discusion at work

[roger]

a 3000 sq ft house at 3 watt /sqft = 9000w
9000/120v=75a
75amp/15a cir breaker = 5 required
that leaves you 5 circiuts to pick up all convience outlets and general room lights
Isn't that how it calculated for dwelling units

For the general lighting load you are correct.

Roger

 

[ibew501ed]

roger
dosent 220.14J say that receptacles are included in general ltg load
therefore my earlier post would be accurate for ltg and plugs?

 

[lefty]

#80 that is right that is the minimum required
#79 I would not advocate ext cords either
I guess my question would be what does 220.14 pertain to in relation to dwellings, in the 2008 nec, it seems real straight forward there.

 

[iwire]

I think it is also worth remembering that any receptacle circuit that has more then one single receptacle can be easily overloaded and that is also allowed by the NEC.

 

[roger]

#80 that is right that is the minimum required
#79 I would not advocate ext cords either
I guess my question would be what does 220.14 pertain to in relation to dwellings, in the 2008 nec, it seems real straight forward there.

Lefty, you have to look at each part of 220.14 (there are 12 parts) and see what each one is addressing.

#80 that is right that is the minimum required

But each of these circuits can have as many receptacles as you choose to put on them


Roger

 

[lefty]

Okay your right, my comprehension lacks a lot. I am curious as to what receps the 180va would apply to in (I) can you give me an example?

 

[roger]

(I) Receptacle Outlets. Except as covered in 220.14(J) and (K), receptacle outlets shall be calculated at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke. A single piece of equipment consisting of a multiple receptacle comprised of four or more receptacles shall be calculated at not less than 90 volt-amperes per receptacle. This provision shall not be applicable to the receptacle outlets specified in 210.11(C)(1) and (C)(2).

This would cover most everything outside of dwelling units such as, office buildings, hospitals, retail spaces, etc...

Roger

 

[lefty]

thanks roger, now I under stand what they were implying. I appreciate your explanation.

 

[roger]

You're welcome.

Roger

 

[Vertex]

My interpretation and practice for general lighting circuits for dwellings is based on 220.12 and 210.11B. The way I see it, the intent of the 210.11B is to limit the area served for each circuit.

15A circuit: 15x120/3=600 square feet
20A circuit: 20x120/3=800 square feet

In no case shall the actual load (if known) be greater than 80% of the circuit rating. This is only a minimum standard. If you wish to practice a higher standard, go for it.

Do I have it right?

 

[K2X]

Breakers are rated for 100% of the load. "Continuous load" derating only applies to conductors.



A 20a breaker can actually hold more than 20 amps. It will not magically trip at 20.0000001 amps, but the higher the amperage goes, the quicker it trips. 21 amps may never trip it, 22 amps may take 4 hours, 23 amps may take an hour, 24 amps may take 10 minutes.... It's called a trip rating curve or something like that.



I'll be there! Where is it?

The NEC permits 100% loading on an overcurret device only if that overcurrent device is listed for 100% loading. See 210.20 and 215.3. At the time of this writing, UL has no listing of residential-type molded-case circuit breakers that are suitable for 100% loading. A maximum of 80% is a good practice- less is better.

Quote from Residential Electrical Wiring 16th edition, Ray C. Mullin.

Not that Ray is always right.

 

[iwire]

This thread clears the issue up.

I can't believe it!