REMKO HTS 90 ALU - Manual (Page 30)

Heat pump operating mode
Heat pumps can work in various operating modes.
Monovalent
The heat pump the only source of heat for a
building all year round. This mode is particularly
suitable for heating plants with low supply-water
temperatures and is primarily used in combination
with brine/water and water/water heat pumps.
Monoenergetic
The heat pump has an E-heater to handle peak
loads. The heat pump covers the majority of the
required heating power. Occasionally, when it is
extremely cold outside, an electrical booster-
heating system switches on as required in order to
support the heat pump.
Bivalent alternative
The heat pump provides the entire heating energy
down to a predetermined outdoor temperature. If
the ambient temperature drops below this value, a
second heat source switches on to support the
heat pump, which shuts down at this point. At this
point, a distinction is made between alternative
operation with oil or gas heating and regenera-
tive operation with solar energy or wood heating.
This operating mode is possible for all heating sys-
tems.
Layout
A precise calculation of the building's heating load
according to EN 12831 is required for the design
and dimensioning of a heating system. However,
approximate requirements can be determined
based on the year of construction and the type of
building. This table Ä on page 31 provides an
approximate specific heating load for a few types
of building. The required heating system output
can be calculated by multiplying the area to be
heated with the given values.
For a precise calculation, various factors must be
considered. The transmission-heat requirement,
the infiltration heat-loss and an allowance for water
heating comprise the total heating output which the
heating system must provide.
The total area of the floor surfaces, exterior wall
windows, doors and roofing is required in order to
determine the transmission heat requirement. In
addition, information about the materials used in
the building is required, as well as about the dif-
ferent thermal transmission coefficients (known as
the K value). Also required are the room tempera-
ture and the standard outdoor temperature, that is,
the lowest outdoor-temperature on average that
will occur during the year. The equation for deter-
mining the thermal transmission requirement is
Q=A x U x (t
R
-t
A
) and must be calculated for all
enclosed room floor areas.
The infiltration heat requirement takes into consid-
eration how often the heated room air is
exchanged for cold external air. The room volume
(V), the air exchange frequency (n) and the spe-
cific heat capacity (c) of the air is also required in
addition to the room temperature and average low
temperature. The equation is: Q=V x n x c (t
R
-t
A
)
An approximate addition for the preparation of
domestic water per person amounts in acc. with
VDI 2067: 0.2 kW.
Design example
By way of a design example, a residential home
with a living area of 150 m² and a heating require-
ment of approx. 80 W/m² was selected. A total of
five persons live in the house. The heat load
amount to 11.5 kW. Adding a drinking water allow-
ance of 0.2 kW results in a required heat output of
12.5 kW. Depending on the power company, an
additional charge must then be made in order to
factor in any service time-out periods that may
apply. The rating and determination of the heat
pump's balance-point temperature derives graphi-
cally from the heat pump's inlet temperature-speci-
fication heat-output diagram (in this example 35°C
for underfloor heating). Next, the heat load for the
standard outdoor temperature (the lowest tempera-
ture of the year locally) and the heat threshold are
marked on the graph. The outdoor-temperature-
dependent heating requirement, (Fig. 9) simplified
here as a straight-line relationship between heat-
load and the start of the heating season, is
recorded in the graph of heat-load curves. The
intersection of the two straight lines with the rated
heat-load curve is plotted on the X axis, where the
balance-point temperature is read (in this example
approx. -3°C). The minimum performance of the
2nd heat source is the difference between heat
load and the heat pump's maximum heat output on
these days (in this example, the required power
required to cover peak load requirements is
approx. 3 kW).
REMKO HTS
30