8 Copyright © Enphase Energy, Inc. 2011 06/15/2011
DC Too Low
The inverter reports that DC input voltage from the PV module is too low. This is a normal
condition that occurs in the morning and in the evening, but during the day may results
from any of the following conditions:
• This message can appear during extended periods of low solar irradiance (for example, a
period that includes the night hours plus a few hours of low sunlight after sunrise).
• This event may indicate a bad or missing DC connection to the inverter. If this condition
occurs during daylight hours, we recommend that a qualied electrician inspect the DC
connection between the module and the inverter. The connection may need to be tight-
ened or may be experiencing wear and tear and require replacement.
• If the microinverter is having DC Too Low events during daylight hours, it may have
been paired with an incompatible PV module. Is the PV module on the Enphase Compat-
ibility list? If the PV module is not compatible it may work sometimes, but will not work
consistently or effectively. Some incompatible PV modules will not produce enough DC
to start up the microinverter. To check DC input measurements to a microinverter, see
“Check DC measurements” in this document.
• Is it producing at all, or does it show zero production? If it shows zero production, does
the site use adaptors (or jumpers) between the PV module and the microinverter? It
may be that polarity is reversed. Verify by measuring the PV modules VOC (Open Circuit
Voltage) and inspect the positive and negative markings on the PV module and microin-
verter.
• To determine if the problem is with the microinverter or with the PV module, it may be
necessary to swap the DC leads from the suspect unit and an adjacent unit. If after
checking Enlighten periodically (this may take up to 30 minutes), the problem moves to
the adjacent module, this indicates that the PV module isn’t functioning correctly. If it
stays in place, the problem is with the microinverter. Call Enphase Customer for help in
reading most current microinverter data and for help in obtaining a replacement microin-
verter, if needed.
Never rule out the possibility of a damaged or defective PV module. They are somewhat
fragile, directly exposed to the elements, and have a very long service-life expectation.
The glass on the surface of the PV module can become cracked, lowering the PV mod-
ule’s output or causing it to trip a “Ground Fault” (GFI).
DC Too High
The inverter reports that DC input voltage from the PV module is too high.
• If the microinverter is having DC Too High events, it may have been paired with an in-
compatible PV module. It may be that the PV module generates a higher voltage than is
recommended for the inverter. Check that the PV module and inverter are compatible by
referring to the Module Compatibility List: http://www.enphase.com/support/downloads.
• If the DC Too High is being reported across multiple units, and incompatible PV modules
have been ruled-out, contact Enphase customer support to verify the rmware version
running on the microinverters.
