240.3 and 240.4(G)

[bwat]

Are 240.3 (really Table 240.3) and 240.4(G) (really Table 240.4(G)) redundant? If not, what are they saying differently?

For example, Table 240.3 lists 690 for PV specific applications. However, Table 240.4(G), which is the one for specific conductor applications, does not list 690. To me, that would mean there aren't specific conductor applications in 690 that you can use, and that rest of the 240.4 applies for PV applications as normal. Anyone familiar with 690 knows that this isn't true and there are are a lot of things in 690 about specific conductor applications and OCPD. I've always justified that this is ok because 690 is listed in 240.3. But if that's the case, what's the purpose of 240.4(G)?

 

[Elect117]

240.3 is for equipment specified in that table.

240.4(G) is specific conductor applications specified in that table.

That is how I read it.

 

[wwhitney]

For example, Table 240.3 lists 690 for PV specific applications. However, Table 240.4(G), which is the one for specific conductor applications, does not list 690. To me, that would mean there aren't specific conductor applications in 690 that you can use, and that rest of the 240.4 applies for PV applications as normal. Anyone familiar with 690 knows that this isn't true and there are are a lot of things in 690 about specific conductor applications and OCPD. I've always justified that this is ok because 690 is listed in 240.3. But if that's the case, what's the purpose of 240.4(G)?

Can you give an example of an allowance in 690 that is in conflict with the basic requirement of 240.4 that conductors "shall be protected against overcurrent in accordance with their ampacities"?

Note that it doesn't say protected with OCPD. So sizing a conductor larger than the maximum available fault current from a source complies with that basic 240.4 requirement.

Cheers, Wayne

 

[bwat]

Can you give an example of an allowance in 690 that is in conflict with the basic requirement of 240.4 that conductors "shall be protected against overcurrent in accordance with their ampacities"?

Note that it doesn't say protected with OCPD. So sizing a conductor larger than the maximum available fault current from a source complies with that basic 240.4 requirement.

Cheers, Wayne

Ahhh... The part that I bolded is a really good point, and maybe that's the key to resolving my perceived issue. If "protected against overcurrent" can mean sized larger than max fault current and no OCPD needed, then you're still meeting 240.4. I may have fallen into the trap of wanting to make "protected against overcurrent" to mean something like "protected against overcurrent by a overcurrent protection device".

I'll have to think if there's another scenario where you can size something according to 690 that would be in violation of 240.4 using that (I would assume correct) interpretation.

 

[bwat]

I believe I found at least one conflict between 240.4 and 690: 240.4(D) with the small conductors rule. (D) specifically references OCPD. So having #10 CU being protected by something larger than 30A (or even no OCPD at all) would be violation of this, but you can do this according to 690.


My stance is that 690 should be listed in Table 240.4(G)

 

[wwhitney]

I believe I found at least one conflict between 240.4 and 690: 240.4(D) with the small conductors rule. (D) specifically references OCPD.

240.4(D)(3)-(7) do not actually reference OCPD, just (D)(1) and (D)(2). The base text in (D) just refers to "the overcurrent protection," and (D)(3)-(D)(7) just refer to a value of 15, 20, 25, or 30 amps. So if you have #14 Cu with an adjusted ampacity of 20A on the roof, you still can only connect 12A of microinverters to it, not 16A.

(D)(1) and (D)(2) do specifically call for fuses or circuit breakers, so you can't install #16 AWG on the roof and connect 8A of microinverters to it without OCPD. That's not in direct conflict with Article 690 but does further restrict it, intentionally or not.

Cheers, Wayne

 

[jaggedben]

I believe I found at least one conflict between 240.4 and 690: 240.4(D) with the small conductors rule. (D) specifically references OCPD. So having #10 CU being protected by something larger than 30A (or even no OCPD at all) would be violation of this, but you can do this according to 690.

IIRC, 690 allows you to omit the OCPD in certain circumstances, but wouldn't allow you to use 10awg cu where a larger than 30A is required.

My stance is that 690 should be listed in Table 240.4(G)

If we look at 90.3 it isn't really necessary for Table 240.04(G) to mention 690 in order for 690 to modify 240 requirements. Throwing chapter 6 and 7 into that table just provides guidance, kind of like an informational note.

 

[bwat]

IIRC, 690 allows you to omit the OCPD in certain circumstances, but wouldn't allow you to use 10awg cu where a larger than 30A is required.

240.4(D) says that the OCPD shall not exceed 30A on 10awg CU. Are you really saying omitting an OCPD altogether doesn't violate this? That's very slippery slope if we start saying a non-existent OCPD is just as code compliant as not exceeding an OCPD rating.

If we look at 90.3 it isn't really necessary for Table 240.04(G) to mention 690 in order for 690 to modify 240 requirements. Throwing chapter 6 and 7 into that table just provides guidance, kind of like an informational note.

Wouldn't that apply to everything else in Table 240.4(G), so Table 240.4(G) isn't even necessary because of 90.3? That's a little unique of a position, but I could buy that vowel.

