AC power

[Smart $]

The specific rules rules in the Articles/Sections in Table 240.4(G) make all the rest of 240.4 moot for those specific applications.

Using that logic it follows that it wouldn't be necessary to so specify that in 240.4(D)... but yet it does. So there is a conflict of logic within 240.4.

 

[augie47]

I presume that you're talking about nameplate 'data'? What multipliers are you thinking of? Certainly not ambient teperature as the feeder could originate in a different area.

yes "data", typo..sorry
I was referring to the "multipliers" referenced in 440. Part IV.
The nameplate would simply state the minimum ampacity. All relative circumstances such as ambient, conduit fill, etc. would have to be taken into consideration, of course.

 

[don_resqcapt19]

Using that logic it follows that it wouldn't be necessary to so specify that in 240.4(D)... but yet it does. So there is a conflict of logic within 240.4.

I see no reason for the specification in 240.4(D). The first sentence of the section permits the use of any of the provisions found in subsections (A) through (G). No one subsection overrides another. It is the users choice to use what ever subsection fits the installation. The fact that extraneous wording has been included in subsection (D) does not change this.

 

[e57]

(Outside of the topic of the OP?)

If you'll note that 240.4(D) states, "Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed that required by (D)(1) through (D)(7) after any correction factors for ambient temperature and number of conductors have been applied."

I too also think there are some holes - as I really don't think that 440 'specifically' permits 'small conductors' under #10.... But I am sure there will be some disagreement on that... :roll:

240.4 Protection of Conductors.
Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G)

If 240.4(G) is permitted - is not 240.4(B), and 240.4(D) still applicable??? I see nothing in 440 specifically over-riding 240.4(D)??? Which IMO is still a requirement.

 

[don_resqcapt19]

...
If 240.4(G) is permitted - is not 240.4(B), and 240.4(D) still applicable??? I see nothing in 440 specifically over-riding 240.4(D)??? Which IMO is still a requirement.

I don't see it that way. The main part of 240.4 lets us use any of the requirements found in (A) through (G). The rules in Article 440 tell us how to size the AC conductors and how to provide the short circuit and ground fault protection as well as the overload protection.

 

[e57]

I don't see it that way. The main part of 240.4 lets us use any of the requirements found in (A) through (G). The rules in Article 440 tell us how to size the AC conductors and how to provide the short circuit and ground fault protection as well as the overload protection.

Alright - I know this sounds circular but it is....

• 240.4(G) allows use of 440 part 3&4... (since we're talking conductors part 4)
• 440.31 has two options - Article 310 or if applicable 440.6(A), Exception No. 1. (dealing specifically with 'hermetic refrigerant motor-compressors')

440.31 General.
The provisions of Part IV and Article 310 specify ampacities of conductors required to carry the motor current without overheating under the conditions specified, except as modified in 440.6(A), Exception No. 1.
The provisions of these articles shall not apply to integral conductors of motors, motor controllers and the like, or to conductors that form an integral part of approved equipment.

As far as I can see at the moment - this is the only way out of going BACK to Article 310....

Exception No. 1: Where so marked, the branch-circuit selection current shall be used instead of the rated-load current to determine the rating or ampacity of the disconnecting means, the branch-circuit conductors, the controller, and the branch-circuit short-circuit and ground-fault protection.

Because otherwise 440.6(A) itself would also put you BACK at Table 310.16~19....

• Go BACK to Article 310 unless covered in the exception 1 of 440.6(A)
• BACK at Article 310 you then end up in 310.15 and the Table(s) 310.16~19
• Table 310.16 and 310.17 have a few little *'s to remind you about 240.4(D) - (While it is assumed only to be a reminder??? We would otherwise not ignore it, only in a choice instance have we been told to ignore it.)

My conclusion is that unless the AC unit compresor is hermetic, and "as modified in 440.6(A), Exception No. 1" then 240.4(D) is still valid....

And no others in part 4 specifically permit or require to ingore 240.4(D)

240.4 Protection of Conductors.
Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G).

What 240.4(G) gives you, 240.4(D) takes away, unless it is hermetic "as modified in 440.6(A), Exception No. 1"

 

[Rewire]

yes "data", typo..sorry
I was referring to the "multipliers" referenced in 440. Part IV.
The nameplate would simply state the minimum ampacity. All relative circumstances such as ambient, conduit fill, etc. would have to be taken into consideration, of course.

this is relavent as #10/2 romex is limitred to the ampere rating in the 60c column which is 30 amps.

