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 (A0), CN77.2 is the floor pump (B0). 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 B7→B4, B3→B1, A1→A3 and A4→A7 from left to right. Public drawings use these physical zone labels. The owner confirms that thermostat selections use these same zone names directly: A1 is A1 and B7 is B7.
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 | Heat source control |
| CN91 | Heat source season |
| 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 |
|---|---|---|---|---|---|
| CN77.1 | Pump | GPA0 | RL_PUMP2 | K27 | 21 |
| CN6.3 | A1 | GPA1 | RLx_A1 | K35 | 22 |
| CN6.2 | A2 | GPA2 | RLx_A2 | K6 | 23 |
| CN6.1 | A3 | GPA3 | RLx_A3 | K5 | 24 |
| CN5.4 | A4 | GPA4 | RLx_A4 | K32 | 25 |
| CN5.3 | A5 | GPA5 | RLx_A5 | K4 | 26 |
| CN5.2 | A6 | GPA6 | RLx_A6 | K30 | 27 |
| CN5.1 | A7 | GPA7 | RLx_A7 | K1 | 28 |
| CN77.2 | Pump | GPB0 | RL_PUMP1 | K26 | 1 |
| CN4.1 | B1 | GPB1 | RLx_B1 | K3 | 2 |
| CN4.2 | B2 | GPB2 | RLx_B2 | K19 | 3 |
| CN4.3 | B3 | GPB3 | RLx_B3 | K20 | 4 |
| CN3.1 | B4 | GPB4 | RLx_B4 | K2 | 5 |
| CN3.2 | B5 | GPB5 | RLx_B5 | K22 | 6 |
| CN3.3 | B6 | GPB6 | RLx_B6 | K23 | 7 |
| CN3.4 | B7 | GPB7 | RLx_B7 | K7 | 8 |
Source and interpretation
Locations and electrical connections: HeatingMain9b.epro2, the HeatingMain V9B board. 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. Zone labels, relay designators and MCP ports come from the HeatingMain V9B PCB netlist, on which each MCP port is the zone printed on the board. 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.