ask Me Help Desk - Load calculations

I want to add 10 ceiling recessed lighting fixtures rated at 65W each to an existing 15A circuit. In addition to these the circuit will have 7 outlets, ceiling fan with 4 bulb light kit and porch light. The ceiling fan is older so I am going to guess its power consumption at 75W without the bulbs (new Hunter fans are at 45-55W). The light kit I would estimate at 75W each bulb and the porch light at 75W. Am I overloading a 15A circuit with all this?

Quote:

Originally Posted by mauricee

I want to add 10 ceiling recessed lighting fixtures rated at 65W each to an existing 15A circuit. In addition to these the circuit will have 7 outlets, ceiling fan with 4 bulb light kit and porch light. The ceiling fan is older so I am going to guess its power consumption at 75W without the bulbs (new Hunter fans are at 45-55W). The light kit I would estimate at 75W each bulb and the porch light at 75W. Am I overloading a 15A circuit with all this?

Let's start this way, please. Because your circuit feeds multiple receptacles you are restricted to an 80% load. Effectivley this means that you sholud not have more than a 12 Amp load on the entire circuit, This is because at any given point in time the load on the receptacles may vary and could cause an overcurrent condition.

With that out of the way, the load on the lights (65 Watts X 10= 650 Watts)
(75 Watts X 5 = 375 Watts) I do not trust your guestimate on the fan motor, can you get the amperage off the motor label?

650 Watts + 375 Watts = 1,025 Watts / 120 Volts = 9 Amps (rounded up.

That just leaves you 3 amps for all 7 outlets, Way to low!

Two suggestions:

1) Add a new 15 ampbranch circuit for 10 new lights.
2) Convert the entire circuit to 20 amps using 12 AWG copper cable. At 20 Amps you will be allowed to bring the circuit load up to16 Amps.

Looks like I will add a 15A circuit for the recessed lighting.

The fan motor reads .6A 65W. I wasn't far off.

For future reference how do I figure outlets into load calcs?

"Because your circuit feeds multiple receptacles you are restricted to an 80% load." Can you elaborate on this? Are there circumstances where you can be at 100% load?

Just the new lights alone = 33% of a 15 Amp circuit. Add the other lamps and you have minimal possibility of running any decent load on the outlets. Add another 15 Amp circuit for the lights.