Double de-rating?

[david]

That is correct. If your design choice is circuit breakers then 1, 3, 6, 10, and 601 are not standard sizes.

The problem you have with that is before you can go up to the next higher ampacity rating You have to look at the ampacity of the conductor and compare it to standard fuse sizes as well as standard breaker sizes

Remember this is an a permissive statement the main rule is the conductor must be protected at its ampacity rating.

Lets say that the permissive statement was not in the code you had to abide by the main rule that the conductor had to be protected by a standard fuse or breaker in accordance with the ampacity rating of the conductor.

Would you protect a 10 amp conductor with a 10 amp fuse or a 15 amp breaker?

 

[david luchini]

lets start here
Additional standard ampere ratings for fuses shall be 1, 3, 6, 10, and 601.

would you agree that 10 amps is a standard OC protection device

As kwired already pointed out, the smallest standard circuit breaker size is 15. If we're protecting the circuit with a circuit breaker OCPD, then we don't need to provide protection smaller than 15A.

210.23 (A) 15- and 20-Ampere Branch Circuits. A 15- or 20-ampere branch circuit shall be permitted to supply lighting units or other utilization equipment, or a combination of both, and shall comply with 210.23(A)(1) and (A)(2)

It doesn?t say a 15 amp rated branch circuit.
It does say 15 and 20 amp branch circuits

210.23(A) says a 15amp branch circuit OR a 20amp branch circuit shall be permitted to supply lighting units. In this case, we are using a 15amp branch circuit to supply lighting units, so we meet 210.23(A).

I see a 15 amp branch circuits as one having 15 amp over- current protection and conductors with an ampacity in accordance with table 310.16..

The end result would mean a 15 amp branch circuit would need a conductor with adjusted 20 amp capacity table 310.16

I don't follow you're logic here. 210.23(A) doesn't say anything about conductor size. 210.19(A)(1) says branch circuit conductors shall have an ampacity not less than the load to be served. We are meeting that requirement.

Unless it under supervised engineering
I do not see where the table ampacities are allowed to be reduced.

I do see where the ampacities in these tables have to be maintained by adjusting the conductor sizes.

Not only are the ampacities in T310.16 "allowed" to be reduced, but they are required to be reduced in specific instances (not under supervised engineering.)

310.15(B) says "Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Tables 310.16 thru 310.19...as modified by (B)(1) thru (B)(6).

310.15(B)(2) says "Where the number of current-carrying conductors in a raceway or cable exceeds three...the allowable ampacity of each conductor shall be reduced as shown in T310.15(B)(2)(a)." (These section numbers are based on 2008 NEC, I think they have changed in 2011).

 

[kwired]

The problem you have with that is before you can go up to the next higher ampacity rating You have to look at the ampacity of the conductor and compare it to standard fuse sizes as well as standard breaker sizes

Remember this is an a permissive statement the main rule is the conductor must be protected at its ampacity rating.

Lets say that the permissive statement was not in the code you had to abide by the main rule that the conductor had to be protected by a standard fuse or breaker in accordance with the ampacity rating of the conductor.

Would you protect a 10 amp conductor with a 10 amp fuse or a 15 amp breaker?

If I had a 10 amp conductor and there was no exception allowing for higher overcurrent protection yes.

We would be looking at 16 AWG conductors here. There places I run into the most that allow 16 AWG to be on more than 10 amp overcurrent device are for control circuits and flexible cords.

Putting 10 amps of lighting load on a 14 AWG conductor does not give the conductor an ampacity of 10 amps. You could have a 100 amp service conductor that only has 10 amps of load connected to it and still protect it with 100 amps overcurrent protection.

Now if you derated a 14 AWG and the resulting ampacity is 10 amps you could protect it with a 10 amp overcurrent device, fuse or breaker. If you choose to use a 15 amp device then you will need to increase the conductor size.

 

[david luchini]

The problem you have with that is before you can go up to the next higher ampacity rating You have to look at the ampacity of the conductor and compare it to standard fuse sizes as well as standard breaker sizes

No you don't, you need only to look at the standard size for the type of OCPD that you are using. 240.15(A) says that the required OCPD can be "a fuse OR an overcurrent trip unit of a circuit breaker."

