# Thread: Broken Main breaker and not capacity indicated

1. ## Broken Main breaker and not capacity indicated

Did inspection of a 1977 remodel with a GE panel board with two issues: FIRST: The capacity was not indicated anywhere. My guess is 150 amps based on incoming line, but that is a guess. What am I missing?
SECOND: The far right side of the main breaker was damaged and that position was no longer tied to the rest of the breaker. It was in the off position when I arrived. I put in on position and showed to owner and My client, suggesting a licensed electrician replace the main. Question-- What is happening when this one is in the off position?

2. ## Re: Broken Main breaker and not capacity indicated

That main C/B was legal, but funky at best. I'd say your amperage guess is close. Perspective with photos can be tough, but those conductors look to be at least #2cu and on the large side 1/0cu which could serve for a 200 amp service. The circuit breakers used for that main have a fairly small contact surface area and max out around 100 amps per breaker / slot, ( 125s live, but not safe IMHO ). To get the desired amperage using that size circuit breaker they double them up, ( two circuit breakers on each leg ). Assuming each breaker is 100 amps; On leg "A", ( the left side ) 100 amps through one C/B ~ 100 amps through the second C/B ~ totaling 200 amps capacity on leg "A". Ditto leg "B", ( the right side. Your C/Bs are probably 70s or there-about, but you can do the same math. If you really want to know the main rating, that handle tie covering all four of the C/Bs is removeable and the individual breaker handles should be labeled w/ the amperage. With one of the leg "B" C/Bs in the off position that leg would / should trip and the 100 amps or whatever the individual rating is on each individual C/B rather than the 200 they add up to, ( in theory ). Noticed there are two conductors in a lug that can legally have one. With that one C/B handle broken, ( one fourth of the main in this case ), the main can no longer perform it's function fully and it must be replaced.

Last edited by Garry Blankenship; 06-27-2012 at 08:50 AM. Reason: said "at" rather than "and"

3. ## Re: Broken Main breaker and not capacity indicated

Garry:

Thank you for the feed back, It was helpful.

4. ## Re: Broken Main breaker and not capacity indicated

My guess is that it's a 200 amp CB which would require a minimum of #2/0 copper if this is a dwelling service. Yes, the main should be replaced. How many slots did this panel have? Typically a 40 slot GE panel would have 200 amp bus.

5. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Robert Meier
My guess is that it's a 200 amp CB which would require a minimum of #2/0 copper if this is a dwelling service. Yes, the main should be replaced. How many slots did this panel have? Typically a 40 slot GE panel would have 200 amp bus.
Thanks Robert. One wire size smaller allowed for residential "hots", two sizes smaller than that for the neutral and I did not hit either one

6. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Garry Blankenship
Thanks Robert. One wire size smaller allowed for residential "hots", two sizes smaller than that for the neutral and I did not hit either one

7. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Garry Blankenship
two sizes smaller than that for the neutral
Garry,

I know that used to be stated in the code, however, I thought that allowance was removed - was that just relocated and I missed it?

8. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Jerry Peck
Garry,

I know that used to be stated in the code, however, I thought that allowance was removed - was that just relocated and I missed it?
230.42(C) refers you to 250.24(C), which tells you to use table 250.66. Confusing, a bit, as the NEC allows the grounded conductor to be the same size as a grounding electrode conductor.

Of course, this is a minimum and a load calc HAS to be done to make sure the grounded conductor is big enough.

9. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Bill Kriegh
230.42(C) refers you to 250.24(C), which tells you to use table 250.66. Confusing, a bit, as the NEC allows the grounded conductor to be the same size as a grounding electrode conductor.
Actually, that's not quite what it say, it says: "shall not be smaller than the required grounding electrode conductor specified in Table 250.66 but shall not be required to be larger than the largest ungrounded service-entrance phase conductor".

That section allows for the grounded conductor to fall within the stated *size range*.

Of course, this is a minimum and a load calc HAS to be done to make sure the grounded conductor is big enough.
Correct.

And that is a lot different than stating what Garry stated: "two sizes smaller than that for the neutral". What Garry stated indicates, actually states, that the grounded conductor can be two sizes smaller, you provided the code which states that the grounded conductor may be *between* these two sizes: "shall not be smaller than the required grounding electrode conductor specified in Table 250.66 but shall not be required to be larger than the largest ungrounded service-entrance phase conductor".

Jim, thank you for showing that the grounded conductor is not automatically allowed to be "two sizes smaller than that for the neutral". As I recall, that "two sizes smaller" used to be specifically stated many NEC editions ago, I thought that I had missed it coming back in or missed where it was relocated - but I had not.

Based on Garry's statement, the people reading it would only be looking for the neutral to be "two sizes smaller" than the grounded conductors. While that condition *may* exist at times, it is not a necessary *truth* to be looking for during the inspection.

10. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Jerry Peck
Actually, that's not quite what it say, it says: "shall not be smaller than the required grounding electrode conductor specified in Table 250.66 but shall not be required to be larger than the largest ungrounded service-entrance phase conductor".

That section allows for the grounded conductor to fall within the stated *size range*.

Correct.

And that is a lot different than stating what Garry stated: "two sizes smaller than that for the neutral". What Garry stated indicates, actually states, that the grounded conductor can be two sizes smaller, you provided the code which states that the grounded conductor may be *between* these two sizes: "shall not be smaller than the required grounding electrode conductor specified in Table 250.66 but shall not be required to be larger than the largest ungrounded service-entrance phase conductor".

