Wilo MVI 2..-6 Betriebsanleitung Seite 137

ENGLISH
Heating/air-conditioning installations
Connecting and disconnecting the peak-load pumps with FC
Connection and disconnection of the peak-load pumps is determined
by the deviations from the current setpoint set in menus 3.12 (S e)
and 3.13 (S a) and also by the delay times set in menus 3.14 (Te) and
3.15 (Ta).
In the event of a power failure all pumps shut down simultaneously. Only in emergency operation do all pumps start up simultaneously when
switched on.
Connecting and disconnecting the peak-load pumps in mains operation or with a defective FC
Without a frequency convertor the controller can only continue to function as a two-position controller.
The peak loads are controlled as in FC operation via the limiting values
for connection and disconnection, to be set in menu 3.12 (S e) and
3.13 (S a).
During pure mains operation the peak loads are delayed by the time
set in menus 3.14/3.15.
In mains stand-by operation because of an FC fault, peak load is
disconnected after 180 s.
Frequency convertor overload
Causes: defective convertor or pump running with flat system curve characteristic.
If the controller is running normally the next peak-load pump is connected when maximum capacity of the base-load pump and max. frequency
of the FC are reached. The convertor frequency follows the modified load of the base-load pump. If the FC remains in overload, the base-load
pump is deemed to be faulty and is blocked for operation at the FC.
In multi-pump installations with a flat characteristic curve it may be that the base-load pump does not provide the necessary delivery rate
because the requirement is too great. In this case the FC adjusts to max. frequency and max. current consumption.
The overload, is an excessive current consumption by the base-load pump, this can have two main causes, a hydraulic overload, or a defect
(blockage). With overload recognition the cause is determined automatically and the system reacts with the necessary steps as follows:
When the overload recognition is switched on in menu 2.08 the FC adjusts the motor down to the nominal current by lowering the frequency.
If f < 0.9 x f , there is an overload. If the FC remains in overload despite a peak-load pump being connected for an adjustable time
act set
(5 - 60 s), the base-load pump is faulty, and disconnected only remaining available as a peak-load pump. The controller then connects the next
pump to the FC. If all available pumps have been disconnected due to control faults, the FC itself is faulty or incorrectly adjusted and is blocked.
The controller then switches over to pure mains operation.
The pump at the convertor is also disconnected in the event of a convertor fault if the first peak-load connection has had no effect and the delay
times have expired.
The following applies regardless of whether the overload recognition is switched on: after switching on the supply voltage the message "ready
for operation" must appear after 15 s as an internal criterion. Otherwise the FC becomes faulty and is blocked. The fault must be acknowledged
(see Fitting and Operating Instructions for FC).
Pump swap (in multi-pump installations)
If the base-load pump would always start as the first pump, the load on it would be greater than the peak-load pumps. To distribute the running
times of the pumps evenly and thus prevent a pump from failing prematurely, the installation can be set to "Pump swap", i.e. after a set time
(menu 4.31 and 4.32) pump 2 takes over the base-load function. After a further period the sequence of the pumps which are switched
on consecutively moves on by one pump. If in menu 4xx no pump swap is activated, the system will execute a base-load pump swap with
each switch-off through EXT-OFF or Zero flow.
Times of low power requirements are therefore set in menu 4.29, "Pump swap".
When switching on the "running time optimization" menu (menu 2.25) a pump swap occurs if the difference in running time between the
base-load pump and another pump is greater than 24 hrs. This change-over is superimposed on the pump swap switch. The change-over can
also be initiated by remote control using the DDC board.
When connecting the peak-load pumps the pump with the shortest running time is always switched on first.
Pump swap cycle
In menu 2.29 a cyclic pump swap can be set between 5 min and 12 h. After the time setting a pump swap occurs if one motor is free. If this is
activated, the pump swap will no longer be displayed from menu 4.29.
Reserve pump (in multi-pump installations)
In the menu a pump can be reserved as a reserve pump or also released (menu 2.24). With reserve operation "ON" a pump is not incuded in
the operation of the base- or peak-load pumps. It is only switched on if a pump fails because of a fault. The reserve pump is however subject to
down-time monitoring and is included in the trial run. Since the sequence of base-load pump and the peak-load pumps that are connected one
after the other advances by one pump after each pump swap, each pump is the reserve pump once. The rotation pattern is also maintained
after the installation is switched off.
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Pressure-boosting installations
For the convertor, a frequency setpoint can be set for the time of
connection or disconnection of a peak-load pump in menu 3.25 and
3.26, separately for connection and disconnection. After connection
reference setpoint 1 or 2 is again set. A rise or drop in pressure should
be avoided at the change-over time. The peak-load pumps should
never start up simultaneously. To ensure that the pumps also start up
again consecutively following a power failure, a waiting time between
1 and 30 s can be set in menu 3.14/3.15.
The deviations from the setpoint required for connecting/disconnecting
the peak-load pumps according to the requirements of mains
operation with regard to control sensitivity are set in menu points
3.12/3.13.
Should the FC fail during mains operation the tolerance band for
the setpoint for connection is increased by a factor of 5, and for
disconnection reduced by a factor of 5, to avoid ragged switching.