Viessmann BW 301.A090, Installation And Service Instructions Manual

Page: 61 / 160

61
Plug
sXS
Terminals Function Explanation
222.3
222.4 Switching external heat gen-
erators with two high limit
safety cut-outs (max. 70 °C)
for the heat pump and to
stop the secondary pump Floating contact
Note
■ The switching contact is a floating N/O
contact that is closed when a heat de-
mand is issued.
■ Never route low voltage via this con-
tact; for that fit a relay on-site.
■ The boiler water temperature sensor in
the external heat generator (plug F20)
must capture the average temperature
of the external heat generator.
Connection values (contact rating):
■ Voltage: 230 V~
■ Max. switching current: 4(2) A
Connect the high limit safety cut-out on
site:
■ In series with the secondary pump (ter-
minal 211.2 on main PCB), see sepa-
rate "Connection and wiring diagram"
sheet 20
■ In series for switching external heat
generators, see separate "Connection
and wiring diagram" sheet 170,
sheet 171, sheet 172
Installation sequence
Overview of electrical connections
(cont.)
5848 164 GB
Installation