Jim, thank you for showing that the grounded conductor is not automatically allowed to be "two sizes smaller than that for the neutral". As I recall, that "two sizes smaller" used to be specifically stated many NEC editions ago, I thought that I had missed it coming back in or missed where it was relocated - but I had not.

Based on Garry's statement, the people reading it would only be looking for the neutral to be "two sizes smaller" than the grounded conductors. While that condition *may* exist at times, it is not a necessary *truth* to be looking for during the inspection.
As has gotten to be a habit with the NEC on many, many things, the answers aren't always in one place - you gotta look at several. And in some cases, without electronic means to look up things (that aren't referenced between articles) you may miss part of the rule

11. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Bill Kriegh
As has gotten to be a habit with the NEC on many, many things, the answers aren't always in one place - you gotta look at several. And in some cases, without electronic means to look up things (that aren't referenced between articles) you may miss part of the rule
A very true statement that applies to the NEC more so than the other codes, but, sadly, also applies to other codes too.

12. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Jerry Peck
Garry,

I know that used to be stated in the code, however, I thought that allowance was removed - was that just relocated and I missed it?
I'm not sure where it was, but in the 2011 NEC it is Table 310.15 (B) (6) ~ page 70-147 ~ Article 310.15 bla, bla, bla

Apologies; that is the 2008 NEC. 2011 NEC is Table 310.15 (B) (7) ~ page 70-153

Last edited by Garry Blankenship; 06-28-2012 at 10:19 AM. Reason: Wrong Code Book

13. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Garry Blankenship
I'm not sure where it was, but in the 2011 NEC it is Table 310.15 (B) (6) ~ page 70-147 ~ Article 310.15 bla, bla, bla

Apologies; that is the 2008 NEC. 2011 NEC is Table 310.15 (B) (7) ~ page 70-153
Still does not say what you stated:
- (7) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of onefamily, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(7), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.

14. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Jerry Peck
Still does not say what you stated:
- (7) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of onefamily, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(7), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.
Hi J.P. I thought you were asking about the ungrounded conductor sizing. I made the neutral statement based on experience - - - never saw a residential neutral that was not two sizes smaller, unless the installer did not have it and then all the same size. If that were not the case the cable mfgs would have to eat a lot of 4/0, 4/0, 2/0 alum triplex. The copper alternative is not typically used due to cost. The NEC back & forth is too much for my patience & keyboarding capacity. The reason residential neutrals are allowed to be two sizes smaller looks most likely to be in 220.61 (B) which allows a 70% demand factor. Depending on how you read it, 215.2 and 230.42 are reliant on or defer to 220.61. Certianly would be a lot easier, if they would just include the allowable neutral sizes in the chart/s. The reality is you will never see a residential neutral load of more than 50 amps. From a safety perspective, it don't matter.

15. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Bill Kriegh
As has gotten to be a habit with the NEC on many, many things, the answers aren't always in one place - you gotta look at several. And in some cases, without electronic means to look up things (that aren't referenced between articles) you may miss part of the rule
Bill, don't get caught depending too much on an electronic version of something. I know this seems to be the trend right now, include the manual or whatever on electronic media. It's great for looking up one thing, but if you bounce around, as you can in the NEC, you may loose or miss the actual intent with the electronic version.

An example was when I was working on a piece of equipment that came with 5 CDs. Problem was when you looked up something---you always needed to go somewhere else. From there---somewhere else. After loosing track of what was going on for the third or forth time----we ordered the paper copies. There is nothing like having it in front of you, flipping to whatever, putting you big thumb in that spot, and just flipping back to check!

16. ## Re: Broken Main breaker and not capacity indicated

Originally Posted by Rich Goeken
Bill, don't get caught depending too much on an electronic version of something. I know this seems to be the trend right now, include the manual or whatever on electronic media. It's great for looking up one thing, but if you bounce around, as you can in the NEC, you may loose or miss the actual intent with the electronic version.

An example was when I was working on a piece of equipment that came with 5 CDs. Problem was when you looked up something---you always needed to go somewhere else. From there---somewhere else. After loosing track of what was going on for the third or forth time----we ordered the paper copies. There is nothing like having it in front of you, flipping to whatever, putting you big thumb in that spot, and just flipping back to check!
Rich, I'm well aware of the problems you can get into. I have a full copy of Adobe and make a habit of making PDFs that contain all the pages related to various issues when I have to look them up, and have them titled appropriately. I also bookmark the various additional references at the original code reference so I have everything at hand if I need to refer to them again. Makes it easy to print up all the related info if necessary. I update the NEC copy on my phone weekly to add new bookmarks I've made.

Sadly lacking from from all the electronic readers I see is the ability to do exactly what you describe doing with the thumb - ability to tag several pages and flip between them easily. Making the mini PDFs of the document works but still lacks what I want to see. Then, there's the issue of getting a copy of the NEC that is (ahem)"adjusted" so you can manipulate it like you need to. I find myself delving into areas of computer use I don't like and shouldn't have use to sometimes.

17. ## Re: Broken Main breaker and not capacity indicated

The last time i seen one of those breakers it was 200 amp, and they had it wired backwards also. The electric company had to come out and shut the power off till it was fixed.

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