Module wiring safety [RE-wrenches]

William Miller wrmiller at charter.net
Thu Jan 24 22:06:15 PST 2008


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Steve:

By AC I assume you mean air conditioning.  Air conditioning disconnects are 
not allowed to be installed in accessible locations if live parts inside 
are accessible.  Correct practice is to use "pull-out" disconnects that 
have a "dead-front" panel.  Below is the pertinent code citation:

110.27 Guarding of Live Parts.
(A) Live Parts Guarded Against Accidental Contact. Except as elsewhere 
required or permitted by this Code, live parts of electrical equipment 
operating at 50 volts or more shall be guarded against accidental contact 
by approved enclosures or by any of the following means:
(1) By location in a room, vault, or similar enclosure that is accessible 
only to qualified persons.
(2) By suitable permanent, substantial partitions or screens arranged so 
that only qualified persons have access to the space within reach of the 
live parts. Any openings in such partitions or screens shall be sized and 
located so that persons are not likely to come into accidental contact with 
the live parts or to bring conducting objects into contact with them.
(3) By location on a suitable balcony, gallery, or platform elevated and 
arranged so as to exclude unqualified persons.
(4) By elevation of 2.5 m (8 ft) or more above the floor or other working 
surface.

In the PV industry, we are forced to use industrial disconnects for DC and 
sometimes AC (alternating current) circuits.  Being industrial equipment, 
there are no dead-front panels inside.  We deal with this by securing the 
covers with wrench tightened bolts and ensure that this practice is 
followed through training.  Below is a link to our web-base training text.

http://mpandc.com/practices/Procedures/Disconnect_locking/Disconnect_Locking.html

I hope you are not presenting the logic:  "well, there are lots of illegal 
air conditioning disconnects out there so we don't need to worry about PV 
wiring safety..."  This would not be a prudent line of deduction.


William Miller

At 08:25 AM 1/24/2008, you wrote:

>Most every house has 240 AC disconnects at kid level that can be fairly
>easily opened and has exposed live metal inside.  This hasn't been a
>problem and it is everywhere.

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