The Pichler PKOM4 is a heat pump combination unit that integrates ventilation, heating, cooling and domestic hot water production (Classic models) in a single appliance. It is available in four variants — PKOM4A classic, PKOM4A trend, PKOM4AK classic and PKOM4AK trend — covering living areas from 50 to 250 m². TapHome connects to the unit via Modbus TCP over Ethernet.
The template provides operating mode control, ventilation level selection (Auto + 9 levels), room and DHW temperature setpoints, active cooling configuration, energy consumption monitoring and filter maintenance tracking.
Network connection
The PKOM4 has a built-in LAN (Ethernet) port on the main board for network connectivity. Connect it to the same local network as TapHome Core using a standard Ethernet cable.
- Protocol: Modbus TCP
- Port: 502
- Default Slave ID: 1 (configurable at import)
Assign a static IP address to the PKOM4 unit in the router’s DHCP settings to prevent the address from changing after a power cycle.
Main board layout
The main board is located at the top of the unit in the electrical connection box. Key connectors relevant for TapHome integration:
| Connector | Function |
|---|---|
| LAN | Ethernet — network connection for Pichler app, Pichler Connect and Modbus TCP |
| M1 | Modbus RTU — external BMS / KNX gateway connection (A+/B-/GND) |
| M2 | Internal Modbus — ventilation board (do not use for external systems) |
| M3 | Internal Modbus — heat pump board (do not use for external systems) |
| B1 | Touch control unit connection |
| Label (DE) | Translation (EN) | Connector |
|---|---|---|
| RJ45 Stecker für LAN | RJ45 connector for LAN | K13 |
| Modbus für externe Anbindung (Datalogger/GLT) | Modbus for external connection (Datalogger/BMS) | M1 |
| Modbus zur Lüftungsplatine | Modbus to ventilation PCB | M2 |
| Modbus zur Wärmepumpenplatine | Modbus to heat pump PCB | M3 |
| Modbus zum Display | Modbus to display | M4 |
| Schnellerkontakt / Normaly open contact | Quick-action contact / Normally open contact | K12, K13 |
| Steuerspannung für Solarpumpe oder Nachheizregister | Control voltage for solar pump or duct heater | U5 |
| Temperaturfühler für Solar oder Nachheizregister | Temperature sensor for solar or duct heater | T9 |
| T40 Raumfühler extern oder Heizkreis | T40 ext. room temp. sensor or heating circuit | T40 |
| Relais für Kanalheizregister | Relay for duct heater | K4 |
| Pumpe für Solar- oder Heizkreis | Pump for solar or heating circuit | K5 |
| E-Heizung Warmwasserspeicher 1,5kW | E-heater for hot water tank 1.5 kW | K6 |
| Spannungsversorgung Hauptplatine | Power supply main PCB | H1 |
| Spannungsversorgung Wärmepumpenplatine | Power supply heat pump PCB | H3 |
| Spannungsversorgung Lüftungsplatine | Power supply ventilation PCB | H2 |
| CO2-Sensor | CO2 sensor | S2 |
| Feuchtesensor | Humidity sensor | S1 |
The M1 terminal is for Modbus RTU (RS-485) only. For Modbus TCP communication with TapHome, use the LAN (Ethernet) port. The internal Modbus connections (M2, M3) are reserved for communication between the unit’s PCBs and must not be used for external systems.
Modbus/KNX gateway connection
If a Modbus/KNX gateway (08KNXGAC) is installed, it connects to the M1 terminal on the main board via RS-485 (A+/B-/GND). The gateway acts as a Modbus master. This connection path is an alternative to direct Modbus TCP — TapHome typically uses the LAN port directly.
Configuration
When importing the template in TapHome, provide:
- IP Address — the unit’s IP on the local network
- Slave ID — Modbus slave address (default: 1)
The Homebridge plugin references slave ID 41 for Modbus RTU connections. For Modbus TCP via the LAN port (as used by TapHome), the default slave ID is 1. If communication fails, verify the slave ID configured on the unit.
