Sizing The Heat Pump; Mono-Mode Operation - Viessmann VITOCAL 300-G Technical Manual

Design information
Example:
3
System version 6b: Heating circuit without mixer A1, heating circuit
with mixer M2, DHW cylinder, heating water buffer cylinder

3.5 Sizing the heat pump

Note
Sizing is of particular relevance to heat pump systems that are to be operated in mono-mode, since oversized equipment will incur dispropor-
tionate system costs. Therefore avoid oversizing!
First establish the standard heat load of the building Φ
sions with customers and for the preparation of a quotation, in most
cases estimating the heat load is adequate.

Mono-mode operation

According to DIN EN 12831, the heat pump system in mono-mode
must, as sole heat source, be able to cover the entire heating demand
of the building.
When sizing the heat pump, observe the following:
■ Take supplements to the heat load of the building to cover power-
OFF periods into account. [In Germany] the power supply utility may
cut off the power supply to heat pumps for up to 3 × 2 hours within
a 24 hour period.
Observe additional individual arrangements for customers with spe-
cial tariffs.
■ The building inertia means that 2 hours of power-OFF periods are
not taken into consideration.
Note
However, the "enable time" between power-OFF periods must be at
least as long as the preceding power-OFF period.
Estimate of the heat load based on the heated area
The heated surface area (in m
heat demand:
Passive house
Low energy house
New build (to EnEV)
House (built prior to 1995 with standard thermal insu-
lation)
Older house (without thermal insulation)
VIESMANN
34
(cont.)
. For discus-
HL
2 ) is multiplied by the following specific
10 W/m
40 W/m
50 W/m
80 W/m
120 W/m
For further examples, see "Heat pump system examples".
As with all heating systems, determine the standard heat load of the
building in accordance with DIN EN 12831 before selecting the appro-
priate heat pump.
Theoretical sizing with the power supply blocked for 3 × 2 hour
periods
Example:
For a new building with good thermal insulation (50 W/m
heated area of 170 m 2
■ Estimated heat load: 8.4 kW
■ Maximum blocking time of 3 × 2 hours at a minimum outside tem-
perature in accordance with DIN EN 12831
24 h, therefore, result in a daily heat volume of:
■ 8.4 kW ∙ 24 h = 202 kWh
To cover the maximum daily heat amount, only 18 h/day are available
for heat pump operation on account of the power-OFF periods. The
building inertia means that 2 hours of the period during which power
is blocked are not taken into consideration.
■ 202 kWh / (18 + 2) h = 10.1 kW
In other words, the heat pump output would need to be increased by
20 %, if power-OFF periods of 3 × 2 hours per day were to be
applied.
Frequently, power-OFF periods are only invoked if there is a need to
2
do so. Please contact the customer's power supply utility to enquire
2 about power-OFF periods.
2
2
2
2
) and a
VITOCAL 300-G