---
title: "Daikin RTD-RA"
description: "Control Daikin residential RA-series splits — setpoint, operating mode, fan speed and ON/OFF — over Modbus RTU via S21. TapHome integration for Daikin RTD-RA."
url: "https://taphome.com/en/compatibility/daikin-rtd-ra/"
language: en
lastmod: 2026-10-08
generator: hugo
ai:
  topics: ["modbus-rtu","air-conditioning","rs485","dip-switch","s21","residential-split"]
  questions: ["How to integrate Daikin RTD-RA with TapHome?","What does the Daikin RTD-RA TapHome template control?","How to connect Daikin RTD-RA via Modbus RTU to TapHome?","How to set the Modbus slave address on the Daikin RTD-RA?","Which Daikin indoor units are compatible with the RTD-RA adapter?","How does the Global Update mode affect remote-controller behaviour on RTD-RA?"]
---

# Daikin RTD-RA

Communication: Modbus RTU

- [Daikin RTD-RA Product Page](https://www.daikin.eu/en_us/products/product.html/RTD-RA.html)

## Integration guide

The Daikin RTD-RA is a Modbus RTU adapter that connects residential **Daikin Room Air-Conditioner** indoor units (wall-mounted splits, Multi-split residential — the **RA-series** with an **S21** remote-controller connector) to TapHome via RS-485. The adapter is supplied with a pre-fitted S21 lead that plugs directly into the indoor-unit PCB and exposes setpoint, operating mode, fan speed, ON/OFF and group readback registers (holding `H0001`–`H0037`, input `I0021`–`I0131`) over a 3-wire D-Bus.

Up to 63 RTD-RA devices can share a single RS-485 bus, with each adapter assigned a unique slave address (1–63) via on-board DIP switches. The RTD-RA itself is the Modbus gateway — no additional IntesisBOX or BMS converter is required.

## Hardware connection

### PCB layout and S21 connection

![Daikin RTD-RA PCB component layout — SW1 DIP switches, J5 RS-485 connector, J6 inputs, J1 S21 cable, LEDs](https://taphome.com/images/compatibility/daikin-rtd-ra/pcb-layout_hu_15fa10ab33c31ee1.jpg)

**Key components on the PCB:**

- **J1** — S21 cable to indoor-unit PCB (factory pre-fitted, max 950 mm)
- **J5** — RS-485 D-Bus connector (DB+, DA-, GND)
- **J6** — S1 / S2 volt-free input contacts (used only in Stand-Alone / RTD-20 modes)
- **SW1** — 8-position DIP switch (mode and address select)
- **LED1, LED2** — Status / fault indicators

The S21 lead is supplied with a pre-fitted connector that plugs into **port S21** on the Daikin Room Air-Conditioner indoor PCB. The lead must enter the RTD-RA enclosure through Port D and the strain-relief band must be located on the inside of the enclosure.

![Daikin RTD-RA S21 connection — pre-fitted lead plugs directly into the S21 port on the indoor-unit PCB](https://taphome.com/images/compatibility/daikin-rtd-ra/wiring-s21_hu_f852a4a0f8bd39ee.jpg)

> [!WARNING]
> Do **not** install the RTD-RA inside the air-conditioning unit. Mount the adapter in a separate metal or V-1-rated plastic enclosure that prevents access by non-qualified persons. The S21 lead between the RTD-RA and the indoor PCB must not exceed 950 mm.

### Compatible indoor units

The RTD-RA targets **residential RA-series** units only — wall-mounted Daikin splits, Multi-split residential and Multi+ ranges that expose an **S21 remote-controller port** on the indoor PCB. It is **not compatible** with Sky Air, VRV or commercial ducted units, which use F1/F2 (DIII-NET) or P1/P2 buses and require [Daikin EKMBPP1](https://taphome.com/en/compatibility/daikin-ekmbpp1/), RTD-NET, RTD-10 or RTD-W instead.

