Troubleshooting an Enphase System
2014 Enphase Energy Inc. August 2014
Messages and Alerts
You can view event messages in Enlighten or in the Envoy
interface. Event messages show a summary of the
detected issue and a recommended action.
ACFOOR (AC Frequency Out of Range)
The microinverter reports that the frequency coming from
the utility is either too low or too high as specified by UL
standards (UL1741). The typical frequency is 60.0 Hz.
Nominal Frequency Range (Hz)
AC Frequency Out of Range events are usually transient, indicating an anomaly from the utility, and
usually self-correcting by the utility. If Frequency Out of Range events persist, troubleshoot as follows.
Although ACFOOR events can happen because of an actual frequency out-of-spec condition, these
events more likely to occur because of either a poorly shaped AC waveform or excessive THD (Total
Harmonic Distortion) emanating from the utility service. This type of error rarely affects just one unit, and
usually indicates an AC service issue.
Along with ACFOOR events, “Grid Gone” might be occurring. This indicates Anti-Islanding, which also
sometimes occurs during ACVOOR (AC Voltage Out of Range) and ACFOOR events.
What is “Anti-Islanding”?
“Anti-islanding” is protection against the continuous operation of the inverter and part of the utility
load while isolated from the remainder of the electric utility system.
If power from the utility is disconnected, the utility-interactive inverter ceases to export power
within two seconds. Anti-Islanding protects utility line workers and loads.
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