The IntesisBOX HS-RC-MBS-1 (order code INMBSHIS001R000, legacy HS-RC-MBS-1) is a Modbus gateway by Intesis (HMS Networks) that interfaces Hisense VRF systems and commercial-line RAC air conditioners with Modbus RTU (EIA-485) networks. The gateway attaches to the Hisense AB two-wire bus — the same bus used by the Hisense wired remote controller — and supports up to 16 Hisense indoor units per gateway, controlled as a single logical unit (not individually).

TapHome connects to the gateway via Modbus TCP through a TCP-to-RTU bridge — the gateway itself is a native Modbus RTU slave. The template provides ON/OFF control, operating mode selection, fan speed adjustment, vane position control, thermostat with setpoint and current temperature, and error code monitoring.

Hardware connection#

The gateway has two plug-in screw terminal blocks (2 poles each):

• AB bus (terminals A / B) — connects to the Hisense AB two-wire bus on the indoor unit’s electronic control board, in parallel with any Hisense wired remote controller.
• EIA-485 bus (terminals A+ / B-) — connects to the Modbus RTU bus where TapHome’s TCP-to-RTU bridge sits as Modbus master.

The gateway is powered directly from the AC indoor unit via the Hisense AB bus (14 VDC, ~1.54 W) — no external power supply is needed. The AC indoor unit must therefore be connected to mains for the gateway to communicate.

System topology

Up to 63 HS-RC-MBS-1 gateways can share the same Modbus RTU EIA-485 bus. Each gateway in turn connects to up to 16 Hisense AC indoor units on its own AB bus. TapHome (acting as Modbus master through a TCP-to-RTU bridge) sees every gateway as a separate Modbus slave addressed via SW3-P1..P6.

Wiring

The AB bus connects to the AC indoor unit’s internal electronic control board at any point on the bus. The bus is not polarity-sensitive — terminals A and B can be swapped without affecting communication. Maximum AB bus length is 500 m / 1,640 ft.

The EIA-485 bus polarity must be respected: A+ to A+, B- to B- across all devices on the bus. Maximum EIA-485 bus length is 1,200 m / 3,937 ft. Loop and star topologies are not allowed on EIA-485.

Disconnect the AC unit from mains power before opening the indoor unit. If a Hisense wired remote controller is also on the AB bus, only one of {gateway, controller} can be configured as Master — if both are configured as Master, communication may shut down. If multiple AC units share the same AB bus, a Hisense wired remote controller (set as Master) is required and the gateway must be Slave.

EIA-485 bus termination

A 120 Ω termination resistor is required at each end of the EIA-485 bus. The gateway has a built-in 120 Ω resistor that can be activated via DIP switch SW4-P4. Enable it only if the gateway sits at one end of the bus. A fail-safe biasing mechanism is required and must be supplied by the Modbus master (typically built into the TCP-to-RTU bridge).

Connector layout

The enclosure is 93 × 53 × 58 mm (DIN-rail TH35 or wall-mount). The AB connection is on one side of the housing; the EIA-485 port is on the opposite side. The DIP switches (SW1, SW3, SW4) and the two status LEDs (L1 green, L2 red) are accessible on the top face.

Configuration#

The HS-RC-MBS-1 is configurable via on-board DIP switches and via Modbus registers. Default settings (slave address 1, 9600 bps, all other DIP switches OFF) work out of the box on a typical installation, so usually only the slave address and the EIA-485 termination need to be reviewed. Every DIP switch change requires a power cycle to take effect.

DIP-switch layout

The gateway has three DIP-switch banks: SW1 (4 positions, AC indoor-unit features), SW3 (8 positions, Modbus slave address + baud rate) and SW4 (4 positions, temperature format + EIA-485 termination).

Enabling Modbus communication

The HS-RC-MBS-1 ships with Modbus RTU communication enabled by default — there is no menu navigation or web UI to activate it. Setting up Modbus is a matter of selecting the correct slave address, baud rate and frame format on the DIP switches.

SW1 — Master/Slave on the AB bus

On the HS-RC-MBS-1, only one SW1 position is used (Master/Slave selector); positions P2–P4 are reserved.

