Calculating how many lights on circuit

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Jmaclicious
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Calculating how many lights on circuit

Post by Jmaclicious » Sun Mar 05, 2017 10:03 pm

I was thinking... according to code they suggest a maximum of 12 lights or outlets per circuit, or 80% of the load of 15 amp circuit... idk if I am getting confused here but I am planning to use slimled 9w 120v lights, 80% of the load is 12 amps which is approx 1440 watts.. I am looking to put about 22 lights throughout entire basement with a few switches... each light according to my math would be 9w or 0.075 amps.. so technically I could put all of these lights onto 1 circuit ? in Canada btw.

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Shannon
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Re: Calculating how many lights on circuit

Post by Shannon » Mon Mar 06, 2017 7:19 am

The codes have not really caught up with the LED lights yet , I think you are fine as long as these are light fixtures with a Led diode and not an LED bulb that could be removed and replaced with a different type of bulb.
Wait and see what Aaron and Wayne have to say on this.
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Aaron
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Re: Calculating how many lights on circuit

Post by Aaron » Mon Mar 06, 2017 10:33 am

Yeah in the NEC code for the US, there actually is no limit to the number of outlets (which refers to both lights and receptacles) per branch circuit. You have to make the load calculation yourself. I think Canada CSA code does have a limit on the number of outlets per branch circuit - it may be 12 as you say, Wayne would know for sure.

Either way, you shouldn't assume that the lights will always be LED. I would still wire the circuits with the assumption that an old-fashioned 100W incadescent could be screwed in to the socket.

Shannon's right that the codes haven't caught up with LEDs. I think it still follows a sort of worst-case scenario for high-wattage lights.

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emtnut
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Re: Calculating how many lights on circuit

Post by emtnut » Mon Mar 06, 2017 11:46 am

Jmaclicious wrote:I was thinking... according to code they suggest a maximum of 12 lights or outlets per circuit, or 80% of the load of 15 amp circuit... idk if I am getting confused here but I am planning to use slimled 9w 120v lights, 80% of the load is 12 amps which is approx 1440 watts.. I am looking to put about 22 lights throughout entire basement with a few switches... each light according to my math would be 9w or 0.075 amps.. so technically I could put all of these lights onto 1 circuit ? in Canada btw.
If your circuit has ONLY lighting, then you are not bound to the '12' devices rule.
As Shannon said, you have to calculate the wattage of the fixture, not the light. ie. if the fixture says maximum 100Watts ... that's what you have to calculate.
Many of the newer LEDs (don't accept standard bulbs) are rated very low .... so you can put A LOT of them on the circuit.

If you put even 1 receptacle on this circuit ... you're back at the 12 max devices thou !
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Shannon
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Re: Calculating how many lights on circuit

Post by Shannon » Mon Mar 06, 2017 6:53 pm

With AFCIs being needed now in most areas it make sense to keep lighting circuits and receptacle circuits separated IMO.
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Aaron
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Re: Calculating how many lights on circuit

Post by Aaron » Tue Mar 07, 2017 10:37 pm

Yes, agreed... I would always keep lighting separate from receptacles. That way you have the freedom to have just two or three lighting circuits in your entire house, and run them in with low-cost 14/2.

I can see some time in the future where we may even run LED-exclusive lighting circuits with 16/2 or even 18/2, connected to a 10A or 5A breaker.

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Re: Calculating how many lights on circuit

Post by emtnut » Wed Mar 08, 2017 9:32 am

Shannon wrote:With AFCIs being needed now in most areas it make sense to keep lighting circuits and receptacle circuits separated IMO.
Most guys are wiring that way now. Saves on an AFCI breaker ... also, smoke detectors need to be run off a lighting circuit. If that circuit has AFCI, you either need to run a separate circuit to it, or have the smoke det with battery backup.
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Aaron
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Re: Calculating how many lights on circuit

Post by Aaron » Wed Mar 08, 2017 12:25 pm

I think smoke/CO detectors ought to have their own dedicated plain breaker with 14/3 run from the panel to the first detector and daisy-chained to each one down the line. You need that third red conductor for alarm interconnection.

The red wire remains stubbed in the breaker panel for future add-on alarm interconnection.

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Re: Calculating how many lights on circuit

Post by Shannon » Wed Mar 08, 2017 7:02 pm

Aaron wrote:I think smoke/CO detectors ought to have their own dedicated plain breaker with 14/3 run from the panel to the first detector and daisy-chained to each one down the line. You need that third red conductor for alarm interconnection.

The red wire remains stubbed in the breaker panel for future add-on alarm interconnection.

I believe they are usually placed on a lighting circuit so that if the breaker trips for some reason you will be aware of it sooner and get the problem fixed . If they are on there own and tripped the breaker for some strange reason you may not even realize it and they will not be activated.
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Aaron
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Re: Calculating how many lights on circuit

Post by Aaron » Thu Mar 09, 2017 10:15 am

Oh, that's actually a very good point.

