Siemens RVW26.000B27 Basic Documentation page 17

Control of the
actuators
Readiness contact
Siemens Building Technologies
HVAC Products
The programmed curves define the actuators' required positions depending on the
current «Load». Each actuator has a feedback potentiometer «P» that delivers the ac-
tual position signal.
The cables of the feedback potentiometers must be screened.
On the RVW26..., the shield must be connected to terminal «M».
The shield may never be connected to «PE».
The 3-position converters compare the setpoint with the actual value and pass appro-
priate positioning commands to the actuators.
AUX1(1)
Position
Load
Load
AUX1(2)
Position
Load
Fig. 11 Control of the actuators
:
Note
The positioning accuracy (neutral zone) of the 3-position converter is 40 mV.
The RVW26... selects the smallest positioning pulse such that the actuator makes a
movement of 40 mV (D position = 40 mV).
During normal burner operation and burner off periods, readiness contact «Q4 - Q5» is
closed.
Readiness contact «Q4 - Q5» opens:
·
When the RVW26... detects inadmissible states at its inputs or outputs
·
When the RVW26... detects a fault while performing the self-tests
·
When the RVW26... is not live
· After a reset or after switching on the RVW26... as long as the unit performs the
self-tests
This contact must be included in the burner control's control loop, thus ensuring that the
burner can be started only when no fault is signaled by the RVW26...
If the plant shall lock itself when the RVW26... detects a fault, the readiness contact
must be included in the burner's locking loop (refer to chapter «Functional readiness
and faults»).
Note:
When readiness contact «Q4 - Q5» is open, «Q4» is connected to «H» and signals
nonreadiness or a fault of the RVW26... when contact «H» is sensed.
RVW26... by a short removal of power, contact
During this period of time, the RVW26... makes a self-test. If successful,
(also refer to section «Function description of power ON and reset»).
Electronic Air / Fuel Ratio Control System
5 Description of functions
Position
78731d03/0601
«H» remains active for about 2 seconds.
Y3
P
M
Y4
B2
After resetting the
«Q4 - Q5»
closes
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CC1P7873.1en
15.10.2002