The BAXI Auriga M/T-A is an inverter air-to-water monobloc heat pump, sold as AURIGA 4-16 M-A (single-phase, 4–16 kW) and AURIGA 12-16 T-A (three-phase, 12–16 kW). The wired controller supplied with the unit has an RS-485 Modbus port, through which TapHome reads and writes the holding registers of the whole unit using Modbus RTU at 9600 baud, 8N1.
The template switches zone 1, zone 2 and domestic hot water (DHW) on and off, selects the operating mode, sets the water, room and DHW setpoints, toggles ECO and silent mode and selects the weather-dependent curve. It reads four temperature sensors, shows the full set of operating data as service attributes, turns the current fault code into error messages and offers the main installer parameters as service actions.
This is a community template. Device names, service attributes, service actions and error messages appear in TapHome in Italian, as the author created them. The guide gives the Italian name first and its English meaning next to it.
Hardware connection
Where the Modbus port is
The Modbus port is on the wired controller, not on the hydraulic module. According to the wired controller manual, the controller connects to the hydraulic module through its terminals A, B, X, Y, E, and the separate terminals H1 and H2 are the Modbus communication port. TapHome therefore connects to H1 and H2 of the wired controller.
| TapHome RS-485 bus | Wired controller terminal |
|---|---|
| A+ | H2 (A+ Modbus) |
| B- | H1 (B-) |
| Cable shield | E |
The terminals A and B of the wired controller are not RS-485 lines: the manual lists them as the 13.5 V AC input of the controller, wired with 0.75 mm² conductors.
The terminal strip CN30 inside the hydraulic module also has terminals labelled H1 and H2 (pins 9 and 10). The installation manual assigns them to the internal cascade between units, not to Modbus. Connect TapHome to H1 and H2 of the wired controller only.
The wired controller must stay connected to the hydraulic module: the manual states that the parameters of the whole unit (registers 100 and up) can be read only when the wired controller is connected to the hydraulic module.
Cabling rules from the manufacturer
The wired controller manual and the installation manual give these rules for the controller’s communication cabling:
- The controller circuit is a low-voltage circuit. Never connect it to a 220 V / 380 V circuit and never route it in the same conduit as one; lay power and communication cables separately.
- Use shielded cable and connect the shield firmly to earth, otherwise transmission can fail.
- Do not extend a shielded cable by cutting and joining it; use a terminal block for the connection.
- The cable between the unit and the wired controller is a sheathed 5 × 0.75 mm² cable, at most 50 m long.
Do not test the signal cable insulation with a Megger (insulation tester) after the wiring is finished — the manual explicitly forbids it.
Configuration
Modbus address (switch S3)
The Modbus address is set with the rotary coded switch S3 (0–F) on the main control board of the hydraulic module. Position 0, the factory setting, corresponds to address 16; every other position equals its number (position 2 = address 2, position 5 = address 5, position F = address 15).
| S3 position | Modbus address |
|---|---|
| 0 (factory default) | 16 |
| 1 | 1 |
| 2 … 9 | 2 … 9 |
| A … F | 10 … 15 |
The template imports with Slave ID 1 by default, which matches S3 = 1. Either turn S3 to position 1, or keep the factory position 0 and enter 16 as the Slave ID when importing the template.
The hydraulic module and PCB B (the main control board of the heat pump system) each carry a rotary switch labelled S3. The wired controller manual names the one on the hydraulic module main board as the Modbus address switch.
Communication parameters
| Parameter | Value |
|---|---|
| Interface | RS-485 |
| Protocol | Modbus RTU (Modbus ASCII is not supported) |
| Baud rate | 9600 |
| Data bits | 8 |
| Parity | None |
| Stop bits | 1 |
| Function codes | 03H (read holding registers), 06H (write single register), 10H (write multiple registers) |
In TapHome, import the template into a Modbus RTU interface set to 9600 baud, 8 data bits, no parity, 1 stop bit, and enter the S3 address as the Slave ID.
Device capabilities
Zone and DHW on/off
Three switches control bits of register 0. Each switch reads the register, changes only its own bit and writes it back, so the other functions keep their state:
- Pompa di calore — Zona 1 On/Off (heat pump zone 1 on/off) — register 0, bit 1
- Pompa di calore — Zona 2 On/Off (heat pump zone 2 on/off) — register 0, bit 3
- ACS — Riscaldamento On/Off (DHW heating on/off) — register 0, bit 2
Operating mode
Modalità di funzionamento (operating mode) is a multi-value switch on register 1 with three values: Auto (1), Raffreddamento (cooling, 2) and Riscaldamento (heating, 3).
Setpoints
Three read/write variables set the targets directly, in °C:
- Setpoint temperatura acqua T1s (water flow setpoint T1s) — register 2
- Setpoint temperatura ambiente Ts (room setpoint Ts) — register 3; the manual gives a range of 17–30 °C, valid only when the room temperature sensor Ta is present
- Setpoint temperatura ACS T5s (DHW tank setpoint T5s) — register 4; range 40–60 °C
ECO and silent mode
Two switches change single bits of register 5 (function settings) with the same read-modify-write method:
- Modalità ECO (ECO mode) — register 5, bit 10
- Modalità Silenziosa (silent mode) — register 5, bit 6
Weather-dependent curve
Curva climatica — selezione (climate curve selection) on register 6 selects one of the preset curves 1–8, which set the water setpoint T1s from the outdoor temperature T4. The two points of the user-defined curve are available as service attributes and service actions on the module (registers 261–268, see below).