### J5 RS-485 D-Bus pinout

![Daikin RTD-RA J5 connector pinout and RS-485 daisy-chain wiring example](https://taphome.com/images/compatibility/daikin-rtd-ra/wiring-rs485_hu_f03e613694bcedef.jpg)

| Pin | Label | Function |
|-----|-------|----------|
| 1 | 0 V | Reference for S1 |
| 2 | S1 | Volt-free input S1 (Stand-Alone mode only) |
| 3 | 0 V | Reference for S2 |
| 4 | S2 | Volt-free input S2 (Stand-Alone / Clone mode) |
| **5** | **DB+** | **RS-485 D-Bus — Modbus B / D+** |
| **6** | **DA-** | **RS-485 D-Bus — Modbus A / D-** |
| **7** | **GND** | **Common ground / shield** |

**RS-485 wiring:**

- **DB+** → A+/D+ on TapHome RS-485
- **DA-** → B-/D- on TapHome RS-485
- **GND** → GND on TapHome power supply (**mandatory** — earth at one point only)

**Cable specification:**

- Type: stranded 24 AWG twisted pair, shielded or unshielded (Cat 3 / 4 / 5)
- Topology: **daisy-chained point-to-point** only — star and ring are NOT supported
- Maximum bus length: 500 m without repeaters
- Maximum 63 devices per bus

> [!WARNING]
> The GND wire **must** be connected between every RTD-RA on the bus and the TapHome power-supply ground. Without proper grounding, communication errors and intermittent fault flags are likely. Earth the shield at one point only.

## Configuration

### Operating modes

The RTD-RA supports five operating modes selected by the SW1 DIP switches. **Only Modbus Slave mode is used by TapHome** — the remaining modes are listed for reference.

| Mode | Address (SW1.3–SW1.8) | Notes |
|------|------------------------|-------|
| Stand-Alone | 0 (all OFF) | No Modbus; S1/S2 contacts control unit. Bypassed in Modbus mode. |
| **Modbus Slave** | **1–63** | **Used by TapHome — full BMS control via RS-485** |
| RTD Clone | >0, S2 closed | Clones operating settings from another RTD device on the bus |
| RTD-10 Duty/Standby | 1–8 | Slave under an RTD-10 master controlling Sky Air / VRV |
| RTD-20 UCZ | >0 | User Control Zone in an RTD-20 retail-control network |

Once SW1.3–SW1.8 are set to a non-zero address the adapter operates as a Modbus RTU slave; all stand-alone S1/S2 functions are disabled and SW1.1 / SW1.2 control the Modbus master timeout instead.

### Enabling Modbus communication

To put the RTD-RA into Modbus Slave mode, set the slave address on **SW1.3 (LSB) – SW1.8 (MSB)** to a value between 1 and 63. The address is encoded as a 6-bit binary number:

| Switch | Bit value |
|--------|-----------|
| SW1.3 | 1 (LSB) |
| SW1.4 | 2 |
| SW1.5 | 4 |
| SW1.6 | 8 |
| SW1.7 | 16 |
| SW1.8 | 32 (MSB) |

**Example for Slave ID 1:** SW1.3 = ON, SW1.4–SW1.8 = OFF.
**Example for Slave ID 5:** SW1.3 = ON, SW1.5 = ON, all others OFF.

Setting all six switches to OFF activates Stand-Alone mode (no Modbus) — this must be avoided for TapHome integration.

![Daikin RTD-RA DIP switch addressing chart for slave addresses 0–63](https://taphome.com/images/compatibility/daikin-rtd-ra/dip-switch-addresses_hu_b52c3cbbe199f03c.jpg)

### Modbus master timeout

SW1.1 and SW1.2 configure the Modbus master timeout once the adapter is in Modbus Slave mode. If no holding-register WRITE occurs for 120 seconds, the configured timeout action is triggered.

| SW1.1 | SW1.2 | Timeout behaviour |
|-------|-------|-------------------|
| OFF | OFF | No timeout |
| **ON** | **OFF** | **Timeout after 120 s — units switched ON with current settings, remote controllers UNLOCKED (recommended for TapHome)** |
| ON | ON | Timeout after 120 s — units switched ON with current settings, remote-controller lock state unchanged |

