Sentinel™ EFI-MLZ User’s Manual
Version 4.1 Page 9 of 15
5.2 INDICATING UNIT
The primary indication on the EFI-MLZ is a light-emitting-diode (LED). The LED will flash at
approximately 1Hz when the EFI is in a tripped state and remain extinguished when the EFI is in a
reset state.
The indicating unit is powered from the mains supply and also uses the presence of healthy mains
to reset the unit. When healthy mains is first applied or when it returns after a cleared fault
condition, the unit will first require up to 5 minutes to charge the onboard supply capacitors before
it is functional. The presence of mains voltage will also reset the unit if it is in a tripped state.
The indicating unit continuously monitors the output signal from the current sensor. The current
sensor transmits a voltage which is proportional to the measured current. For primary currents in
excess of the trip level (default 50A) the current sensor saturates and a limiting circuit inside the
indicating unit clamps the output voltage to below 10V even for high fault currents. When an
imbalance is detected, onboard circuitry analyses the fault current. The magnitude and duration of
the half cycles of fault current are measured. Current spikes and glitches are ignored. As soon as
valid fault current has been detected, the Sentinel triggers and enters a tripped state. A trip will
initiate flashing of the LED.
5.2.1 AUXILIARY RELAY (OPTIONAL)
An on-board auxiliary relay provides a potential-free, normally-open contact for additional signaling.
A 2-way screw terminal is provided on-board to which the user can connect a signaling cable. The
auxiliary relay is operated from the same circuitry controlling the LED. Thus when healthy mains is
first applied or when it returns after a cleared fault condition, the unit may require up to 5 minutes
to charge the onboard supply capacitors after which it then resets. A reset will latch the relay into
the reset position (open). A tripped state will latch the relay into a tripped position (closed).
5.2.2 REMOTE INDICATOR (OPTIONAL)
An optional remote indicator can be ordered pre-installed or ordered separately. A 2-way screw
terminal is provided on-board for connection of the remote indicator. It provides flashing LED
indication at some distance from the main indicating unit. During a tripped state the unit will flash
at a rate of about 1Hz. The remote indicator is weather-proof and is housed inside a stainless steel
bolt which also makes it vandal-proof. The on-board circuitry which drives the remote indicator
requires at least 5 minutes of mains charging when first connected to the mains supply.
5.2.3 MANUAL TEST AND RESET
A pushbutton located on the front panel allows the unit to be manually tested or reset. The button
must be depressed for at least 3 seconds before it will activate. This is to avoid accidental operation.
The EFI can only be manually tested if the unit has been charged by the mains supply for up to 5
minutes. The manual test feature can both trip and reset the EFI.
