Troubleshooting Steps for the APsmart MLRSD Solution

When one or more MLRSD's are believed to be malfunctioning, troubleshoot via the following paths:

  1. Measure DC voltage at the inverter side.  Look for voltage differences from the expected voltage that may indicate a MLRSD (RSD-S-PLC) has failed.
    • After AC Grid is turned on, the transmitter starts sending heartbeat signals, the RSD-S-PLC enables PV modules to generate power. The inverter input voltages show as total voltages in the array:  Vm1+Vm2+….Vmn = Vinputs
    • When AC Grid is turned off, the transmitter stops sending heartbeat signals, the RSD-S-PLC goes into RSD mode and shuts down the PV modules' power outputs. Because each RSD-S-PLC outputs a voltage of 0.7V during shutdown mode, by monitoring the total inverter input voltages, it is easily to calculate the total functioning RSD-S-PLC within the array: 0.7v * Number of Receivers = Vinputs

  2. Use an IR camera to find the module(s) that appears "black," indicating no current is flowing.  --> Replace the RSD.
  3. If a whole string is not functioning --> Examine/replace the transmitter.

To replace a faulty RSD-S-PLC, follow the steps below:

1. Switch off the supply.

2. Disconnect the AC by turning off the inverter switch.

3. Disconnect the DC by turning off the inverter switch.

4. Wait for at least 5 minutes after switching off the power and then disconnect the PV module with the RSD-S-PLC.

5. Remove the RSD-S-PLC from the PV array racking.

6. Install a replacement RSD-S-PLC to the rack .

7. Turn on the DC side switch and then turn on the AC side switch and recover the system.

John is the author of this solution article.

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