I-Gard MGFR Series, Instruction Manual

DANGER

THE FOLLOWING APPLIES ONLY TO QUALIFIED PERSONNEL:

Hazard of electrical shock, fi re or explosion. All installation, servicing and testing 

referred to in this manual must be performed by qualifi ed personnel. All power should 

be disconnected prior to removing covers or enclosures and where live conductors 

may otherwise be exposed.

Failure to observe these precautions will result in death or severe personal injury.

The MGFR is designed with solid state electronics to ensure long-term trouble-free operation. Since a relay is 
an intermediate device between a current sensor and a circuit breaker, any malfunction of the breaker during a 
fault may not necessarily be attributed to the relay. If any abnormal behaviour is noted, it is better to perform the 
SELF TEST operation, including breaker trip operation. This will help to determine which of the three devices is 
responsible for the problem. The following sections outline some problems and their
probable causes, and suggest appropriate corrective action.

7.2.1 FAILURE TO TRIP

Failure of the circuit breaker to trip in response to a fault may be caused by any of the reasons below:

a) Relay set too high - Check that the pick-up settings on the relay are correct.
b) Supply not grounded or neutral grounded on the downstream side of the main sensor.
c) ZSCT improperly connected - Check that all connections are tight, wiring is correct and leads are not 
broken. Any current sensor with an open circuited secondary must be replaced.
d) Failure to trip on SELF TEST on -SE Types may result when the TEST current is not present, because of 
TEST winding connections, or control supply is not adequate (Should be 120V, 250 VA minimum). The self-
test winding is only available on I-Gard type RZ sensors, therefore if any other types are used, the self-test 
will not work.
e) Shunt-trip solenoid open circuited - Check that the wiring of the trip solenoid is not broken.

7.2.2 FAILURE TO CLOSE BREAKER

DANGER

Personnel Safety Hazard

It is not advisable to turn off the relay power supply and close the breaker under

this situation. If a fault already exists in the system, this kind of operation may cause

personal injury and/or damage to the equipment connected to the system.

Failure to observe these precautions may result in death or severe personal injury.

7.2 TROUBLESHOOTING