Remember this is an a permissive statement the main rule is the conductor must be protected at its ampacity rating.

What is the point of a "permissive statement" if you are not "permitted" to use it?

Lets say that the permissive statement was not in the code you had to abide by the main rule that the conductor had to be protected by a standard fuse or breaker in accordance with the ampacity rating of the conductor.

Would you protect a 10 amp conductor with a 10 amp fuse or a 15 amp breaker?

It's kind of silly to give a "what if" a statement wasn't in the code. If you were not permitted to use the next size up to protect the conductor, then a 10 amp conductor would need to be protected by a 10 A fuse or a 10A c/b. But the statement is in the code, so by following the statements in the code we can protect the 10A conductor with a 15A c/b.

 

[david]

Now if you derated a 14 AWG and the resulting ampacity is 10 amps you could protect it with a 10 amp overcurrent device, fuse or breaker. If you choose to use a 15 amp device then you will need to increase the conductor size.

"will need to increase the conductor size"

We may not be saying it the same way but according to that we are both saying the same thing.

 

[david]

No you don't, you need only to look at the standard size for the type of OCPD that you are using. 240.15(A) says that the required OCPD can be "a fuse OR an overcurrent trip unit of a circuit breaker."




What is the point of a "permissive statement" if you are not "permitted" to use it?



It's kind of silly to give a "what if" a statement wasn't in the code. If you were not permitted to use the next size up to protect the conductor, then a 10 amp conductor would need to be protected by a 10 A fuse or a 10A c/b. But the statement is in the code, so by following the statements in the code we can protect the 10A conductor with a 15A c/b.

I can’t help it if you think it is silly. What it has illustrated is what you compare the conductor ampacity to. Weather you look at just the breaker standard sizes or you also consider standard fuse sizes when protecting a 10 amp conductor

I didn't remove standard fuse or breaker sizes in my illustration you both concluded that you would look to the fuse size if the permissive statement wasn't in the code. How does the permissive statement change weather you look to standard fuse sizes or standard breaker sizes

Once that’s clear in your head then you can decide what you can round up to. 10 amps or 15 amps

 

[david luchini]

I can’t help it if you think it is silly. What it has illustrated is what you compare the conductor ampacity to. Weather you look at just the breaker standard sizes or you also consider standard fuse sizes when protecting a 10 amp conductor

It hasn't illustrated anything like that. What it has illustrated is that if you change the rules of the code regarding protection of conductors, then you have to change the way you protect the conductors based on the new rules.

I didn't remove standard fuse or breaker sizes in my illustration you both concluded that you would look to the fuse size if the permissive statement wasn't in the code. How does the permissive statement change weather you look to standard fuse sizes or standard breaker sizes

Once that’s clear in your head then you can decide what you can round up to. 10 amps or 15 amps

That is not what I concluded at all (can't speak for kwired.) What I said is that if you remove the next standard size up permissive statement, then you must protect a conductor with an ampacity of 10 with an OCPD (fuse or circuit breaker) with a rating of 10.

If you remove the permissive statement allowing the use of "the next higher STANDARD OVERCURRENT DEVICE RATING," (in 240.4 and 430 and 450, etc) then the standard ampere ratings in 240.6 are meaningless.

 

[kwired]

"will need to increase the conductor size"

We may not be saying it the same way but according to that we are both saying the same thing.

We are probably saying the same thing. The confusion is I am reading other posts to require 10 amp overcurrent protection on a 14 AWG with a 10 amp load. This is only true if the 14AWG has been derated to a maximum allowable capacity of 10 amps, I think. The confusion is because 10 amps is not a standard breaker size. Change the conductor to 16 AWG and it is less confusing because 15 amp protection is not an option in general.

Actually thought about it again and my conclusion is 14AWG derated to 10 amps is no different than 16 AWG that has not been derated. It must be protected at 10 amps by general rules, there are exceptions. If higher overcurrent protection is desired then the conductor size must be increased to a size that is equal or higher in ampacity to the overcurrent device - again the general rule, there are exceptions.

