Hi Christine:
First, verify that the NRTL is accepted
in the jurisdiction where the unit is
installed. You do this by obtaining a
copy of the local jurisdiction's
"electrical code." This document usually
simply adopts the NEC and defines the
NRTLs that are accepted by the jurisdiction.
Second, in the jurisdiction, determine
how disagreements with the inspector are
to be resolved. Probably, you will need
to take this to the local inspection board
for resolution.
Assuming the NRTL is accepted in the
jurisdiction, then you should go to the
board and provide copies of the NRTL
report.
Keep in mind that neither the board nor
the inspector are likely to understand the
technical details why the accessible part
need not be grounded. I would not take up
this argument unless specific questions are
asked. They are working from the NEC
requirements, not the standards applied by
the NRTL.
So, wave the NRTL report in front of the
board, and quote the jurisdiction's own
acceptance of NRTL certifications. This
is usually in the local jurisdiction's
electrical code. See NEC definition for
"approved" and 110-2, especially the FPN.
Good luck!
Rich
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Christine
Rodham
Sent: Wednesday, May 13, 2009 7:38 AM
To: [email protected]
Subject: Re:NRTL Mark vs. NEC Inspector
List Members,
We have an interesting problem. We sold an OEM product ( very high end Home
Theater Movie Projector , better than a movie theater quality) which was
listed by a well known NRTL. ( We modify and enhance the SW for high end
performance)
The projector was installed in a public place and the installation was
evaluated by a NEC ( National Electrical Code ) inspector.
The projector has a metal ungrounded heat sink attached to the chassis that
was added for cooling but was evaluated and approved by the NRTL.
The NEC inspector will not sign off on the installation stating non-current
carrying exposed metal parts that may be accidentally energized must be
grounded to the chassis. Grounding the heat-sink to the chassis will be
difficult due to the design of this special aluminum heat-sink.
Here are my questions:
* What is the criteria to determine if a metal part can become accidentally
energized?
The only way it could happen in this case is if the power cord that is near
the heat-sink is
damaged and then touches the heat-sink. The power cord is UL approved and
properly
rated.
* How many fault conditions ( single vs multiple ) are considered to determine
if a metal part can become accidentally energized.
* What would be our best option in arguing this ruling. Should we request
another inspector or get the NRTL involved?
Note that this unit is ceiling mounted and only trained service people would
have access to it after the initial installation.
Thank you!
Christine Rodham
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