Rectifier MCSU-4 - MCSU-4 Fault Finding and Repair Procedures

Installation, Operation and Technical Manual Rectifier Technologies
158-1872-01 81 19-Feb-14
Alarm Condition
Possible Cause
Action Suggested
Battery Disch
Output voltage low due to SMRs off
Check AC voltage & restore if possible;
Float level set too low
Set float level to correct value
Battery Disch level set too high
Set correct Battery Disch level
SMR Comms Fail
Comms cable faulty
Replace cable
SMR communication circuits faulty
Replace SMR
Faulty MCSU-4
Replace MCSU-4
AC Volt Fault
(System alarm)
AC voltage out of tolerance
Check AC voltages and fix if possible
AC voltage threshold levels incorrect
Set correct levels
Faulty AC monitoring unit MMIB1or2
Replace monitoring unit
MUIB or MCSU-4 faulty
Replace MCSU-4
Communications link failure
(Only on systems not fitted with AC
monitoring module)
In SMR menu check status of all SMRs.
If all show “No Response” check 4-way
communications cable between MCSU-4
and all SMRs
AC Freq Fault
AC frequency out of tolerance
Check AC frequency and fix if possible
AC frequency threshold levels incorrect
Set correct levels
Faulty AC monitoring unit MMIB1 or 2
Replace monitoring unit
MUIB or MCSU-4 faulty
Replace MCSU-4
Batt I-Limit
Battery charging current is being limited
to preset value
No action necessary
Battery current limit set too low
Set correct limit
Battery current sensor faulty
replace sensor
Faulty MUIB or MCSU-4
Replace MCSU-4
Batt Sym Alarm
One Battery string is faulty
Repair/replace battery if necessary
Battery discharge current differential
level set too low
Set correct level of Disch I Diff in BATT
menu
Battery current sensor is faulty
Check and replace sensor if necessary
Faulty MUIB or MCSU
Replace MCSU-4
Earth Leak Alarm
(Only on systems
fitted with MUIB3)
Excessive Earth current due to either
failure of load supply isolation or faulty
load equipment.
Locate source of earth leakage current
and correct accordingly.
9.2 MCSU-4 Fault Finding and Repair Procedures
In addition to performing a supervisory function by monitoring output voltage and current
and the various system alarms, the MCSU-4 also performs a voltage control function in
order to achieve battery charging current control, battery temperature compensation,
battery equalisation and active current sharing.
To control current to the lowest battery voltage, the MCSU-4 has the ability to suppress
the SMR output voltage to a value lower than the minimum battery voltage.