Functions; General Functions; Functions For Constant-Pressure Systems - Grundfos Hydro Multi-B Instrucciones De Instalación Y Funcionamiento

11. Functions

Hydro Multi-B booster systems include application-optimised
software.

11.1 General functions

11.1.1 Dry-running protection (optional)
When a pump is running in manual mode, it is not
Caution
protected against dry running.
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 possible tank on the suction side.
The pressure or level can be monitored by one of the following:
• pressure switch
• 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.
WS
Press when the water supply has been re-established.
RESET
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.
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.
RESET
11.1.2 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
In an ES-system, the CME pump has higher priority than the
mains-operated pumps and will always be the first pump to start
and the last to stop. The mains-operated pumps in an ES-system
will operate alternately as described above.
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.
If the CME pump in an ES-system is stopped due
to an alarm, the system will function as an
Note S-system.
See section 11.2.5 S-system mode (start/stop
band).
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.
11.1.3 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.
If the system is stopped due to an alarm, the
minimum time between start and stop will be
Note
ignored, and the pumps will be stopped
immediately.

11.2 Functions for constant-pressure systems

11.2.1 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.
WS
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 11.2.4 Low-flow operation.
The number of possible starts/stops per hour for all pumps is
limited by the maximum number of starts per hour.
11.2.2 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.
11.2.3 Maximum pressure exceeded
This function protects the piping on the discharge side of the
booster system against damaging high pressures. The pressure
is monitored, and if the pressure is higher than 1.5 bar above the
setpoint for more than 5 seconds, the pumps are stopped, the
indicator light
H.L
.
When the pressure falls below the setpoint, the system will
automatically restart.
PT illuminates, and the display indicates high limit
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