### Modbus communication parameters

| Parameter | Value |
|-----------|-------|
| Network | 3-wire RS-485 |
| Mode | Modbus RTU Slave |
| Baud rate | 9600 (default; configurable on request) |
| Parity | None (default; configurable on request) |
| Stop bits | 1 |
| Register base | 0 |
| Address range | 1–63 (Modbus Slave mode) |

**Supported function codes:** 03 (read holding), 04 (read input), 06 (write single holding), 16 (write multiple holding) — up to 10 registers per request.

### Recommended Global Update mode

By default the RTD-RA boots with all update modes set to **Last Touch**, which means every Modbus write — even with an unchanged value — is applied to the indoor unit and overrides the user's manual setting on the wired remote controller. If the TapHome poll cycle re-writes registers periodically, set **Global Update** (`H:10`) to **OnChange** at startup so that values are applied only when they actually change. This is exposed as a service action on the Daikin RTD-RA module in TapHome.

## Device capabilities

### Climate control

The template exposes the four core control registers as full TapHome devices:

- **Operating Mode** (`H:3`) — selects between **Auto**, **Heat**, **Fan**, **Cool** and **Dry** (values 0–4 per the RTD-RA manual).
- **Thermostat** (setpoint `H:1`, current temperature from `I:23 ÷ 100`) — writes the integer °C setpoint to the indoor unit and reads back the group return-air average. Setpoint range depends on the indoor model (typically 10–30 °C in heat, 18–32 °C in cool).
- **Fan Speed** (`H:2`) — six-step selector: **Auto** (0), **Low** (1), **Medium Low** (2), **Medium** (3), **Medium High** (4) and **High** (5). Some RA-series indoor models support fewer than five fan steps; unsupported values are clipped by the indoor unit.
- **Power Switch** (`H:5`) — turns the indoor unit ON or OFF.

### Module-level service attributes

The Daikin RTD-RA module surfaces a set of read-only attributes for monitoring and configuration:

- **Summary of unit operation** (`I:30`) — aggregated thermo state across the bus (Idle/Fan, Heating, Cooling, Heat & Cool).
- **Unit Count** (`I:20`) — number of indoor units detected on the S21 / P1P2 link.
- **Setpoint** (`H:1`), **Setpoint Min** (`H:20`), **Setpoint Max** (`H:21`) — current setpoint and configured limiter values.
- **Global Update / Setpoint Update / Fanspeed Update / Mode Update / Louvre Update / Power Update** (`H:10`–`H:15`) — per-parameter lock/update mode read-back (Last Touch, Central, Local, OnChange).
- **Fanspeed Inhibit / Mode Inhibit / Louvre Inhibit** — bitmask attributes that report which fan steps, operating modes or louvre positions are currently disabled by the unit's inhibit registers.

### Control Update service action

The module exposes a single service action — **Control Update** — that writes all six per-parameter update modes (Global, Setpoint, Fanspeed, Mode, Louvre, Power) into `H:10`–`H:15` atomically. Each parameter accepts one of four lock modes:

| Update mode | RC buttons | Behaviour |
|-------------|-----------|-----------|
| **Last Touch** (default) | Unlocked | Updates the unit on every WRITE, even if the value is unchanged |
| **Central** | Locked | Remote-controller buttons locked; value is repeatedly written |
| **Local** | Unlocked | Modbus WRITEs are NOT propagated to the unit |
| **OnChange** | Unlocked | Updates the unit only when the WRITE value differs from the current setting |

