Viessmann VITOCAL 300-A Installation And Service Instructions Manual page 88

Installation sequence
Electrical connections in the control unit
External heat source
!
Please note
Protect the heat pump against
temperatures over 70 °C from
the external heat source.
Install a high limit safety cut-
out (STB) or take further mea-
sures if required.
Note
& The switching contact to demand
heat from an external heat source
("Ext. HS for DHW") in the heat
pump is a zero volt N/O contact that
closes in case of heat demand.
& This contact can be subjected to a
load of 230 V~/4(2) A in case of an
external voltage supply. Never route
low voltage via this contact; for that
an on-site relay is required.
& Sensor F20 must capture the med-
ium temperature of the external heat
source.
A Heat pump connection: Contact
load 230 V~, 4(2) A, zero volt con-
tact
B Transfer jumper from 1X3.1 (PCB
1) to 2X7.1 (PCB 2)
88
(cont.)
C Connection at the external heat
source on the terminals for exter-
nal demand