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Siemens Building Technologies Electronic Air / Fuel Ratio Control System CC1P7873.1en
HVAC Products 5 Description of functions 15.10.2002
5.2 Startup
Burner control
LKA
LKM
QUIT
BV1
LR
G
RVW25
Q2 = 230 V
+ RVW25
Q1 = 230 V
+ RVW25
Q1 = 230 V
LR
RVW25
X1
78731f02e/1201
RVW26... indicates it is ready to
start when Q1 = AC 230 V
RVW26... identifies burner startup
Sets Q1 = 0 V
End switch test of actuators:
All actuators are briefly driven toward
fully open and are then closed again.
If test is successful, all actuators will
open
Full opening of all actuators is
indicated when Q1 = AC 230 V
Sets Q1 = 0 V
Drives actuators to the ignition
position
Indicates that these positions are
reached when Q1 = AC 230 V.
Starts the set interval
«INTERVA»
and indicates to the RVW25...
that burner operation (Q2 = AC 230 V)
has been detected (Y8 = AC 230 V)
INTERVA
On completion of
«INTERVA»,
the actuators are driven to the ratio
control positions as quiquly as possible.
That position can be different from the
ignition load position. The RVW26...
has thus reached its operating position.
The signal at terminal
«U1» will be
interpreted as a controller signal to
be passed on to the actuators
The digital signals at TxD and RxD are
used for optimizing the dynamic
behavior of air / fuel ratio control
RVW26 Display
Q1
Q3
Y10
Y20
Q1
Q2
U1
-0.-
-1.-
-2.-
-3.-
-4.-
-5.-
-6.-
-7.-
.
Y8
QUIT
+ RVW25
Q1 = 230 V
Q1
QUIT
When control contact
«R»
in the start control loop closes,
the burner control initiates its
startup sequence:
Startup
Delivers positioning command
to open the actuators.
Starts prepurge time
«t1»
Prepurging
«t1»
On completion of «t1»:
Delivers positioning command
to close the actuators until
ignition load is reached.
Continues with its program:
Opens the first fuel valve and
starts interval
«t4»
.
t4
On completion of
«t4», the
second fuel valve opens (if
present). After another
interval, the load controller
will be released.
TxD
RxD
RxD
TxD
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