REMKO CMF-80 v.2 - Manual (Page 7)

Layout
Building type
Specifi c heating
output in W/m 2
Passive energy house approx. 10
Low-energy house built in 2002 approx. 40
according to energy conservation order regarding heat
insulation 1995
approx. 60
Modern building constructed around 1984 approx. 80
Partially renovated old building constructed pre-1977 approx. 100
Non-renovated old building constructed pre-1977 approx. 200
The diagram with the heating ca-
pacity characteristics shows a sim-
plified linear heating requirement.
A connecting line is drawn from the
desired room temperature (20°C)
and the point where the average
low outdoor temperature (local low
for the year) and the heat require-
ment meets (in this case: -14°C and
7.4kW). The intersection of the two
curves are plotted on the X axis
and the temperature of the balance
point is read off. In this case it is
-5°C.
The size of the submersion tube
heater is the difference between
the maximum heat requirement on
the coldest days of the year and the
heating output on these days. In
the example, the required output is
7.4kW – 4.7kW = 2.7kW.
A residential home comprised of
160m² living-space and a heat
requirement of 40 W/m² has been
selected for the example design.
A total of five persons live in the
house. The heating load amounts
to 160m
2 40W/m 2 =6,400W. Add-
ing a drinking water allowance of
1 kW results in a required heating
power of 7.4kW.
The dimensioning of the heat pump
is given graphically on the diagram
below together with the outdoor-
temperature-dependent building heat
requirements and the heating capacity
characteristics for the heat pump.
A precise calculation of the build-
ing's heating load according to EN
12831 is required for the design
and dimensioning of a heating
system.
However, approximate require-
ments can be determined based
on the year of construction and
the type of building. The adjacent
table shows the approximate spe-
cific heating loads for a number of
building types. The required heat-
ing system output can be calcu-
lated by multiplying the area to be
heated with the given values.
Various factors have to be consid-
ered in order to achieve a precise
calculation.The transmission heat
requirement, the infiltration heat
loss and an allowance for water
heating comprise the total heating
output which has to be provided by
the heating system.
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, informa-
tion about the materials used in the
building is required, as these lead
to extremely varied thermal trans-
mission coefficients (the so called
K value). Also required is the room
temperature and the average low,
the lowest average outdoor tem-
perature of the year.
The formula for determining the
transmission heat requirement
isQ=A U (t
R
-T
A
) and this must be
calculated individually for the areas
surrounding all rooms.
The infiltration heat requirement
takes into consideration how often
the heated room air is exchanged
for cold external air. The room vol-
ume V, the air exchange frequency
n and the specific heat capacity of
the air is also required in addition to
the room temperature and average
low temperature. The formula for
this is Q=V n c (t
R
-t
A
).
An approximate allowance for wa-
ter heating per person amounts to
0.2 kW according to VDI 2067.
Temperature in °C
Bivalence point
Necessary additional
power
Heating capacity in kW
7