Technical data

Heating and Cooling with a Single System 3.3.2
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3 Heating and Cooling with a Single System
3.1 Energy-Efficient Operation
In the same way that national standards demand building and
system-specific measures for reducing the heating energy
consumption, measures should also be taken to save energy by
thermally insulating buildings for the warm summer months.
Cooling loads in any room that can nevertheless not be avoided
using such measures can be discharged by introducing cooled
air, by cooling the air using a heat exchanger installed in the
room or by directly cooling structural parts of the building.
NOTE
In order to increase effectiveness, dimensioning of the combined heating
and cooling system should be implemented with heating water
temperatures that are as low as possible and cooling water temperatures
that are as high as possible.
3.2 Hydraulic Integration of a Combined Heating and Cooling System
In heating operation, the heat output generated by the heat pump
is transferred to a water-bearing pipe system via the circulating
pump. Switching to the cooling mode transfers the generated
refrigerating capacity to the heat distribution system which is also
designed for distributing cold water (see Chap. 8 on p. 52).
Making double use of the distribution system reduces the
additional investment costs for cooling.
Depending on the type of cooling distribution system installed,
cooling water flow temperatures can be reduced to a minimum of
approx. 16 °C to 18 °C for surface cooling systems and approx.
8 °C for fan convectors.
ATTENTION!
A combined heating and cooling system must be insulated to prevent the
formation of moisture in cooling operation. The pipes require insulation
resistant against vapor diffusion.
3.3 Dynamic Cooling
The indoor air flows through a heat exchanger in which the
cooling water is circulating. The use of flow temperatures below
the dew point enables the transfer of greater cooling capacities
by reducing the sensitive stored heat in the indoor air and
simultaneously dehumidifying it by producing condensate (latent
heat).
NOTE
A climate controller which has particular requirements regarding the
humidity in a room can only be used in combination with an air-
conditioning system with active humidification and dehumidification.
3.3.1 Fan convectors
Fan convectors that are designed as case, wall or cassette
devices offer the option of dynamic cooling using a
decentralized, modular system. Integrated ventilators ensure
multi-level controllable air recirculation, variable cooling
capacities and short response times. Fan convectors are not only
used solely to cool the air, they can also be used for combined
heating and cooling.
The cooling capacity of a fan convector is essentially dependent
on the size, air volume flow, the relative humidity of the ambient
air as calculated in the design, and the cooling water flow
temperature and spread. If the requirements in the DIN 1946 T2
standard are taken into consideration when the device is
dimensioned, specific cooling capacities ranging from 30 to 60
W/m
2
are feasible. By following the standard practice of
dimensioning the device for a medium fan level, the user has the
option of reacting quickly to varying heat loads (fast fan level).
NOTE
To ensure the minimum water flow rate through the chiller for all possible
operating conditions, we recommend the use of fan convectors. These
regulate using different fan levels, but do not reduce or block the water
flow.
Fig. 3.1: Fan convector for heating and cooling
3.3.2 Cooling with Ventilation Systems
Besides dissipating heat loads, the required minimum air
exchanges must also be ensured during cooling. A controlled
domestic ventilation unit is a useful supplement to the cooling
and can permit a defined exchange of air.
If necessary, the fresh air flow can be heated or cooled using so-
called heating and cooling coils.