Troubleshooting Parallel Inverter Setup Errors

Key Takeaways

• The most likely cause of parallel inverter errors is incorrect communication wiring or mismatched settings.
• Always verify physical cable connections and individual inverter settings as your first check.
• Disconnect all power sources (PV, battery, AC grid) before handling any wiring to prevent electric shock.
• If fault codes persist after performing basic checks and confirming settings, contact a qualified technician.

Why is my parallel inverter system not working or showing errors?

Parallel inverter systems can fail or display errors due to several common issues, primarily incorrect communication wiring, mismatched configuration settings between units, or an improper power-up sequence. The first step in troubleshooting is always to inspect all physical cable connections.

It is important to note that not all inverters support parallel operation. For instance, the Solis S5-EH1P-L Series explicitly states that it does not support parallel operation on the AC-BACKUP port, and connecting multiple units in parallel will void the warranty. The Axpert VM III manual also does not mention parallel operation. If your inverter does not support parallel operation, attempting to set it up in parallel will inevitably lead to errors or damage.

Diagnosis Steps for Parallel Inverter Errors

Follow these steps to diagnose common problems in your parallel inverter setup.

1. Verify Physical Connections

Ensure all communication and power cables are correctly installed and securely fastened.

• Parallel Communication Cables:
• • Deye SG01LP1 and SG03LP1: Check that the parallel communication cable is connected between the "Parallel A" and "Parallel B" ports (SG01LP1) or "Parallel 1" and "Parallel 2" ports (SG03LP1) on each inverter. These use a CAN interface.
  • Growatt SPF 5000 ES: Confirm that the parallel communication cable is connected between units.
  • GoodWe ET: If using the SEC1000S for parallel connection, ensure an STP (shielded twisted pair) cable is used, with a single twisted pair per span, connected in a daisy-chain.
  • Fox ESS H1(G2): Verify RJ45 network cables are used to connect the "Parallel" ports of the inverters. For CAN-CAN connections, use standard CAT 7 network cables.
• Current Sharing Cables (Growatt SPF 5000 ES):
• • Ensure current sharing cables are connected between all parallel units.
  • Safety Warning: Do not connect the current sharing cable between inverters that are in different phases, as this may damage the inverters.
• Battery Cable Length (Growatt SPF 5000 ES):
• • All inverters must be connected to the same batteries.
  • Ensure each group of cables from the inverters to the batteries is of the same length.

2. Check Inverter Settings

Incorrect settings are a frequent cause of parallel system malfunctions.

• Parallel Function Enable:
• • Deye SG01LP1 and SG03LP1: Ensure the "Parallel" function is enabled in the inverter settings when multiple units are connected in parallel.
  • Growatt SPF 5000 ES: For single-phase parallel operation, select "PAL" in program 23. For three-phase, select "3P1" for L1, "3P2" for L2, and "3P3" for L3.
  • Fox ESS H1(G2): Set the "Number" of parallel machines to the same value on each unit. If the address is set to 250, the parallel mode is exited.
• Modbus SN / Address Setting:
• • Deye SG01LP1 and SG03LP1: Each inverter must have a different "Modbus SN" (Modbus address).
  • GoodWe ET: If using SEC1000S, assign different Modbus addresses to each inverter, ranging from 1 to 10.
  • Fox ESS H1(G2): Set a unique CAN address for each machine, using any three non-repeating values between 1 and 249.
• Master/Slave Configuration:
• • Deye SG01LP1 and SG03LP1: Select one hybrid inverter as the "Master" to manage the parallel system's working mode. Set all other inverters as "Slave."
  • Growatt SPF 5000 ES (3-phase): In a three-phase setup, if there is only one inverter in L1-phase, its LCD will show "HST" (Host). If there are multiple inverters in L1-phase, one will show "HST" and the rest will show "3P1."
  • Fox ESS H1(G2): In off-grid (EPS) state, there is no master/slave distinction. In grid-connected state, the inverter connected to the CT/Meter is the "Master inverter," and others are "slave inverters."
• Phase Setting (for 3-phase parallel systems):
• • Deye SG01LP1 and SG03LP1: When forming a three-phase system, set the A/B/C Phase to indicate which phase the inverter belongs to.
  • Growatt SPF 5000 ES: Select "3P1" for L1, "3P2" for L2, and "3P3" for L3 in program 23.

3. Inspect DIP Switches and Termination Resistors

These components are crucial for signal integrity in communication lines.

• Deye SG03LP1:
• • The DIP switch controls the parallel communication resistor.
  • If the parallel system has 6 or fewer inverters, set DIP switches 1&2 to the ON position on all inverters.
  • If the system has more than 6 inverters, the first 6 inverters should have DIP switches 1&2 ON, and the remaining inverters should have them OFF.
• Fox ESS H1(G2):
• • If parallel machines are far apart and the network cable between Parallel ports is long, enable the terminal resistor.
  • Push the white DIP switch to the "ON" position (from down to up) using tweezers.
  • Only the parallel machines at both ends of the communication chain need to have the termination resistor enabled.

