The IntesisBOX SM-RC-MBS-1 (order code INMBSSAM001R000) is a Modbus RTU gateway by Intesis (HMS Networks) for Samsung NON-NASA commercial and VRF air conditioners. The gateway connects to the Samsung indoor unit via the F3F4 V1V2 bus and exposes control and status registers over an EIA-485 (RS-485) serial interface.

Although the physical communication is Modbus RTU over RS-485, the TapHome template uses the Modbus TCP CCU model. TapHome Core connects to the gateway’s RS-485 bus directly via its built-in RS-485 port or through an external RS-485-to-TCP converter, depending on the installation.

The template provides full HVAC control: ON/OFF switching, operating mode selection, fan speed adjustment, vertical vane positioning, temperature setpoint with room temperature feedback, and error code monitoring.

Hardware connection#

The gateway has three sets of plug-in terminal blocks:

Connection diagram

Two connection scenarios are supported:

1. With Samsung wired remote controller — connect the gateway as Slave in parallel with the remote controller (remote acts as Master on the F3F4 V1V2 bus).
2. Without remote controller — connect the gateway directly to the F3F4 V1V2 bus as Master.

The F3F4 V1V2 bus is polarity sensitive. Maximum bus length is 100 m (328 ft). If a wired remote controller of the AC manufacturer is connected on the same bus, communication may shut down — configure Master/Slave roles correctly via DIP switch SW1-P1.

The EIA-485 (Modbus RTU) bus requires:

• Correct polarity on A+ and B- terminals
• Maximum distance: 1,200 m (3,937 ft)
• 120 Ohm termination resistor at each end of the bus (the gateway has a built-in terminator activated via DIP switch SW4-P4)
• Fail-safe biasing on the bus (supplied by the Modbus Master)
• Only daisy-chain topology — loop or star topologies are not allowed

Configuration#

DIP switch layout

The gateway has three DIP switches: SW1 (AC unit features), SW3 (Modbus slave address and baud rate), and SW4 (temperature format, baud rate, termination).

All DIP switch changes require a full power cycle of the AC system to take effect.

SW1 — Master/Slave selection:

SW3/SW4 — Baud rate (SW3-P7, SW3-P8, SW4-P3):

Default is 9600 bps (SW3-P7=OFF, SW3-P8=ON, SW4-P3=OFF). Available rates: 2400, 4800, 9600, 19200, 38400, 57600, 76800, 115200 bps.

SW3 — Modbus slave address (SW3-P1..6):

Binary encoding using 6 DIP switches for addresses 0–63. Default: address 1 (SW3-P1=ON, rest OFF).

SW4 — Temperature format and termination:

The TapHome template expects decidegrees (x10) format (SW4-P1=ON, SW4-P2=OFF). In this mode, the gateway sends temperature values multiplied by 10 (e.g., 220 = 22.0 °C), and the template divides by 100 internally.

Communication format: 8N2 (8 data bits, no parity, 2 stop bits) by default. The gateway also auto-detects 8N1.

Adding the gateway in TapHome

When importing the template in TapHome, provide:

• IP Address — the IP of the TapHome Core’s RS-485 interface or the RS-485-to-TCP converter
• Port — Modbus TCP port (default: 502)
• Slave ID — Modbus slave address configured on the gateway (default: 1)

Device capabilities#

The template exposes 6 devices for controlling and monitoring the Samsung AC unit through the IntesisBOX gateway.

Power and mode control

• AC Unit ON/OFF — switch to turn the AC unit on or off via holding register H:0.
• AC Unit Mode — multi-value switch to select the operating mode: Auto, Heat, Dry, Fan, or Cool (H:1). Values 5–9 in the template are placeholders — Samsung units use only values 0–4.
• AC Unit Fan Speed — multi-value switch for fan speed: Auto, Low, Mid, or High (H:2). The template includes additional positions (Mid 2, Position 5–7) for Samsung models that support more fan speeds.

Vane and thermostat

• AC Unit Vane Position — multi-value switch for vertical vane (louver) position: Auto, Horizontal, Position 2–4, Swing, Vertical, and Swirl (H:3). Available positions depend on the Samsung indoor unit model.
• AC Unit Thermostat — temperature setpoint (18–30 °C) via H:4 and current room temperature reference from the indoor unit via H:5. The gateway transmits temperatures in decidegrees (x10) and the template applies the appropriate scaling.

Error monitoring

• AC Unit Error Code — read-only sensor showing the Samsung error code from H:11. A value of 0 means no error. A value of 65535 (0xFFFF) indicates a communication error between the gateway (or remote controller) and the AC indoor unit. Other values map to specific Samsung fault codes (indoor sensor errors, outdoor sensor errors, communication errors, protection faults) — over 40 codes are documented in the user manual.

Additional capabilities

The IntesisBOX SM-RC-MBS-1 also exposes Modbus registers for window contact input (automatic AC shutoff after configurable timeout), gateway and remote controller enable/disable, operation time counter, alarm status, external temperature reference with virtual temperature compensation, left/right vane position, return path temperature, and firmware version. These can be added to the TapHome template in a future update.

Troubleshooting#

Error code 65535

Error code 65535 (-1 signed) indicates a communication failure between the IntesisBOX gateway and the Samsung AC indoor unit. Check:

1. F3F4 V1V2 bus wiring and polarity
2. Master/Slave DIP switch setting (SW1-P1) matches the installation scenario
3. The AC unit is powered on

No Modbus communication

1. Verify EIA-485 wiring polarity (A+ and B-)
2. Confirm the slave address matches the DIP switch configuration on SW3
3. Check the baud rate setting on SW3/SW4 — default is 9600 bps, 8N2
4. Ensure the gateway is powered (it requires connection to the AC unit via V1V2)
5. The green LED (L1) should flash briefly every 2 seconds during normal operation — continuous 500 ms blinking indicates a communication error

LED indicators