## LED diagnostics

![Daikin RTD-RA LED1 / LED2 status patterns — power-up, no fault, unit fault, configuration error, A/C not found, RS-485 timeout](https://taphome.com/images/compatibility/daikin-rtd-ra/led-diagnostics_hu_30c8e5eed7804856.jpg)

| Pattern | LED1 (green) | LED2 (red) | Meaning |
|---------|-------------|-----------|---------|
| **5a** | Flashing rapidly | Flashing rapidly | Power-up sequence — factory configuration |
| **5b** | Flashing | Flashing | Power-up sequence — custom configuration |
| **5c** | Flashing | Off | A/C unit search after power-up / during configuration |
| **6a** | Steady ON | Off | **No fault — normal operation** |
| **6b** | Off | Steady ON | Indoor unit reported a fault (read fault code from `I:22`) |
| **7a** | Pattern | Pattern | Device configuration error |
| **7b** | Flashing | Flashing | A/C unit missing — U5 fault, S21 link down |
| **7c** | Flashing | Flashing | RS-485 communications timeout |

## Fault codes

Indoor-unit fault codes are read from input register `I:22` (group) and encoded as **two 8-bit ASCII characters** packed into a single 16-bit value — high byte = first character, low byte = second character.

| Raw value | Meaning |
|-----------|---------|
| **0** | Waiting for data |
| **255** | No fault |
| **14384** (0x3830, ASCII „80“) | Group fault — communications timeout, no units found |
| Other | Standard Daikin fault code (e.g. `16689` → `'A'` + `'1'` = **A1**) |

Refer to the Daikin indoor-unit service manual or the [RealTime Control Systems fault-code table](https://www.realtime-controls.co.uk/) to decode specific codes.

## Troubleshooting

### No Modbus communication (LED2 flashing — RS-485 timeout)

1. Check **RS-485 wiring** at J5: DB+ to A+/D+, DA- to B-/D-, GND to TapHome power-supply ground.
2. Verify the slave address on **SW1.3–SW1.8** is non-zero (Address 0 disables Modbus completely).
3. Confirm TapHome serial settings are **9600 baud, 8 data bits, no parity, 1 stop bit**.
4. Verify the daisy-chain topology — star and ring layouts are not supported.
5. Measure DC voltage between DB+ and DA- — idle level should be around 1.5–5 V.

### A/C unit not found (LED1 flashing, LED2 off)

1. Check the **S21 lead** between J1 on the RTD-RA and the S21 port on the indoor PCB — the connector must be fully seated.
2. Verify the indoor unit is powered on.
3. Confirm the indoor unit is from the **RA-series** (residential split with S21 port) — Sky Air / VRV / commercial ducted units are not supported.
4. Power-cycle the RTD-RA (disconnect / reconnect the S21 lead).

### Indoor unit fault (LED2 steady)

1. Read input register `I:22` from the Daikin RTD-RA module.
2. Decode the value as two ASCII characters (high / low byte) to obtain the standard Daikin fault code.
3. Look up the code in the indoor-unit service manual or at [realtime-controls.co.uk](https://www.realtime-controls.co.uk/).

### Manual writes are overridden by TapHome

If users complain that adjustments made on the wired remote controller revert as soon as TapHome polls, set **Global Update** to **OnChange** via the *Control Update* service action on the Daikin RTD-RA module. The default **Last Touch** mode re-applies every TapHome write even when the value has not changed.

## Notes and known limitations

- **Residential RA-series only.** The RTD-RA is designed exclusively for indoor units with an S21 connector (wall-mounted Daikin splits and Multi-split residential). For Sky Air, VRV and commercial ducted units use [Daikin EKMBPP1](https://taphome.com/en/compatibility/daikin-ekmbpp1/), RTD-NET, RTD-10 or RTD-W instead.
- **Inhibit register mapping.** The current template reads `H:23` for *Fanspeed Inhibit* and `H:24` for *Mode Inhibit*; per the RTD-RA manual the correct registers are `H:22` (Fanspeed Inhibit) and `H:23` (Mode Inhibit). The *Louvre Inhibit* attribute correctly references `H:24`. The reported inhibit values may therefore be shifted by one register relative to the manufacturer documentation.
- **VAM-related service attributes.** The Fan Speed device exposes *Damper Control* (`H:30`) and *VAM Fan Speed* (`H:31`) attributes that target VAM/VKM ventilation lines. Because the RTD-RA controls only RA-series residential splits, these attributes typically return 0 / *Unknown* on real hardware and can be ignored.
- **Operating-mode value range.** The mode selector accepts values 0–9; only 0–4 are valid on the indoor unit (Auto / Heat / Fan / Cool / Dry). Writing values 5–9 will be rejected.

