21
9. MAINTENENCE
The BA474ND indicating temperature transmitter
should only be maintained by trained competent
personnel.
BEKA Application Guide AG310 provides
comprehensive information on the maintenance of
[Extra low voltage dc] Ex nA instrumentation. The
guide may be downloaded from the BEKA website.
9.1 Fault finding during
commissioning
If a BA474ND fails to function during commissioning
the following procedure should be followed:
Symptom
Cause
Check
No display or
output current
Incorrect wiring
Low supply
voltage
Wiring
That voltage
between terminals
5 & 6 is between 9
& 30V at all output
currents. Terminal
5 positive.
or between
15 .5 & 30V at all
output currents if
optional backlight
is fitted.
Digital display is
over or under
range showing
9.9.9.9.9
or
-9.9.9.9.9
with all decimal
points flashing.
Incorrect wiring of
THC or RTD input
Input is outside
specified range for
voltage or
resistance input.
Wiring and input
configuration.
Wiring and input
configuration.
Bargraph is over
or under range.
with scale flashing,
bargraph
displaying all or
just one segment.
Input is outside
specified range for
bargraph.
Reconfigure
bargraph display.
Digital display &
bargraph flashing
and 4/20mA fixed
at 3.6, 3.8 or
21.0mA
Sensor fault
detection has
been activated.
Sensor and input
wiring.
9.2 Fault finding after
commissioning
ENSURE PLANT SAFETY BEFORE STARTING
MAINTENANCE
Use as a Type nA instrument
Transmitter and sensor in Zone 2
Maintenance may only be performed when the
transmitter loop is not energised, or there is
no risk of a flammable atmosphere being
present.
The BA474ND terminal cover should only be
removed when dust and water can not enter
the enclosure. Before replacing the terminal
cover ensure that the sealing gasket is
undamaged and that it is free from foreign
bodies.
Use as a Type nL instrument with an
intrinsically safe Ex [ia] sensor input
Transmitter in Zone 2, sensor in Zone 0 or 1
Maintenance may only be performed on the
transmitter and the 4/20mA output loop when
it is not energised, or there is no risk of a
flammable atmosphere being present.
The BA474ND terminal cover should only be
removed when dust and water can not enter
the enclosure. Before replacing the terminal
cover ensure that the sealing gasket is
undamaged and that it is free from foreign
bodies.
The transmitter input terminals, the sensor
and the wiring between them are intrinsically
safe. Live maintenance is permitted but only
certified test equipment may be used unless
there is no risk of a flammable atmosphere
being present.