8.3.6
Mixed air temperature control (MAT)
The mixed air temperature controller is activated by feeding the mixed air
temperature signal to the HR block (HREC). With the help of the mixing dampers,
the mixed air temperature is controlled to an adjustable setpoint.
Activation
AO
°C
.X...
.Y...
AI
M
M
M
T
w
Y
Q
0 %
100 %
Y
y1 y2
x x
HR
EC
....................
x
IN
X
Cooler
HREC
ME
CH
1
ME
CH
2
x
MA
T
31
50
S
43
de
The startup circuit or MECH, if configured, act on the controlling output with higher
priority.
Note
8.3.7
Startup circuit
The startup ciruit for air dampers is activated by entering a value >0.00 for “Startup
time”.
Activation
The purpose of the startup circuit is to prevent the air heating coils from freezing up
by first opening the air damper with a certain delay, then it opens steplessly.
Purpose
If an outside temperature signal is available, the startup circuit is active only when
the outside temperature lies below 15 °C. At outside temperatures above 15 °C, the
plant is started up without making use of the startup circuit. If no outside
temperature signal is available, the startup circuit is always active, provided the
startup time entered is > 00.00.
When the plant is started up, the air damper operates according to the following
diagram:
70 / 174
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