Clause 13.1 from UL 1741 and 690.17 from the 2011 NEC both require that
disconnects consist of a manually operated switch or circuit breaker (this part
of 2014 NEC has been modified). It may be a bit of a judgment call as to
whether a contactor can meet the intent of these requirements. As least some
folks have judged that it can on the PV side, since there are combiner boxes on
the market now that use a contactor instead of a traditional disconnect switch
or circuit breaker. Here is one example with a photo showing the Gigavac
contactor inside with a manually operated switch in the coil circuit:
http://www.solarbos.com/products/combiner-boxes/arc-fault-combiner-boxes
This combiner box was listed to UL 1741 by ETL.
It is important not to touch a circuit isolated this way without first
verifying with a meter that it is safe.
This type of contactor is typically certified to UL 508 for the USA market
though this should be moving to the UL 60947 standards going forward.
I am not aware of any application that currently uses this sort of arrangement
on the AC side. There are additional requirements for the AC side disconnect
since this is the PV system disconnect from the grid, often as part of
interconnect requirements imposed by utilities. The Canadian code, 84-024,
requires a visible blade arrangement for verification of disconnection if
required by the supply authority. Utilities often require the visible blade.
Scott Aldous
Compliance Manager/Engineering Lab Manager
AE Solar Energy
+1.970.492.2065 Direct
+1.970.407.5872 Fax
+1.541.312.3832 Main
scott.ald...@aei.com
1625 Sharp Point Drive
Fort Collins, CO 80525
www.advanced-energy.com/solarenergy
-Original Message-
From: Boštjan Glavič [mailto:bostjan.gla...@siq.si]
Sent: Thursday, March 13, 2014 2:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] use of AC contactor in PV application in US/CAN
Dear Experts,
Is anyone familiar if it is allowed to use a contactor instead of circuit
breaker in PV application to disconnect inverter from the grid?
NEC in Article 690 does not specify it precisely.
What standard needs to comply this contactor?
Best regards,
Boštjan Glavič
Safety and Electromagnetics
Laboratory of Electronic Engineering
Head of Laboratory
SIQ, Tržaška cesta 2
SI-1000 Ljubljana, Slovenia
T: + 386 (0)1 47 78 265
F: + 386 (0)1 47 78 444
E-Mail: bostjan.gla...@siq.si
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