MC connectors and 690.31/690.33 [RE-wrenches]

William Miller wrmiller at charter.net
Tue Jan 22 15:39:06 PST 2008


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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

At 03:22 PM 1/22/2008, you wrote:

>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


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