Number of holes/boxes on a circuit

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Old 11-08-14, 11:58 AM
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Number of holes/boxes on a circuit

Hi,

Is there a certain number of boxes like light fixtures or outlets that can be on a 15 amp circuit? I have heard 10 is the number but then I have heard that it depends on the expected load. For example, can you add more outlets in a bedroom for convince or if installing led recessed lights that use 10.5 watts each, 10 of them would only use 105 watts.
 
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Old 11-08-14, 12:22 PM
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You add up the maximum watts each fixture is rated for. If it exceeds 1440 watts best to split it. (Assumes only the lights on the circuit.) If the fixture can not use incandescent bulbs then you can go with the 105 watts. If they can use incandescent bulbs best to figure on what that total would be.
 
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Old 11-08-14, 02:10 PM
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Canada has a limit on number of devices per circuit. The NEC in the US does not.
 
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Old 11-08-14, 04:00 PM
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ray, boss, explain this one to me so I'm clear.
Our rules call for each light socket to assume 1A of draw since you could potentially put anything from a 9W LED to a 200W incandescent in. Following the 80% rule, thats 12 on a 15A circuit max. Known loads like an LED wallpack or fluorescent ballast are factored in as stamped on the device.
By NEC standards, lets say I have decided I wish to buy boxes of 14W CFL bulbs and put nothing but lampholders in my home. Based on what I'm reading, I can now put 100 bulbs and fixtures on a circuit? Even though the next homeowner might enjoy 100W incandescent and replace them?
 
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Old 11-08-14, 04:09 PM
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I can now put 100 bulbs and fixtures on a circuit? Even though the next homeowner might enjoy 100W incandescent and replace them?
That is why I wrote:
If they can use incandescent bulbs best to figure on what that total would be.
That means if the bulb base is Edison and says 60 watts max then you would figure ten at 600 watts. The 1440 watt figure I used was based on 12 amps continuous on a 15 amp circuit with no other loads.
 
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Old 11-08-14, 04:11 PM
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Ahh ok. So you factor in the rating of the fixture itself and assume nobody exceeds it?
 
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Old 11-08-14, 04:23 PM
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All electrical is based on reasonable assumption not Darwin exceptions.
 
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Old 11-08-14, 07:33 PM
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Lighting loads are figured at maximum bulb size allowed, not what is installed.

The 80% rule only applies for continuous loads which is 3 hours or more.
 
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Old 11-09-14, 05:51 AM
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What I normally use as a calculation for determining load on a lighting/receptacle circuit is:

Each duplex is rated at 180 watts each, each light as it is rated by the unit (manufacturer) itself.

Simply:

If I have a 15 amp circuit with #14 I figure as follows:

15amp x 120v = 1,800 watts x .8 = 1,440 watts allowed.

1,440 / 180 = 8 (180 watt) duplex receptacles on the circuit.

If you have a light rated at max of 100watts on this circuit then

1,440 - 100 = 1,340 watts / 180 watts (per duplex receptacle) = 7.44 (7) receptacles allowed.

I use the .8 as a cushion knowing many people will end up plugging in window a/c's and things like that.
It has worked well for me.
 
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