Installation manual

166
6.7
6.7 Comparison of the Convenience and the Costs of Different Types of
Domestic Hot Water Heating Systems
6.7.1 Decentralized domestic hot water supply (e.g. continuous-flow heaters)
Advantages in comparison to heat pumps for
heating purposes:
a) Smaller investment
b) Minimal space requirement
c) Increased heat pump availability for space heating
(particularly in the case of monovalent operation and during
shut-off times)
d) Low water losses
e) No downtime losses or circulation losses
Disadvantages in comparison to heat pumps for
heating purposes:
a) Higher operating costs
b) Loss of comfort because the hot water temperatures are
dependent on the tap speed (in the case of hydraulic
devices)
6.7.2 Cylinder with electric immersion heater (off-peak electricity)
Advantages in comparison to heat pumps for
heating purposes:
a) Smaller investment
b) Higher hot water temperatures possible in the cylinder (but
often not required!)
c) Increased heat pump availability for space heating
(particularly in the case of monovalent operation and during
shut-off times).
Disadvantages in comparison to heat pumps for
heating purposes:
a) Higher operating costs
b) Only limited availability
c) Increased lime scaling possible
d) Longer heating-up periods
6.7.3 Domestic hot water heat pump
Advantages in comparison to heat pumps for
heating purposes:
a) A cooling or dehumidification effect can be produced at the
installation location (e.g. storage cellar) in the summertime
b) Increased heat pump availability for space heating
(particularly in the case of monovalent operation and during
shut-off times)
c) Easy integration of solar thermal systems
d) Higher hot water temperatures when only the heat pump is
in operation
Disadvantages in comparison to heat pumps for
heating purposes:
a) Considerably longer domestic hot water cylinder reheating
times
b) Heat output is normally insufficient if the domestic hot water
consumption is high
c) The installation room could become cold in the wintertime
6.7.4 Domestic ventilation unit with domestic hot water preparation
Advantages in comparison to heat pumps for
heating purposes:
a) Comfortable domestic ventilation to ensure hygienic air
circulation
b) Domestic hot water preparation using active year-round
heat recovery from exhaust air
c) Increased heat pump availability for space heating
(particularly in the case of monovalent operation and during
shut-off times)
d) Easy integration of solar thermal systems
e) Higher hot water temperatures when only the heat pump is
in operation
Disadvantages in comparison to heat pumps for
heating purposes:
a) Considerably longer hot water cylinder reheating times with
heat pump operation
b) Combination with a second heat generator is essential if the
hot water consumption is high
6.7.5 Summary
Heating domestic hot water with a heat pump is practical and
economical on account of the good performance factor.
Domestic hot water for normal usage should be prepared using a
domestic ventilation unit if living space ventilation is necessary or
desired. The installed air-to-water heat pump extracts the stored
energy in the exhaust air and uses it for year-round domestic hot
water preparation.
Electric hot water heaters can also be appropriate depending on
the tariff structure of the local utility company, the domestic hot
water consumption, the required temperature level and the
location of the extraction points.