DHW demand at a DHW tem-
perature of 45 °C
Specific available heat
Recommended heat load sup-
plement for DHW heating
*18
in l per person/day
in Wh per person/day
in kW/person
Low demand
15 to 30
600 to 1200
0.08 to 0.15
Standard demand
*19
30 to 60
1200 to 2400
0.15 to 0.30
or
Reference temperature 45 °C
Specific available heat
Recommended heat load sup-
plement for DHW heating
*18
in l per person/day
in Wh per person/day
in kW/person
Apartment
(billing according to demand)
30
approx. 1200
approx. 0.150
Apartment
(flat rate billing)
45
approx. 1800
approx. 0.225
Detached house
*19
(average demand)
50
approx. 2000
approx. 0.250
Supplement for setback mode
As the heat pump control unit is equipped with a temperature limiter
for setback mode, the supplement for setback mode to EN 12831
can be ignored.
In addition, the control unit is equipped with start optimisation, which
means that there is also no need for a supplement for heating up
from setback mode.
Both functions must be enabled in the control unit. If any of the sup-
plements are omitted because of the activated control unit functions
then this must be documented when the system is handed over to
the operator.
If, irrespective of the above mentioned control options, these supple-
ments are nevertheless to be taken into account, the calculation
should be made with reference to EN 12831.
Mono energetic operation
In heating operation, the heat pump system is supported by an
instantaneous heating water heater, which is either integrated or
available as an accessory. The control unit switches the instantane-
ous heating water heater on, subject to the outside temperature
(dual mode temperature) and heat load.
Note
That part of the electric power drawn by the instantaneous heating
water heater will generally
not
be charged at special tariffs.
Sizing of typical system configurations:
■ Size the heating output of the heat pump approx. 70 to 85 % of the
max. required building heat load to EN 12831.
■ The heat pump covers approx. 95 % of the annual heat load.
■ Blocking periods must not be taken into consideration.
Note
Compared to mono mode operation, the heat pump will run for lon-
ger due to its smaller size.
Dual mode operation
External heat source
The heat pump control unit enables dual mode operation of the heat
pump with an external heat generator, e.g. oil boiler.
The external heat source is hydraulically connected in such a way
that the heat pump can also be used as a return temperature raising
facility for the boiler. System separation is provided with either a low
loss header or a heating water buffer cylinder. For optimum heat
pump operation, the external heat source must be integrated via a
mixer into the heating water flow. Direct activation of this mixer by
the heat pump control unit results in a quick response.
The control unit enables operation of the external heat generator if
the outside temperature (long term average) is below the dual mode
temperature. Above the dual mode temperature, the external heat
generator only starts under the following conditions:
■ The heat pump fails to start due to a fault.
■ There is a special heat demand, e.g. frost protection.
The external heat source can also be enabled for DHW heating.
Note
The heat pump control unit does
not
contain any safety functions for
the external heat source. To prevent excessive temperatures in the
heat pump flow and return in case of a fault, high limit safety cut-outs
must be provided to stop the external heat generator (switching
threshold 70 °C).
Sizing the heat pump for
dual mode parallel
operation:
■ Size the heating output of the heat pump to approx. 70 to 85 % of
the maximum required building heat load to EN 12831.
■ The heat pump covers approx. 95 % of the annual heat load.
■ Blocking times do not need to be taken into consideration.
Note
The reduced size of the heat pump, compared to mono mode opera-
tion, means that the runtime will increase.
Determining the dual mode point
Air/water heat pumps are predominantly operated in
mono ener-
getic
mode. At low outside temperatures, the heat pump heating
output falls, but at the same time the heat demand rises.
For operation in mono mode, very large systems would be required
and the heat pump would be oversized for the majority of the run-
time.
*18
With a DHW cylinder heat-up time of 8 h.
*19
Select a higher supplement if the actual DHW demand exceeds the stated values.
Design information
(cont.)
118
VIESMANN
VITOCAL
7
5831388
