MC connectors and 690.31/690.33 [RE-wrenches]

[Mark Frye]

The whole thing about the MC connector and why we are also in trouble with
690.33 is that the MC is not rated for opening under load.  This means that
ALL connectors regardless of location, guarding, fencing, etc. will have to
be locking (until they can shrink a Square D HR331 down to the size of an MC
connector) because they are not designed to open underload.  Forget about
the execption for locking connectors based on location.

The no exposed metal is only part of a "dead front" design to make them safe
to handle, during assembly.

Once they are assembled, and current is running thru them it is a different
story.

So what does happen if they are pulled apart while under load? Low
current-low voltage, high current-high volatage"

Two issues arise, 1- potential injury to operator due to DC arc, 2- damage
to connector such that it cannot be re-made.

The reason there is no proble with accidental open in Europe is the whole
system has GFCI grade protection, correct?

All of this is separate from 690.31, if the "circuit" is readily accessible,
the "conductor" SHALL be in a RACEWAY.

MPF

-----Original Message-----
From: Matt Tritt [mailto:solarone at charter.net] 
Sent: Tuesday, January 22, 2008 2:19 PM
To: RE-wrenches at topica.com
Subject: Re: Module wiring safety [RE-wrenches]



.
Michael,

Isn't that precisely the idea with MC connectors? If you look closely at how
they're made, you will see that NO metal is exposed to inadvertent contact
whilst pulling them apart - or plugging them together. If they wont' pull
apart, the back of the module will most likely do so; same as what would
happen if you pull really hard on a piece of flex conduit attached to a
plastic J-box

This entire subject "appears" to me to be driven by unrealistic
what-iffiness. MC connectors work great, especially the double-insulated
Euro version. You pull hard and they come apart. The circuit is broken. 
No one gets zapped. Everyone is safe. No one gets sued. Systems go together
fast and well. Hiding them behind some kind of shielding is great (though
probably not exactly imperative).

I just can't see why what has been functioning well is suddenly no damn
good.


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