Eng
lish (US)
14
10. Functions
Hydro Multi-B booster systems include application-optimized
software.
10.1 General functions
10.1.1 Dry-running protection (pressure switch on suction
standard)
To protect the pumps against damage from dry running, the Hydro
Multi-B incorporates a water shortage function. This function is
based on the monitoring of the inlet pressure or the level in a tank
on the suction side.
The pressure or level can be monitored by one of the following:
•
pressure switch (standard)
•
float switch
•
level switch
•
external electrode relay
•
analog sensor.
Dry-running protection with pressure switch, float switch,
level switch or external electrode relay
Set the monitoring device to the desired limit.
If water shortage is detected for more than 5 seconds, the system
will stop, and the
indicator light illuminates.
Press
when the water supply has been re-established.
Dry-running protection with analog sensor
The limit for the minimum inlet pressure in the suction manifold is
a factory-set value which can only be changed by a Grundfos
service engineer using PC tools.
If the sensor output is below the limit for minimum inlet pressure
for more than 5 seconds, the system will stop, and the
indicator light illuminates.
Press
when the water supply has been re-established.
10.1.2 Automatic pump changeover
The automatic pump changeover function ensures an equal
number of operating hours of the pumps, but it also ensures that,
in case of an alarm on one pump, another pump is automatically
started.
There are three types of automatic pump changeover:
•
operation-dependent pump change
•
alarm-dependent pump change
•
time-dependent pump change.
Operation-dependent pump change
At increasing demand, the pump with the lowest number of
operating hours will be started first.
At decreasing demand, the pump with the highest number of
operating hours will be stopped first.
Alarm-dependent pump change
If a pump stops due to an alarm, the CU 323 will send a stop
command to the pump to prevent auto-restarting and start
another pump which is ready to start and which has the lowest
number of operating hours.
Time-dependent pump change
In certain applications, the demand remains constant for long
periods and does not require all pumps to run. In such situations,
pump changeover does not take place naturally, and forced pump
changeover may thus be required.
Once every 24 hours, the CU 323 checks if any of the running
pumps has a higher number of operating hours than the pumps
that are stopped. If this is the case, the pump will be stopped, and
a pump with a lower number of operating hours will start.
10.1.3 Minimum time between start and stop
This function ensures a delay between the start/stop of one pump
and the start/stop of another pump. The purpose is to prevent
hunting when pumps start and stop continuously.
10.2 Functions for constant-pressure systems
10.2.1 Pump cascade control
The cascade function ensures that only the required number of
pumps is running. This means that the number of running pumps
always corresponds to the required flow at the entered setpoint.
The first pump is started if the pressure at the discharge manifold
is below the setpoint.
If the first pump is not able to keep the discharge pressure at the
setpoint, and the minimum time between start/stop has passed,
another pump is started.
During the start and stop of a pump, the speed of the speed-
controlled pump is controlled in such way that the pressure
disturbance is kept as low as possible.
At decreasing demand, pumps will be stopped if the pressure
rises above the setpoint. Pumps will not be stopped until the
minimum time between start/stop has passed.
The last pump in operation
If only one pump is operating, this pump can be operated in
energy-saving on/off mode.
See section
.
The number of possible starts/stops per hour for all pumps is
limited by the maximum number of starts per hour.
10.2.2 Standby pumps
This function is optional and available on request. The function
makes it possible to limit the maximum performance of the Hydro
Multi-B by selecting one or more pumps as standby pumps.
If a three-pump system has one standby pump, maximum two
pumps are allowed to operate at a time.
If one of the two pumps in operation has a fault and is stopped,
the standby pump will be started. The performance of the booster
system is thus not reduced.
The status as standby pump alternates between all pumps.
Contact Grundfos for further information.
Caution
When a pump is running in "Emergency" mode, it
is not protected against dry running.
WS
RESET
WS
RESET
Note
Note
If the system is stopped due to an alarm, the
minimum time between start and stop will be
ignored, and the pumps will be stopped
immediately.
