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Siemens Building Technologies Electronic Air / Fuel Ratio Control System CC1P7873.1en
HVAC Products 5 Description of functions 15.10.2002
5.3 Burner operation
To generate the set load signal, the reliable «X1» signal (DC 0...10 V) of the RVW25...
is used.
To offset tolerances, the set load signal is also delivered via digital interface «TxD» and
«RxD» of the RVW25.000B27 to the RVW26.000B27.
The fan speed will be changed as demanded by the RVW25...
Setload
Setload
t
RVW25.000B27
Integrator
U1
U1 0...10 V
Load
X1
t
78731o01/0601
RVW26.000B27
TxD
RxD
RxD
TxD
Fig. 9 Set load
The actuators must be able to follow the fan motor with no delay.
As a basic rule, the running time of the actuators should be 50 % of the variable speed
drive’s ramp time.
This means that the rate of load change is largely dependent on the ramp time of the
variable speed drive.
Should the RVW26.000B27 not be able to follow the load change of the
RVW25.000B27, a stop signal will be sent to the RVW25.000B27, which stops the load
change until the RVW26.000B27 delivers a go signal again.
The actuator positions are determined via the programmable load / position curves and
the set load signal.
In the operating position, this signal is available as an analog DC 0...10 V signal at out-
put terminal «X1» for external use (also refer to section «Load signal output X1»).
Note:
The possibility of stopping the RVW25... in normal operation via the data interface
works reliably only if the AZW20...is not connected.
Set load
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