 

[david]

As kwired already pointed out, the smallest standard circuit breaker size is 15. If we're protecting the circuit with a circuit breaker OCPD, then we don't need to provide protection smaller than 15A.
Yes and Don and others have pointed out that you do have to look to all the stander over current protection devices before moving up to the next higher over-current protection

210.23(A) says a 15amp branch circuit OR a 20amp branch circuit shall be permitted to supply lighting units. In this case, we are using a 15amp branch circuit to supply lighting units, so we meet 210.23(A).

And as illustrated with you 100 amp rated service, The rating only applies to the size of the over-current device.

210.23 address the load in comparison to the rating of the branch circuit. It doesn?t address the conductor size (ampacity)
What does the load have to do with the conductor size,(ampacity)?

But this doesn?t say a 15 amp rated branch circuit.

It says a 15 amp branch circuit, to have a 15 amp circuit you must consider both the conductor ampacity as well as the size of the overcurrent device.


I don't follow you're logic here. 210.23(A) doesn't say anything about conductor size. 210.19(A)(1) says branch circuit conductors shall have an ampacity not less than the load to be served. We are meeting that requirement.

Again the load and rating is only two parts to a three part equation
Go to 310.15 (Table 310.16) for conductor ampacity to make up a 20 amp circuit.


Not only are the ampacities in T310.16 "allowed" to be reduced, but they are required to be reduced in specific instances (not under supervised engineering.)

No the required table ampacity are not.

The ampacity of the conductors are adjusted.

The tables are engineered and give you the conductor required ampacity

When you adjust 14 awg conductors ampacity, it is no longer a 15 amp rated conductor. (20 amp capacity in accordance to with the table) Depending on the end result you will need to adjust the overcurrent protection for that conductor

310.15(B) says "Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Tables 310.16 thru 310.19...as modified by (B)(1) thru (B)(6).

310.15(B)(2) says "Where the number of current-carrying conductors in a raceway or cable exceeds three...the allowable ampacity of each conductor shall be reduced as shown in T310.15(B)(2)(a)." (These section numbers are based on 2008 NEC, I think they have changed in 2011).

Exactly the allowable ampacity of the conductor shall be reduced.
A 10 amp conductor is no longer a 15 amp rated conductor in accordance with table 310.16

You have to increase the size of the conductor to correlate with the required ampacity of 20 amps to be a 15 amp rated conductor table 310.16

Or you have to protect the 10 amp wire in accordance with article 240

Weather you can round up to 10 amps or 15(fuse or breaker) amps may be to far off the OP original question

I dont know whow i included my responce with our qoutes oh well i hope it dosn't confuse things

 

[david luchini]

Exactly the allowable ampacity of the conductor shall be reduced.
A 10 amp conductor is no longer a 15 amp rated conductor in accordance with table 310.16

OK, we're on the same page here. This is what I said back in post #19 - if we had 10 ccc's of #14 awg, 75 deg C, the allowable ampacity of the conductor would be 10 Amps.

You have to increase the size of the conductor to correlate with the required ampacity of 20 amps to be a 15 amp rated conductor table 310.16

You are still losing me here. What "required ampacity of 20 amps to be a 15 amp rated conductor?" Where is this coming from?

What is required for the ampacity of the branch circuit conductors is that they have an ampacity "not less than the maximum load served." (210.19(A)(1)). (It is also required that the ampacity of the conductor before the application of any adjustment factors be not less than 125% of the continuous load, ie, 12.5Amps.) The #14 awg conductors with an allowable ampacity of 10 meets this requirement for the lighting circuits with a 10 A load (and the 20A ampacity before the adjustment factor exceeds 12.5Amps).

 

[david luchini]

I dont know whow i included my responce with our qoutes oh well i hope it dosn't confuse things

Yes, it did confuse things quite a bit. I missed most of your response.

And as illustrated with you 100 amp rated service, The rating only applies to the size of the over-current device.

