SunSpec Model 1 — Common
SunSpec Model 1, the Common Block, is the mandatory identification header present on every SunSpec-compliant device across inverters, energy meters, battery systems, and HVAC controllers. Over Modbus TCP, this template reads the model identifier, block length, manufacturer name, device model, options label, firmware version, and serial number, and exposes the device address register for read and write access. Importing this template into your ModbusCloud portal gives you a verified device fingerprint, making it straightforward to confirm which physical unit is connected at any unit ID before querying its functional models.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 8, read and write
- Brand
- SunSpec
- Last updated
Registers (8)
8 read, 1 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| id | Read | ||||
| l | Read | ||||
| mn | Read | ||||
| md | Read | ||||
| opt | Read | ||||
| vr | Read | ||||
| sn | Read | ||||
| da | Read and write |
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Use cases
- Verify the manufacturer name and model string on newly installed SunSpec devices before commissioning functional monitoring templates.
- Track firmware version strings across a fleet of SunSpec devices to identify units that require a software update.
- Confirm the serial number reported over Modbus matches the device label to detect wiring or unit-ID mismatches on multi-drop buses.
- Monitor the device address register to detect unexpected unit-ID changes that could cause polling conflicts on shared RS485 or TCP segments.
- Audit the options field across multiple sites to verify consistent device configurations during periodic compliance checks.
Installation
Enable Modbus TCP on the target device via its web interface or display menu, under the communication or Modbus section, and note the assigned IP address and port (default 502).
Connect the device and the ModbusCloud Gateway to the same local network, ensuring no firewall rules block TCP port 502 between them.
In the ModbusCloud portal, add the Gateway, import the SunSpec Model 1 Common template, and assign the correct Modbus unit ID matching the device configuration (commonly 1 or 126).
Trigger a manual poll and spot-check the mn and sn registers: the manufacturer name and serial number should match the device nameplate, confirming the connection is live.
Things to watch for
The mn and md registers return empty or garbled strings. Why?
SunSpec string registers are null-padded and encoded in big-endian byte order. If your client swaps byte order or trims null bytes incorrectly, strings appear corrupted. Ensure the ModbusCloud Gateway reads the full register width without byte-swapping: mn spans 16 registers and md spans 16 registers from their respective offsets.
Polling returns a Modbus exception on register 0. What is wrong?
Some devices place the SunSpec map at base address 40000 or 50000, not at offset 0. The register addresses in this template are relative offsets within the SunSpec block. Confirm the device base address in its documentation and configure the ModbusCloud Gateway base offset accordingly so address 0 resolves to the correct absolute register.
No values appear even though the gateway shows a TCP connection.
Check the unit ID. Many SunSpec devices default to unit ID 1, but multi-inverter gateways use higher IDs (for example, 125 for the gateway itself and 126 and above for attached inverters). Assign the correct unit ID in the ModbusCloud portal and re-poll.
Is it safe to write to the da register to change the unit ID remotely?
Writing to da changes the device Modbus unit ID immediately and will break all existing polling sessions targeting the old ID. Before writing, document the current value from the id and sn registers to confirm you are addressing the correct device. On some devices, writing an already-in-use unit ID on the bus causes address conflicts and communication failures for all devices on that segment.
Knowledge base articles for this device
SunSpec Modbus: one register map for many inverters
SunSpec Modbus is the open register map SMA, Fronius, SolarEdge and Kostal share. The layout, int+SF vs float, the TCP port per brand and reading a mixed fleet.
Fronius Modbus: read a Symo GEN24 over Modbus TCP
Fronius Modbus explained: enable Modbus TCP on the Symo GEN24 on port 502, choose between int+SF and float, read the right SunSpec registers and scale them correctly. Practical guide for solar installers.
SMA Modbus: reading a Sunny Boy over Modbus TCP (installers)
SMA Modbus explained: enable the Modbus TCP server on port 502, choose between the SMA profile (unit ID 3) and SunSpec (unit ID 126), read the right registers, and handle the NaN values at night. Practical guide for installers.
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