If multiple AC indoor units share the same AB bus, a Hisense wired remote controller (Master) is required and the gateway must be Slave (SW1-P1 = OFF). With a single indoor unit and no remote controller, the gateway can be Master (SW1-P1 = ON).

SW3 — Modbus slave address (P1..P6) and baud rate (P7..P8)

The slave address is binary-encoded across SW3-P1..P6 with P1 = LSB (P1=1, P2=2, P3=4, P4=8, P5=16, P6=32). Range: 0..63. Common examples:

Baud rate is selected by SW3-P7, SW3-P8 and SW4-P3 combined:

Default frame format is 8N2 (8 data bits, no parity, 2 stop bits). 8N1 is also auto-detected — no manual setting needed.

SW4 — Temperature format and EIA-485 termination

Importing the template in TapHome

Since the gateway communicates over Modbus RTU, a Modbus TCP-to-RTU bridge is required between TapHome Core and the EIA-485 bus. TapHome connects to the bridge over the local network using Modbus TCP. When importing the template, provide:

• IP Address — the bridge’s IP on the local network (default: 192.168.0.1)
• Slave ID — the gateway’s Modbus address set via SW3-P1..P6 (default: 1)

Assign a static IP address to the TCP-to-RTU bridge in the router’s DHCP settings to prevent the address from changing after a power cycle. If the bridge supports multiple slave addresses on the same EIA-485 line, you can chain up to 63 HS-RC-MBS-1 gateways on a single bus.

Device capabilities#

The template exposes 6 devices polled from holding registers H:0 through H:11. Implemented Modbus functions: 3 (Read Holding Registers), 4 (Read Input Registers), 6 (Write Single Register), 16 (Write Multiple Registers — limited to 1 register per request).

ON/OFF

Simple switch to turn the AC unit on or off. Reads and writes register H:0 (Bool). Poll interval: 2.5 s.

Mode

Operating mode selector with the 5 modes documented by Intesis:

The template defines 10 positions (values 0–9). Values 5–9 are placeholder slots that are not documented in the user manual and will not be reachable on real Hisense units. Reads and writes register H:1 (Int16). Poll interval: 2.5 s.

Fan Speed

Fan speed selector. Over the Hisense AB bus the manual documents Auto, Low, Mid, High, Super-high:

The TapHome template introduces a non-standard Mid-1 slot at value 2 and Mid at value 3, which shifts Super-High onto value 4 and High onto value 5. The natural Hisense ordering Auto < Low < Mid < High < Super-high is therefore not contiguous in the UI. Slots 6–9 are placeholders not reachable on real Hisense indoor units. Register H:21 (read-only, not exposed in the template) reports the maximum number of fan speeds the connected unit actually supports.

Reads and writes register H:2 (Int16). Poll interval: 2.5 s.

Vane Position

Vertical (U/D) vane position control. The user manual documents:

Hisense vane positions start at value 1 — register value 0 is not a documented Hisense position. The TapHome template defines a value 0 slot as a placeholder for “no vane / undefined”. The user manual reserves register value 10 for Swing, but the template remaps Swing onto value 5 to keep the multi-value switch range contiguous; this displaces Position 5 (Vertical) onto value 4. The user-facing value labels in strings.yaml correct a typo present in the underlying XML (Poistion-7 → Position 7).

Reads and writes register H:3 (Int16). Poll interval: 2.5 s.

Thermostat

Temperature setpoint (register H:4, read/write) and current reference temperature (register H:5, read-only). The setpoint range on Hisense units is 16–32 °C. The reference temperature reflects the indoor unit’s own control-loop sensor (return-path or remote-controller thermistor); it returns -32768 (0x8000) when no value has yet been received from the AB bus.

The TapHome template applies a /100 divisor to the temperature registers, but the HS-RC-MBS-1 user manual only documents two temperature modes selectable via SW4-P1: ×1 (default, integer °C) and ×10 (decicelsius). There is no documented ×100 (centi-degree) mode for this gateway. The TapHome integration assumes the gateway is configured per the device default — values can be tuned in template scripts if scaling differs in your installation. If you observe setpoints reported as ~0.22 °C instead of 22 °C, verify the raw register values with the TapHome Modbus debug tool and adjust either the gateway’s DIP switches or the template scaling accordingly.

