Buderus Boiler Control Panel R4321/R4322 Wiring Diagram and Installation Notes
Important Notes and Warnings
Note! Installation, circuit breaker, main shutoff switch, emergency shutoff switch, and protective measures must be in accordance with local regulations.
Please note! Never use the ground wire (green/yellow) for control purposes.
Verify that power is connected to the appropriate terminals.
This control must be hard-wired.
1) Contact opens when the selected temperature is exceeded.
2) The total current for each power circuit (L1, L2) must not exceed 10A. This value must be adhered to. Verify maximum current draw after start-up to avoid damage to the device!
3) Please note! Only one MEC2 can be allocated to each control panel. The MEC2 can be plugged into the control panel or room wall-mounted using the wall installation kit (optional) wired to the ZM or FM module.
4) Terminal for optional external safety equipment. Interrupts the burner only!
5) When connecting multiple ECOCAN-BUS components, the S1 hook switches (termination on the NM482) of the two outermost ECOCAN-BUS devices must be closed.
6) L2: fuse protection of the modules in slots A, 1, and 2. L1: fuse protection of the modules in slots 3 and 4.
Control Panel Components
- Boiler module ZM434
- Controller module CM431
- Power module NM482 (located behind the controller module)
- MEC2 or boiler display
- FM modules (for slots 1, 2, 3, 4)
Switching States and Control Modes
The control panel features switches (k1-k6) and buttons for operation. The table below outlines their functions:
| Switch/Button | Stage 1 Control | Stage 2/Modulating Control | Control Mode Description |
|---|---|---|---|
| Switch k1 | Stage 1 | Control mode | |
| Switch k2 | Stage 2/Modulating | Control mode | |
| Switch k3 | Control mode | ||
| Switch k4 | Control mode | ||
| Switch k5 | Control mode | ||
| Switch k6 | Control mode | ||
| Button A (pressed) | AUT (Automatic) | ||
| Button B (pressed) | AUT (Automatic) | ||
| Button 0 | Control mode | ||
| Button max | Control mode | ||
| Button + | Warmer | ||
| Button - | Colder |
Control voltage is 120V~. Extra-low voltage is used for sensors.
Main Wiring Diagram Description (Page 1)
The main wiring diagram illustrates the connections for the Buderus boiler control panel R4321/R4322.
Mains and Power Distribution
Mains input (120V~ 60Hz) connects to terminals L1, N, and PE/PEN. The maximum permissible fuse rating on site is 20AT. Power circuits L1 and L2 are protected by fuses (each 10AT). L2 provides fuse protection for modules in slots A, 1, and 2, while L1 protects modules in slots 3 and 4.
Control Modules and Slots
The control panel houses several modules: Boiler module ZM434, Controller module CM431, and Power module NM482 (positioned behind the controller module). Slots 1 and 2 are designated for FM modules, as are slots 3 and 4. The MEC2 or boiler display connects externally.
ECOCAN-BUS Connection
The ECOCAN-BUS system uses terminals 1, 2, and 3 for communication. For multiple ECOCAN-BUS components, the S1 hook switches on the outermost devices (e.g., NM482) must be closed for termination.
Input Terminals
- STB (1253 high limit): Safety input; contact opens when the selected temperature is exceeded.
- TR (Boiler water temperature controller): Input for boiler water temperature control.
- Automatic Control Input: An input for automatic control signals.
- External Safety Equipment (Terminal 4): For optional external safety equipment that interrupts only the burner.
- ES (External fault input): A zero-volt input for external fault signals.
Output Terminals
- BR (Burner): For Gas/oil burner stage 1 connection (max 8A).
- BRII (Burner): For Burner connection stage 2 or connection for modulating burner (max 5A).
- SG (Vent damper): Terminals for vent damper control.
- UE (Flue gas monitoring): Terminals for flue gas monitoring.
- SR (Return temperature actuator): Connects to a return temperature actuator (120V, max 5A).
- PK (Boiler pump): Connects to a boiler pump (120V, max 5A).
- UBR (Voltage output burner): Provides a 0-10V output voltage for the burner.
- UPU (Voltage output pump): Provides a 0-10V output voltage for the pump.
Sensor Connections
- FK: Boiler water temperature sensor.
- FA: Outdoor temperature sensor.
- FZ: Auxiliary temperature sensor.
Other Connections
- Connector socket for external service units.
- BUS (internal) connection.
- Power supply for additional FM modules at slots 1, 2, or 3 (4).
- Connection example for safety components (on site).
System Examples (Page 2)
Page 2 illustrates four system examples for integrating the control panel with different types of Buderus boilers.
System Example 1
Description: Connects a Buderus Thermostream boiler or LT boiler with base line temperature. Control is achieved via a separate boiler circuit actuator (SR).
Components shown: FA (Outdoor Sensor), BF (Remote Control), ES (Fault Input), R4321 Control Panel, FK (Boiler Water Sensor), UBR (Burner Output), BR (Burner), FZ (Auxiliary Sensor), SR (Return Temp Actuator), PK (Boiler Pump).
System Example 2
Description: Integrates a Buderus Thermostream boiler. Control is via a boiler actuator. Terminal UPu is required for a modulating boiler circuit pump.
Components shown: FA, BF, ES, R4321, FK, BRII (Stage 2 Burner), BR (Stage 1 Burner), FZ, PK, SR.
System Example 3
Description: Connects a Buderus LT boiler. Control is via a separate boiler circuit actuator (SR).
Components shown: FA, BF, ES, R4321, FK, UBR, BR, FZ, SR, PK.
System Example 4
Description: Integrates a Buderus LT boiler with minimum return temperature. Control is via a separate boiler actuator (SR).
Components shown: FA, BF, ES, R4321, FK, BRII, BR, FZ, PK, SR.
Legend for System Examples
- BF: Remote control MEC2 or BFU
- BR: Burner
- ES: External fault input (dry contact)
- FA: Outdoor temperature sensor
- FK: Boiler water temperature sensor
- FZ: Auxiliary temperature sensor
- PK: Boiler pump
- SR: Return temperature actuator
- UPu: Voltage output 0-10V pump
- UBr: Voltage output 0-10V burner
Notes on System Examples:
- A boiler circuit pump may be controlled when using low loss headers.
- Terminal UPu is only required for a modulating boiler circuit pump (0-10V).
