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9.2.2 Standby pumps
This function is optional and available on request. The function
makes it possible to limit the maximum performance of the
booster system 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.
9.2.3 Maximum pressure exceeded
This function protects the piping on the outlet side of the booster
system against damaging high pressures. The pressure is
monitored, and if the pressure is higher than 22 psi (1.5 bar)
above the setpoint for more than 5 seconds, the pumps are
stopped, the indicator light "PT" is on, and the display indicates
high limit "H.L".
When the pressure falls below the setpoint, the system will
automatically restart.
9.2.4 Low-flow operation
When only one pump is operating due to cascade, the booster
system regularly checks for low flow by decreasing the pump
speed.
When low flow is detected, the booster system will change its
mode of operation to "low-flow operation" and run in on/off mode
as described below.
In on/off mode, the system has two phases:
•
Off phase
Water is drawn from the diaphragm tank until the pressure of
the system reaches the lower limit of the on/off band (Pset -
0.5 x on/off band).
•
Boosting phase
The pump runs at 100 % speed until the pressure reaches the
upper limit of the on/off band (Pset + 0.5 x on/off band).
A: Normal operation
B: Pressure boosting
C: Stop
H [m]
A
B
C
Stop
Start
Stop: Hset + 0.5 x on/off band
Start: Hset - 0.5 x on/off band
Fig. 11 On/off operation
16
B
C
Time [s]
9.2.5 S-system mode (start/stop band)
S-system mode is only auto-enabled in an ES system if the CME
pump is out of operation due to a fault.
H [m]
Pump stops
Start/stop band
Hset
Pump starts
Time [s]
Fig. 12 Start/stop band
9.2.6 Proportional-pressure control mode
The proportional-pressure control mode is only available for
E-pump systems.
Description
You can only enable this function in pressure-controlled systems.
The function automatically adapts the setpoint to the actual flow
rate to compensate for flow-dependent dynamic losses.
The adaptation can only be square. See fig. 13.
A filter factor can be set to prevent fluctuation.
H
C
A
Fig. 13 Proportional pressure
Pos.
Description
Pressure at zero flow.
A
Starting point of proportional-pressure control.
Influence at zero flow is equal to x % of the setpoint.
B
Qnom
C
Setpoint
The function has these purposes:
•
compensate for pressure losses
•
reduce the energy consumption
•
increase the comfort for the user.
B
Q
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