430.62

[m sleem]

I understand from 430.62 the next higher size of the breaker shall not be permitted & we have to go for the next down size. This is acceptable in ratings smaller than 800a, what about the ratings over 1000a?
e.g. we got 1500 after applying 430.62 rule & the standard breaker size either 1200a or 1600a, which one we have to go for?

To: moderator
Please remove the previous post.

 

[augie47]

I know of no exception that allows you to go to 1600.

 

[jumper]

To: moderator
Please remove the previous post.

I already took care of it. Redirected it here.

 

[jumper]

I know of no exception that allows you to go to 1600.

Is there any way one could use 240.6(C) and dial the breaker down?

 

[m sleem]

Is there any way one could use 240.6(C) and dial the breaker down?

Of Course using LI or LS or LSIG leading to cost impact, in addition to this, this trick may be not permitted by code.

 

[jumper]

O

Huh? What does O mean?

 

[m sleem]

Huh? What does O mean?

All you need just refresh

 

[petersonra]

there is actually no requirement that you use one of the standard sized CBs.

the rules allow you to select the next higher standard size breaker if the calculations are under 800A. otherwise you have to use a breaker that is less than or equal to the calculated number.

if the calculated number is 1500A, you can use a 1500A CB, or something smaller. You can't exceed 1500A though.

 

[m sleem]

there is actually no requirement that you use one of the standard sized CBs.

the rules allow you to select the next higher standard size breaker if the calculations are under 800A. otherwise you have to use a breaker that is less than or equal to the calculated number.

if the calculated number is 1500A, you can use a 1500A CB, or something smaller. You can't exceed 1500A though.

I got 2200a after calculation, would you think i can specify 2200a in the design layout?

 

[petersonra]

I got 2200a after calculation, would you think i can specify 2200a in the design layout?

if you can find a 2200A CB.

We do not normally use anything over 1600A so I am not real familiar with what is available above 1600A frame size.

 

[petersonra]

if you can find a 2200A CB.

We do not normally use anything over 1600A so I am not real familiar with what is available above 1600A frame size.

incidentally, you can make the feeder CB 10,000A if you want to. You just have to make the wire have 10,000A worth of ampacity.

 

[m sleem]

if you can find a 2200A CB.

We do not normally use anything over 1600A so I am not real familiar with what is available above 1600A frame size.

Easy you can find this rating when practising with chillers plant in hospitals or heavy equipments in factory.

 

[Smart $]

incidentally, you can make the feeder CB 10,000A if you want to. You just have to make the wire have 10,000A worth of ampacity.

Recently had a limited debate on this issue [link to thread]...


At what point must we make conductor ampacity equal or exceed ocpd rating when we have a combination of motor and non-motor load.

If we go by 240.4... greater than 800A ocpd rating.

If we go by 430.62(A), there are cases where ocpd rating can be 3 to 7 times the flc of a motor plus other loads.

What if we have a motor with a 300A flc along with other loads and a 1000A breaker is required for motor starting plus these other loads. Do we have to size the feeder to 1000A or per 430.24...???

 

[m sleem]

Recently had a limited debate on this issue [link to thread]...


At what point must we make conductor ampacity equal or exceed ocpd rating when we have a combination of motor and non-motor load.

If we go by 240.4... greater than 800A ocpd rating.

If we go by 430.62(A), there are cases where ocpd rating can be 3 to 7 times the flc of a motor plus other loads.

What if we have a motor with a 300A flc along with other loads and a 1000A breaker is required for motor starting plus these other loads. Do we have to size the feeder to 1000A or per 430.24...???

Well, that mean we may apply 430.62 up to lv xfmr, IMO 430.62 at the first feeder only and 430.24 at all others.

 

[Smart $]

Well, that mean we may apply 430.62 up to lv xfmr, IMO 430.62 at the first feeder only and 430.24 at all others.

Seems to me that both 430.24 and 430.62 are regarding any feeder (or service?) with a motor load. 430.24 compliance must be coordinated with 430.62 compliance. They are not entirely separate issues.

 

[m sleem]

Recently had a limited debate on this issue [link to thread]...

I posted already in this thread, but i didn't follow the last posts between you and david, it discussed the same issue.