Is this a violation

[david luchini]

Isn't that what post #64 says, the Ex rules only apply to ocpd's 2/3/4/5/6, and not to just one ocpd?

No, that not what post #64 says.

Why would the rules of Ex3 not apply to a single ocpd?

Because a single (1) ocpd is not "two to six circuit breakers or sets of fuses"

I assumed the "sum" rules and "calc load" rules applied to ALL devices used as ocpd's that serve as the disco/ocpd for SEC's.

They do. Your example calculated a load of 310A and gave a service conductor ampacity of 185A. The calculated load exceeds the ampacity of the service conductors, so your example does not comply with 230.90(A) ex 3.

one set 3wire 240vCT SEC » service box » 6 ocpd's

Ampacity of SEC's = 185A

ocpd 1 = rated 200A
ocpd 2 = rated 40A
ocpd 3 = rated 40A
ocpd 4 = rated 40A
ocpd 5 = rated 40A
ocpd 6 = rated 40A Sum of ratings of ocpds = 400A

Calc load for ocpd 1 = 160A
Calc load for ocpd 2 = 30A
Calc load for ocpd 3 = 30A
Calc load for ocpd 4 = 30A
Calc load for ocpd 5 = 30A
Calc load for ocpd 6 = 30A Calculated load = 310A

If your SEC ampacity was 335A, rather than 185A, the installation would be compliant.

 

[FionaZuppa]

They do. Your example calculated a load of 310A and gave a service conductor ampacity of 185A. The calculated load exceeds the ampacity of the service conductors, so your example does not comply with 230.90(A) ex 3.

My example was written specifically to/after post #64. Ex3 only applies to ocpd's 2-6 (you said that, Ex3 says it), so then why are you adding in ocpd #1 to Ex3 if I had six ocpd's?

Is it also the case that if here are 2+ ocpd's then the rating on #1 could not be greater than ampacity of SEC's ?

To me, the OP's example, looks to me like tapped SEC's via SEC equip (a bus'd panel). Does that comply with SEC taps per 230.46?

 

[wwhitney]

ocpd's 2-6

Not following the discussion or the sections very closely, but if by this you mean "OCPDs labeled #2 through #6" then I'm confident that nothing in the NEC is going to use language that means that. Instead, the language likely means "when the total number of OCPDs is between 2 and 6".

Cheers, Wayne

 

[david luchini]

I'm really not sure what why you are having trouble understanding this. Just follow what the Code says.

My example was written specifically to/after post #64. Ex3 only applies to ocpd's 2-6 (you said that, Ex3 says it),

I didn't say that, nor does the Code say that.

so then why are you adding in ocpd #1 to Ex3 if I had six ocpd's?

Your example has SIX ocpds... ocpd #1, ocpd #2, ocpd #3, ocpd #4, ocpd #5, ocpd #6.

Ocpd #1 is ONE of the SIX.

The sum of the ratings of the six ocpd's is permitted to exceed the ampacity of the service conductors per 230.90(A) Ex 3.

The load on the service conductors is not permitted to exceed the ampacity of the service conductors.

Is it also the case that if here are 2+ ocpd's then the rating on #1 could not be greater than ampacity of SEC's ?

I don't understand the question.

 

[GoldDigger]

...
Is it also the case that if here are 2+ ocpd's then the rating on #1 could not be greater than ampacity of SEC's ?
...

No.
If there are 2+ OCPDs then the rating of OCPD #1 alone (or of OCPD #2 alone, etc.) can exceed the ampacity of the SECs as long as the sum of the calculated loads on those breakers are low enough.
However, as a matter of likelihood, if one or more breakers individually exceed the SEC ampacity it is relatively likely that the sum of the calculated loads exceeds the SEC ampacity. Small branch breakers are less likely to be fully loaded than larger branch breakers. If the breakers are all panel feeders, then the probability of oversizing compared to calculated load is, IMHO, greater.
But in the final analysis it all comes down to the actual calculated loads.

 

[jim dungar]

Isn't that what post #64 says, the Ex rules only apply to ocpd's 2/3/4/5/6, and not to just one ocpd? Why would the rules of Ex3 not apply to a single ocpd?
I assumed the "sum" rules and "calc load" rules applied to ALL devices used as ocpd's that serve as the disco/ocpd for SEC's.

No.

The exception says that if there are up to 6 OCPDs, they are permitted to be considered as one service OCPD.

Forget numbering them.
Post #64 says the exception is not applicable if there is only a single OCPD. How do you sum a single value?

 

[FionaZuppa]

No.

The exception says that if there are up to 6 OCPDs, they are permitted to be considered as one service OCPD.

Forget numbering them.
Post #64 says the exception is not applicable if there is only a single OCPD. How do you sum a single value?

You sum the rating of one. Not hard.

So in other words, doesn't really matter how many ocpd's there are (max of 6 though), for the rules to still apply IF I am sum'ing one or all of them. More than one still includes one.

I get what NEC verbiage is supposed to mean, how it's written needs fixing. Why not just exclude the exception and call out "up to six" in the main section? Why is a 2-6 exception even needed?

 

[jim dungar]

I get what NEC verbiage is supposed to mean, how it's written needs fixing.

I don't feel that it is wrong.
The exception allows the rest of the code to refer to a single entity Service OCPD, even if there are actually 6 of them.

 

[david luchini]

You sum the rating of one. Not hard.

So in other words, doesn't really matter how many ocpd's there are (max of 6 though), for the rules to still apply IF I am sum'ing one or all of them. More than one still includes one.

I get what NEC verbiage is supposed to mean, how it's written needs fixing. Why not just exclude the exception and call out "up to six" in the main section? Why is a 2-6 exception even needed?

You can't sum the rating of one. To "sum the ratings", there must be more than one rating.

I agree with Jim. I don't feel that the Code language is wrong.

 

[GoldDigger]

You sum the rating of one. Not hard.

So in other words, doesn't really matter how many ocpd's there are (max of 6 though), for the rules to still apply IF I am sum'ing one or all of them. More than one still includes one.

I get what NEC verbiage is supposed to mean, how it's written needs fixing. Why not just exclude the exception and call out "up to six" in the main section? Why is a 2-6 exception even needed?

A 2-6 exception is needed if you want to apply different rules to a single OCPD versus multiple OCPDs. You can argue whether you think the different treatment is justified or not, but the language implements exactly what is intended. The upper limit of 6 is in line with the 6 throw requirement for a multiple handle disconnect situation.
If 6 were not in there explicitly, I am sure someone would argue that the section overrides the 6 throw limit by not specifying a limit here.

 

[FionaZuppa]

You can't sum the rating of one. To "sum the ratings", there must be more than one rating.

I agree with Jim. I don't feel that the Code language is wrong.

A subset that has only one element is still summable.
Recall that summation always starts at a pre-defined #, in this specific case it's zero, because you want absolute values. With just one OCPD, zero + it's rating = it's rating.

Cheers.

 

[kwired]

You sum the rating of one. Not hard.

So in other words, doesn't really matter how many ocpd's there are (max of 6 though), for the rules to still apply IF I am sum'ing one or all of them. More than one still includes one.

I get what NEC verbiage is supposed to mean, how it's written needs fixing. Why not just exclude the exception and call out "up to six" in the main section? Why is a 2-6 exception even needed?

Because they want protection to correspond with ampacity for a conductor to an individual OCPD.

Even when you have 2-6 devices any so called tap conductors to any individual device must still have ampacity based on the device, but they allow any common supply conductor (which you must have more than one device to have a common) to only have ampacity based on connected load.