Poll interval: 2.5 s.

Error Code

Read-only numeric value from register H:11. Key values:

The full error-code table is published in the user manual (section 7) and covers indoor unit, outdoor unit, transmission, sensor, inverter and pressure faults. Selected categories:

Register H:81 (read-only, not exposed in the template) reports which indoor unit number is reporting an error when more than one Hisense IDU is connected to the same gateway. If a fault recurs, query H:81 manually with a Modbus diagnostic tool to identify the affected unit before sending a service technician.

Poll interval: 15 s (vs 2.5 s for the control registers).

Troubleshooting#

No Modbus communication

1. Verify the AC indoor unit is powered on — the gateway requires 14 VDC supplied via the Hisense AB bus.
2. Check the LED indicators: L1 + L2 pulse together (5 s ON) at startup; L1 flashing (100 ms ON / 1900 ms OFF) indicates normal operation; L1 blinking (500 ms ON / 500 ms OFF) indicates a communication error with the AC unit; L2 pulsing (3 s ON) indicates undervoltage; alternating L1/L2 blink (500 ms / 500 ms) indicates a flash checksum failure.
3. Confirm the slave address in TapHome matches the SW3-P1..P6 binary setting on the gateway.
4. Ensure the TCP-to-RTU bridge is on the same network as TapHome Core and the bridge’s serial settings match SW3 baud rate (default 9600 bps, 8N2 — 8N1 is auto-detected).
5. Verify the EIA-485 polarity — A+ / B- must be consistent across all devices on the bus.
6. Check that 120 Ω termination is enabled at both ends of the EIA-485 bus (one end is typically the bridge, the other is the gateway via SW4-P4 = ON).

Error code 65535 continuously

This indicates the gateway cannot communicate with the Hisense AC indoor unit over the AB bus. Check:

• AB cable is connected at terminals A and B at both ends (no polarity, but both wires must be present).
• The AC indoor unit is powered (mains).
• If a Hisense wired remote controller is also present, confirm only one device (gateway or controller) is configured as Master — verify SW1-P1 against the topology.
• AB bus length does not exceed 500 m.

Master/Slave conflict on the AB bus

If the wired Hisense remote controller and the gateway are both configured as Master, the AB bus will collide and one or both devices will stop responding. Set SW1-P1 to OFF (gateway as Slave) whenever a Hisense wired controller is present on the same bus, and to ON (gateway as Master) only when no Hisense wired controller is connected. Also note: when multiple AC indoor units share one AB bus, a Hisense wired remote controller (Master) is required by Hisense — the gateway can only operate as Slave in that topology.

Temperature values are incorrect

The template uses a /100 divisor on registers H:4 and H:5. The default Hisense DIP setting (SW4-P1 = OFF) sends temperature in integer degrees (×1) — with /100 scaling on the TapHome side, a setpoint of 22 °C will be reported as 0.22 °C. Use the Modbus debug tool in TapHome to read raw register values and compare with the expected setpoint, then either reconfigure the gateway DIP switches or adjust the divisor in the template scripts.

Setpoint differs from the Hisense remote controller display

When the Virtual Temperature mechanism is in use (an external ambient reference written to register H:22, gateway acting as Slave), the indoor unit applies an adjusted internal setpoint following S_AC = S_u − (T_u − T_AC). The Hisense remote controller may then display a different number than the user-requested setpoint (register H:4). This is expected behaviour — register H:23 (real temperature setpoint, not exposed in the template) reports the value actually applied to the IDU. To make the IDU use the wired remote controller’s thermistor as control-loop reference, the AC unit must be configured by a Hisense installer at commissioning — this is not changeable from the Modbus side.

DIP switch change not taking effect

Every DIP switch change requires a power cycle of the gateway to apply. Power cycling means disconnecting the AC indoor unit from mains (which removes the 14 VDC supply on the AB bus) and reconnecting after a few seconds. Modifying DIP switches while the gateway is powered will not change the active configuration.