Temperature sensors
- Temperatura ingresso acqua TW_in (water inlet temperature) — register 104
- Temperatura uscita acqua TW_out (water outlet temperature) — register 105
- Temperatura esterna T4 (outdoor temperature) — register 107
- Temperatura serbatoio ACS T5 (DHW tank temperature) — register 115
Operating data (module service attributes)
The module BAXI Auriga M/T-A shows the operating data of the whole unit as service attributes:
- Compressor: frequency in Hz (register 100), actual operating mode — off, cooling, heating (101), compressor operating hours (122)
- Outdoor unit: fan speed in RPM (102), electronic expansion valve opening in steps (103), high and low refrigerant pressure in kPa (116, 117), current in A (118), voltage in V (119)
- Refrigerant and water temperatures: condenser T3 (106), compressor discharge Tp (108), compressor suction (109), total water outlet T1 (110), water outlet after the backup heater T1B (111), refrigerant liquid T2 (112), refrigerant gas T2B (113), room temperature Ta (114)
- Inverter: DC bus current (133), DC bus voltage (134), module temperature TF (135)
- Hydraulics: water flow in m³/h (138) and hydraulic module capacity in kW (140); the unit sends both multiplied by 100 and the template divides them by 100
- Versions: unit firmware version (130) and wired controller firmware version (131)
- Installer parameters (read only): T1S upper and lower limits for cooling and heating (201–204), DHW pump running time (209), disinfection temperature T5s_DI (220), maximum disinfection duration (221), holiday setpoints for heating and DHW (245, 246) and the user-defined curve points T1SetC1/C2, T4C1/C2, T1SetH1/H2, T4H1/H2 (261–268)
Fault and status messages
The module script reads the current fault code from register 124 and turns 30 codes of the E, P, H and L families (for example E0 water flow fault, E2 communication error between wired controller and hydraulic module, P1 high-pressure protection, L1 DC generator low-voltage protection) into error messages in Italian. Any non-zero code also raises the warning Codice guasto attivo: n, where n is the raw code number from register 124.
From the status words the module also reports:
- register 128: defrost running, anti-freeze protection active, oil return running (information messages)
- register 129: defrost active and external heater active (information messages), system alarm (error)
Installer parameters (module service actions)
Service actions on the module write the main installer parameters. The input range of each action is set by the template:
| Service action | Parameter | Register | Range |
|---|---|---|---|
| Imposta limite superiore T1S raffreddamento | T1S upper limit, cooling | 201 | 18–25 °C |
| Imposta limite inferiore T1S raffreddamento | T1S lower limit, cooling | 202 | 5–25 °C |
| Imposta limite T1S riscaldamento superiore | T1S upper limit, heating | 203 | 25–60 °C |
| Imposta limite T1S riscaldamento inferiore | T1S lower limit, heating | 204 | 22–55 °C |
| Imposta tempo funzionamento pompa ACS | DHW pump running time | 209 | 5–120 min |
| Imposta temperatura disinfezione T5s_DI | Disinfection temperature | 220 | 60–70 °C |
| Imposta temperatura esterna abilitazione IBH | Outdoor temperature enabling the backup heater IBH | 233 | -15–10 °C |
| Imposta ritardo avvio IBH | Backup heater IBH start delay | 235 | 15–120 min |
| Imposta setpoint riscaldamento holiday T1S | Holiday heating setpoint | 245 | 20–25 °C |
| Imposta setpoint ACS holiday T5S | Holiday DHW setpoint | 246 | 20–25 °C |
| Imposta T1SetC1 / T1SetC2 | User curve, cooling: water temperature points | 261, 262 | 5–25 °C |
| Imposta T4C1 / T4C2 | User curve, cooling: outdoor temperature points | 263, 264 | -5–46 °C |
| Imposta T1SetH1 / T1SetH2 | User curve, heating: water temperature points | 265, 266 | 25–60 °C |
| Imposta T4H1 / T4H2 | User curve, heating: outdoor temperature points | 267, 268 | -25–30 °C |
When both heating zones are used, the dual-zone setting must be enabled on the unit — the manual lists it as bit 3 of register 211 (“dual zone setting is valid”).
Troubleshooting
No response from the heat pump
- Check that TapHome is wired to H1 and H2 of the wired controller — H2 to A+, H1 to B- — and not to the controller terminals A and B (13.5 V AC supply) or to the H1/H2 cascade terminals on CN30 in the hydraulic module.
- Check the position of switch S3 on the hydraulic module main board: position 0 is address 16, not 1. The Slave ID entered at import must match.
- Check that the interface runs Modbus RTU at 9600 baud, 8 data bits, no parity, 1 stop bit; Modbus ASCII is not supported.
- Check that the cable shield is connected to E and firmly earthed.
- The installation manual also lists a service menu item MENU > FOR SERVICEMAN > HMI ADDRESS SET with 17.2 HMI ADDRESS FOR BMS (default 1, range 1–16) and 17.3 STOP BIT (default 1). If the unit still does not answer at the S3 address, check these values on the wired controller and keep STOP BIT at 1.
Operating data stay empty or zero
The parameters of the whole unit (registers 100 and up) are available only when the wired controller is connected to the hydraulic module. Check the A, B, X, Y, E connection between the controller and the unit. The room setpoint Ts is valid only when the room temperature sensor Ta is installed.
Reading fault codes
The number in the warning Codice guasto attivo: n is the raw value of register 124. Look it up in the error code table of the wired controller manual (section 7.1.3), which lists each code letter with its number — for example 1 = E0, 9 = E8, 21 = P1, 39 = H0, 43 = H4, 44 = H5, 49 = HA, 50 = Hb, 134 = L0.
For raw values 44 to 50 the Italian error texts of the template are one step off the manual’s table (the template names 44 as H4, while the manual lists 43 = H4 and 44 = H5). For these codes, rely on the raw number in the warning. Codes the template does not decode (for example Pb, Hd, HE, F1, L4–L9) appear only as the warning with their number.
