SunSpec Model 139 — LVRTX

Installation

1. 1Enable Modbus TCP on the inverter or gateway under the communication or Modbus section of its web interface, and note the IP address and TCP port (default 502).
2. 2Connect the inverter or its communications gateway to the same LAN segment as the ModbusCloud Gateway, confirming the device is reachable on port 502.
3. 3In your ModbusCloud portal, add the ModbusCloud Gateway, import the SunSpec Model 139 LVRTX template, and assign the correct Modbus unit ID (commonly 1 or 126 for SunSpec devices).
4. 4After import, poll register address 0 (id) and verify the returned value equals 139; then check address 3 (modena) to confirm the function-enable state matches your grid-code requirement.

Things to watch for

01

Register address 0 returns 0xFFFF instead of 139. Why?

A value of 0xFFFF is the SunSpec not-implemented sentinel. The connected device does not expose Model 139 at the base address you have configured. Verify the SunSpec model map by scanning from the device base address (often 40001) and locating the model block that starts with 139 before assigning the template.

02

The gateway connects but tms_sf and v_sf read as unexpected large negative numbers.

tms_sf and v_sf are signed SunSpec scale-factor registers (int16). A value such as -2 means multiply the raw time or voltage reading by 10 to the power of -2. This is normal. Ensure your client applies the scale factor before displaying or logging curve point values; reading them raw without scaling will always appear incorrect.

03

Writing to modena or actcrv has no visible effect on the inverter.

Many inverters require the SunSpec ENABLED bit in modena to be set to 1 and a separate commit or write to the actcrv register in the same transaction. Also confirm the unit ID matches the inverter, not a gateway or logger. Some firmware versions ignore writes unless Modbus write-access is explicitly unlocked in the device settings.

04

Is it safe to write actcrv or modena on a live grid-connected inverter?

Use caution. Changing the active curve or disabling the LVRTX function on a live inverter can alter disturbance-response behaviour required by your grid-code or interconnection agreement, and may invalidate utility approval. Always schedule configuration changes during a maintenance window, verify the target curve meets local IEEE 1547 or EN 50549 requirements, and consult the inverter manufacturer before writing to these registers in production.

Registers (12)

12 read / 5 write

More SunSpec templates

SunSpec Model 135 — LFRT

SunSpec

Modbus TCP

11 registers

SunSpec Model 709 — DER Trip LF

SunSpec

Modbus TCP

9 registers

SunSpec Model 601 — Tracker Controller DRAFT 2

SunSpec

Modbus TCP

13 registers

SunSpec Model 64412 — DER Cyber Exploitation

SunSpec

Modbus TCP

45 registers

SunSpec Model 11 — Ethernet Link Layer

SunSpec

Modbus TCP

8 registers

SunSpec Model 101 — Inverter (Single Phase)

SunSpec

Modbus TCP

45 registers

More TCP templates

Fronius - Modbus TCP

Fronius

Modbus TCP

Monitors Fronius Symo and Primo inverters via Modbus TCP

15 registers597

Domekt R 400 V

Komfovent

Modbus TCP

Controls Komfovent Domekt recuperator ventilation via Modbus TCP

25 registers118

SMA StpSe Battery

SMA

Modbus TCP

16 registers

GoodWe ET/EH/BH/BT Hybrid Inverter (grid)

GoodWe

Modbus TCP

8 registers

Marstek Venus D (battery)

Marstek

Modbus TCP

7 registers

GoodWe EmergencyPowerMeter

GoodWe

Modbus TCP

12 registers