That's exactly what I said. We are using 15A c/b's to protect the circuits. It is a 15A Branch Circuit.

210.23 address the load in comparison to the rating of the branch circuit. It doesn?t address the conductor size (ampacity)

I didn't say 210.23 address the conductor size. I've said over and over that 210.19(A)(1) addresses the conductor size. 210.23 only addresses the load in comparison to the rating of the branch circuit for certain types of loads. 210.23 does NOT place any limitations on the percentage size of a lighting load that can be on a 15A branch circuit. I could put 15 amps of non-continuous lighting load, or 12 amps of continuous lighting load on a 15A branch circuit.

What does the load have to do with the conductor size,(ampacity)?

I should think this is pretty basic, and I've pointed it out many times - the conductor must have an ampacity not less than the maximum load to be served (210.19(A)(1).) If the maximum load was 12 amps, you could not put it on a conductor with an ampacity of 10.

But this doesn?t say a 15 amp rated branch circuit.

It says a 15 amp branch circuit, to have a 15 amp circuit you must consider both the conductor ampacity as well as the size of the overcurrent device.

I will have to disagree with you here. A 15 amp branch circuit is a circuit with a 15A OCPD, the conductor size doesn't change the size of the circuit. A circuit with 15A OCPD with #14 conductors, or #12 conductors or #4 conductors is still a 15A circuit.

What would you call a branch circuit with a 70A c/b and with #6 THWN (with an ampacity of 65?)

Again the load and rating is only two parts to a three part equation
Go to 310.15 (Table 310.16) for conductor ampacity to make up a 20 amp circuit.

I am still struggling with this concept. 310.15 and T310.16 don't say anything about conductor ampacity to make up a 20A circuit (or any size circuit for that matter.) 310.15 and T310.16 give you the "allowable ampacities" of conductors. You have to look at 210.19, 210.20 together with 240.4 for the required conductor ampacities to make a circuit.

No the required table ampacity are not.

The ampacity of the conductors are adjusted.

:? That is what I said. The allowable ampacity of ten (10) #14 ccc's in the same raceway is adjusted to 10.

The tables are engineered and give you the conductor required ampacity

This is not correct. The table gives you the "Allowable" conductor ampacity based on not more than 3 ccc's in a raceway based on an ambient temperature of 30 deg C. There is nothing in T310.16 about "required" ampacity. The "required" ampacity for a branch circuit is derived from 210.19 - "Conductors - Minimum Ampacity and Size."

When you adjust 14 awg conductors ampacity, it is no longer a 15 amp rated conductor. (20 amp capacity in accordance to with the table) Depending on the end result you will need to adjust the overcurrent protection for that conductor

Again, I repeated over and over that the #14 conductors adjusted for 10 ccc's in the same raceway now have an ampacity of 10. It has the proper "required" ampacity for the lighting circuits with a max. load of 10 Amps. The overcurrent protection is a 15A c/b based on the next standard ampere rating for c/b's per 240.4(B).

 

[david]

OK, we're on the same page here. This is what I said back in post #19 - if we had 10 ccc's of #14 awg, 75 deg C, the allowable ampacity of the conductor would be 10 Amps.



You are still losing me here. What "required ampacity of 20 amps to be a 15 amp rated conductor?" Where is this coming from?

What is required for the ampacity of the branch circuit conductors is that they have an ampacity "not less than the maximum load served." (210.19(A)(1)). (It is also required that the ampacity of the conductor before the application of any adjustment factors be not less than 125% of the continuous load, ie, 12.5Amps.) The #14 awg conductors with an allowable ampacity of 10 meets this requirement for the lighting circuits with a 10 A load (and the 20A ampacity before the adjustment factor exceeds 12.5Amps).

210.19(A)(1) only compares the allowable load to the branch circuit rating.

I agree that a 10 amp load would not exceed the 15 amp rating of a 15 amp over current device.

I do not agree that a 10 amp rated conductor (weather it be 14 AWG or # 6 AWG for that matter) Is the correct ampacity conductor to build a 15 amp branch circuit.

What ampacity conductor does a 15 amp branch circuit have to have?

