Critical Temperature; Dc Resistance Low - Power Off - enphase M250 Troubleshooting Manual

A step-up transformer installed on site between the primary load center and the
o
Enphase branch circuits can create ACVOOR conditions.
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If you checked and verified all of the previous conditions and ACVOOR nuisance tripping is
still occurring, and neither the installer nor the utility can mitigate, Enphase can modify all of
the microinverter grid profiles to allow for slightly expanded trip-points, while still remaining
within spec.

Critical Temperature

A Critical Temperature condition is rare and occurs if the microinverter reports an internal temperature
that exceeds the rated range. The microinverter reacts by producing less power to reduce internal
temperature. Once the internal temperature of the microinverter diminishes, the microinverter resumes full
power production and the error message clears. No action is required unless the condition persists. If it
persists, contact Enphase Energy customer support.
This reflects internal temperature coming from a sensor inside the microinverter, not the ambient
temperature. For more information, see the Enphase Technical Brief on temperature at
http://www.enphase.com/support.
DC Resistance Low – Power Off
A DC Resistance Low – Power Off event occurs only with the M250 Microinverter and some models of
the M215 Microinverter and is indicated with a solid red status LED on the microinverter. The LED
remains red and the Envoy continues to report the fault until the error clears.
An insulation resistance (IR) sensor in the microinverter measures the resistance between positive and
negative PV inputs to ground. If either resistance drops below a threshold, the microinverter stops power
production and raises this event. This may indicate defective module insulation, defective wiring or
connectors, moisture ingress, etc. Although the cause may be temporary, this microinverter condition
persists until the sensor is manually reset.
If a microinverter registers a DC Resistance Low condition, clear this condition through the Envoy
Interface. An Envoy is required to send the clear-dc-resistance-low message to clear the condition. If
the condition does not clear after you perform the following procedure, contact Enphase Energy customer
support at support@enphaseenergy.com.
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 2014 Enphase Energy Inc.
Troubleshooting an Enphase System
August 2014