Most modern ones will sound or display an alarm or something if they do not have AC power, and I think all AC-wired ones have a 9V battery backup. But yeah, they take hardly any AC power at all so tapping them off a light circuit is actually not a bad idea and really nudges the homeowner to take care of the circuit rather than just ignoring it--as people tend to do.

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Re: Calculating how many lights on circuit

Post by AdamJamma » Tue May 15, 2018 7:51 am

Newer codes in some places require the AFCI circuits to disable the lights when they blow... not happy with that, because you then need to bring a light in to fix the problem...
If I am right and the AFCI circuit is the same as the RCD circuit in the UK, then it is recommended and expectedto be required that the lighting circuits be on such a circuit, to reduce shock from changing the bulbs.
But, UK also does something a bit different in using what is a split panel, where two RCD breakers cover the whole of the panel, and neutral and ground are always kept separate... but you can actually check the wiring because the grounds, and neutrals, are put on numbered bars, corresponding to the appropriate breakers, so you know which neutral goes with which ground and which live wire...

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Re: Calculating how many lights on circuit

Post by AdamJamma » Tue May 15, 2018 7:54 am

Also, my practice in the past for wired alarm circuits such as fire alarms, etc, usually meant that the red wire used to interconnect from one alarm to the next also connected to a main panel that had a visual (light) showing it as in use, along with a green light showing power on the circuit. Usually it contained a UPS system of some type. I agree to using the three core and ground for such use.

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Aaron
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Re: Calculating how many lights on circuit

Post by Aaron » Tue May 15, 2018 9:29 am

AdamJamma wrote:
Tue May 15, 2018 7:51 am
Newer codes in some places require the AFCI circuits to disable the lights when they blow... not happy with that, because you then need to bring a light in to fix the problem...
Yes, in the United States (NEC code), all residential circuits are required to be AFCI in newly-constructed or renovated homes. In Canada (CEC code), you can still use just standard over-current protection if and only if all outlets on the circuit are fixture boxes for lights and/or smoke detectors (no receptacles).

At least that's the case for now.
AdamJamma wrote:
Tue May 15, 2018 7:51 am
If I am right and the AFCI circuit is the same as the RCD circuit in the UK, then it is recommended and expected to be required that the lighting circuits be on such a circuit, to reduce shock from changing the bulbs.
RCD and RCCB, Residual-Circuit Device and Residual-Current Circuit Breaker, are equivalent to GFCI plugs/receptacles and GFCI breakers in North America (ground fault circuit interrupter). Some people here casually shorten the acronym to GFI.

AFCI, arc-fault circuit interrupter, is a newer safety technology. I'm not sure what the EU/CE equivalent is called. It does not supersede GFCI, so you may need both protections in parts of a building where GFCI are required. Typically the panel will have an AFCI breaker, and the receptacle will be a GFCI type.
AdamJamma wrote:
Tue May 15, 2018 7:51 am
But, UK also does something a bit different in using what is a split panel, where two RCD breakers cover the whole of the panel, and neutral and ground are always kept separate... but you can actually check the wiring because the grounds, and neutrals, are put on numbered bars, corresponding to the appropriate breakers, so you know which neutral goes with which ground and which live wire...
Yes, the UK has a very interesting branch circuit wiring topology which I really like. Circuits are run throughout a building in "rings", where a circuit both originates and terminates in the panel (adding literal meaning to the word "circuit"). From this ring, there are what are called "spur" circuits.

Because of this, GFCI (or RCD) is not really possible or practical except as a circuit breaker in the panel (or consumer unit, as it's called there) for the whole ring. So you do not really see RCD receptacles in the UK, if they even exist at all. I think the RCD protection might actually be incorporated into the plug of devices that warrant RCD protection.

There are also far fewer breakers in a typical Consumer Unit than a North American breaker panel because there are often fuses for over-current protection in the plugs of devices themselves.

The UK has probably the safest electrical system in the world. The fact there are rings that originate and terminate in the panel cuts the resistance on the copper wire running a ring around the building in half.
AdamJamma wrote:
Tue May 15, 2018 7:54 am
Also, my practice in the past for wired alarm circuits such as fire alarms, etc, usually meant that the red wire used to interconnect from one alarm to the next also connected to a main panel that had a visual (light) showing it as in use, along with a green light showing power on the circuit. Usually it contained a UPS system of some type. I agree to using the three core and ground for such use.
There is no formal wiring standard for fire alarms in North America. It's still largely de facto and ad hoc. Modern building code requires interconnected alarms throughout a house. But manufacturers of alarms have seemed to agree on their own industry standard for alarm interoperability in terms of the signaling between alarms. I'm not sure, but I'm guessing it's just a constant 9 volts gets sent across the wire to the other alarms as a signal.

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