Table 310.16 is engineered to give you that answer It has to look identical in regards to its ampacity as the #14 AWG conductor in table 310.16

What your saying is I have a 10 amp lighting load. I have a 15 amp breaker, I have 14 AWG conductors therefore I have a 15 amp lighting Circuit.

What you do have is a 10 amp lighting load. A 15 amp breaker,
A 10 amp rated conductor( 14 AWG just happens to be the wire size)
What you need is 15 amp rated conductor to build a 15 amp branch cercuit

I know you realize that a lighting branch circuit is a multi-outlet circuit.
The only load restriction put on this branch circuit is for continuous loading

If I m building a 15 amp branch circuit my conductors have to have an ampacity rating for a 15 amp rated branch circuit

 

[david luchini]

210.19(A)(1) only compares the allowable load to the branch circuit rating.

I don't see anything in 210.19(A)(1) about "branch circuit rating." I only see minimum conductor size based on load.

I agree that a 10 amp load would not exceed the 15 amp rating of a 15 amp over current device.

I do not agree that a 10 amp rated conductor (weather it be 14 AWG or # 6 AWG for that matter) Is the correct ampacity conductor to build a 15 amp branch circuit.

Then do you agree that a 65 amp rated conductor is the correct ampacity for a 70A branch circuit or an 85 amp rated conductor is the correct ampacity for a 90A branch circuit or a 115 amp rated conductor is the correct ampacity for a 125 amp rated branch circuit?

What ampacity conductor does a 15 amp branch circuit have to have?

The required ampacity for a 15A branch circuit conductor is "not less than the maximum load to be served." This is straight out of 210.19.

Table 310.16 is engineered to give you that answer It has to look identical in regards to its ampacity as the #14 AWG conductor in table 310.1

I think you are reading something into Table 310.16 that is just not there. Table 310.16 together with its correction factors and adjustment factors gives you the "allowable ampacity" of conductors. It doesn't say anything about "required" conductors sizes for specific circuit ratings.

What your saying is I have a 10 amp lighting load. I have a 15 amp breaker, I have 14 AWG conductors therefore I have a 15 amp lighting Circuit.

I'm saying that I have a 10 amp lighting load on a branch circuit with a 15A c/b, therefore, I have a 15A light branch-circuit. The conductor size has nothing to do with it.

What you do have is a 10 amp lighting load. A 15 amp breaker,
A 10 amp rated conductor( 14 AWG just happens to be the wire size)
What you need is 15 amp rated conductor to build a 15 amp branch cercuit

Again, I will have to disagree. What about my examples of a 65A conductor on a 70A c/b, etc.

I know you realize that a lighting branch circuit is a multi-outlet circuit.
The only load restriction put on this branch circuit is for continuous loading

Yes I realize that we are talking about a multi-outlet branch circuit. It is not relevant to this circuit. I have already addressed the continuous loading aspect, and the #14 is OK.

If I m building a 15 amp branch circuit my conductors have to have an ampacity rating for a 15 amp rated branch circuit

Based on what? There is not a code section that says this. 210.19(A)(1) says the conductors shall have an ampacity not less than the maximum load served. 210.19(A)(4) also says the conductors shall have an ampacity sufficient for the loads served and shall not be less than #14 AWG.

What if it were 4 lighting circuits (8 ccc's) with a maximum load of 10A ea in the same raceway. The ampacity of #14 (75 deg) would be 14 amps. Would this not be acceptable to you on a 15A c/b.

 

[david]

Lets forget about conduit fill lets forget about any load at all.

I want to install a 15 amp lighting branch circuit for an unknown future load.
Lets only consider the temp. limitations of the equipment 75 Deg. C.

I have conductors that can handle 20 amps (heat) for with various insulation types. I have the heat sink in the size of the 14 AWG copper. I have a note because the copper properties that limit 14AWG to a 15 amp rated branch circuit ( with exceptions) for further prortection even though the ampacity of 14 AWG is really 20 amps.

To get all of the protections built into table 310.16 I have to have a 15 amp Branch circuit that looks like this.

