Nec 408.36

[cdcengineer]

I haven't had any experience with the 84 circuit panelboards. In review of the 2008 & 2011 NEC (section 408.36), I am wondering if there is a possible typo or am I reading things wrong.

To paraphrase: The exception #2 states that individual protection shall not be required for a pnlbd protected on it's supply side by two mcb's or two sets of fuses having a combined rating not greater than that of the pnlbd. A pnbld wired under this exception must have no more than 42 ckts....

Am I to assume that by individual protection the code is inferring to a main ckt brkr located within the pnlbd itself? And, if so, what about an example of a 800A service utilizing the (6) handle rule with (6) 200A main brkrs serving (6) separate 42 ckt MLO panels. If I am reading this article correctly, this would not be an acceptable installation because there wouldn't be two breakers ahead of each panel. I'm thinking there was a typo that left out the previous (NEC 2005) reference of ... "not more than" two mcb's or two sets of fuses.... from the earlier edition of 408.36.

Thx to all for comments and input.

I'm a bit confused here and would appreciate any comments.

 

[infinity]

Can your arrangement comply with 408.36? If so then the exceptions would not be applicable.

408.36 Overcurrent Protection.
In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard.
Exception No. 1: Individual protection shall not be required for a panelboard used as service equipment with multiple disconnecting means in accordance with 230.71. In panelboards protected by three or more main circuit breakers or sets of fuses, the circuit breakers or sets of fuses shall not supply a second bus structure within the same panelboard assembly.
Exception No. 2: Individual protection shall not be required for a panelboard protected on its supply side by two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard. A panelboard constructed or wired under this exception shall not contain more than 42 overcurrent devices. For the purposes of determining the maximum of 42 overcurrent devices, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively.
Exception No. 3: For existing panelboards, individual protection shall not be required for a panelboard used as service equipment for an individual residential occupancy.

 

[raider1]

Am I to assume that by individual protection the code is inferring to a main ckt brkr located within the pnlbd itself?

No the individual protection can be at any location upstream from the panelboard.

And, if so, what about an example of a 800A service utilizing the (6) handle rule with (6) 200A main brkrs serving (6) separate 42 ckt MLO panels.

Exception #1 to 408.36 permits services to still use the 6 disconnect rule.

The changes to 408.36 were designed to eliminate the differences between lighting and appliance panelboards and power panelboards and the way each was provided with overcurrent protection.

Now panelboards are required to be protected from overcurrents with a single device located ahead of the panelboard.

In the 2005 NEC a power panelboard could have been protected by multiple breakers within the panelboard.

Chris

 

[cdcengineer]

Infinity & Raider,

Let me provide a bit of background. I designed a 400A, 120/240CV, single phase service for a residence. The one-line includes a combo CT/meter-main (mfg -AMP) with two 200A/2P mains serving the panelboards in question, one 60A/2P main serving a TVSS and one 30A/2P main for future.

The two 200A/2P breakers were designed to serve two 225A, main lug only (84) circuit lighting and appliance panelboards.

During plan review, I got a call from the building official saying this violates 408.36 (specifically Exc #2). It got me reading into the code which is where this question came up. I hadn't specified panelboards larger than (42) ckt until now. I went back to my earlier editions of NEC to see how the verbiage had evolved and somewhere I got confused with how to interpret this article.

Thx.

 

[raider1]

Infinity & Raider,

Let me provide a bit of background. I designed a 400A, 120/240CV, single phase service for a residence. The one-line includes a combo CT/meter-main (mfg -AMP) with two 200A/2P mains serving the panelboards in question, one 60A/2P main serving a TVSS and one 30A/2P main for future.

The two 200A/2P breakers were designed to serve two 225A, main lug only (84) circuit lighting and appliance panelboards.

During plan review, I got a call from the building official saying this violates 408.36 (specifically Exc #2). It got me reading into the code which is where this question came up. I hadn't specified panelboards larger than (42) ckt until now. I went back to my earlier editions of NEC to see how the verbiage had evolved and somewhere I got confused with how to interpret this article.

Thx.

The plan review is incorrect.

Each 225 amp panelboard is being protected a single 2 pole 200 amp breaker in the meter/panel. So you do not need to comply with exception #2. Again the single overcurrent protective device required by 408.36 can be located within or at any point on the supply side of the panelboard.

Chris

 

[augie47]

FWIW, I agree with Chris.

 

[dana1028]

The plan review is incorrect.

Each 225 amp panelboard is being protected a single 2 pole 200 amp breaker in the meter/panel. So you do not need to comply with exception #2. Again the single overcurrent protective device required by 408.36 can be located within or at any point on the supply side of the panelboard.

Chris

I agree completely.

However... I am confused by X-2...I certainly understand having a downstream panelboard being protected upstream by a single OCPD....but I don't understand the "protected on the supply side by two main circuit breakers" language.

Chris - could you provide an example? thanx

 

[raider1]

I agree completely.

However... I am confused by X-2...I certainly understand having a downstream panelboard being protected upstream by a single OCPD....but I don't understand the "protected on the supply side by two main circuit breakers" language.

Chris - could you provide an example? thanx

Basically Exception #2 permits a split buss panelboard to be protected with no more than 2 breakers provided that the panelboard has no more than 42 breakers.

Chris

 

[cdcengineer]

Thanks to all for the input. I responded to the inspector this AM and posed my rebuttal to his question. He followed up this afternoon agreeing with my response. You guys are on the money with your interpretations, and I appreciate the description of exception #2 (re: split bus).

Thx