Xylem 2 Pump Booster Sets GXS20, GMD20, GMY20 - Manual (Page 17)

Single-Phase Version
The motor is protected against overload by a built-in motor protector. If required by local codes, install an
additional protection device. Suitable cable of appropriate gauge must be connected to the panel :
- L1 and N to the main switch terminals
- PE to the ground terminal marked
Three-Phase Version
The motor is protected against overload by an automatic manual reset switch. Suitable cable of appro-
priate gauge must be connected to the panel :
- L1, L2, L3 to the main switch terminals
- N, to the neutral terminal, if provided.
- PE to the ground terminal marked
5. Settings
DANGER
RISK OF
ELECTRIC SHOCK
Disconnect the power supply before making any adjustments.
Operation
The starting and stopping of the pumps are determined based on the pressure switch settings. Each
pressure switch is connected to a single pump, though the pump will change according to cyclic chan-
geover.
The pressure differential is the difference between the starting and stopping pressures. Set the same dif-
ferential pressure for both pumps.
The typical value of P1s is approx. Pmax-0.5 bar. The typical value of the differential (P1s-P1) is 0.6-1.0 bar.
The typical value of P2s is approx. Pmax-1.0 bar
Figure 3 shows the operating method
- The tank supplies water upon demand by a user.
- When the pressure drops to the P1 value, the first pump is
started.
- If the demand increases and the pressure drops to the P2
value, the second pump is started.
- When the demand decreases and the pressure rises to the
P2s value, one of the pumps is deactivated.
- If the demand decreases further, the pump fills the tank
and then stops when the P1s value is reached
Pressure switch
The pressure switches are set at the factory according to values that
depend on the type of pump.
The settings are shown on a plate attached to the set or the electrical
panel.
The settings can be modified according to the hydraulic conditions of
the system and the suction pressure.
Make the required adjustments to the pressure switch to modify the
settings :
- Stop pressure Ps
- Differential pressure Ps-P
Adjustment of the differential pressure determines the start pressure P.
1 Ps stop pressure
2 Ps-P differential pressure
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