I need 15 amp OC protection / fault protection (not part of this discussion)

I need a conductor that has a rated ampacity of 20 amps ( 14 AWG)

I need the correct insulation for 75 Deg, C.

I can go to the correct table and use a conductor with these properties or I can have an engineer design me a 15 amp branch circuit.

Once I reduce the allowable ampacity of the conductors as summarized in table 310.16 I no longer have a conductor designed to the specifications built into these tables.
I lose the protection from over heating.

The only way I can consider a 15 amp rated circuit to be designed in compliance with the ampacity tables is to bring the ampacity of the conductors(once the rated ampacities have benn reduced) back up to those of table 310.16

I am not an engineer so I’m going with the ampacity of 14 AWG (20 Amps)

Yes I am in compliance through a range of conductors protected at a max. circuit rating as long as the rules of 310.15 are adhered to.

 

[cadpoint]

If the correction factor for conduit fill and continuous load exists, do you have to correct them both? Does the NEC make provisions so you dont have correct twice?
The two correction factors are both aimed at reducing heat around conductors so it seems only the most stringent of the two would apply. How do you handle this instance.

My example is parking lot lighting. I have voltage drop, conductor deration for more than 3 current carrying conductors and continuos load deration.

Happy new year. Hope you all had a good Christmas.

We in the NEC like to think that we'll address all the needs that are required of a circuit thus making it a requirement to be met!

 

[david luchini]

To get all of the protections built into table 310.16 I have to have a 15 amp Branch circuit that looks like this.

I need 15 amp OC protection / fault protection (not part of this discussion)

So far, so good

I need a conductor that has a rated ampacity of 20 amps ( 14 AWG)

No you don't. You need a conductor with an ampacity of at least the maximum load to be served. If your maximum load to be served is 15A, then you could put three (2 wire) #14 awg (75 deg) circuits in the same raceway. The 6 current carrying conductors would give the #14 an ampacity of 16 Amps. This would be fine.

I need the correct insulation for 75 Deg, C.

OK

I can go to the correct table and use a conductor with these properties or I can have an engineer design me a 15 amp branch circuit.

Let's avoid "engineering supervision" and stick with the tables.

Once I reduce the allowable ampacity of the conductors as summarized in table 310.16 I no longer have a conductor designed to the specifications built into these tables.

You seem to be missing the fact that the ampacity determined by the tables (See 310.15(B)) shall be "as specified in the Allowable Ampacity Table...As Modified By (B)(1) thru (B)(6). "

The ampacity in Table 310.16 is only for "Not More Than 3 Current Carrying Conductors in a Raceway." The ampacity in the table is required to be modified per 310.15(B)(1) thru (B)(6), with (B)(2) being the reduction in ampacity for more than 3 ccc's in a raceway.

I lose the protection from over heating.

You don't lose the protection from overheating. This is exactly what the "adjustment factors" are there for. If up to 3 #14 awg (75 deg) conductors in the same raceway can safely carry 20 Amps without overheating, then we would obviously have an overheating concern if we had 6 conductors or 10 conductors in the same raceway also carrying 20 Amps.

So six #14 conductors in the same raceway would be limited to an ampacity of 16. The additional heat generated by having more conductors in the raceway would be offset by allowing the conductors to carry less current. In my example, the 10 ccc's in the same raceway are protected from overheating by allowing a max load of 10A on the conductors.

The only way I can consider a 15 amp rated circuit to be designed in compliance with the ampacity tables is to bring the ampacity of the conductors(once the rated ampacities have benn reduced) back up to those of table 310.16

Again, this is incorrect. The Table 310.16 is for the allowable ampacities of "not more than 3 ccc's" in a raceway or cable based on an ambient temperature of 30degC. The table itself tells us to use correction factors for ambient temperatures other than 30deg, and 310.15(B)(2) tells us to apply adjustment factors for more than 3 ccc's in a raceway or cable. As long as the adjusted ampacity is sufficient for the load to be served, and as long as the overcurrent protection for the conductor's adjusted ampacity is not greater than the next standard ampere rating, then there is no need to bring the ampacity of the conductors back up to those of table 310.16.

