Correct Application of NEC Table 220.12

[bradp]

We have a code comment regarding applying article 220.12 to a branch circuit panelboard in a parking garage. It looks like it a canned plan review comment. Upon calling the city, the plans examiner who answered the phone (but did not make the comment) said it was a standard comment.

This has caused debate in our office regarding the application of NEC Table 220.12. I apply this table to a service calculation, and use the connected lighting load at 125% for branch circuit panelboard calculations. I think what is confusing the issue is that 220.12 is listed under branch-circuit load calculations.

Some are saying that 220.12 needs to be applied to a standard 1P-20A lighting circuit (although never done in our office)
Some are saying that the feeder to the parking garage panel should take NEC 220.12 into account
Some are saying that the service calculations should reflect NEC 220.12

What is the correct application of this code section? In my opinion NEC 220.12 is applied at a service calculation. I think this is backed up by the change in the 2014 code that allows the exception as follows:

Lighting loads are now permitted to be calculated at values specified in an applicable energy code where it is adopted by the jurisdiction. Three conditions of the new exception include monitoring, alarms and not applying demand factors to the general lighting load as provided in 220.42.

Thanks in advance for any responses.

 

[Smart $]

Sorry, but I can't determine exactly what it is that you are asking...

200.12 applies to all the "Some are saying..." statements... :happyyes:

Perhaps the only one that needs finesse, is applying to the 1P-20A circuit.

 

[bradp]

Sorry, but I can't determine exactly what it is that you are asking...

200.12 applies to all the "Some are saying..." statements... :happyyes:

Perhaps the only one that needs finesse, is applying to the 1P-20A circuit.

My specific question is as follows.

Does the VA/Square Foot apply to a branch circuit calculation or a branch circuit panelboard?

I contend that it applies to a service calculation. Here are my reasons in addition to never seeing the calculation done for branch circuits or branch circuit panelboards.

Branch Circuit - You have (10) 150 SF offices each with (2) 3-Lamp parabolic troffers (91VA). The total connected lighting load is 1820VA and can be handled by a single 1P-20A, 120V lighting circuit from a branch circuit panelboard. If I take into account the VA/Square Foot of table 220.12 (10 x 150 x 3.5 = 5250VA), I would need 3 1P-20A, 120V lighting circuits to serve the offices.

Branch Circuit Panelboard - I'm not so convinced on the branch circuit panelboard other than never having seen a calculation using the VA/Square foot indicated in table 220.12. I also think the exception for metering in the 2014 Code lends itself to a separate lighting distribution that allows the metering at the switchboard breaker.

 

[Smart $]

Branch circuit...

Let's say your example is served by a subpanel. Actual footage of service is offices at 40,000ft? and general lighting is handled by two subpanels. As you can probably already determine the footage covered by the example subpanel (15,000) is less than half the entire footage. The other subpanel would have a higher calculated general lighting load. This is why 220.12 applies at both the feeder and service levels. While the connected load of the example subpanel is only 1820VA, the subpanel must have available 5250VA for general lighting regardless of connected load, because the connected load is less than 220.12 requires.

Next we have 210.11 which requires the calculated minimum number of circuits to be available and the load evenly distributed on those circuits. Some use the play on words and will only install one circuit, and claim the connected load is evenly distributed on that one circuit because the "not-connected" load would be distributed on the other circuits not installed. I do not believe that to be the intent, but who am I to argue...

 

[bradp]

Branch circuit...

Let's say your example is served by a subpanel. Actual footage of service is offices at 40,000ft? and general lighting is handled by two subpanels. As you can probably already determine the footage covered by the example subpanel (15,000) is less than half the entire footage. The other subpanel would have a higher calculated general lighting load. This is why 220.12 applies at both the feeder and service levels. While the connected load of the example subpanel is only 1820VA, the subpanel must have available 5250VA for general lighting regardless of connected load, because the connected load is less than 220.12 requires.

