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The voltage here in the Philippines is 230 volts. I searched for the calculation of the capacity of a circuit breaker. So I found out that 15-amp breaker at 230 volts can handle 15x230x.80 percent = 2760 watts. Now, 2760 watts/75 watts = 36.8 lights. So, if I understand correctly, I can install 30 lights in a 15-amp breaker. However, I don't want to miss something, is this calculation correct? Also, will it be fine if I will turn on all 30 lights at the same time?

EDIT We will use #14 thick wire. Is this also correct?

Thanks!

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    Off-topic: Do they not have LED or compact fluorescent bulbs in your area? This seems like a prime opportunity to "do it right the first time", and your power consumption would be cut by 75%. – isherwood Dec 2 '16 at 19:30
  • @mmathis, separate receptacles. 1 light per receptable. So, may I know if my calculation is correct? That I can have as much as 30 lights in 1 circuit breaker? If I turn on all 30 lights at once, will there be no issues with the #14 wire? – user1764381 Dec 2 '16 at 19:34
  • @mmathis, I will certainly limit the number of receptacles on a circuit according to the code, however, I just want to make sure that my understanding of the calculation is correct. – user1764381 Dec 2 '16 at 19:35
  • @isherwood, we also have LED here and I would agree to less power consumption. However, I just want to make sure first if my calculation is correct. After that, I can decide about how to reduce power consumption, limit the number of receptacles/lights according to the code, etc. – user1764381 Dec 2 '16 at 19:38
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Strictly speaking, you are correct. The circuit can handle 15 A * 230 V = 3450 W before tripping*. As a safety margin, you want to stay below 80% of that, or 2760 W. Your 30 bulbs, at 75 W per bulb, draw 2250 W total, which is within the safe operating load of the circuit. So, from a physical standpoint, you're good. #14 wire is appropriate for a 15 A circuit.

However, as mentioned, you want to be aware of any local codes which limit the number of fixtures or receptacles on the circuit. As @isherwood mentions, too, you may want to consider a lower-power bulb (like LED or CFL) if it works in your situation, or an alternative lighting solution - e.g., do you really need 30 bulbs? Could you get the same result using half as many bulbs that output more light? 2200 W is a lot of power usage for lighting, so any way you can reduce that will be beneficial to your wallet :)


*In a perfect world. In the real world, breakers don't trip immediately when reaching their current limit, etc, etc.

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    Thanks! Yes, I don't really need 30 bulbs, I just want to understand it theoretically so that I could decide how many amps should I use for different appliances (e.g.: ref, washing machine, stove, etc.) – user1764381 Dec 2 '16 at 19:53
  • I have problems with the local AHJ restricting outlets in residences but lighting loads are not an issue as long as 80% of the OCPD is not exceeded, for Residential, Commercial and Industrial installations. – Ed Beal Dec 2 '16 at 19:54
  • @user1764381: Note that in some jursidictions, local code or regulations may require a specific calculation that takes into account the likely usage of different types of device - for example, lights are likely to be on continuously for hours at their rated power, some other devices are not. Also there can be guidelines about not mixing lighting with other loads. Check local regulations. – RedGrittyBrick Dec 2 '16 at 21:55
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30 lights at 75W is 2250 total, 15 amps on a 230V breaker 3450 available. generally we use 80% for lighting loads 2750 is left so this would pass code in the U.S. (Your local regulations may be different).

  • Actually the later answer is at the top but it is not a problem you got the same info from multiple sources so you can have confidence in the answers. – Ed Beal Dec 2 '16 at 19:57
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    Not a problem good luck with your project. – Ed Beal Dec 2 '16 at 20:02

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