41
Start and stop conditions for DHW heating
■
If the cylinder temperature has fallen below the set
cylinder temperature by the amount of the start hys-
teresis, DHW heating starts under the following con-
ditions:
–
A time phase for DHW heating is active.
–
The min. delay until the next DHW heating period
has expired (parameter 1087.1).
Or
–
One-off DHW heating is switched on.
■
If 1 of the following conditions is met, DHW heating
ends:
–
The cylinder temperature exceeds the set cylinder
temperature by the amount of the stop hysteresis.
–
The set max. duration for DHW heating has
expired (parameter 1087.0).
Note
After DHW heating ends, the circulation pump for cylin-
der heating continues to run for the run-on time set in
parameter 534.0.
Fig. 12
A
Stop hysteresis (parameter 1085.1)
B
Start hysteresis (parameter 1085.0)
C
Set cylinder temperature
D
Cylinder temperature
E
Demand for DHW heating by the heat pump
F
Compressor OFF
G
Compressor ON
Note
DHW heating takes place according to the mode set
by the system user:
Eco Energy saving DHW heating
Comfort Fast DHW heating, possibly with higher
energy demand
Operating instructions for the heat pump
Booster heaters for DHW heating
The following booster heaters can be switched on by
the heat pump control unit for DHW heating:
■
Instantaneous heating water heater integrated into
the indoor unit
■
External heat generator
■
Immersion heater EHE in the DHW cylinder
Within the application limits of the heat pump, the
booster heater is only switched on in addition to the
heat pump if required. If the outside temperature falls
below the application limit of the heat pump, DHW is
heated solely via the integral instantaneous heating
water heater or the external heat generator.
The heating output required for DHW heating depends
on the amount of heat required and the heat-up time.
For example, the heating output is limited in Eco
mode. DHW heating therefore takes longer than in
Comfort mode.
Instantaneous heating water heater
When DHW heating is called for, the control unit first
determines the available heating output of the heat
pump. This heating output depends on the outside
temperature and the required flow temperature. If the
current heating output of the heat pump is not suffi-
cient, the instantaneous heating water heater is
switched on after a delay of 5 min. The heating output
of the instantaneous heating water heater is gradually
increased depending on the heat demand.
In the following cases, the instantaneous heating water
heater is switched on without a delay:
■
For a temporary high output demand with an
increase of ≥ 4 K in the set cylinder temperature, e.g.
when starting the hygiene function
■
Frost protection function for the DHW cylinder is
active.
DHW heating priority
Simultaneous DHW heating and room heating/cooling
is not possible:
■
DHW heating always takes priority over room cool-
ing.
■
With the factory settings, DHW heating has priority
over room heating. This setting can be adjusted sep-
arately for each of the max. 4 heating/cooling circuits
via parameters 933.3, 934.3, 935.3, 936.3.
Control of DHW heating with priority over room
heating
If the heating circuits and the DHW cylinder call for
heat at the same time, DHW heating initially only takes
place for the max. duration set in parameter 1087.0.
After this, the rooms are heated. If the set cylinder
temperature was not reached within the max. duration
(parameter 1087.0), the rooms are only heated for the
delay set in parameter 1087.1 before DHW heating is
switched on again.
Function description
DHW heating (cont.)
6218234
Functions
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