M-TEC Energy Butler GEN3 (grid)

Installation

1. 1Confirm the Energy Butler GEN3 is connected to your local network via its onboard Wi-Fi or LAN port and note its IP address, visible as the 'espressif' device in your router's device list.
2. 2Connect the ModbusCloud Gateway to the same LAN segment as the Energy Butler GEN3, ensuring both devices can reach each other on TCP port 502 (firmware 27.52.4.0 or newer) or port 5743 (older firmware).
3. 3In the ModbusCloud portal, add a new device, import the M-TEC Energy Butler GEN3 (grid) template, and set the unit ID to 247 and the target IP address to the inverter's local address.
4. 4Spot-check register 11000 in the portal's live register view: with the site drawing from the grid, the value should be a positive integer in watts; confirm the sign matches expected grid direction.

Things to watch for

01

The gateway connects but register 11000 always times out. Why?

The M-TEC Energy Butler GEN3 changed its Modbus TCP port from 5743 to 502 starting with firmware version 27.52.4.0. Check which firmware your unit runs, then set the portal's port field accordingly. Also confirm the unit ID is 247, not the default 1.

02

Register 11000 returns a value, but the sign seems inverted. What is correct?

The register is a signed int32. A positive value means the site is importing power from the grid; a negative value means it is exporting. Some third-party tools apply a scale of -1 to flip the convention. In ModbusCloud the raw signed value is preserved: positive = import, negative = export.

03

I get no response at all, even though the inverter is online. What should I check?

The M-TEC Energy Butler GEN3 internally uses RTU framing over TCP, not standard Modbus TCP framing. Ensure the ModbusCloud Gateway is configured for RTU-over-TCP mode. Additionally, the inverter's own cloud polling can temporarily block external Modbus queries; a brief retry interval of at least two seconds is recommended.

04

The gateway shows constant zero watts even during peak solar hours. Why?

A reading of zero at register 11000 often means the inverter is in island or standby mode, or that the smart meter connected to the Energy Butler GEN3 is not reporting correctly. Verify the inverter's own display shows a non-zero grid value, and check that the meter on the EMS bus is active and communicating.

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