Lights On A 20A Circuit

[gmhill33]

How many lights can you put on a 20A circuit? I will have 6 2'x4' 4 bulb fixtures, 2 ceiling fans, and the 2 outside lights. My questions is, can I run that on one circuit or will I need 2? I guessing 2 but I want to ask the pro's.

Thanks in advance,
Gary

 

[sberry]

Depends on how big the outside lights are but generally these could be ran on a single circuit but often the choice is somewhat a matter of convenience of being able to work on one circuit without having to disable the other.

 

[Random Guy]

I'd recommend running them off of two circuits, just so in the event one of the breakers trips, you are not left in total darkness.

 

[gmhill33]

Depends on how big the outside lights are but generally these could be ran on a single circuit but often the choice is somewhat a matter of convenience of being able to work on one circuit without having to disable the other.

Thanks for the reply. One of the outsides lights is just a single bulb light fixture beside a entry door (probably with a sensor). The other is a going to be some kind of light (with a sensor) so when we pull in the driveway it will come on.

Thanks,
Gary

 

[gmhill33]

I'd recommend running them off of two circuits, just so in the event one of the breakers trips, you are not left in total darkness.

That is a good point.


Gary

 

[sberry]

Sometimes the routing with a couple circuits makes it easier to add things at a later date. If I had the panel spaces the main cost is an additional breaker, maybe a few feet of wire, neither that big of deal. In my own case I have several circuits with only one duplex on them, wire right straight from breaker to outlet.

 

[Charles (in GA)]

Lighting is considered a continuous load under the NEC, and continuous loads cannot exceed 80% of a circuit or device's rated capacity. Thus a 15 amp circuit is limited to 12 amps max load and a 20 amp circuit is limited to 16 amps in this situation (and a good rule to follow in any situation, not just continuous loads).

Look at your lighting devices, the ID tags on them will have the total load of the fixture or device, add these up and as long as they do not exceed 12 amps or 16 amps, depending on the circuit, you are OK.

Random Guy makes a good point of separating the circuits however, and that is a good policy to follow also.

Charles

 

[tfi racing]

Looks like you are up to a whopping 6 or 7 amp load on that circuit,I would add more lights...

 

[gmhill33]

Looks like you are up to a whopping 6 or 7 amp load on that circuit,I would add more lights...

I think it will be pretty bright with the six.

Gary

 

[p_mori7]

Amps = Watts / Volts

so...

if you were to run 10 x 100W bulbs, the constant draw on that circuit would be 9.0A

10 x 100W = 1000W / 110V = 9.0A

20A circuits require 12GA wiring (in Canada anyways)

 

[Norcal]

Amps = Watts / Volts

so...

if you were to run 10 x 100W bulbs, the constant draw on that circuit would be 9.0A

10 x 100W = 1000W / 110V = 9.0A

20A circuits require 12GA wiring (in Canada anyways)

110V should NEVER be used to calculate circuits,since it does not exist as a supply voltage.

 

[Charles (in GA)]

110V should NEVER be used to calculate circuits,since it does not exist as a supply voltage.

And..... if they are anything other than incandescent lights, you cannot use the wattage, you need to use the data plate amperage to be accurate.

My house runs 122 to 123 volts and 59.9 Hz.

Charles

 

[p_mori7]

The rule still applies, the higher the voltage, the lower the amps.

10 x 100W bulbs = 1000W / 120V = 8.3A

Of course, if the Amperage is listed on the doodad your hooking up to the circuit, it makes it a lot easier...

 

[Charles (in GA)]

The rule still applies, the higher the voltage, the lower the amps.

10 x 100W bulbs = 1000W / 120V = 8.3A

Of course, if the Amperage is listed on the doodad your hooking up to the circuit, it makes it a lot easier...

As I noted earlier, that works with incandescent lighting, but not with other types of lighting. I have Metal Halide lighting, which is ballasted. The bulbs are "400 watt" and marked that way, yet 400/120 is 3.33 amps, yet, if you read the data plate, or measure the draw with a clamp amp meter, they draw 4.0 amps. Fluorescent lighting works the same way, however with the new electronic ballast the calculated and actual draws are very close, while with the older magnetic ballast the actual and calculated draws are much further apart.

Charles