Emerson Liebert CRV 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 C R 0 2 0 R A 1 C 7 S D 1 8 1 1 E L 1 0 P A - Manual (Page 47)

Electrical Connections
39 Liebert ® CRV ™
8.2 Protective Features of the Electrically Commutated Fans
The EC fans are protected against:
• Overtemperature of electronics
• Overtemperature of motor
• Locked rotor protection
• Short circuit at the motor output
When any of these failures occurs, the motor stops, electronically, with no potential for separation,
and the status relay is released.
The unit does not restart automatic automatically. To reset the alarm, the power supply must be
switched Off for 20 minutes once motor is at standstill.
• Input power undervoltage detection:
If the utility power falls below 3ph/290VAC (typical value) for 5 seconds or longer, the motor is
switched Off, electronically, with no potential for separation, and the status relay is released.
When the utility voltage returns to a correct value, the motor restarts automatically.
• Phase failure recognition:
If one phase fails for 5 seconds or longer, the motor is switched Off, electronically, with no poten-
tial for separation, and the status relay is released.
When all three phases return to correct values, the motor restarts automatically in 10 to 40 sec-
onds.
The power supply for an external speed-setting potentiometer is protected against short-circuiting.
The motor is overload-protected via motor current limitation.
8.3 Protective Features of Electrical Heaters
Figure 28 Electrical heating with temperature sensor protection
When the temperature sensor detects overtemperature of electrical heating, the thermal protection
turns Off the current. To reset the thermal protection, push the button on the front of the unit (see
Figure 28).
Temperature
sensor
protection