MC connectors and 690.31/690.33 [RE-wrenches]

[Mark Frye]

William,

I guess my understanding is in flux.

I assumed due to all the talk about how the new Code was going to require
locking connectors that in fact the current MC connectors did not meet the
requirement "Be rated for interrupting current without hazard to the
operator." However, this requirement appears to have been met for the last 6
years.  Therefore, by the overwhelming amount of precedent, the current MC
connectors must be "... rated for interrupting current without hazard to the
operator.", regardless of the UL requirement to label them "Do Not Open
Under Load".

So what is the intent of the new Code?  Did the Code makers believe that the
vast majority of systems installed in the last six years were installed in
violation of the intent of the Code? Has MC been providing us a connector
that in fact is not rate for interrupting current without hazard to the
operator? If this was the thinking of the Code makers, why didn't they make
significant changes to the language of 2008 690.33 (E) which is functionally
the same as previous versions?

Is there a confounding overlap between 2008 690.31 and 2008 690.33?

2008 690.31 says for any circuit over 30 V in a readily accessible location
the conductors shall be in a raceway, while 690.33 says that if a connector
is readily accessible it shall require a tool to open. Can a connector exist
in a raceway? Regardless, there will never be such a thing as connector in a
readily accessible location, so there is no need to require that it be
opened by a tool.

2008 690.31 has some pretty clear language however.  Circuits over 30 V in
readily accessible location shall be installed in a raceway.

So now my head is spinning nicely again.  It is a real mess.  One of the
problems with our system is that low voltage ground mounts are different
from higher voltage ground mounts are different from commercial roof mount
are different from residential roof mount.  But all we got is one silly Code
that can't even address itself properly.

To boil it down, I guess I feel that the current MC connectors are fine and
I don't see anything in the new Code that changes our ability to continue to
use them in non-readily accessible locations such as roof tops without stair
access and pretty much doing what we have been doing (keep it clean and
don't let those leads dangle down and rub on the comp. shingles).

Folks with equipment in readily accessible location got to come up with
something better cause the Code wants it all tuckes away.

MPF

-----Original Message-----
From: William Miller [mailto:wrmiller at charter.net] 
Sent: Tuesday, January 22, 2008 3:39 PM
To: RE-wrenches at topica.com
Subject: Re: MC connectors and 690.31/690.33 [RE-wrenches]


Mark:

Interesting commentary.  Thanks for your input.

Regarding 690.33 E today:  This problem is not with a future code version,
it is a problem with current code version (2002 at least).  If so, ALL
installations happening in the US as of today are in violation.  Is this
your understanding?

Regarding 690.33 E in 2008:  There are new restrictions proposed in 2008
that require conduit protection of PV wire accessible to the public.  Is
this your interpretation?

Regarding European applications:  Ground fault protection will not prevent
arcing across connectors opening under load until ground fault diversion is
reached.  In US inverters, the ground fault detection is typically 1 amp and
will not open until some time delay has occurred.  The ground fault
protection in modern inverters is more aptly named ground fault detection
and is designed to shout down inverters and prevent fires, not protect
personnel.  The ground fault currents in a US Inverter system are definitely
fatal.

William Miller


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