Device capabilities
The template exposes the following devices:
Operating mode control
- Operating Mode (multi-value switch) — selects the unit’s operating mode via register H:0. Available modes: OFF, Summer, Winter, Auto, Holiday, Hot Water, Ventilation Valve Adjustment and Test.
- Room Temperature Regulation (switch) — enables or disables active room temperature regulation via register H:1.
Temperature control
Three thermostat devices are provided for temperature setpoint management:
- Room Temperature Setpoint — reads the current room temperature from input register A:19 and writes the desired setpoint to H:10. Default setpoint is 22 °C (parameter A12).
- Cooling Start Temperature — reads the current temperature from A:19 and writes the cooling activation threshold to H:19. Active cooling does not start below this temperature.
- DHW Temperature — reads the current domestic hot water temperature from A:162 and writes the desired setpoint to H:129. The heat pump heats water up to 55 °C, the electric heater up to 65 °C. Available on Classic models only.
Ventilation control
- Ventilation Level (multi-value switch) — selects the ventilation level via register H:46. Level 0 is automatic mode, levels 1–9 correspond to increasing airflow. Actual air volumes for levels 1–4 are configurable via parameters C08–C11 (PKOM4A: 85–250 m³/h, PKOM4AK: 50–150 m³/h).
- Current Air Volume (sensor) — reads the actual airflow from input register A:23, displayed in m³/h.
Cooling control
- Active Cooling (multi-value switch) — enables or disables active cooling via register H:9. Available options: No (0), Yes (1), Yes at Eco Tariff (2). The Eco Tariff option uses the Smart Grid contact E1 for cost-optimized cooling.
Humidity and air quality
- Max. Allowed Humidity (dimmer) — sets the maximum allowed relative humidity threshold via register H:102. Used for demand-driven ventilation control when a humidity sensor is installed.
Hot water management
- Legionella Protection (multi-value switch) — enables or disables the legionella protection function via register H:141. When active, the unit periodically heats the DHW tank to a disinfection temperature. The protection interval is configurable via parameter W13 (default: 14 days).
Energy monitoring
Three read-only sensors track cumulative energy consumption:
- Ventilation Energy Consumption — ventilation fan energy from A:29 (kWh)
- Heating Energy Consumption — heat pump heating energy from A:64 (kWh)
- Total Energy Consumption — combined energy counter (ventilation + heating + DHW + cooling) from A:65 (kWh)
Filter maintenance
- Filter Operating Hours — reads the filter usage counter from H:314 (hours)
- Filter Remaining Time — reads the remaining filter life from H:315. The filter replacement interval is configurable via parameter Y2 (default: 4 months).
Additional capabilities
The PKOM4 also exposes Modbus registers for outside air temperature, supply air temperature, current ventilation level, error codes, device status, room temperature regulation mode, scheduler/timer settings, CO2 concentration threshold, minimum humidity threshold and firmware version. These can be added to the TapHome template in a future update.
Troubleshooting
No Modbus communication
- Verify the Ethernet cable is connected to the LAN port on the main board
- Confirm the unit’s IP address — check the router’s DHCP lease table or the Pichler app
- Ensure TapHome Core and the PKOM4 unit are on the same network/subnet
- Check that no firewall is blocking port 502
- Verify the slave ID matches (default: 1 for Modbus TCP)
Incorrect temperature readings
Temperature values use a scaling factor of 1/100 (register value divided by 100). If displayed values appear 100 times too large or too small, verify the template scaling configuration.
DHW not heating
DHW heating is available only on Classic models (PKOM4A classic, PKOM4AK classic). Trend models do not include a hot water tank. Verify that the Hot Water operating mode is available and the DHW temperature setpoint is within the allowed range (up to 55 °C for heat pump, 65 °C for electric heater).
Communication errors 31/32
Error codes 31 (communication ventilation board) and 32 (communication heat pump board) indicate internal Modbus bus faults between the unit’s PCBs, not issues with the external TapHome connection. Contact a qualified service technician.
