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Building Technologies
Boiler Sequence Controller RMK770
CE1P3132en
HVAC Products
10 Heating circuit control
01.03.2005
The controller provides a common outside temperature for all applications. This means
that outside temperature-dependent functions of the same controller operate with the
same outside temperature as the compensating variable.
Depending on the type of building construction, the outside temperature has a delayed
impact on the room. For this reason, the compensating variable used by the heating
curve is not the actual but a composite outside temperature.
To determine the heating limit (summer / winter operation), the attenuated outside tem-
perature is required (refer to section below).
The heating curve is defined by the 2 curvepoints at the design temperature and the
theoretical heating limit. Heat transmission in the space is not linear, however. When
the difference between flow temperature and room temperature is small, the rate of
heat transmission diminishes. This is considered by the heating curve.
The setpoint predefined by the heating curve can additionally be influenced by the
following factors:
•
Room temperature setpoint
•
Current room temperature (room temperature influence)
For more detailed information, refer to subsection 10.6.3 “Influences on the flow tem-
perature setpoint”.
10.6.1 The composite and the attenuated outside temperature
Identifiers used:
To Outside
temperature
Toeff Outside
temperature
Tofil
Outside temperature filtered with the building time constant
ToStrDmp Outside
temperature
τ
Bldg
Building time constant
p
Window
Proportion of windows in %
The composite outside temperature is made up of the current outside temperature To
and the outside temperature Tofil filtered with the building time constant
τ
Bldg. The
proportion of windows p
Window
(adjustable from 0…100 %) determines the proportions
with which the 2 temperatures are considered.
The composite outside temperature is used for the heating curve and the heating limit.
To obtain the attenuated outside temperature, the actual outside temperature To is
filtered twice with the building time constant
τ
Bldg.
p
Window
100-p
Window
+
+
Toeff
ToStrDmp
Tofil
100
100
To
τ
Bldg
31
31
B
0
8
τ
Bldg
For the heating limit, the actual, the composite and the attenuated outside temperature
are considered.
Composite outside
temperature
Attenuated outside
temperature
Heating curve
Other influences
Composite outside
temperature
⇒
Outside temperature
⇒