Operation Manual
FT128 Rev 2.4
112
24.3 Service Mode for COM-Loop (H5/A3)
This mode can be used when commissioning an installation and by maintenance
personnel. The COM loop communication (polling) will be turned off but there will still be
voltage (24 V
DC
) on the loop in the A-direction only, in the B-direction only or in both
directions at the same time.
A volt meter can be used, e.g. to check the voltage / voltage drop on different places on
the loop or to find a single break on the loop. (Since there is voltage on the loop, short
circuit isolators will work normally).
It is recommended to do this check also when FT128 is powered via the backup battery
only, since the voltage can be up to 3 V lower (compared with the switch mode power
supply) due to the battery condition, backup duration, etc.
The "Service mode for COM-loop" is indicated by LED "Disablements" is lit and LED
“Service” is flashing.
If the user stays in this menu window, without doing any actions, there will be a timeout
after 1 hour, and the user is logged off. If the user logs off this menu, the "Service mode
for COM-loop" will be terminated automatically.
Note: If short-circuit is detected on the loop when in service mode, the loop will be
disabled and a fault message will be displayed:
FAULT: SHORT CIRCUIT SCI A <-> SCI B
…independent of where the short-circuit on the loop is situated.
Action Text in display Comments
"Access"
Log on to FT128 as shown in page
35.
Scroll to menu H5.
Service
ACCEPT? H5
"A"
Calibration of supervised outputs
ACCEPT? A1
Scroll to menu A3
Service mode for COM-loop
ACCEPT? A3
Press "A" to accept.
"A" Service mode for COM-loop: 0
0=Off 1=A-dir 2=B-dir 3=Both ACCEPT?
Press:
0=Service mode is off.
1=Voltage in A-direction.
2=Voltage in B-direction.
3=Voltage in both directions.
1, 2 or 3 selected is indicated by LED
"Disablements" (L8)
e.g. "1"
"A"
COM-loop in service mode. Powered in
A-direction.
The communication is now turned off
on the COM loop but 24V still exist in
the A-direction. This state will last
until you press ”A” or “Return” to
menu A3.
"A" or
“Return”
Service mode for COM-loop
ACCEPT? A3
Scroll or press "Return" to H3.
“Return”
Service
ACCEPT? H5
Scroll or press "Return"
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