AC Unit conductor ampacity and over current protection.

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The oldest code I have is the 75 and the rule was incorrect even in that edition. In the 75 the rule was found as Exception #3 to 240.3 and referenced parts C and F in Article 440. Those parts are now Parts III and VI. This needs to be fixed because without a reference to the branch circuit conductor sizing rule in Article 440 we can't protect air conditioning circuits like we think we can.
 
Obviously a misprint that has existed for decades. The NFPA should issue an immediate TIA.
 
This rule has read the same since it first appeared in the 1971 code, the year that Article 440 was added to the code. The proposals never requested a reference to Part D, Branch Circuit Conductors. The original proposal references submitted for Exception #3 to 240.5 were to sections 440-22, 440-51 and 44-52. 440-22 is in Part C (now Part III) and both 440-51 and 51 are in Part F (now part VI). The specific section references from the proposal were changed to Part references in the next step of the cope adoption process. The sections referenced for the 1971 code cover the same subject matter as those same sections cover in the current code.
 
don_resqcapt19 said:
This rule has read the same since it first appeared in the 1971 code, the year that Article 440 was added to the code. The proposals never requested a reference to Part D, Branch Circuit Conductors. The original proposal references submitted for Exception #3 to 240.5 were to sections 440-22, 440-51 and 44-52. 440-22 is in Part C (now Part III) and both 440-51 and 51 are in Part F (now part VI). The specific section references from the proposal were changed to Part references in the next step of the cope adoption process. The sections referenced for the 1971 code cover the same subject matter as those same sections cover in the current code.
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My bad Don, I should have known to not questioned anything you posted in reference to the code. :) Hope it get corrected.
 
Michael15956 said:
My bad Don, I should have known to not questioned anything you posted in reference to the code. :) Hope it get corrected.
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It is the same in the 2020 code and I am not aware of any proposals being made over the years to correct the code. Actually prior to this, I was not aware that there even was a problem with this rule. Most everyone reads the language as saying we can do what we do...conductor sized to the minimum circuit ampacity and OCPD sized to the maximum OCPD as shown on the nameplate...I did too. When this was published in Electrical Contractor, I was 100% sure that Jim Dollard was wrong with his answer and even sent him an e-mail telling him that his answer was incorrect. However, since I know Jim and he is a code expert and code making panel member, I went back and looked at the actual code language. The code language does not reference the branch circuit conductor sizing in Article 440 like it should. The references for Article 430 correctly reference both the conductor sizing and the conductor protection. No idea why the Article 440 references don't do the same. I think that the intent is that we are permitted to do it like we have been doing it, but I just don't see the current language as actually saying we can.
 
I'm not sure what you guys are seeing as the mistake?

240.4 says that conductors shall be protected in accordance with their ampacities unless otherwise permitted in 240.4(A) thru (G).

240.4(G) says that Air-conditioning and refrigeration equipment circuit conductors can be protected in accordance with 440 part III (Short-Circuit and Ground Fault Protection) and 440 Part VI (Overload Protection.)
 
david luchini said:
I'm not sure what you guys are seeing as the mistake?

240.4 says that conductors shall be protected in accordance with their ampacities unless otherwise permitted in 240.4(A) thru (G).

240.4(G) says that Air-conditioning and refrigeration equipment circuit conductors can be protected in accordance with 440 part III (Short-Circuit and Ground Fault Protection) and 440 Part VI (Overload Protection.)
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I think the issue is that the sections you cited are for overload, gr. fault and short circuit but Part IV does not give allowance for the conductor to be sized for the higher ampacities. We all do it but I have always wondered why we were allowed with that rule as written
 
Dennis Alwon said:
I think the issue is that the sections you cited are for overload, gr. fault and short circuit but Part IV does not give allowance for the conductor to be sized for the higher ampacities. We all do it but I have always wondered why we were allowed with that rule as written
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I'm not sure I follow. Part IV is for conductor sizing, not overcurrent protection. The allowance to provide overcurrent protection greater than the ampacity of the conductor is given in 240.4(G).
 
david luchini said:
I'm not sure I follow. Part IV is for conductor sizing, not overcurrent protection. The allowance to provide overcurrent protection greater than the ampacity of the conductor is given in 240.4(G).
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Because Part 4 section 440.31 reference section 440.6(A) and that section gives direction to motor compressors
 
kwired said:
Makes no sense to refer to part VI, does make sense to refer to part IV.
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The reference to parts III and VI is relative to the Overcurrent Protection for Specific Conductor Applications.

The referenced sections (parts III and VI) provide specific information for the Overcurrent Protection of the conductors (Short-circuit/ground fault in Part III, Overload in Part VI.)