Yes I am in compliance through a range of conductors protected at a max. circuit rating as long as the rules of 310.15 are adhered to.

That's what I've been trying to point out. The rules of 310.15 (specifically 310.15(B)(2)) require you to reduce the ampacity of a conductor for more than 3 ccc's in a raceway. If the adjusted ampacity is sufficient for the load to be served and the OCP is in accordance with 240.4, then there is NO rule that requires bring the conductors back up to those of table 310.16.

 

[david]

So six #14 conductors in the same raceway would be limited to an ampacity of 16. The additional heat generated by having more conductors in the raceway would be offset by allowing the conductors to carry less current. In my example, the 10 ccc's in the same raceway are protected from overheating by allowing a max load of 10A on the conductors.

If we took every point (point by point ) in this discussion I would agree with most of what you are saying.

“In my example, the 10 ccc's in the same raceway are protected from overheating by allowing a max load of 10A on the conductors”

It is my belief that load diversity is not a consideration. 10 ccc's (14 AWG) in the same raceway are 10 amp conductors in your example and the only consideration is weather you need 10 OCP or you can say as you and others believe because you are choosing to provide overcurrent protection by means of a breaker you can use a 15 amp OCP.

But if I choose to design my circuit using a fuse panel I cannot use a 15 amp fuse I have to use a 10 amp fuse.

But because this is a multi-outlet branch circuit 210.3 Rating coupled with 210.23 says I need a 15 amp branch circuit so I have to bump my AWG wire size up to 10 AWG in order to have a 15 AMP fuse protected Lighting branch circuit

So if you guys are applying 240.6 correctly to this, I guess a 10 amp wire is safe on a 15 amp breaker circuit but a 10 amp wire is not safe on a 15 amp fused circuit.

If you want to consider load diversity maybe Table B.310.11 annex B, with current caring conductors in a raceway. You have 12 conductors maybe you would desire 6 current caring conductors (20 amps at 80% (16 amp conductor table 310.16) ) But this table looks at load diversity more on the lines of I have 12 conductors total but only six will have current at any given time.

But if you could apply this table that way your 10 amp wire mathematically would be good for 28 amps limited to the lesser of 20 amps from table 310.16

50 % diversity 0n 12 current caring conductors with 12 current caring conductors in a raceway

 

[david]

But because this is a multi-outlet branch circuit 210.3 Rating coupled with 210.23 says I need a 15 amp branch circuit so I have to bump my AWG wire size up to 12 AWG in order to have a 15 AMP fuse protected Lighting branch circuit

 

[david]

We look at multi-outlet branch circuits differently you build your branch circuit conductors based on the load in this discussion a 10 amp load.
I build a multi-outlet circuit based on the rating of the circuit.

General purpose multi-outlet lighting circuit.

The one point you would most likely not agree is in 210.23 (A) it says a 15 amp circuit. That to me includes a circuit that has conductors rated at 15 amps Min. Without any initial consideration to what size load you put on it. After I build the circuit do not violated the rules , I build the circuit and limit the loads,

You build the circuit to handle the load. If t is was an individual branch circuit I build it the way you do.

After I build my 15 amp circuit with 12 CCC in conduit I will increase my conductors to 12AWG THHN And put your 10 amp load on it. Someone wants to add a lighting load to my circuit throw an amp probe on the circuit decide if you can add the lighting load to my 15 amp general purpose lighting branch circuit.

You built your circuit with 10 amp rated conductors my amp probe doesn?t tell me if i can add a load on your 15 amp general purpose branch circuit

 

[david]

But if you could apply this table that way your 10 amp wire mathematically would be good for 28 amps limited to the lesser of 20 amps from table 310.16

to tired to do the math 28 amps is wrong sorry

(ampacity limit for the current-carrying conductors in the raceway or cable) =The Sg root of ( ( 12 Conductors * 0.5) / 12 Conductors ) x (25 amps THHN Table 310.16 X .7 Table B.310.11)

.707 * 17.5 Amps =

12.3725 Amps