Siemens RVW26.000B27 Basic Documentation page 25

Legend
Impact of the cor-
recting variable on the
amount of excess air
Siemens Building Technologies
HVAC Products
Fig. 14 shows how a correcting variable signal at «X2» produces a change in fan speed
via the «AUX1» curve.
Load Load signal without the correcting variable
Load´ Load signal for the fan speed
Position Position of auxiliary actuator with correcting variable «X2 = 0»
D Pos Change of actuator position due to correcting variable «X2 > 0»
X2 Correcting variable
DISTURB Programmable influencing factor (maximum correction)
Setload Load signal without the correcting variable
Setload´ Load signal for the actuator position
DISTURB
Setload'
X2 X2'
Setload
Fig. 14 Impact of the correcting variable signal on the actuator position
Note:
To ensure the impact of the correcting variable on the volumetric airflow is large
enough, the load displayed by the RVW25... must correspond to the real burner output.
Correcting variable signal at
«X2»
«X2» not connected
«X2» = 0 V
«X2» rises
«X2» = 9.8 V
«X2» = 10 V
Note:
If the value of the correcting variable signal «X2» constantly exceeds 9.8 V for more
than 30 seconds, the RVW25... and RVW26... interprete this as a fault (e.g. short-
circuit). In that case, the correcting variable is not taken into consideration, which
means that a maximum amount of excess air will be delivered. However, readiness
contact «Q4 - Q5» does not open, so that no lockout will be initiated. As a warning, the
display of the unit will flash. If steep slopes and / or a large correcting effect is pro-
grammed on the RVW26..., lockout with code «-56» can occur. The correcting variable
becomes active
below 8 V.
When feeding a correcting variable signal to «X2», screened cable should be
used, whereby one end of the screen must be connected to terminal «M» of the RVW25...
Electronic Air / Fuel Ratio Control System
5 Description of functions
Position [V]
Position
D
Pos
Impact on excess air
No impact = maximum amount of excess air
No impact = maximum amount of excess air
Impact increases, amount of excess air diminishes
Maximum impact = minimum amount of excess air
Maximum impact, but will be interpreted as a fault after 30
seconds, which automatically sets the impact to 0 (= maxi-
mum amount of excess air)
again when the
AUX1
Load [%]
Load' Load
78731a02e/1001
voltage «X2»
CC1P7873.1en
15.10.2002
Set
posit.
Actual
posit.
drops
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