124/238
Building Technologies
Modular Heating Controller RMH760B
CE1P3133en
HVAC Products
9 Heating circuit control
05.02.2007
To determine the heating limit (summer / winter operation), the attenuated outside
temperature is also required (see below).
The heating curve is determined by the 2 curvepoints at the design temperature and
the theoretical heating limit. Heat transmission in the space is not linear, however.
When there is a small differential between flow temperature and room temperature, the
ability of heat transmission decreases. This is taken into account by the heating curve.
The setpoint predefined by the heating curve can also be influenced by the following
factors:
•
The room temperature setpoint
•
The current room temperature (room temperature influence)
For more detailed information, refer to subsection 9.5.3 “Influences on the flow tem-
perature setpoint”.
9.5.1
The composite and the attenuated outside temperature
Identifiers used:
TO
Actual outside temperature
TOeff
Composite (effectively acting) outside temperature
TOfil
Outside temperature filtered with the building time constant
TOstrDmp Attenuated outside temperature
τ
Bldg
Building time constant
pWindow Proportion of windows in %
The composite outside temperature is made up of the actual 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.
The controller is supplied with the proportion of windows set to 50 % so that the com-
posite outside temperature represents the mean value of the actual and the 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
⇒
Attenuated outside
temperature
⇒
p
Window
= 50%
