Electrical Connection - Viessmann SCU 123 Manual

SCU 123
5.3

Electrical connection

The controller is mostly prewired in the factory. Sensors
S1 (collector temperature) and S3 (upper tank) must be
connected on site. Use appropriate 1812 or 1612 low vol-
tage sensor wire, and connect to terminals as shown below.
The following points only serve as information.
| 16
The station is connected to the power supply (100 ... 240 V~)
with the already mounted connection cable. Works on cur-
rent-carrying parts of the installation may only be carried out
by a licensed specialist firm. Relevant regulations and norms
must be observed.
Make sure that the hydronic parts of the installation are
appropriately grounded.
WARNING! Electric shock!
Opening the housing will expose live
parts!
Î Switch off power supply and discon-
nect the device from power supply
before opening the housing!
ATTENTION! ESD damage!
Electrostatic discharge can lead to da-
mage to electronic components!
Î Take care to discharge properly
before touching the inside of the
device. To do so, touch a grounded
surface such as a radiator or tap!
Note:
The power supply connection must be con-
nected to the common ground of the building, to
which the pipework of the solar thermal system
is connected!
Note:
When the display does not work, check the po-
wer supply of the controller. If the power supply
is not interrupted, the fuse in the controller is
defective.
The controller is equipped with two semiconductor relays,
to which loads such as pumps, valves etc. can be connected:
Relay 1
18 = conductor R1
17 = neutral conductor N
13 = ground conductor
Relay 2
16 = conductor R2
15 = neutral conductor N
14 = ground conductor
The power supply is at the terminals:
19 = neutral conductor N
20 = conductor L
12 = ground terminal
The temperature sensors (S1 up to S4) are connected
to the following terminals with either polarity:
1 / 2 = Sensor 1 (collector sensor)
3 / 4 = Sensor 2 (secondary loop heat exchanger sensor)
5 / 6 = Sensor 3 (upper tank sensor)
7 / 8 = Sensor 4 (primary loop heat exchanger sensor)