 

[e57]

Don,

(Sorry Rewire if it seems I'm thread jacking - since you're under 30a and on #10... That is if this a hermetic compressor? )

Lets just stay in 240.4.... Which has both permissions and requirements.

(A) Power Loss Hazard. A specific permission.
(B) Devices Rated 800 Amperes or Less. A requirement and a permission under certain conditions.
(C) Devices Rated Over 800 Amperes. A requirement.
(D) Small Conductors. "Unless specifically permitted in 240.4(E) through (G)" A requirement, needing 'specific permissions' to the contrary.
(E) Tap Conductors. A requirement.
(G) Overcurrent Protection for Specific Conductor Applications. A permission in this case to go to 440...

I see nothing in 440, except one case, that could allow you to ignore requirements in 240.4(B), or (C), or (E). And only one exception to the rest of 440, that allows you to stop there, and otherwise ingore 240.4(D)

 

[Minuteman]

Gentlemen.

Hermetic compressors have internal overload protection. The over sized OCP that is allowed by code is for starting purposes. The Manufacturer has calculated what the minimum amperage is to start the motor, and thus the minimum size branch circuit conductors.

Test this for yourself. Clamp your A/C compressor and see what amps it's running. Betcha lunch it's LESS than the minimum rated amps.

 

[e57]

Gentlemen.

Hermetic compressors have internal overload protection.

Which is why it seems to me that they get out of 240.4(D)..... And the others don't...

 

[don_resqcapt19]

Alright - I know this sounds circular but it is....

• 240.4(G) allows use of 440 part 3&4... (since we're talking conductors part 4)
• 440.31 has two options - Article 310 or if applicable 440.6(A), Exception No. 1. (dealing specifically with 'hermetic refrigerant motor-compressors')

As far as I can see at the moment - this is the only way out of going BACK to Article 310....
Because otherwise 440.6(A) itself would also put you BACK at Table 310.16~19....

• Go BACK to Article 310 unless covered in the exception 1 of 440.6(A)
• BACK at Article 310 you then end up in 310.15 and the Table(s) 310.16~19
• Table 310.16 and 310.17 have a few little *'s to remind you about 240.4(D) - (While it is assumed only to be a reminder??? We would otherwise not ignore it, only in a choice instance have we been told to ignore it.)

My conclusion is that unless the AC unit compresor is hermetic, and "as modified in 440.6(A), Exception No. 1" then 240.4(D) is still valid....

And no others in part 4 specifically permit or require to ingore 240.4(D)


What 240.4(G) gives you, 240.4(D) takes away, unless it is hermetic "as modified in 440.6(A), Exception No. 1"

Article 310 only tells us the ampacity of the conductors, Article 240 tells us how to protect them. Article 440 tells us what ampacity the conductor must have and we use Article 310 to find a conductor with a suitable ampacity. Article 240 tells us that we are permitted to size the branch circuit short circuit and ground fault protective device per the rules in Article 440.
The rules in 440.6 have nothing to do with the OCPD selection...they only cover the ampacity of the conductor. The only rules that cover the overcurrent protection of these conductors are those found in Part III of Article 440.

440.21 General.
The provisions of Part III specify devices intended to protect the branch-circuit conductors, control apparatus, and motors in circuits supplying hermetic refrigerant motor-compressors against overcurrent due to short circuits and ground faults. They are in addition to or amendatory of the provisions of Article 240.

 

[don_resqcapt19]

Don,

(Sorry Rewire if it seems I'm thread jacking - since you're under 30a and on #10... That is if this a hermetic compressor? )

Lets just stay in 240.4.... Which has both permissions and requirements.

(A) Power Loss Hazard. A specific permission.
(B) Devices Rated 800 Amperes or Less. A requirement and a permission under certain conditions.
(C) Devices Rated Over 800 Amperes. A requirement.
(D) Small Conductors. "Unless specifically permitted in 240.4(E) through (G)" A requirement, needing 'specific permissions' to the contrary.
(E) Tap Conductors. A requirement.
(G) Overcurrent Protection for Specific Conductor Applications. A permission in this case to go to 440...

