Switchboard OCP

[mityeltu]

I am installing some equipment and am trying my best to make sure it meets code. With respect to my residential switchboard (I assume this can also be referred to sa a breaker panel), I am stuck at NEC 408.36.EXC 2 & 3

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.


EXC 2: First, what is meant by "individual protection"? Second, Does this mean that if I put a 2-pole beaker in as main on a breaker panel, I can only have 42 branch breakers (assuming ALL are 1-pole)?

EXC 3: I don't understand this at all. This makes it sound like I don't even need breakers or fuses. All I need is the main breaker.

Can someone please help me understand this?

Thanks.

 

[RUWired]

Exception # 2 applies to a split buss panel board. The main lugs supply 2 breakers. Breaker 1 supplies a section of breakers below the 2 main breakers and breaker number 2 can supply another section of breakers below the first section of breakers or it can supply another panel board. The split bus panel board is limited to 42 breakers and two main breakers.

Exception # 3 is also a split bus panel board. The main lugs can supply up to 6 breakers in the first section. One of those 6 breakers feeds a lower section of breakers.

Hope that made sense.

Rick

 

[augie47]

For a new install just make sure your panel has a main as part of the panel, or as a separate unit ahead of the panel, and, if you are under the '08 Code the 42 circuit limit has been removed.

 

[mityeltu]

So it is merely talking about a breaker panel of what I would call typical construction with a main breaker that supplies power to the single pole slots. The double pole breakers simply take 2 adjacent slots to complete the 240V.

What though is meant by by "individual protection"?

The section I posted comes from NEC 2008. How then can it have been removed?

 

[augie47]

There is no "removal". As Rick mentioned the panelboards listed in the exceptions are not "standard" today. Split buss panels were common a few years back

 

[mityeltu]

But what is meant by individual protection? Is this the OC protection of the panel or branch circuits or something else?

 

[augie47]

In the exceptions, it means a service panel can have up to six mains (no individual protectio) and "split buss" panels do not.

 

[mityeltu]

Thank you.