5.11 Measuring instruments
5.11.1 Pressure gauge and mano-vacuum gauge
To ensure continuous monitoring of the operation, we recommend
that you install a pressure gauge on the outlet side and a mano-
vacuum gauge on the inlet side. The pressure gauge tappings must
only be opened for test purposes. The measuring range of the
gauges must be 20 % above the maximum pump pressure.
When measuring with pressure gauge on the pump flanges, note
that a pressure gauge does not register dynamic pressure.
On all pumps, the diameters of the inlet and outlet flanges are
different which results in different flow velocities at the two flanges.
Consequently, the pressure gauge on the outlet flange will not show
the pressure stated in the technical documentation, but a value
which may be up to 22 PSI (1.5 bar) or approximately 50 ft (15 m)
of head lower.
5.11.2 Ammeter
We recommend connecting an ammeter to check the motor load.
6. Electrical connection
The electrical connection must be carried out by a qualified
electrician in accordance with local regulations.
DANGER
Electric shock
Death or serious personal injury
‐ Before removing the terminal box cover, and before
removing or dismantling the pump, make sure that the
power supply has been switched off and that it cannot
be accidentally switched on again. Use lockout-tagout
if available. The pump must be connected to an
external main switch.
DANGER
Explosive environment
Death or serious personal injury
‐ Whenever powered equipment is used in explosive
surroundings, the rules and regulations generally or
specifically imposed by the relevant authorities or
trade organizations must be observed.
The operating voltage and frequency are stated on the nameplate.
Make sure that the motor is suitable for the power supply of the
installation site.
The electrical connection must be carried out as shown in the wiring
diagram inside the terminal box cover.
6.1 Voltage and frequency variation
The motor will operate satisfactorily under the following voltage and
frequency variations, but not necessarily in accordance with the
standards established for operation under rated conditions:
• The voltage variation must not exceed 10 % above or below the
rating specified on the motor nameplate.
• The frequency variation must not exceed 5 % above or below
the motor rating.
6.2
Motor protection
DANGER
Automatic startup
Death or serious personal injury
‐ Before starting any repair work on motors
incorporating a thermal switch or thermistors, make
sure that the motor cannot restart automatically after
cooling.
Three-phase motors must be connected to a motor-protective circuit
breaker. The electrical connection must be carried out as shown in
the wiring diagram on the back side of the terminal box cover.
6.3
Synchronous motors
Pumps fitted with synchronous motors must be connected to a
Grundfos CUE frequency converter.
TM044289
Example of installation without filter
Symbol Designation
1 CUE
4 Standard motor
One line Unscreened cable
Double line Screened cable
Synchronous motors must not be connected directly to
mains supply.
The CUE must be of T/C CUE203 followed by additional numbers
and characters. See the CUE Installation and operating instruction
to setup frequency driver together with synchronous motor.
If another frequency driver brand other than CUE is required or
specified, contact Grundfos.
T/C: CUE203 P1M2T5E20H1BXCXXXSXXXXAXBXCXXXXDX
IN: 3x380-500 V 50/60Hz 3.7A
OUT: 3x0-Vin 0-100Hz 4.1 A 2.8 kVA
CHASSIS/IP20 Tamb. 45C/122F
IIIIIIIIIIIBAR CODEIIIIIIIIIII
Listed 76X1 E134261 Ind. Contr. Eq.
STORED CHARGE DO NOT TOUCH UNTIL
TM077181
Example of CUE nameplate
Text description
T/C
CUE (product name)
203... (internal code)
21
English (US)
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