## Available devices 4

These devices appear in TapHome after import.

Daikin RTD-RA Module

Service Attributes

|                           |                                                                                                                                         |
|---------------------------|-----------------------------------------------------------------------------------------------------------------------------------------|
| Summary of unit operation | Aggregated thermo state across all indoor units on the bus — Idle/Fan, Heating, Cooling or Heat & Cool                                  |
| Global Update             | Current global lock/update mode — Last Touch, Central, Local or OnChange (controls how Modbus writes are propagated to the indoor unit) |
| Setpoint Update           | Update mode for setpoint writes — Last Touch, Central, Local or OnChange                                                                |
| Fan Speed Update          | Update mode for fan-speed writes — Last Touch, Central, Local or OnChange                                                               |
| Mode Update               | Update mode for operating-mode writes — Last Touch, Central, Local or OnChange                                                          |
| Louvre Update             | Update mode for louvre writes — Last Touch, Central, Local or OnChange                                                                  |
| Power Update              | Update mode for ON/OFF writes — Last Touch, Central, Local or OnChange                                                                  |
| Setpoint                  | Current temperature setpoint (°C) read back from the indoor unit                                                                        |
| Setpoint Min              | Minimum allowed setpoint enforced by the adapter (16–32 °C, or 0 = no limit)                                                            |
| Setpoint Max              | Maximum allowed setpoint enforced by the adapter (16–32 °C, or 0 = no limit)                                                            |
| Fan Speed Inhibit         | Bitmask of fan steps disabled on the indoor unit (Auto, Fan 1–5; 0 = no inhibit)                                                        |
| Mode Inhibit              | Bitmask of operating modes disabled on the indoor unit (Auto, Heat, Fan, Cool, Dry; 0 = no inhibit)                                     |
| Louvre Inhibit            | Bitmask of louvre positions disabled on the indoor unit (Stop, Swing; 0 = no inhibit)                                                   |
| Unit Count                | Number of indoor units detected on the S21 / P1P2 link                                                                                  |

Service Actions

|                |                                                                                                                             |
|----------------|-----------------------------------------------------------------------------------------------------------------------------|
| Control Update | Atomically writes all six per-parameter lock/update modes (Global, Setpoint, Fan Speed, Mode, Louvre, Power) to the adapter |

Read (module)

```taphome
IF(MODBUSR(A, 21, Uint16) = 1, ADDERROR("At least one unit in fault", MODBUSR(A, 22, Uint16)));
```

Service Attributes

Summary of unit operation

```taphome
Switch(MODBUSR(A, 30, Uint16), 0, "Idle/Fan", 1, "Heating", 2, "Cooling", 3, "Heat & Cool", "Unknown");
```

Global Update

```taphome
var gu := MODBUSR(H, 10, Uint16);
SWITCH(gu, 0, "Last Touch", 1, "Central", 2, "Local", 3,"OnChange", "Unknown")
```

Setpoint Update

```taphome
var se := MODBUSR(H, 11, Uint16);
SWITCH(se, 0, "Last Touch", 1, "Central", 2, "Local", 3,"OnChange", "Unknown")
```

Fanspeed Update

```taphome
var fe := MODBUSR(H, 12, Uint16);
SWITCH(fe, 0, "Last Touch", 1, "Central", 2, "Local", 3,"OnChange", "Unknown")
```

Mode Update

```taphome
var mu := MODBUSR(H, 13, Uint16);
SWITCH(mu, 0, "Last Touch", 1, "Central", 2, "Local", 3,"OnChange", "Unknown")
```

