Maintenance and care
Ex p Control unit
APEX
py
Page 86 of 96
01-37A2-7D0006_py_Manual_Exp-Control-Unit_20210923_a_en.docx
Rev. 0
Faults
Error / Fault
Possible cause
Remedy
Sporadic failure
Cable break
Check connections
Pressure drop / leakage
Check tightness and leak
compensation
Control unit without
function
(all LEDs off)
Mains voltage not
available
Check supply voltage
Device defective
Return to manufacturer
The protected devices are
switched on without pre-
purging
Bypass activated
Deactivate bypass
Incorrect purging program
activated
Check purging program
During pre-purging, the
purging gas valve switches
off for a short time
Excessive amounts of
purging gas are introduced
into the pressurized
enclosure
Reduce the purging gas
nozzle
“Operate” LED does not
flash during purging time
No purging gas
Check purging gas valve
for the presence of supply
voltage
Purging gas valve does not
open or opens only
partially
Check purging gas valve
for foreign particles in the
mechanical part
Increase inlet pressure to
set point value
An insufficient amount of
purging gas flows through
the Ex p enclosure
Check purging gas nozzle
for correct value
Check set point values
“p3” and “p1” of the
control unit
Increase the cross section
of the purging gas supply
line
Purging gas supply line too
small. Enlarge cross
section of the supply line
Set point pressure of the
pressure reducer is not
reached
Remove the cap or
eliminate the reduction by
taking suitable measures
Pressure monitor of the
control unit is
inadmissibly closed or has
a reducer
Seal enclosure using
suitable measures
Enclosure leaks during the
pre-purging phase due to
increased internal
pressure
Check purging gas valve
for the presence of supply
voltage