4. Follow Commissioning Order

An incorrect power-up sequence can prevent inverters from synchronizing.

• Growatt SPF 5000 ES (Parallel Commissioning):

1. 1. Ensure correct wire connections and that all breakers in Line wires of the load side are open. All Neutral wires of each unit must be connected together.
   2. Turn on each unit and set "PAL" in LCD setting program 23 of each unit. Then, shut down all units. (Note: The switch must be off when setting the LCD program for the setting to be programmed.)
   3. Turn on each unit.
   4. Switch on all AC breakers of Line wires in AC input. It is best to connect all inverters to the utility at the same time. If not, Warning 15 may display.
   5. If no other fault alarms appear, the parallel system is installed.
   6. Switch on all breakers of Line wires in the load side. The system will then power the load.

• Growatt SPF 5000 ES (Three-Phase Commissioning):

1. 1. Turn on all units sequentially. Turn on the HOST inverter first, then turn on the rest one by one.

Cause/Fix Table for Parallel Inverter Errors

Parallel Communication and Configuration

Effective parallel operation relies on robust communication and precise configuration. Inverters use communication cables to synchronize their operations, share load, and maintain system stability.

• Communication Protocols: Many inverters, like the Deye SG01LP1 and SG03LP1, use a CAN (Controller Area Network) interface for parallel communication. Fox ESS H1(G2) also utilizes CAN for its parallel ports.
• Cabling:
• • Deye SG01LP1 and SG03LP1: Use a dedicated parallel communication cable connecting the CAN interface ports.
  • Growatt SPF 5000 ES: Requires both a parallel communication cable and a current sharing cable. All battery cables from inverters to batteries must be of the same length.
  • GoodWe ET: When using the SEC1000S for parallel connection, use STP (shielded twisted pair) cables, ensuring a single twisted pair per span.
  • Fox ESS H1(G2): Uses RJ45 network cables for parallel port connections. For CAN-CAN connections, use standard CAT 7 network cables.
• Addressing and Roles:
• • Modbus SN/CAN Address: Each inverter in a parallel system must have a unique identifier. Deye inverters use a "Modbus SN" that must be different for each unit. Fox ESS H1(G2) requires unique CAN addresses between 1 and 249. GoodWe ET with SEC1000S requires Modbus addresses from 1 to 10.
  • Master/Slave Configuration: In systems like Deye SG01LP1 and SG03LP1, one inverter is designated as the "Master" to control the system, while others are "Slave." Fox ESS H1(G2) distinguishes between master and slave only in grid-connected states, with the master connected to the CT/Meter. Growatt SPF 5000 ES designates a "HOST" inverter in three-phase setups.
• Termination Resistors/DIP Switches: These are critical for maintaining signal integrity, especially over longer communication cable runs.
• • Deye SG03LP1: Uses DIP switches 1&2 to enable the parallel communication resistor. The setting depends on the number of inverters in the system (ON for up to 6, first 6 ON and others OFF for more than 6).
  • Fox ESS H1(G2): Requires termination resistors to be enabled on the first and last two devices in the communication chain if the network cable between parallel ports is long. This is done by pushing a white DIP switch to the "ON" position.

For more detailed information on specific inverter models or general firmware updates, you may refer to our firmware update guide.

Safety: Working with Parallel Inverter Systems

Working with multiple inverters and high-voltage DC and AC circuits carries significant risks. Always prioritize safety.

• Disconnect All Power: Before inspecting or working on any wiring, always disconnect all power sources to the inverter system: the solar PV array, the battery bank, and the AC grid connection. Wait for the manufacturer's specified capacitor discharge time before touching internal components.
• Insulated Tools: Use only insulated tools to prevent accidental short circuits and electric shock.
• Short Circuit Hazard: A spanner or other metal object accidentally bridging terminals on a battery bank or inverter can cause a severe short circuit, leading to sparks, fire, and serious injury.
• Qualified Personnel: Many tasks, especially those involving opening the inverter enclosure or complex wiring, should only be performed by authorized service personnel. Opening the unit may void your warranty.

When to call a technician instead

While basic troubleshooting can resolve many parallel inverter issues, there are clear limits to DIY repairs. You should call a qualified technician if:

• Persistent Fault Codes: If parallel-specific fault codes or warnings (e.g., Growatt's Fault code 81 Host loss, Fox ESS's RDSP Smpl Fault) persist after you have carefully followed all diagnosis and fix steps.
• Internal Component Damage: If you observe any physical damage to internal components, burnt smells, or unusual noises from the inverters.
• Inverter Does Not Support Parallel Operation: If your inverter model, such as the Solis S5-EH1P-L Series, explicitly states it does not support parallel operation, do not attempt to force it. Doing so will void the warranty and may damage the unit.
• Uncertainty with Wiring or Settings: If you are unsure about any wiring connections, settings configurations, or the proper commissioning sequence, it is safer to consult a professional.
• Warranty Concerns: Any unauthorized modifications or repairs can void your inverter's warranty. If the issue is complex, a technician can ensure repairs are done correctly and maintain warranty validity.