Louvre Update

```taphome
var se := MODBUSR(H, 14, Uint16);
SWITCH(se, 0, "Last Touch", 1, "Central", 2, "Local", 3,"OnChange", "Unknown")
```

Power Update

```taphome
var pow := MODBUSR(H, 15, Uint16);
SWITCH(pow, 0, "Last Touch", 1, "Central", 2, "Local", 3,"OnChange", "Unknown")
```

SetPoint

```taphome
MODBUSR(H, 1, Uint16);
```

SetPoint Min

```taphome
var sm := MODBUSR(H, 20, Uint16);
IF(sm = 0,"No limit", sm);
```

Setpoint Max

```taphome
var sm := MODBUSR(H, 21, Uint16);
IF(sm = 0,"No limit", sm);
```

Fanspeed Inhibit

```taphome
var sm := MODBUSR(H, 23, Uint16);
IF(sm = 0,"No limit", sm);
```

Mode Inhibit

```taphome
var sm := MODBUSR(H, 24, Uint16);
IF(sm = 0,"No limit", sm);
```

Louvre Inhibit

```taphome
var sm := MODBUSR(H, 24, Uint16);
IF(sm = 0,"No limit", sm);
```

Unit Count

```taphome
var uc := MODBUSR(A, 20, Uint16);
uc + " unit" + IF(uc != 1, "s", "");
```

Service Actions

Control Update

Parameters: Global Update, Setpoint Update, Fanspeed Update, Mode Update, Louvre Update, Power Update

```taphome
MODBUSW(H, 10, Uint16, gu);
MODBUSW(H, 11, Uint16, su);
MODBUSW(H, 12, Uint16, fu);
MODBUSW(H, 13, Uint16, mu);
MODBUSW(H, 14, Uint16, lu);
MODBUSW(H, 15, Uint16, pu);
```

Operating Mode Multi-value Switch Read and write

Operating-mode selector for the indoor unit — Auto, Heat, Fan, Cool or Dry

Register: H:3 Int16 numeric

Values / States: Auto · Kúrenie · Vetranie · Chladenie · Odvlhčovanie

Read switch state

```taphome
MODBUSR(H, 3, Int16)
```

Write switch state

```taphome
MODBUSW(H, 3, Int16, Mu)
```

Thermostat Thermostat Read and write

Reads the group return-air average temperature and writes the desired setpoint (integer °C) to the indoor unit

Register: H:1 Int16 Unit: °C

Read temperature

```taphome
MODBUSR(A, 23, Int16) /100
```

Read desired temperature

```taphome
MODBUSR(H, 1, Int16)
```

Write desired temperature

```taphome
MODBUSW(H, 1, Int16, Se)
```

Fan Speed Multi-value Switch Read and write

Fan-speed selector — Auto plus five steps (Low, Medium Low, Medium, Medium High, High); some RA-series indoor models support fewer steps

Register: H:2 UInt16 numeric

Values / States: Auto · Nízky · Stredne nízky · Stredný · Stredne vysoký · Vysoký

Read switch state

```taphome
MODBUSR(H, 2, UInt16)
```

Write switch state

```taphome
MODBUSW(H, 2, UInt16, Mu)
```

Service Attributes

Damper Control

```taphome
Switch(MODBUSR(H, 30, Uint16), 0, "Auto", 1, "Cross Flow / Heat Recovery", 2, "Bypass", "Unknown");
```

VAM Fanspeed

```taphome
Switch(MODBUSR(H, 31, Uint16),1, "Low", 2, "High", "Unknown");
```

Power Switch Switch Read and write

ON/OFF switch for the indoor unit

Register: H:5 UInt16

Values / States: ON · OFF

Read switch state

```taphome
MODBUSR(H, 5, Uint16)
```

Write switch state

```taphome
MODBUSW(H, 5, Uint16, St)
```

**Connection:** Modbus RTU • 9600 baud• 8N1 • Slave ID: $\[SlaveId]

Possible improvements (16)

