The board, by reference.
Use this page when discussing individual connectors. The installation manual uses equipment names and zone assignments.
Owner-confirmed wiring
CN77 common is neutral, and its physical bottom contact is the common. The electrical netlist identifies that net as CN77.3 / RL_NETRAL; CN77.1 is the ceiling pump (A7), CN77.2 is the floor pump (B7). The owner’s latest correction specifies ceiling pump / floor pump / N from top to bottom: physical order 1, 2, 3. This supersedes the older viewer’s middle-N silkscreen. Zone blocks have pin 1 on the right; their source silkscreen runs B6→B3, B2→B0, A0→A2 and A3→A6 from left to right. Public drawings use these physical zone labels. The owner confirms that thermostat selections use these same zone names directly: A0 is A0 and B6 is B6.
Mixing-valve pin 3 is Vout 0–10 V, the command output to the actuator. Pin 4 is Vin 0–10 V, optional feedback input from the actuator. Leave pin 4 open when feedback is not used. Pin 1 is +24 V and pin 2 is 0 V. Both analogue voltage ranges are confirmed by the board owner.
| Reference | Equipment |
|---|---|
| CN38 | 24 V DC input |
| CN68 | T-Bus pair |
| CN1 | T1 · floor return |
| CN82 | T2 · ceiling source probe |
| CN83 | T3 · buffer tank |
| CN84 | T4 · ceiling return |
| CN85 | T5 · spare |
| CN2 | T6 · floor source probe |
| CN86 | T7 · system supply |
| CN64 | Ceiling mixing valve |
| CN63 | Floor mixing valve |
| CN90 | Spare channel 3 |
| CN91 | Spare channel 4 |
| CN3 | Upper left outer actuator block |
| CN4 | Upper left inner actuator block |
| CN5 | Upper right outer actuator block |
| CN6 | Upper right inner actuator block |
| CN77 | Pumps / common |
| RJ1 | Ethernet |
| CN89 | RS-485 · not T-Bus |
| H1 | RS-485 termination |
| H2 | Programming header |
| U28 | USB-C service |
| Electrical terminal | Physical zone | MCP port from netlist | Controller net | Relay | MCP package pin |
|---|---|---|---|---|---|
| CN6.2 | A1 | GPA0 | RL_A1 | K34 | 21 |
| CN6.1 | A2 | GPA1 | RL_A2 | K33 | 22 |
| CN5.4 | A3 | GPA2 | RL_A3 | K32 | 23 |
| CN5.3 | A4 | GPA3 | RL_A4 | K31 | 24 |
| CN5.2 | A5 | GPA4 | RL_A5 | K30 | 25 |
| CN5.1 | A6 | GPA5 | RL_A6 | K1 | 26 |
| CN3.4 | B6 | GPA6 | RL_B6 | K37 | 27 |
| CN77.1 | Pump | GPA7 | RL_PUMP2 | K27 | 28 |
| CN4.2 | B1 | GPB0 | RL_B1 | K19 | 1 |
| CN4.3 | B2 | GPB1 | RL_B2 | K20 | 2 |
| CN3.1 | B3 | GPB2 | RL_B3 | K21 | 3 |
| CN3.2 | B4 | GPB3 | RL_B4 | K22 | 4 |
| CN3.3 | B5 | GPB4 | RL_B5 | K23 | 5 |
| CN4.1 | B0 | GPB5 | RL_B0 | K3 | 6 |
| CN6.3 | A0 | GPB6 | RL_A0 | K35 | 7 |
| CN77.2 | Pump | GPB7 | RL_PUMP1 | K26 | 8 |
Source and interpretation
Locations: InteractiveBOM_PCB1_2026-9-13.html. Electrical connections: Netlist_PCB1_2026-09-13.tel. Firmware roles: pins.h, thermostat_wiring.cpp and valve_control_core.cpp. The technical trace follows the relay, optocoupler and resistor back to the MCP23017. Its port identifiers describe the supplied netlist; they are not thermostat menu selections. For installation, select the zone printed on the board.
Microchip MCP23017 pinout · Espressif module pinout. Load ratings, protection and cable limits require the equipment specification. The diagrams are source-based references, not an electrical test record.