Re: Lighting & appliance branch circuit panelboards
The next section B says in part:
"Note that a panelboard marked ?Suitable for use as service equipment when not more than six main disconnecting means are provided? may permit some combinations of switching units varying in
ampere ratings and physical size that would exceed the six disconnect rule on a completely filled panelboard."
Yes a 12 circuit panel board will permit one to install more disconnects than allowed, They could very well put in 4 two pole breakers and then install 4 single pole breakers which would violate the NEC and UL listing if it was a service equipment panel, but what I'm getting out of the item 20 is UL must have a requirement that a main lug panel board that has an isolated neutral bar must not have any more spaces then that which could be filled by handle tied breakers which would not exceed the 6 disconnect rule.
Example would be a panel that has 12 spaces but with two pole breakers would only allow 6 two pole breakers installed.
This would also allow 18 space panel if 3-pole handle tie were available? But for the most part I have only seen ML panels that had the label with 12 circuits and under.
I think this is saying that a 20 circuit and up would not be Suitable for use as service equipment because it would allow more then 6 disconnects when the largest combination of switching units that can be mounted to occupy all available space for switching units are used and the maximum combining of them with handle ties is done.
I know we are not supposed to use a 3-pole breaker in a single phase panel unless it is marked with the "for use on 1? systems.
That is from UL's marking guide "Molded Case Circuit Breakers 600 Volts or Less June 2004
Which can be read
HERE
Page 14 item 33 33. 3-Pole ? 1-Phase Rated ? 3?pole circuit breakers are suitable for use on 3-phase systems
only, unless marked to indicate use on 1-phase systems, such as, ?For 1?phase connections, use two
outside poles,? or an equivalent statement. A 3-pole breaker used in place of a 2-pole breaker on a 3-
phase system, such as a 2-pole breaker used in a branch circuit that is actually two legs of a 3-phase
system, is acceptable without the 3-pole breaker being specifically marked.
They also have to meet the voltage requirement and have 120/240 volt rating on them. As per page 10 item 3 of the same marking guide.
So this could be complicated?
Too bad we don't have anyone from UL on here.
