ECN Forum Forums Code Related Discussion NEC & other Code issues 404.8(B)

How come?
"Voltage Between Adjacent Devices
A snap switch shall not be grouped or ganged in enclosures with other snap switches, receptacles, or similar devices, unless they are arranged so that the voltage between adjacent devices does not exceed 300 volts, or unless they are install in enclosures equipped with permanently installed barriers between adjacent devices."

Fine, but it's OK to install a single switch (Leviton makes them with ratings of up to 40A, 3 pole/20HP 600V) or a 480V recp in the box.
I Don't Get It

Proposal 9-79, SUBSTANTIATION: Circuit breakers should be included in
Exception No. 2 since switches with fuses are permitted by
Section 240-24(a)(4), and that section implies circuit breakers are
permitted.
Switches on 277 volt circuits may also be installed in enclosures
adjacent to receptacles on 120 volt circuits where the voltage
difference can exceed 300. The hazard of such exposed terminals
is just as great regardless of the type of device.
The phrase “can be arranged” does not invoke a rule, only a
possibility.
PANEL ACTION: Accept in Principle.
Revise (b) of the proposal to read as follows:
“(b) Voltage Between Adjacent Switch(es). A snap switch shall
not be grouped or ganged in enclosures with other snap switches,
receptacles, or similiar devices unless they are arranged so that
the voltage between adjacent devices does not exceed 300 volts, or
unless they are installed in enclosures equipped with permanently
installed barriers between adjacent devices.”
PANEL STATEMENT: The panel wishes to assure that the
restriction is not applied to motor starter control circuits and the
like.
NUMBER OF PANEL MEMBERS ELIGIBLE TO VOTE: 11

Thank you, Joe.
I still, though, don't understand the reason that it's necessary to keep the voltage below 300V between the adjacent switches.
Is there an inherent problem with flashover. I've seen some 277V switches that were pretty ugly(oxymoron) after failing.
If so, why would ganged receptacles (or a single device) be any less likely to fail in the same fashion?

electure:

Look here, and if you need more information send Mark an email, his address is at the bottom of his article.

http://www.ul.com/regulators/ode/0301.pdf