English
Installation and operating instructions Wilo-SC/SCe-HVAC
51
6.2
Function and operation
DANGER! Risk of fatal injury!
When working on the open switchgear, there’s a danger of electric
shock from touching the live components.
• The work must be carried out only by qualified personnel!
• Adhere to regulations for accident prevention!
NOTE:
After connecting the switchgear to the supply voltage, as well as after
every mains interruption, the switchgear returns to the operating
mode set before the power interruption.
6.2.1
Operating modes of the switchgear
Normal operation of SC switchgear
with frequency converter (FC)
(see Fig. 2)
An electronic signal transmitter (measurement range to be set in
menu 5.2.1.0) supplies the control variable actual value as a 4...20 mA
current signal. Then the controller holds the current control variable
constant by comparing the setpoint and the actual value (for setting
of the reference setpoint (see Fig. 2, item 1), see menu 1.2.1.1). If
there is no “external off” signal and no fault, at least the base-load
pump runs at minimum speed. If the power requirement rises, the
speed of the base-load pump is first increased. If the power require-
ment cannot be met by this pump, the control system switches on a
peak-load pump and, if the requirement increases further, other
peak-load pumps (activation threshold: see Fig. 2, item 2; can be set
individually for each pump; menu 1.2.2.3/5/7). The peak-load pumps
run at constant speed; the speed of the base-load pump is controlled
to the setpoint in each case (see Fig. 2, item 4).
If the requirement drops until the controlling pump is working in its
lower performance range and no peak-load pump is required any
longer in order to meet the requirement, then the peak-load pump
switches off (deactivation threshold: see Fig. 2, item 3; can be set
individually for each pump; menu 1.2.2.4/6/8).
Delay times can be set in the menus 1.2.5.2 and 1.2.5.3 for activation
and deactivation of the peak-load pump.
If the frequency converter has a fault, the switchgear behaves like
switchgear without a frequency converter (see next section).
Normal operation of SC switchgear
without frequency converter
(see Fig. 3)
An electronic signal transmitter (measurement range to be set in
menu 5.2.1.0) supplies the control variable actual value as a 4...20 mA
current signal. Because there is no possibility for load-sensitive speed
adaptation of the base-load pump, the system works as a two-point
controller and keeps the control variable in the range between the
activation and deactivation thresholds (menus 1.2.2.3 to 1.2.2.8).
These must be set in relation to the reference setpoint (menu 1.2.1.1).
If there is no “external off” signal and no fault, at least the base-load
pump runs. If the power requirement cannot be met by this pump, the
control system switches on a peak-load pump and, if the requirement
increases further, other peak-load pumps (activation threshold: see
Fig. 3, item 2; can be set individually for each pump; menu 1.2.2.3/5/7).
If the requirement drops until no peak-load pump is required any
longer in order to meet the requirement, then the peak-load pump
switches off (deactivation threshold: see Fig. 3, item 3; can be set
individually for each pump; menu 1.2.2.4/6/8).
Delay times can be set in the menus 1.2.5.2 and 1.2.5.3 for activation
and deactivation of the peak-load pump.
Normal operation of SCe switchgear
(see Fig. 3)
An electronic signal transmitter (measurement range to be set in
menu 5.2.1.0) supplies the control variable actual value as a 4...20 mA
current signal. Then the controller holds the control variable constant
by comparing the setpoint and the actual value (for setting of the ref-
erence setpoint (see Fig. 3, item 1), see menu 1.2.1.1). If there is no
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