VIESSMANN VITOCROSSAL 300 CU3A Gas Condensing Boiler User Guide

October 27, 2023
VIESSMANN

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VIESSMANN VITOCROSSAL 300 CU3A Gas Condensing Boiler

ITOCROSSAL

This Quick Start Guide is designed to provide an overview to an experienced licensed professional heating contractor with the a general wiring and operational knowledge of the Vitocrossal 300 CU3A boiler. It is NOT a substitute for the technical support literature supplied with the Vitocrossal 300 CU3A boiler and its accessories. The technical support literature of each product contains the necessary safety and national/local code requirements which, if not followed exactly, will lead to property damages, personal injuries and/or loss of life. Viessmann Manufacturing assumes no responsibility for damage(s) of any kind caused by inappropriate use of this Quick Start-up Guide and/or failure to read the technical literature provided

Before wiring the boiler

  • Connect fuel supply and all hydronic piping.
  • Ensure gas pressure matches 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 boiler wiring diagram for electrical requirements of boiler.
  • 120VAC wiring! The boiler can only be connected to a 120/1/60 power supply.
  • Proper polarity must be maintained for 120VAC wiring.
  • The control unit requires an earth ground for proper operation.
  • Use shielded wire for sensor wiring to prevent electromagnetic interference.

Access to the CU3A Wiring

VIESSMANN-ITOCROSSAL-300-CU3A-Gas-Condensing-Boiler-
fig-1

Power and Sensor Connection

VIESSMANN-ITOCROSSAL-300-CU3A-Gas-Condensing-Boiler-
fig-2

Heating Circuits Connection

with mixing valve extension module (max. 2)

VIESSMANN-ITOCROSSAL-300-CU3A-Gas-Condensing-Boiler-
fig-3

DHW Connection

External Heat Demand Connection

VIESSMANN-ITOCROSSAL-300-CU3A-Gas-Condensing-Boiler-
fig-6

References

Read User Manual Online (PDF format)

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Download This Manual (PDF format)

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