Maintenance and repair
Ex p control unit
Motor Purge Controller
Page 78 of 96
01-37A2-7D0003_Operating instructions_MPC_20210923_0_en.docx
Rev. 0
10.4
Faults and troubleshooting
CAUTION
A CHANGE IN OPERATING BEHAVIOUR MAY BE AN INDICATION OF PRE-
EXISTING DAMAGE TO THE CONTROL UNIT.
Do not put the Ex p system back into operation until the cause of the
fault has been eliminated.
It is assumed that the connection of all external electrical and mechanical
devices has been carried out correctly. Therefore, the proper setup and
connection of the electrical equipment should be checked first.
Faults
Error / Fault
Possible cause
Remedy
Sporadic failure
Cable break
Check connections
Pressure drop / leakage
Check tightness and
leakage compensation
Control unit out of order
Mains voltage not
available
Check supply voltage
Device defective
Return to manufacturer
The protected devices are
switched on without pre-
purge
Bypass activated
Deactivate bypass
Wrong purging program
activated
Check purging program
During the pre-purging,
the purging gas valve
switches off briefly
Excessive amount of
purging gas is introduced
into the pressurised
enclosure
Reduce the size of the
purging gas nozzle
The “Operate” LED does
not flash during the
purging time
Purging gas is not
available
Check purging gas valve
for supply voltage
Purging gas valve does not
open or it opens only
partially
Check purging gas valve
for foreign particles in the
mechanical part
Increase inlet pressure to
setpoint
Purging gas does not flow
through the Ex p enclosure
in sufficient quantity
Check purging gas nozzle
for the correct value
Check setpoints “p3”, and
“p1” of the control unit
Increase cross-section of
the purging gas supply line
The purging gas supply
line too small. Increase
cross-section of the
supply line
The target pressure of
pressure reducer is not
reached.
Remove closure or take
appropriate measures to
eliminate the reduction
