REMKO LWM 110, Инструкции по эксплуатации и монтажу, Страница: 32 / 64

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 32 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 capacity 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 outside temperature, that is,
the lowest outside 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 m
2
and a heating require-
ment of approx. 40 W/m 2 was selected. A total of
five persons live in the house. The heat load
amount to 6.0 kW. Adding a drinking water allow-
ance of 0.2 kW results in a required heating
capacity of 7.0 kW. Depending on the power com-
pany, 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
graphically from the heat pump’s inlet temperature
specific 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 outside-temperature-
dependent heating requirement, (Fig. 30) 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 heating
capacity on these days (in this example, the
required power required to cover peak load
requirements is approx. 3 kW).
Building type
Specific heating capacity in W/m
2
Passive energy house 10
Low-energy house built in 2002 40
According to energy conservation order regarding heat insulation
1995
60
Modern building constructed around 1984 80
Partially renovated old building constructed pre-1977 100
Non-renovated old building constructed pre-1977 200
REMKO LWM series
32