Will I overload this circuit?

Question

I currently have 9 items on one 15 amp circuit.

On one 15 amp wire (one 15 amp circuit) there are the following 9 items:

1) Back Door outside Light (one bulb, 75 watt)

2) Light fixture above Washer and Dryer (two 75 watt bulbs)

3) Light in Garage (one 100 watt bulb)

4) Lights for automatic Garage Door Opener (two 60 watt bulbs)

5) Automatic Garage Door Opener (unknown wattage)

6) Two outlets in the garage (sometimes used, for example, to vacuum car)

7) Garage roof Attic Fan (unknown wattage)

8) Two light fixtures on the outside of the garage door (one on either side) (two 60 watt bulbs)

9) One outdoor motion light fixture with two 100 watt bulbs.

Here is my question. There are currently 9 items shown above. I want to add another item so the future total will be 10 items. This is what I want to add : I want to add ANOTHER outdoor automatic motion light with two 100 watt bulbs. Will I be overloading this 15 amp circuit?
Thank you.

Answer 1

I believe it is ok to add your 200 watts of power. However, you need to determine the wattage or amperage of the garage roof attic fan. It typically doesn't get hot enough here in Montana for these so, I'm not sure how much power they use.

All of your current lights are using 765 watts of power. If you divide that by 120 volts you get 6.375 amps. Adding the additional 200 wats of lighting only increases your load by another 1.67 amps.

If you need further assistance, please visit -
http://electricalblog.gilchrist-electric.com

Answer 2

You are currently using 865W in total on the lighting and your other unknown wattage items. The attic fan will be pretty much nothing (20-100w?). The garage door opener motor is probably about 1/2hp (about 300-400W). If you use a vacuum cleaner your talking maybe 1-2kW depending on the cleaner. So, if everything went off at once and we used worst case you'd be using a total of about 3365W.

To work out the power of your 15A supply we need to know the voltage. Power=Voltage X Current, so at 240V a 15A supply will give a max of 3600W so you've got about 235W spare to run your two extra 100W lights. It might be close, but you'll only get close to blowing the fuse when your closing the garage door while hoovering the car while an intruder cuts past the lights at night with all lights blazing!

If you're on 110v you've only got a maximum of 1650W and the answers don't add up, so at least we've got a better voltage in the UK and MORE POWER!!!!

Answer 3

I believe gilchristelectric is your best answer in this case but I would like to add that if you do in the future put enough on the circuit to max out the 15 amp breaker, DO NOT just go to the breaker box and put in a 20 amp breaker. If it has a 15 amp breaker, the wire running from that breaker is only rated for 15 amps. If you put in a 20 amp breaker you run the chance of overloading the wire and causing an electrical fire.

Answer 4

Total all the watts you want to have on the circuit, divide by 120 and that gives you the amperes you will be using. That figure should not be more that 80% of the rating of the circuit breaker. (You can cheat on that 80% for a few seconds but not too long.

Answer 5

Its ok to add to two more items, but if a short circuit or a earth leakage happens, than all the ten items would goes off, its better to break it up with five each. And 10 amp circuit for each five items.

Answer 6

Add the total wattage the circuit will draw and divide it by 120, this will equal the circuit draw. Amps = watts/volts

Answer 7

no it should be fine. as long as all your lights arent on while youre vacuuming car,opening garage door,attic fan running,and youre also using the other recpt in garage. then you could overload it but what are the chances. seriously it should be fine. you are allowed by code 80% of the breaker which is 12 amps continuous load so add them

Answer 8

No problem. Amperage will be less than the calculated amounted determined by the imperical formula method.
Go ahead and add it!!