The IntesisBOX TO-RC-MBS-1 (order code INMBSTOS001R000) is a Modbus gateway by Intesis (HMS Networks) that interfaces Toshiba VRF and Digital Inverter air conditioning indoor units with Modbus RTU (EIA-485) networks. TapHome connects to the gateway via Modbus TCP using a TCP-to-RTU bridge — the gateway itself communicates with the AC unit over the proprietary Toshiba AB bus.
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. Up to 16 indoor units can be connected to a single gateway but are controlled as one group (not individually).
Wiring
The gateway has two connection ports:
- AB bus connector (2 poles) — connects to the Toshiba AC indoor unit’s AB bus (no polarity, max 500 m / 1,640 ft)
- EIA-485 connector (2 poles, A+ B-) — connects to the Modbus RTU bus (polarity must be observed, max 1,200 m / 3,937 ft)
The gateway is powered directly from the AC indoor unit (14 VDC) — no external power supply is needed.
Connection methods:
- With wired remote controller: The gateway connects in parallel on the AB bus alongside the Toshiba remote controller
- Without remote controller: The gateway connects directly to the AC indoor unit AB bus terminals
If a wired remote controller of the AC manufacturer is connected on the same AB bus, communication may shut down. The gateway can coexist with a remote controller only when configured as bus slave (SW1 positions 1-2 set to ON, and the remote controller configured as Header).
EIA-485 bus termination
A 120 ohm termination resistor is required at each end of the EIA-485 bus. The gateway has a built-in 120 ohm resistor controlled by DIP switch SW4-P4 (OFF = connected, ON = disconnected). Leave SW4-P4 at OFF only if the gateway is at the physical end of the bus. Loop or star topologies are not allowed — use daisy-chain only.
DIP switch configuration
The gateway has three DIP switch banks: SW1 (AC unit features), SW3 (Modbus slave address and baud rate), and SW4 (temperature format, baud rate, termination). All DIP switch changes require a power cycle to take effect.
AC indoor unit type (SW1-P1..P2)
Positions 1 and 2 select the AC indoor unit type. Leave both OFF for standard operation.
| SW1-P1 | SW1-P2 | Unit type |
|---|---|---|
| OFF | OFF | Not specified — communicates with all indoor units (Default, recommended) |
| OFF | ON | RAV — advanced features for RAV units |
| ON | OFF | VRF (SMMS) — advanced features for VRF units |
| ON | ON | VRF (SHRM) — advanced features for VRF units |
Bus master/slave mode (SW1-P4)
Position 4 selects the bus mode. Position 3 is not used.
| SW1-P4 | Bus mode |
|---|---|
| OFF | Master of bus AB (Default) — no Toshiba Remote Controller required |
| ON | Slave of bus AB — Toshiba Controller must be present, configured as Header |
For most installations, leave all SW1 positions at OFF (factory default). Only change if you need advanced indoor unit features (RAV/VRF) or bus slave mode (when a Toshiba remote controller is also connected).
Temperature scaling (SW4-P1) — important for TapHome
The TapHome template divides temperature register values by 100. The default DIP switch setting transmits temperature in degrees (x1), so a setpoint of 22 C is sent as register value 22. The template then divides by 100, yielding 0.22 C — which is incorrect.
Set SW4-P1 to ON (decicelsius / x10 mode) so that 22.0 C is transmitted as register value 220. The template divides by 100, yielding 2.2 C — still incorrect at x10.
The template uses a division factor of 100, but neither the x1 nor x10 DIP switch setting produces correct values with this divisor. Verify the actual register values with the Modbus debug tool in TapHome and adjust the DIP switch or template scaling as needed for your installation. The same inconsistency exists in the Panasonic variant (PA-RC2-MBS-1).
| SW4 | Position | Description |
|---|---|---|
| P1 | OFF | Temperature in degrees, x1 (Default) |
| P1 | ON | Temperature in decidegrees, x10 |
| P2 | OFF | Temperature in Celsius (Default) |
| P2 | ON | Temperature in Fahrenheit |
| P4 | OFF | Internal 120 ohm termination resistor connected |
| P4 | ON | No termination (Default) |
Modbus address (SW3-P1..P6)
Binary-encoded slave address, range 0–63. Default: 0 (all positions OFF). Set to match the Slave ID entered during template import in TapHome.
Each DIP switch position has a binary weight — sum the ON positions to get the address:
| SW3 Position | P1 | P2 | P3 | P4 | P5 | P6 |
|---|---|---|---|---|---|---|
| Weight | 1 | 2 | 4 | 8 | 16 | 32 |
Common addresses:
| Address | P1 | P2 | P3 | P4 | P5 | P6 |
|---|---|---|---|---|---|---|
| 0 (default) | OFF | OFF | OFF | OFF | OFF | OFF |
| 1 | ON | OFF | OFF | OFF | OFF | OFF |
| 2 | OFF | ON | OFF | OFF | OFF | OFF |
| 3 | ON | ON | OFF | OFF | OFF | OFF |
| 4 | OFF | OFF | ON | OFF | OFF | OFF |
| 5 | ON | OFF | ON | OFF | OFF | OFF |
| 10 | OFF | ON | OFF | ON | OFF | OFF |
| 16 | OFF | OFF | OFF | OFF | ON | OFF |
| 32 | OFF | OFF | OFF | OFF | OFF | ON |
| 63 | ON | ON | ON | ON | ON | ON |
Baud rate (SW3-P7..P8 + SW4-P3)
Default: 9600 bps.
