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Building Technologies
Boiler sequence controller RMK770
CE1P3132en
HVAC Products
10 Heating circuit control
23.04.2009
To determine the heating limit (summer / winter operation), the attenuated outside
temperature 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)
10.5.1 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 to 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.
The controller is supplied with the proportion of windows set to 50% so that the com-
posite outside temperature represents the mean value of actual and filtered outside
temperature.
It is calculated as follows:
Toeff = (0.5 × To) + (0.5 × Tofil)
Attenuated outside
temperature
Heating curve
Other influences
Composite outside
temperature
⇒
Outside temperature
⇒
p
Window
= 50%