Next we have 210.11 which requires the calculated minimum number of circuits to be available and the load evenly distributed on those circuits. Some use the play on words and will only install one circuit, and claim the connected load is evenly distributed on that one circuit because the "not-connected" load would be distributed on the other circuits not installed. I do not believe that to be the intent, but who am I to argue...

That makes sense to me. Thanks for the help.

 

[xformer]

We have a code comment regarding applying article 220.12 to a branch circuit panelboard in a parking garage. It looks like it a canned plan review comment. Upon calling the city, the plans examiner who answered the phone (but did not make the comment) said it was a standard comment.

This has caused debate in our office regarding the application of NEC Table 220.12. I apply this table to a service calculation, and use the connected lighting load at 125% for branch circuit panelboard calculations. I think what is confusing the issue is that 220.12 is listed under branch-circuit load calculations.

Some are saying that 220.12 needs to be applied to a standard 1P-20A lighting circuit (although never done in our office)
Some are saying that the feeder to the parking garage panel should take NEC 220.12 into account
Some are saying that the service calculations should reflect NEC 220.12

What is the correct application of this code section? In my opinion NEC 220.12 is applied at a service calculation. I think this is backed up by the change in the 2014 code that allows the exception as follows:

Lighting loads are now permitted to be calculated at values specified in an applicable energy code where it is adopted by the jurisdiction. Three conditions of the new exception include monitoring, alarms and not applying demand factors to the general lighting load as provided in 220.42.

Thanks in advance for any responses.

IMHO... The Code book is an outlined manual. In article 220 we start off with roman numeral II. then 220.10. 220.10 tells us to look at 220.12, 14 and 16. Then we take that and then go to roman numeral III. and look at 220.40. Think of this as a 3 tier cake. 220.10 is the base layer.

 

[S Arle]

Question re NEC loads for lighting v IECC:

Why should the size of a panel (serving an Office building for instance) be calculated at 3.5 watts/ SF for the lighting load, when the IECC will only allow 1.0 watts/ SF?

 

[Smart $]

Question re NEC loads for lighting v IECC:

Why should the size of a panel (serving an Office building for instance) be calculated at 3.5 watts/ SF for the lighting load, when the IECC will only allow 1.0 watts/ SF?

Because both are conservative in opposite directions...

NEC wants to make certain the panel can provide 3.5W/ft?. You don't actually have to connect enough lighting to equal this amount.

IECC wants to make certain you use no more than 1.0 W/ft?.

 

[texie]

Question re NEC loads for lighting v IECC:

Why should the size of a panel (serving an Office building for instance) be calculated at 3.5 watts/ SF for the lighting load, when the IECC will only allow 1.0 watts/ SF?

You are not alone in asking this. Take a look at the new Exception in 2014 220.12.

 

[north star]

~ & ~

"Why should the size of a panel (serving an Office building for instance) be calculated at 3.5 watts/ SF for the lighting load, when the IECC will only allow 1.0 watts/ SF?"

Because, in applying the IECC, ...a total site design should be performed.
A Total Site Design will take all of the information applicable to that particular site to
come up with a Total Site evaluation......There are always trade-offs in the different areas of
energy consumption \ reduction. [ i.e. - a little more lighting in watts consumption here,
versus a little less energy consumption by planting different species of trees to block the
sunlight there, and on and on and on it goes. ]......In the end, the whole site should be energy
compliant [ allegedly ].

~ & ~

 

[S Arle]

You are not alone in asking this. Take a look at the new Exception in 2014 220.12.

That's great they (NEC) have made some movement toward reality - I've heard that most of those numbers in 220.12 have been around since 1975.

I do not mean to sound glib, but does anyone really follow the 3-3.5 w/SF numbers any more?
- Even if a building changes functionality in the future, there are not any 'whole building' IECC numbers higher than 1.6.

There obviously are exceptions for Show/Theatrical lighting, Sports lighting etc, but I haven't seen an electrical panel (totally dedicated to lighting) in a building design, be sized three and a half sizes larger than actual load (ie: I would never see 100 amps of load be served by a 400 amp panel).

Interesting