Question about 220.12 table

[tomito]

Hello everybody, i'm new on the forum and this is my first post, I am from Mexico and I have a doubt with the table 220.12 table.
If I have a complete electrical project (lighting, receptacles, load centers) everything calculated and I have the total demanded current, Do I need to used this table to calculate my principal feeder ampacity? even tough I have a lot less of lighting load calculated on my project and, at the end, it is what it will be at the building?

Sorry for my english, I know that i'm not that good, I hope that I have made a little of sense on what I wrote.

Thank you
Tom

 

[Smart $]

Welcome!

If you are installing to the NEC, yes, you need to calculate your service and feeder general lighting loads per 220.12... and that is the minimum. Doesn't matter if your lighting load is less than what is determined.

...and your English is fine :happyyes:

 

[tomito]

Thank you for your answer! what I don't understand completely is why I have to calculate the number of branch circuits breakers if I already have all this information on my electrical project, on example D3 on Annex C they calculate the lighting load like you said but they calculate the number of branch circuits required, that's what I don't understand (well that too LOL).
The official NOM (Norma Oficial Mexicana) on Mexico it is based almost completely on 2002 NEC.

Thank you
Tom

 

[ActionDave]

Sorry for my english, I know that i'm not that good, I hope that I have made a little of sense on what I wrote.

Thank you
Tom

Hola, hombre. Yo intiendes espanol un poco. Yo estoy un Americano con muchos esposas.

Proof that your English is better than my Spanish.

Thank you for your answer! what I don't understand completely is why I have to calculate the number of branch circuits breakers if I already have all this information on my electrical project, on example D3 on Annex C they calculate the lighting load like you said but they calculate the number of branch circuits required, that's what I don't understand (well that too LOL).
The official NOM (Norma Oficial Mexicana) on Mexico it is based almost completely on 2002 NEC.

Thank you
Tom

The number of branch circuits on your project is what an engineer or someone else has chosen, it is not the same as what the NEC requires as a minimum.

 

[Smart $]

... what I don't understand completely is why I have to calculate the number of branch circuits breakers if I already have all this information on my electrical project...

What that's really saying is that you have to have that number of "available" branch circuits. As you said, your "connected" general lighting load is less than the minimum per 220.12. This is one area where the code applies to possible future loads. This number of branch circuits being "available" means there must be that number of spaces in the system (e.g. in the branch circuit panelboards) for general lighting... at all times. Doesn't mean there must actually be that number of circuits, or breakers for such. If I recall correctly, there is wording to this extent in the NEC. It is quite likely that if different personel (or the same ) are involved with a future non-general lighting load addition, they'll see the spaces as available for this new load or loads, but it will not dawn on them they could be reserved for general lighting circuits.

 

[tomito]

What that's really saying is that you have to have that number of "available" branch circuits. As you said, your "connected" general lighting load is less than the minimum per 220.12. This is one area where the code applies to possible future loads. This number of branch circuits being "available" means there must be that number of spaces in the system (e.g. in the branch circuit panelboards) for general lighting... at all times. Doesn't mean there must actually be that number of circuits, or breakers for such. If I recall correctly, there is wording to this extent in the NEC. It is quite likely that if different personel (or the same ) are involved with a future non-general lighting load addition, they'll see the spaces as available for this new load or loads, but it will not dawn on them they could be reserved for general lighting circuits.

Ok, now I get it a little, this are a little confusing articles, I thought that this were used for when you do an electrical project and you just calculate the main feeder and general panelboard and when a client comes and rent the building he can do whatever he wants with the installation (lighting, receptacles, AAC, etc).

ActionDave
Hola, hombre. Yo intiendes espanol un poco. Yo estoy un Americano con muchos esposas.

Proof that your English is better than my Spanish.

The number of branch circuits on your project is what an engineer or someone else has chosen, it is not the same as what the NEC requires as a minimum.

Very well explained! your spanish is not that bad either.

 

[Smart $]

Ok, now I get it a little, this are a little confusing articles, I thought that this were used for when you do an electrical project and you just calculate the main feeder and general panelboard and when a client comes and rent the building he can do whatever he wants with the installation (lighting, receptacles, AAC, etc).

...

If you are just installing the service, you are correct... but you mentioned "general panelboard". Where you go from there depends on whether general lighting branch circuits come out of that panelboard, and it is the only panelboard, or there will be other panelboards. If it is the only panelboard, the calculated number of breaker "spaces" for general lighting must be available after all your other loads are connected. But if you are not doing the build out (i.e. branch circuit wiring), its not on you to maintain those "spaces" as long as they are there to begin with.

 

[tomito]

If you are just installing the service, you are correct... but you mentioned "general panelboard". Where you go from there depends on whether general lighting branch circuits come out of that panelboard, and it is the only panelboard, or there will be other panelboards. If it is the only panelboard, the calculated number of breaker "spaces" for general lighting must be available after all your other loads are connected. But if you are not doing the build out (i.e. branch circuit wiring), its not on you to maintain those "spaces" as long as they are there to begin with.

Ok! that clears the water a little bit for me! thank you for your answers!