I see nothing in 440, except one case, that could allow you to ignore requirements in 240.4(B), or (C), or (E). And only one exception to the rest of 440, that allows you to stop there, and otherwise ingore 240.4(D)

I just don't read it that way. For conductors that supply equipment within the scope of Article 440, the only overcurrent protection rules that apply are those found in Article 440. Those found in Article 240 just don't apply to these conductors.

 

[Smart $]

I see no reason for the specification in 240.4(D). The first sentence of the section permits the use of any of the provisions found in subsections (A) through (G). No one subsection overrides another. It is the users choice to use what ever subsection fits the installation. The fact that extraneous wording has been included in subsection (D) does not change this.

"Objection: Counsel for the defense is testifying as to facts not yet entered into evidence."

Additionally, I disagree with your statement that I have highlighted in bold blue. A simple example of your statement demonstrates it to be illogical: "I'm going to protect a #10 THHN circuit with a 40A breaker as I chose to use 240.4(B) instead of 240.4(D)".

My perspective on 240.4(A) through (G) is any subsection that can apply does apply... and this is the reason for the relinquishment stated in 240.4(D) regarding those situations that apply under 240.4(G). However, the requirement of 240.4(B) has not been relinquished by any statement I have seen thus far. As logic has it, 240.4(B) can be applied to Article 440 applications, so it does apply... unless you can find an Article 440 section statement in Part III or IV which amends 240.4(B).


You seem to be ignoring the part I highlighted below in bold green...

440.21 General.
The provisions of Part III specify devices intended to protect the branch-circuit conductors, control apparatus, and motors in circuits supplying hermetic refrigerant motor-compressors against overcurrent due to short circuits and ground faults. They are in addition to or amendatory of the provisions of Article 240.

 

[e57]

Article 310 only tells us the ampacity of the conductors, Article 240 tells us how to protect them. Article 440 tells us what ampacity the conductor must have and we use Article 310 to find a conductor with a suitable ampacity. Article 240 tells us that we are permitted to size the branch circuit short circuit and ground fault protective device per the rules in Article 440.
The rules in 440.6 have nothing to do with the OCPD selection...they only cover the ampacity of the conductor. The only rules that cover the overcurrent protection of these conductors are those found in Part III of Article 440.

440.21 General.
The provisions of Part III specify devices intended to protect the branch-circuit conductors, control apparatus, and motors in circuits supplying hermetic refrigerant motor-compressors against overcurrent due to short circuits and ground faults. They are in addition to or amendatory of the provisions of Article 240.

I still see no place (except for one), that ammends 240.4(D) out of the scene....

 

[don_resqcapt19]

I still see no place (except for one), that ammends 240.4(D) out of the scene....

And I see no reason to even look at 240.4(D) for conductors within the scope of Article 440.

 

[don_resqcapt19]

...
Additionally, I disagree with your statement that I have highlighted in bold blue. A simple example of your statement demonstrates it to be illogical: "I'm going to protect a #10 THHN circuit with a 40A breaker as I chose to use 240.4(B) instead of 240.4(D)". ...

You are correct about that part of my statement.

 

[e57]

And I see no reason to even look at 240.4(D) for conductors within the scope of Article 440.

240.4 allowing you to even consider looking at 440 says,

unless otherwise permitted or required in 240.4(A) through (G).

I'd say B & D are still requirements, and not specifical over-riden in 440.

 

[LarryFine]

I'd say B & D are still requirements, and not specifical over-riden in 440.

I believe it means any one of A through G, not all of them simultaneously.

 

[Pierre C Belarge]

e57
What you may not understand about the nameplate rating of A/C.
The manufacturer has already performed the calculations. The reason for the higher OCPD is the provide relief from the CBer tripping during startup/inrush. (very similar to motors - which an A/C unit has)
As you can see from the nameplate rating, the unit draws much less current during normal running. If there is a ground fault, the CBer will pick it up.

240.(D) is not applicable, and that is stated in the first paragraph of 240.4, which goes on to allow 240.4(G) as the section we reference.

 

[Smart $]

I believe it means any one of A through G, not all of them simultaneously.

Not just one, but any that apply simultaneously to the installation. Yes it could be just one, but there is nothing which states only one shall apply... and as we are discussing, it is possible, as it seems to me, that two can apply.