 

[bwat]

240.4(D)(3)-(7) do not actually reference OCPD, just (D)(1) and (D)(2). The base text in (D) just refers to "the overcurrent protection," and (D)(3)-(D)(7) just refer to a value of 15, 20, 25, or 30 amps. So if you have #14 Cu with an adjusted ampacity of 20A on the roof, you still can only connect 12A of microinverters to it, not 16A.

(D)(1) and (D)(2) do specifically call for fuses or circuit breakers, so you can't install #16 AWG on the roof and connect 8A of microinverters to it without OCPD. That's not in direct conflict with Article 690 but does further restrict it, intentionally or not.

Cheers, Wayne

The base text in (D) refers to overcurrent protection, as you said. It sounds like you're reading "the overcurrent protection" in the same way as the "protected against overcurrent" from our posts above, meaning that fault current less than that is sufficient. Am I correct with your position? I don't agree off hand, if so.

"Protected against overcurrent" could be lack of fault current, but I don't see it as correct to say it has overcurrent protection in that scenario. To your point, it is missing that important word of "device" though, and (D)(3)-(7) don't actually reference an OCPD the same way that (D)(1) and (D)(2) do ..

 

[wwhitney]

The following conversation makes complete sense and is how I expect the language to be used:

A: "This circuit is protected against overcurrent"
B: "What is the form of the overcurrent protection?"
A: "The available fault current is less than the conductor ampacity."

Cheers, Wayne

 

[bwat]

The following conversation makes complete sense and is how I expect the language to be used:

A: "This circuit is protected against overcurrent"
B: "What is the form of the overcurrent protection?"
A: "The available fault current is less than the conductor ampacity."

Cheers, Wayne

Your wording choice for person B's question is very convenient for your interpretation

I'd say B's question would follow closer to the actual code wording if it was:
"Does the overcurrent protection exceed 30A?"

It is then hard to say "yes" to that if there isn't an OCPD.



I'm aware that I'm really dragging us off into the weeds on this one. I appreciate you humoring me on this. I'm starting to come around to that it would be an interesting hill for me to die on to say that "the overcurrent protection" is substantially different from "protected against overcurrent".

 

[wwhitney]

I'd say B's question would follow closer to the actual code wording if it was:
"Does the overcurrent protection exceed 30A?"

OK, so then A says "no, the available fault current is limited to 30A".

Cheers, Wayne

 

[jaggedben]

240.4(D) says that the OCPD shall not exceed 30A on 10awg CU. Are you really saying omitting an OCPD altogether doesn't violate this?

Yes, but you can only omit the OCPD where that is explicitly allowed. Such as for PV in the situation Wayne describes in post #10.

The 30A rule for 10awg is no more or less ironclad for PV conductors without an OCPD than it is for air-conditioner conductors having a >30A rated OCPD. Both are allowed by specific sections of the code.

That's very slippery slope if we start saying a non-existent OCPD is just as code compliant as not exceeding an OCPD rating.

It's not a slippery slope when it's only allowed under very specific circumstances laid out in other sections of the code.

Wouldn't that apply to everything else in Table 240.4(G), so Table 240.4(G) isn't even necessary because of 90.3?

No, 90.3 only says Chapters 5, 6, and 7 may modify chapter 2. The articles in 240.4(G) that are in Chapter 3 and 4 need to be called out there in order not to be overridden by other sections of 240.4.

 

[bwat]

The 30A rule for 10awg is no more or less ironclad for PV conductors without an OCPD than it is for air-conditioner conductors having a >30A rated OCPD. Both are allowed by specific sections of the code.

A lot of good points, but I'll cherry-pick this part and point to the fact that conductors for air conditioning circuits is called out in Table 240.4(G). So one is specifically called out as permissible (AC units in 440) and one isn't (PV). This was most of what was driving my initial post.

No, 90.3 only says Chapters 5, 6, and 7 may modify chapter 2. The articles in 240.4(G) that are in Chapter 3 and 4 need to be called out there in order not to be overridden by other sections of 240.4.

So by that logic, wouldn't articles in chapter 6 and 7 that are in Table 240.4(G) be unnecessary since 90.3 already gives them permission?


I don't want to put words in anyone's mouth but:
- I see you (jaggedben) as saying there are already provisions for allowing 690 to override 240.4, so there's no need to list in Table 240.4(G)
- I see Wayne as saying there isn't anything in 690 that conflicts with 240.4, so there's no need to list in Table 240.4(G)

 

[jaggedben]

Well, I don't see why we can't both be right.

I think I agree with Wayne, but if I didn't, explicit permissions in 690 would still override explicit requirements in 240, with or without mention in a 240 table.

 

[jaggedben]

...

So by that logic, wouldn't articles in chapter 6 and 7 that are in Table 240.4(G) be unnecessary since 90.3 already gives them permission?

...

Yes, but this doesn't create any conflict between code requirements or permissions. It amounts to a non-consequential copy-editing nitpick. They could remove all the Chapter 6 and 7 references or put in ones that are missing and it would make no difference to requirements or permissions.