OCP

[ohmhead]

Question I have a 480v 208 /120 v 225 kva transformer which feeds a panel 25 feet away what is the rule the inspector says 10 foot .
I have a main breaker in panel but the inspector says it must have a disconnect with protection ahead of panel and 10 foot is the cut off .
What is the rule can it be 25 ft or is 10 foot correct and no exceptions.

 

[david luchini]

If you can comply with the requirements of 240.21(C)(6), you can run the secondaries up to 25'.

 

[Smart $]

Question I have a 480v 208 /120 v 225 kva transformer which feeds a panel 25 feet away what is the rule the inspector says 10 foot .
I have a main breaker in panel but the inspector says it must have a disconnect with protection ahead of panel and 10 foot is the cut off .
What is the rule can it be 25 ft or is 10 foot correct and no exceptions.

Refer to 240.21(C). There are several conditions involved for compliance where secondary conductors run more than 10 ft.

Additionally, if this a supervised industrial installation, see 240.92(C).

 

[ohmhead]

Refer to 240.21(C). There are several conditions involved for compliance where secondary conductors run more than 10 ft.

Additionally, if this a supervised industrial installation, see 240.92(C).

What if its not over 25 feet and the tap conductors terminate in a single breaker in the panel which the conductors are feeding . Which is 240.21(2) not over 25 foot long would we comply with the NEC or is there something else I need . Thanks for the responses Iam using the 2014 code book page 154 top left .

 

[Smart $]

What if its not over 25 feet and the tap conductors terminate in a single breaker in the panel which the conductors are feeding . Which is 240.21(2) not over 25 foot long would we comply with the NEC or is there something else I need . Thanks for the responses Iam using the 2014 code book page 154 top left .

I am limited to the 2011 NEC for now. I tried looking at the online version of 2014 but after flipping countless pages to get there, I accidentally clicked the First button instead of Previous to go back one page. Didn't feel like flipping through countless pages again. Nonetheless, I recall 240.21 being around page 100.

Also, your reference to 240.21(2) is in error. There should be a letter after the section number. However, I think you are referencing 240.21(B)(2). That, too, is not the correct.

These are conductors coming directly off a transformer secondary, and as such have to comply with 240.21(C). If you want to go 25ft, 240.21(C)(6) in particular applies (assuming 2014 subsection are unchanged). There are three conditions for compliance. If your installation meets all three conditions, the inspector should have no problem with approving such.

 

[ohmhead]

I am limited to the 2011 NEC for now. I tried looking at the online version of 2014 but after flipping countless pages to get there, I accidentally clicked the First button instead of Previous to go back one page. Didn't feel like flipping through countless pages again. Nonetheless, I recall 240.21 being around page 100.

Also, your reference to 240.21(2) is in error. There should be a letter after the section number. However, I think you are referencing 240.21(B)(2). That, too, is not the correct.

These are conductors coming directly off a transformer secondary, and as such have to comply with 240.21(C). If you want to go 25ft, 240.21(C)(6) in particular applies (assuming 2014 subsection are unchanged). There are three conditions for compliance. If your installation meets all three conditions, the inspector should have no problem with approving such.

Thank you Smart $ 240.21 (C) (6) yes I can do all three heres what I have 480/208 =2.3 the pri breaker is a 350 A 1/3 of that is 116 amps 116 x 2.3 = 266.8 amps
secondary conductors are 3 sets of 400 MCM Alu which 310.16 gives me 270 x 3 = 810 amps total secondary conductors are not less than 266.8 amps .

The secondary conductors terminate in a single 3 phase 800 amp breaker in panel down stream at 25 foot .

The secondary conductors are installed in conduit EMT completely .

Is this ok you said all three must be met I just want ask because I don't like telling a inspector he maybe wrong ever .

 

[electrofelon]

Question I have a 480v 208 /120 v 225 kva transformer which feeds a panel 25 feet away what is the rule the inspector says 10 foot .
I have a main breaker in panel but the inspector says it must have a disconnect with protection ahead of panel and 10 foot is the cut off .
What is the rule can it be 25 ft or is 10 foot correct and no exceptions.

Is the inspector saying this OCPD needs to be stand alone before the panel and it cant be the main breaker in the panel? Or is he saying you cant meet the 25' tap rule so you need the OCPD at 10' and then continue with a feeder to the panelboard? Remember you need to protect the panelboard too, not sure if that has something to do with it. If you have an 800 MB most likely your panelboard is rated at least that unless someone goofed.

 

[ohmhead]

Is the inspector saying this OCPD needs to be stand alone before the panel and it cant be the main breaker in the panel? Or is he saying you cant meet the 25' tap rule so you need the OCPD at 10' and then continue with a feeder to the panelboard? Remember you need to protect the panelboard too, not sure if that has something to do with it. If you have an 800 MB most likely your panelboard is rated at least that unless someone goofed.

Well yes the inspectors rejection was the 10 foot tap rule we are at 16 foot not over 25 ft he stated that the 25 ft tap rule could be only applied in a industrial application .
After looking in the code book I found that to be false that theres another 25 ft tap rule . Smart $ thanks for the article and help we actually had the inspector read it today and went over each step he pass it today . Don't get me wrong our inspector is a great guy very sharp and fair and I think we both learned something new this week . Thanks again for the help Smart$

 

[Smart $]

Well yes the inspectors rejection was the 10 foot tap rule we are at 16 foot not over 25 ft he stated that the 25 ft tap rule could be only applied in a industrial application .
After looking in the code book I found that to be false that theres another 25 ft tap rule . Smart $ thanks for the article and help we actually had the inspector read it today and went over each step he pass it today . Don't get me wrong our inspector is a great guy very sharp and fair and I think we both learned something new this week . Thanks again for the help Smart$

Glad to help. Must also mention David Luchini because he actually pointed you to 240.21(C)(6) first.

Mostly glad you got it passed without having to modify...

 

[ohmhead]

Glad to help. Must also mention David Luchini because he actually pointed you to 240.21(C)(6) first.

Mostly glad you got it passed without having to modify...

Believe me no one is more delighted then me it would have a big impact on the project yes sorry guys thanks David Luchini .