- H:4 Louvre — Louvre control 0=Stop, 1=Swing — basic airflow direction control missing from template
- H:22 Fanspeed Inhibit (correct register) — Manual specifies H0022 for Fanspeed Inhibit, but template reads H:23 in service attribute (off-by-one swap with Mode Inhibit). Not exposed as a writable device
- H:35 Filter Clear Command — 0=Idle, 1=Filter Clear — useful as periodic/triggered service action; typically tied to VAM/VKM but the register exists in the common map
- H:37 Force Thermo Off — 0=Enable Thermo, 1=Force Thermo Off — overrides indoor-unit thermostat, useful for energy-saving / load-shedding scenarios
- I:23 Return Air Average — Already used as thermostat current-temp source; could additionally be exposed as a standalone temperature sensor for logging / smart rules
- I:24 Filter Alarm (group) — 0=No alarm, 1=≥1 unit needs filter cleaning — important maintenance flag, not exposed by template
- I:25 Return Air Min — Minimum return-air temperature across the unit group (°C × 100). Single-unit RTD-RA: equal to I:23
- I:26 Return Air Max — Maximum return-air temperature across the unit group (°C × 100)
- I:35 Defrost — 0=No defrost, 1=≥1 unit in pressure-equalisation, hot-start/pre-heat or outdoor defrost
- I:36 Self-Clean Alarm Level — 0=No alarm, 1..4=alarm level (self-cleaning indoor units)
- I:37 Self-Clean Operation — 0=Idle, 1=Self-Clean cycle in progress
- I:50 RC Temperature — Wired remote-controller measured temperature (°C × 100). Only valid when 1 indoor unit on the P1/P2 network
- I:51 RC Operation Mode — Wired remote-controller operation mode — 0=Idle/Fan, 1=Heating, 2=Cooling, 3=Heat & Cool
- I:121 Per-Unit Is Fault (Unit 1) — Per-unit fault flag. Template uses group register A:21 instead, which works for both single-unit and multi-unit
- I:122 Per-Unit Fault Code (Unit 1) — Per-unit fault code (16-bit ASCII pair, e.g. 'A1'). Template uses group register A:22 instead
- I:131 Coil Inlet Temperature (Unit 1) — Per-unit coil-in temperature (°C × 100). Useful for diagnosing heat-pump performance

## Import parameters

Enter these values when you import the XML.

| Asked in the app | Default       |
|------------------|---------------|
| Slave ID         | `1`           |
| IP address       | `192.168.1.0` |

## Sources

- Daikin RTD-RA Installation Instructions (21070-1.07.04, EN)
  
  [www.daikin.es](https://www.daikin.es/content/dam/MDM/TechnicalDrawings/Split/EN/RTD-RA%20Installation%20Instructions%2021070-1.07_EN.pdf) 2026-04-25
  
  [PDF](https://taphome.com/compatibility/devices/daikin-rtd-ra/manufacturer/rtd-ra-installation-instructions.pdf)
- RTD Common Modbus Registers, Issue 1.06.00
  
  [tinlavir.ro](https://tinlavir.ro/parteneri/2_VRV/4_Control_Systems/10_RTD_Adaptors/Documents/Common_Documents/RTD%20Common%20Modbus%20Registers%20v1.06.00.pdf) 2026-04-25
  
  [PDF](https://taphome.com/compatibility/devices/daikin-rtd-ra/manufacturer/rtd-common-modbus-registers.pdf)

Manufacturer documents are © their respective owners. They are provided as published by the manufacturer, for reference only.

## Related Documentation

- [Modbus Integration](https://taphome.com/en/compatibility/modbus-guide/)
- [Modbus](https://taphome.com/en/docs/integration/modbus/)
- [Simple configuration using templates](https://taphome.com/en/docs/integration/modbus/templates/)
- [Modbus scripts and prefetch](https://taphome.com/en/docs/script/modbus-scripts/)
- [Modbus functions](https://taphome.com/en/docs/script/modbus/)
- [Modbus data types](https://taphome.com/en/docs/script/modbus-data-types/)