Troubleshooting; Fault Codes - Emerson MRLDS-250 Installation And Operation Manual

8

Troubleshooting

8.1.

Fault Codes

To comply with the requirements of EN378 and the
European F-GAS regulation, gas detectors must be
tested annually. However, local regulations may
specify the nature and frequency of this test.
The MRLDS-250 features sophisticated internal
status monitoring and will indicate whether a fault
condition exists on the front display (F.-XX, with XX
being the fault number).
There are two classes of fault conditions: critical and
non-critical. In general, non-critical faults occur when
environmental conditions exist that are outside the
product's specified operating range, or if an
installation error has occurred (for example, incorrect
wiring).
The gas detector will typically continue to monitor its
surroundings (except for fault F.-08), and may report
inaccurate readings and false alarms.
Correcting non-critical faults is a matter of waiting for
the environmental conditions to return to a more
typical condition, correcting wiring mistakes, or in
some cases, relocating the gas detector. For example,
placing the gas detector near a forced air heater may
cause temperature faults. The non-critical fault range
is F.-01 to F.-08.
Critical faults indicate a functional problem that
results in the gas detector no longer monitoring its
surroundings for refrigerant.
The fault number is displayed and the power LED is
turned off, indicating that the gas detector is offline.
The critical fault range is F.-09 to F.-16. If any of these
faults occur, first try to clear the faults by cycling
power to the sensor. The easiest way to do this is by
removing the sensor from the base and reattaching. If
the fault returns after cycling power, the gas detector
should be removed from service and replaced.
Additionally, the faults are stored as a hex number and
can be accessed in the Diagnostics menu P.-18. The
associated hex codes are listed next to the Fault Code
in (Table 8-1). Refer to Diagnostics Menu P.-18 in
Section 8.2., Diagnostic Attributes (P.-18) for
additional information.
Fault Codes
Fault
Description
Code
Gas Detector
Temperature
Fault
Gas Detector
Temperature
Rate of
Change
Fault
RS485 RX
Fault
RS485 CRC
Fault
Open Loop
Fault
Table 8-1 - Fault Codes
Possible 
Hex
Code Causes
Gas Detector
temperature
0x00
reports >
01
55°C or < -
35°C.
Temperature
rate of
change
0x00
exceeds
02
~1°C/min for
more than 15
minutes.
0x00 Message too
long for 
04
receive buf-
fer.
0X00 Transmis-
sion is 
08
corrupted 
(computed
CRC doesn't
match 
transmitted
CRC).
Possible
wiring,
connection,
and/or
termination
issue exists.
When analog
output type is
4-20ma and
0x00 loop is open,
use 
10
18-24AWG
shielded
twisted pair
with 120
ohm
characteristic
impedance
for Modbus
connections.
Troubleshooting • 27