Viessmann VITOCAL 250-A - Page 93

93
2404.0 Dual mode operation, external heat generator
This parameter specifies the temperature ranges in
which the external heat generator may be switched on
simultaneously with or as an alternative to the heat
pump.
Value Meaning
0 Do not adjust!
1 Mono mode operation:
Heat is generated with the heat pump only.
The external heat generator is not activated.
2 Dual mode parallel operation:
See Fig. 25.
3 Dual mode alternative operation:
See Fig. 26.
Note
In most cases, dual mode parallel operation is more
efficient than dual mode alternative operation.
Dual mode parallel operation
A
B
A
+
Fig. 25
ϑ
A
Outside temperature
A
Alternative operation temperature limit: Value is set
by the control unit according to the control strategy
set in parameter 2404.3.
B
Dual mode temperature in parameter 2404.1
The heat pump is switched on for room heating/
room cooling and DHW heating as required.
The external heat generator is switched on for
room heating and DHW heating as required.
■
When the outside temperature is above dual mode
temperature
B
:
–
Room heating/room cooling and DHW heating are
supplied only by the heat pump.
–
The external heat generator does not start.
■
When the outside temperature is between tempera-
ture limits
A
and
B
:
–
For normal heat demand, only the heat pump is
switched on.
–
For increased heat demand, the external heat gen-
erator is switched on in addition to the heat pump.
–
The heat pump can be switched on for room cool-
ing.
■
When the outside temperature is below alternative
operation temperature limit
A
:
–
The heat pump does not operate.
–
Room heating and DHW heating are supplied only
by the external heat generator.
–
Room cooling is switched off.
Dual mode alternative operation
A
A
Fig. 26
ϑ
A
Outside temperature
A
Alternative operation temperature limit: Value is set
by the control unit according to the control strategy
set in parameter 2404.3.
The heat pump is switched on for room heating/
room cooling and DHW heating as required.
The external heat generator is switched on for
room heating and DHW heating as required.
■
When the outside temperature is above temperature
limit
A
:
–
Room heating/room cooling and DHW heating are
supplied only by the heat pump.
–
The external heat generator does not start.
■
When the outside temperature is below temperature
limit
A
:
–
The heat pump does not operate.
–
Room heating and DHW heating are supplied only
by the external heat generator.
–
Room cooling is switched off.
Parameter group for external heat generator
2404 Dual mode control mode
6218234
Parameter