Viessmann Vitocrossal 300 CA3 2.5 Installation And Service Instructions Manual page 22

Installation
Electrical Connections
Note: The DIN terminals can be used with solid, stranded
or stranded with ferrule termination. The ferrule
will help to prevent 'fraying' of the stranded wires
during installation.
Specific connections are detailed throughout the manual,
refer to the appropriate section prior to making any
connections.
Legend
A DIN terminal accessory connections
B Push-in button
C DIN rail (typical)
D Terminal insertion point
22
(continued)
Top
Bottom
Vitocrossal 300 CA3 Series 2.5 to 6.0 Installation/Service
Accessory connections
The accessory terminals include a L, N terminal connection
orientated at the top of the rail which is pre-wired to the
cable harness set. The L, N, G terminals orientated at the
bottom of the DIN rail for accessory connection is used to
for connections to external equipment (ie. Pumps, mixing
valves, etc). The individual terminals are a 'push-in'
design, meaning to install or release a wire, the orange
button must be pushed in (refer to image below for location
of orange buttons denoted by B), prior to installing or
removing any wires to the terminal.