| SW3-P7 | SW3-P8 | SW4-P3 | Baud rate |
|---|---|---|---|
| OFF | OFF | OFF | 2400 bps |
| ON | OFF | OFF | 4800 bps |
| OFF | ON | OFF | 9600 bps (default) |
| ON | ON | OFF | 19200 bps |
| OFF | OFF | ON | 38400 bps |
| ON | OFF | ON | 57600 bps |
| OFF | ON | ON | 76800 bps |
| ON | ON | ON | 115200 bps |
TapHome connection
Since the IntesisBOX communicates via Modbus RTU (EIA-485), 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 in TapHome, provide:
- IP Address — the TCP-to-RTU bridge’s IP on the local network (default: 192.168.0.1)
- Slave ID — the gateway’s Modbus address set via DIP switches (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.
Device capabilities
The template exposes 6 devices communicating over holding registers H:0 through H:11.
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 5 standard modes documented by Intesis:
| Value | Mode |
|---|---|
| 0 | Auto |
| 1 | Heat |
| 2 | Dry |
| 3 | Fan |
| 4 | Cool |
The template defines 10 positions (values 0-9). Values 5-9 are not documented in the user manual and may be available on specific Toshiba models — most installations will only use the first five.
Reads and writes register H:1 (Int16). Poll interval: 2.5 s.
Fan Speed
Fan speed selector with documented speeds:
| Value | Speed |
|---|---|
| 0 | Auto |
| 1 | Low |
| 2 | Mid |
| 3 | High |
The template defines 10 positions (values 0-9), including Turbo (value 5). The number of available fan speeds depends on the connected AC model — register H:21 reports the maximum number of fan speeds supported. Values beyond the model’s maximum will have no effect.
Reads and writes register H:2 (Int16). Poll interval: 2.5 s.
Vane Position
Vertical vane (louver) position control:
| Value (template) | Position |
|---|---|
| 0 | Auto |
| 1 | Position 1 (Horizontal) |
| 2 | Position 2 (Horizontal) |
| 3 | Position 3 (Medium) |
| 4 | Position 4 (Vertical) |
| 5 | Swing |
| 6-8 | Additional positions |
| 9 | Swirl |
The user manual documents Swing as value 10, but the template maps it to value 5 to create a contiguous range for the multi-value switch. Swirl (value 9) is a rotational airflow pattern available on select Toshiba models. Available vane positions depend on the connected indoor unit.
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 template divides read values by 100 and multiplies written values by 100.
Temperature range: 16-32 C (default setpoint range, model-dependent). The reference temperature shows the AC unit’s own sensor reading — in Heat mode it reports ambient +0.5 C, in Dry/Fan/Cool mode it reports ambient -0.5 C. If an external temperature sensor value has been written to register H:22, register H:5 reports that value instead.
Poll interval: 2.5 s.
Error Code
Read-only numeric value from register H:11. Key values:
| Value | Meaning |
|---|---|
| 0 | No error |
| 65535 (-1) | Communication error between gateway and AC unit |
| Other | Toshiba error code (see user manual Section 7 for 80+ error codes) |
Common error categories: C01-C31 (central controller), E01-E31 (addressing/communication), F01-F31 (sensor faults), H01-H31 (compressor), L01-L31 (incorrect settings), P01-P31 (indoor/outdoor unit).
Poll interval: 15 s.
Additional capabilities
The gateway exposes several registers not included in the current TapHome template. Window Contact (H:6) provides energy-saving functionality by turning off the AC when a window opens. Interface and Remote Control Disablement registers (H:7, H:8) allow locking the gateway or the AC remote. Operation Time (H:9) tracks running hours, and Alarm Status (H:10) provides a binary alarm indicator.
For VRF and RAV systems, extensive advanced registers (H:4000+) report per-indoor-unit status including duty, defrost state, filter alarms, and detailed temperatures. Outdoor unit registers (H:4200+ for VRF-SMMSi/SHRM/SMMS, H:4400+ for RAV) expose pressures, discharge temperatures, compressor currents, and fan status. These can be added in a future template update.
Troubleshooting
No Modbus communication
- Verify the AB bus is connected between the gateway and the AC indoor unit — the gateway requires AC unit power to operate
- Check the green LED (L1): normal operation shows 100 ms ON / 1,900 ms OFF pattern; 500 ms ON / 500 ms OFF indicates a communication error
- Confirm the slave address in TapHome matches the DIP switch setting on the gateway (SW3)
- Ensure the TCP-to-RTU bridge is on the same network as TapHome Core
- Verify the baud rate on the gateway matches the TCP-to-RTU bridge configuration (default: 9600 bps, 8N2)
Error code 65535 continuously
This indicates the gateway cannot communicate with the Toshiba AC indoor unit over the AB bus. Check the AB bus wiring and verify the AC unit is powered on. If using a wired remote controller, ensure the SW1 bus master/slave configuration is correct.
Temperature values are incorrect
The template uses a division factor of 100 for temperature registers. Verify the DIP switch SW4-P1 and SW4-P2 settings match the expected scaling. Use the Modbus debug tool in TapHome to read raw register values and compare with the actual temperature.
Write operations not taking effect
The gateway supports Modbus function 16 (Write Multiple Registers) with a limitation: only 1 register can be written per request (length field must be 1). TapHome handles this correctly via the MODBUSWNE function in the template scripts. If issues persist, confirm the gateway firmware version — some features require firmware 2.3 or later.