It would make no sense to refer to part IV (there is nothing in Part IV about overcurrent protection,) makes perfect sense to refer to part VI.
 
david luchini said:
The reference to parts III and VI is relative to the Overcurrent Protection for Specific Conductor Applications.

The referenced sections (parts III and VI) provide specific information for the Overcurrent Protection of the conductors (Short-circuit/ground fault in Part III, Overload in Part VI.)

It would make no sense to refer to part IV (there is nothing in Part IV about overcurrent protection,) makes perfect sense to refer to part VI.
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Without a reference to the permitted conductor sizing the rule does absolutely nothing. I have no idea why they did not follow the existing example of how they did this for Article 430, when they added Article 440 to the code in 1971.
 
don_resqcapt19 said:
Without a reference to the permitted conductor sizing the rule does absolutely nothing.
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The reference to the permitted conductor sizing rule is completely unnecessary to the overcurrent protection requirements. They are two separate issues. 240.4(G) tells you that the conductor need not be protected at its ampacity for Air-conditioning and refrigeration equipment...adding a reference to conductor sizing wouldn't affect that.

don_resqcapt19 said:
I have no idea why they did not follow the existing example of how they did this for Article 430, when they added Article 440 to the code in 1971.
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They DID follow the existing example of how they did this for Article 430, when they added Article 440 in 1971. The 1971 Code didn't have a reference to motor conductor sizing...It referenced Article 430 parts C, D, E & F...(Overload, SC/GF, Feeder SC/GF, Motor Control Circuit.) The reference to the conductor sizing in Art 430 didn't exist before 2014.

So a better question would be Why did they add the reference to 430 Part II in 2014? Nobody was having trouble understanding the motor conductor sizing and OC rules. If it wasn't broke, why did they try to fix it?
 
david luchini said:
240.4(G) tells you that the conductor need not be protected at its ampacity for Air-conditioning and refrigeration equipment...adding a reference to conductor sizing wouldn't affect that.
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240.4(G) only give permission to use Article 440, part III & VI. From there is where the over current and conductors sizing can be chosen instead of using the small conductor ruling of 240.4.

Part IV gives direction on over-current and conductor sizing through Section 440.6(A) Exception #1
 
david luchini said:
Part IV doesn't give any direction on overcurrent sizing.

440.6(A) Exception #1 rarely applies.
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So the question is where does 440 state that a conductor can be used other than what Table 310 states. It allows the overcurrent protective device to be larger but under part IV we are talking about the actual conductor.

IMO, 240.4 (D) referencing (G) is enough for me to see that a 10 wire can be on a breaker larger than 30 amps. I think what Don is saying is that it must reference Part IV to allow the conductor to be sized differently. I think that is where the author of the article is coming from in his statement.In the real world everyone does it in spite of the confusion
 
Dennis Alwon said:
So the question is where does 440 state that a conductor can be used other than what Table 310 states. It allows the overcurrent protective device to be larger but under part IV we are talking about the actual conductor.

IMO, 240.4 (D) referencing (G) is enough for me to see that a 10 wire can be on a breaker larger than 30 amps. I think what Don is saying is that it must reference Part IV to allow the conductor to be sized differently. I think that is where the author of the article is coming from in his statement.In the real world everyone does it in spite of the confusion
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There has to be something missing it's not possible that the collective users of the NEC have been getting this wrong for many decades. I wonder what Mike Holt would say about this, after all many of us have learned from him how to properly size the AC conductors.
 
Dennis Alwon said:
So the question is where does 440 state that a conductor can be used other than what Table 310 states. It allows the overcurrent protective device to be larger but under part IV we are talking about the actual conductor.
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You are looking for something in 440 that is already stated in 240.4. 240.4 says that the conductor must be protected in accordance with its ampacity (ie, what Table 310 states) except as permitted in 240.4(A) thru (G). 240.4(G) permits you to protect a conductor for A/C or refrigeration equipment at other than its ampacity.

Dennis Alwon said:
IMO, 240.4 (D) referencing (G) is enough for me to see that a 10 wire can be on a breaker larger than 30 amps. I think what Don is saying is that it must reference Part IV to allow the conductor to be sized differently.
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I do not see the logic here. The basic rule in 240 is that conductors must be protected at their ampacity...240.4(G) tells you that AC-R equipment conductors can be protected at other than their ampacity. Why would we need another reference to tell us the same thing? It would be redundant.

And as I mentioned, the reference in 240.4(G) is for overcurrent protection. Parts III and VI of Art 440 relate to overcurrent protection. Part IV does not relate to overcurrent protection. It doesnt make sense, when talking about overcurrent protection, to reference a section that dosen't tell you anything about overcurrent protection.
 
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