F20
Twin Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 11 of 16
4.4
Wiring connections
F20 wiring connections are provided as screw terminals inside the lid of the
enclosure.
If mounted within a cable termination enclosure, one core of the CT should be
connected to earth for safety.
Battery
EF 1
EF 2
EF 1
EF 2
RESET
L N
+ -
C
O
M
CT
PWR
CT
3 x 500:1
60:1
+ -
12-24V
90-240V
ALARM
ALARM
DC
AC
12-24V
DC
C
T
1
C
T
2
C
T
3
5
6
3
4
1
2
11 12
9
10
7
8
17 18
15 16
13 14
Power Supply
If it is not already connected the
battery should be plugged in.
As an alternative to battery
power the F20 may be powered
from an external 12-24V DC
source connected across
terminals 7 & 8, observe correct
polarity.
AC Reset
Apply 90V-240V ac between
terminals 17 & 18 for 10s to
reset both of the EF elements.
Observe correct polarity.
DC Reset
Apply 12V-24V dc between
terminals 15 & 16 for 1s to reset
both of the EF elements.
Observe correct polarity.
EF element 1: CT connections
Observe the CT ratio expected (in the
example above 500:1)
Connect CT secondary positive
outputs to terminals 1, 2 & 3.
Terminals 1, 2 & 3 are internally
connected together on the F20 pcb.
Connect CT secondary common
output to terminal 4.
EF element 1: Output contacts (Alarm)
Circuit between terminals 9 & 10 is
normally closed and will open when
EF element 1 is indicating.
Circuit between terminals 10 & 11 is
normally open and will close when EF
element 1 is indicating.
EF element 2: CT connections
Observe the CT ratio expected (in the
example above 60:1)
Connect CT secondary output to
terminals 5 & 6.
EF element 2: Output contacts (Alarm)
Circuit between terminals 12 & 13 is
normally closed and will open when
EF element 2 is indicating.
Circuit between terminals 13 & 14 is
normally open and will close when EF
element 2 is indicating.
F20 wiring connections
