Here is the Viessmann CU3A Startup Guide

VITOCROSSAL 300 CU3A CONNECTION QUICK START GUIDE
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.

Connection to Outdoor Temperature Sensor:

 Connection Points (X3 -1, -2)
(sensor supplied with boiler)

Power Connection
Connection Point: 40 -(L, G, N)

1. Turn ON switch A (indicator C is on).
2. Using , select ‘Language’ and press OK.
3. Using , set ‘Time and Date’ and press OK.
4. Access coding level 2;
- Simultaneously press OK and for 4 sec.
- Simultaneously press OK and for 4 sec.
- Using , select desired coding group and press OK.
General
- Using , select the system layout address 00:_ _ and press OK.
- Using , select the system layout coding and press OK.
External Heat Demand (required coding if connected)
- Using , select address 3A:0 and press OK.
- Using , select coding 3A:2 and press OK.
- Using , select address 9B:0 and press OK.
- Using , select coding 9B:_ _ (for set point temp.) and press OK.
For changing to LPG, refer to the fuel conversion instructions.
Boiler
If no adjustments are required for the boiler go to the next group.
Note: ‘DHW’ and ‘Heating Circuit 2 and 3’ will not appear on
the programming unit if not connected to the system.
DHW
If changes are not required to set DHW temp. go to the next group.
Heating Circuit 1, 2 and 3 (each circuit must be adjusted separately)
If adjustments are not required go to the ‘service menu’.
- Press to return to groups, press for ‘service menu’
- Using , select ‘Actuator test’ and press OK, use , to select ‘test’
- Press to return to ‘Actuator test’, press for ‘extended menu’ .
Extended Menu (after each change press to return to ‘extended menu’)
To change display units from °C to °F, use , to select ‘settings’
and press OK.
- Using , select ‘temperature unit’ and press OK, use to select
°F and press OK.
To adjust the heating curve, use to select ‘heating’ and press OK.
- Using , select ‘heating circuit’ and press OK, use , to select
‘heating curve’ and press OK, use to select ‘slope’ or ‘shift’ and
press OK, use to set required value and press OK.
To adjust room temperatures, use to select ‘heating’ and press OK.
- Using , select ‘heating circuit’ and press OK, use , to select
‘room temp. setpoint’ and press OK, use , to set ‘value’ and press
OK, use to set required value and press OK.
To adjust DHW temperature, use to select ‘DHW’ and press OK.
- Using , select ‘DHW temperature setpoint’ and press OK, use
to select value and press OK.
Select repeatedly to return to the home screen.