Vitocrossal 300 CU3A Connection Quick Start Guide

Overview

This Quick Start Guide provides an overview for experienced, licensed professional heating contractors with general wiring and operational knowledge of the Vitocrossal 300 CU3A boiler. It is not a substitute for the technical support literature supplied with the boiler and its accessories. Failure to follow the safety and national/local code requirements in the technical literature may lead to property damage, personal injury, or loss of life. Viessmann Manufacturing is not responsible for damages resulting from inappropriate use of this guide or failure to read the provided technical literature.

Before Wiring the Boiler

Connect fuel supply and all hydronic piping.
Ensure gas pressure matches the rating plate.
Verify that the venting is installed according to the Installation Instructions.
Perform leak tests on the gas supply, heating system, and venting using approved methods.

What You Need to Know About Wiring the Boiler

For detailed installation information of the Vitocrossal 300 CU3A boiler, refer to the appropriate documentation.
Refer to the boiler wiring diagram for electrical requirements.
The boiler requires a 120VAC, 120/1/60 power supply. Proper polarity must be maintained.
The control unit requires an earth ground for proper operation.
Use shielded wire for sensor wiring to prevent electromagnetic interference.

1 Access to the CU3A Wiring

This section illustrates how to access the CU3A wiring. It shows the control unit with its cover panels removed to expose the internal wiring terminals. Multiple views of the unit are provided, indicating the location of various connection points.

2 Power and Sensor Connection

This section details the power and sensor connections. It specifies a minimum wire gauge of 16 AWG and a maximum length of 115 ft. (35 m) for sensor wiring. Connections include:

Power Supply: A 120/1/60 12A power supply with disconnect and protection is required. The power connection is typically labeled 40 -L, G, N.
Outdoor Temperature Sensor: Connection to the outdoor temperature sensor (X3-1, -2), which is supplied with the boiler.

3 Heating Circuits Connection

This section covers connections for heating circuits, supporting up to two mixing valve extension modules. It shows the following connections:

Mixing Valve Extension Modules: For the first module, set the selector to '2'; for the second, set to '4'.
Heating Circuit 1 Pump: Connection for the pump (20 - L, G, N).
Heating Circuit 2 Temperature Sensor: Connection for the sensor (Plug 2).
Heating Circuit 2 Pump: Connection for the pump (20 - L, G, N).
Mixing Valve Motor: Connection to the motor (52 - Y, B, G, N).
KM Bus: Connections labeled KM Bus 145-1, -2 are shown for communication with extension modules or accessories.
Power Supply: A 120/1/60 12A power supply with disconnect and protection is required for each mixing valve extension module.

Diagrams illustrate the routing of wires for system supply and return, as well as KM Bus connections.

4 DHW Connection

This section describes the Domestic Hot Water (DHW) connections. It includes:

DHW Recirculation Pump: Connection for the pump (28 - L, G, N). Wiring is supplied with quick connect fittings.
DHW Pump: Connection for the pump (21 - L, G, N).
DHW Sensor: The DHW sensor (5) is supplied with the boiler.
DHW Temperature Sensor: The DHW temperature sensor (X9) is pre-wired.

Diagrams show the pump connections and sensor locations relative to the system supply and return lines.

5 External Heat Demand Connection

This section outlines the connection for external heat demand, typically used for third-party controls such as snow melt, spa, or pool systems. It utilizes a dry contact connection via Digital Output 1 (DE1 -1, -2). A note indicates that specific coding is required in Section 7 ('Starting the Boiler') for this connection.

6 LWCO Connection

This section explains the connection of a Low Water Cutoff (LWCO) device. To make the connection, a jumper must be removed from the MULTI terminals 1 and L. The diagram shows the LWCO device connected to these terminals, along with a powered accessory connection.

7 Starting the Boiler

This section guides the user through the initial startup and configuration of the boiler.

Legend

1: Programming Unit
2: Vitotronic 200, KW6B
A: ON/OFF switch
B: Reset button
C: On indicator (green)
D: Fault indicator (red)
E: Heating circuit selected for operation in the standard menu
F: Header (displays the heating program for the displayed heating circuit)
G: Current outside temperature
H: Set room temperature

Initial Setup Steps

Turn ON switch A. The indicator C should be on.
Use the navigation buttons [up/down] to select 'Language' and press the OK button.
Use the navigation buttons [up/down] to set 'Time and Date' and press the OK button.
Access coding level 2:
- Simultaneously press the OK button and the [up] button for 4 seconds.
- Simultaneously press the OK button and the [down] button for 4 seconds.
- Use the navigation buttons [up/down] to select the desired coding group and press the OK button.

Coding Configuration

General Settings

Use the navigation buttons [up/down] to select the system layout address 00:__ and press the OK button.
Use the navigation buttons [up/down] to select the system layout coding and press the OK button.

External Heat Demand (Required Coding if Connected)

Use the navigation buttons [up/down] to select address 3A:0 and press the OK button.
Use the navigation buttons [up/down] to select coding 3A:2 and press the OK button.
Use the navigation buttons [up/down] to select address 9B:0 and press the OK button.
Use the navigation buttons [up/down] to select coding 9B:__ (for set point temp.) and press the OK button.

Fuel Conversion

For changing to LPG, refer to the fuel conversion instructions.

Boiler Settings

If no adjustments are required for the boiler, proceed to the next group. Note: 'DHW' and 'Heating Circuit 2 and 3' will only appear on the programming unit if they are connected to the system.

DHW Settings

If no changes are required for DHW temperature, proceed to the next group.

Heating Circuit Settings (1, 2, and 3)

Each heating circuit must be adjusted separately. If no adjustments are required, go to the 'service menu'.

Press the [return] button to return to groups, or press the [service menu] button.
Using the navigation buttons [up/down], select 'Actuator test' and press the OK button. Use the navigation buttons [left/right] to select 'test'.
Press the [return] button to return to 'Actuator test', then press the [extended menu] button.

Extended Menu Operations

After each change, press the OK button to return to the 'extended menu'.

Change Display Units (°C to °F): Use the navigation buttons [up/down] to select 'settings' and press the OK button. Use the navigation buttons [up/down] to select 'temperature unit' and press the OK button. Use the navigation buttons [up/down] to select '°F' and press the OK button.
Adjust Heating Curve: Use the navigation buttons [up/down] to select 'heating' and press the OK button. Use the navigation buttons [up/down] to select 'heating circuit' and press the OK button. Use the navigation buttons [up/down] to select 'heating curve' and press the OK button. Use the navigation buttons [up/down] to select 'slope' or 'shift' and press the OK button. Use the navigation buttons [up/down] to set the required value and press the OK button.
Adjust Room Temperatures: Use the navigation buttons [up/down] to select 'heating' and press the OK button. Use the navigation buttons [up/down] to select 'heating circuit' and press the OK button. Use the navigation buttons [up/down] to select 'room temp. setpoint' and press the OK button. Use the navigation buttons [up/down] to set the 'value' and press the OK button. Use the navigation buttons [up/down] to set the required value and press the OK button.
Adjust DHW Temperature: Use the navigation buttons [up/down] to select 'DHW' and press the OK button. Use the navigation buttons [up/down] to select 'DHW temperature setpoint' and press the OK button. Use the navigation buttons [up/down] to select the value and press the OK button.

Press the [select] button repeatedly to return to the home screen.

Information is subject to change without notice.

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