Residential Lighting Circuit

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tallgirl said:
What's the maximum permissible continuous load? 16A on a 20A circuit, 12A on a 15A circuit.
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Julie the maximum possible load on that mixed use circuit is 20 and 15 respectively.

So if that maximum load is expected for more then 3 hours it will then be a continuous load and you may have to rework the circuit.

But being multiple outlets supplying who knows what we can not say with any certainty at all if the entire load will be on longer then 3 hours.

Its much ado about nada.

Modern NEC compliant homes are usually over wired for average power consuming folks. That do not have a Tim Allen complex. :smile:
 
iwire said:
Julie the maximum possible load on that mixed use circuit is 20 and 15 respectively.

So if that maximum load is expected for more then 3 hours it will then be a continuous load and you may have to rework the circuit.
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You're the one who introduced "teenagers" to the discussion :cool:. Any house containing "teenagers" should be assumed to have all lighting loads be "continuous" loads.

I think you're forgetting that the title of 210.23 is "Permissible Loads", not "Possible Loads".

In no case shall the load exceed the branch-circuit ampere rating. An individual branch circuit shall be permitted to supply any load for which it is rated. A branch circuit supplying two or more outlets or receptacles shall supply only the loads specified according to its size as specified in 210.23(A) through (D) and as summarized in 210.24 and Table 210.24.
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The maximum possible load is .8 * 20A * # of receptacles. See 210.23 (A) (1).
 
tallgirl said:
Any house containing "teenagers" should be assumed to have all lighting loads be "continuous" loads.
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Or not. I never consider any general purpose branch circuit containing lights and receptacles to be a continuous load. Never have, never will. There is theory and then there is reality. The reality is that EC's and electricians like myself wire bedrooms with #14 and put several bedrooms on a circuit without problems all the time.
 
tallgirl said:
I think you're forgetting that the title of 210.23 is "Permissible Loads", not "Possible Loads".
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I do not see the distinction you're trying to make with that statement.

tallgirl said:
The maximum possible load is .8 * 20A * # of receptacles. See 210.23 (A) (1).
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Are you saying if the circuit happens to be a 15A GPBC then suddenly the 'possible load' is going to change?

210.23(A)(1) is requiring manufacturers of appliances to limit their appliance to 80% of the circuit it's expected to be connected to, IMO. So an appliance primarily designed for use in the kitchen or the bathroom would be limited to 80% of a 20A circuit (210.11(C)), and appliances for use in other areas of the home would be limited to 80% of a 15A circuit (hence the abundance of 12A vacuum cleaners, for example.)

Edit to add: The speculation in this thread about teenagers leaving lights on, elaborate entertainment systems in bedrooms and so forth really says to me that the NEC should continue to keep their hands out of the design of circuits in the home, IMO. Carried to the ultimate conclusion of that train of thought, each receptacle in the house would need to be a dedicated circuit for "what-if's", and lighting would have to be based on the highest lamp wattage concievably screwed into a luminaire, as opposed to what it's listed maximum would be. :roll:
 
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Here's how I look at it: the bedroom-area lighting circuit is generally a known load, meaning we know how many of what will be installed: ceiling fan/lights, hall and attic lights, bath lights and fans, etc.

Often, the master bed/bath gets its own lighting circuit, if it's big and elaborate. Often times, all of the lights are on during vacuuming, and I've had more than one complaint that the vacuum turns the lights off.

I almost always give the bedroom, hallway, etc. receptacles their own circuit, or two if there are four or more bedrooms, and I often make this a 20a circuit(s). As need goes up: 1 15a, 1 20a, 2 15a, 2 20a.
 
georgestolz said:
I do not see the distinction you're trying to make with that statement.
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"Possible" is 80% of the circuit's ampacity times the number of receptacles. The NEC doesn't talk about "possible load" except when it talks about permanently attached loads, and then it states that the maximum "possible load" is the nameplate rating -- 220.86(C)(3). Even the Handbook doesn't say anything about "possible loads" -- the notes for 210.24 refer to "permissible loads", as does the rest of the NEC.

Are you saying if the circuit happens to be a 15A GPBC then suddenly the 'possible load' is going to change?
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Of course.

210.23(A)(1) is requiring manufacturers of appliances to limit their appliance to 80% of the circuit it's expected to be connected to, IMO. So an appliance primarily designed for use in the kitchen or the bathroom would be limited to 80% of a 20A circuit (210.11(C)), and appliances for use in other areas of the home would be limited to 80% of a 15A circuit (hence the abundance of 12A vacuum cleaners, for example.)
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Right, so the "possible load", which is never defined except for 220.86 (C) (3), is the total of all the loads I can "possibly" plug in. That's 210.23(A)(1) times the number of receptacles times 80% of the circuit's ampacity. Lower ampacity, lower "possible load". The "permissible load", however, has nothing to do with receptacles or teenagers.

Edit to add: The speculation in this thread about teenagers leaving lights on, elaborate entertainment systems in bedrooms and so forth really says to me that the NEC should continue to keep their hands out of the design of circuits in the home, IMO. Carried to the ultimate conclusion of that train of thought, each receptacle in the house would need to be a dedicated circuit for "what-if's", and lighting would have to be based on the highest lamp wattage concievably screwed into a luminaire, as opposed to what it's listed maximum would be. :roll:
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Yes, but that would be cheating. Exceeding the maximum listed wattage for a luminaire is not "permissible".

If you think a 300 watt television, cable box and stereo is "elaborate", grab your clamp on and go measure a typical late model TV, a digital cable box, and a modest stereo of the Wal-Mart variety. I spent the better part of a month tracking down just about every single last watt in my house and I was fairly shocked.
 
I have two triple-taps in my bag, a six-outlet tap in my living room, and a spare sitting on my desk in my office - where does that figure in with your "possible load" bit? I still don't understand what you're getting at.

The "possible load" on an individual branch circuit with a duplex attached is a million gazillion amps. The technology exists to add to the system with extension cords infinitely.
 
georgestolz said:
I have two triple-taps in my bag, a six-outlet tap in my living room, and a spare sitting on my desk in my office - where does that figure in with your "possible load" bit? I still don't understand what you're getting at.

The "possible load" on an individual branch circuit with a duplex attached is a million gazillion amps. The technology exists to add to the system with extension cords infinitely.
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Right. Now, what is the "permissible load"?
 
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