900-0184-01-00 Rev A
11
Functions
Arc Fault Circuit Interruption
In a PV system, an electrical arc occurs when current bridges a gap between conductive surfaces.
Gaps can occur due to conductor damage, or can be caused by inadequate system connections.
An “arc fault” is a safety concern for several reasons:
Risk of electric shock if the mounting system or other components become electrified.
Fire hazard due to heat buildup from the current flow.
A series arc occurs across open connections in a single conductor. A parallel arc occurs if the current
bridges multiple conductors that were meant to remain separate. The arc fault circuit interrupter
(AFCI) in the ICS Plus is intended to protect against series arcs.
Detection
The combiner has a dedicated arc fault detection device. The device operates by detecting the
distinct electrical noise created by an arc. The detector has two current transducers, each of which
monitors up to three PV circuits. If an arc is detected, the detector sends a signal to the main control
board in the combiner box.
The control board sends a signal to open the combiner’s main contactor. The
AFCI Annunciator
turns on.
The control board also sends a signal to the RSI and turns on the “arc fault detected” indicator.
NOTES:
This is a simple alarm indicating that an arc fault has occurred somewhere in the system. If
multiple combiners are in use, the RSI cannot specify which combiner triggered it.
Only the combiner with the detected arc will open its contactor. Any other combiners in the
system will continue to operate. Relay-trip breakers will continue to operate.
If an arc fault occurs, see the Troubleshooting section on page 19.
Upon an arc fault event, the system is required by NEC 690.11 to be reset manually. The manual reset
also resets the RSI
AFCI
indicator and the combiner
AFCI Annunciator
.
Reset
To reset the detector following an arc fault:
1.
Turn the PV Combiner Disconnect switch (or the Rapid Shutdown switch) to the OFF position. The
AFCI
Annunciator
and
AFCI
indicator should turn off. All combiner box contactors will open.
2.
Turn the same switch to the ON position. The
AFCI Annunciator
and
AFCI
indicator should remain off.
All combiner box contactors will close.
NOTES:
The Rapid Shutdown switch can be used to reset all combiners at once from a central location.
If the Rapid Shutdown switch is used, the relay-trip breakers will turn off at the same time.
Make certain to turn them back on when this step is performed.
An arc fault can also be reset by disconnecting all DC power from the system, including the batteries.
The ICS Plus arc fault detector has been evaluated to have a low instance of nuisance tripping.
However, installing external DC components in the system may increase the risk of nuisance tripping.
