Unit installation

CDU Installation Guide Page 45
Cooling Distribution Unit
TROUBLESHOOTING (continued)
Code: a31 – ‘Room RH out of range’ (self clear)
Reading from room relative humidity sensor is outside the nominated range of 5% to
95% RH.
Action: Check sensor connections to the control board.
Code: a32 – ‘Sec over pressure’ [when set as an alarm] (engineer to clear)
Pressure at PS1 has increased above the set default value of 7.5Bar (105PSI).
Note: Can also be configured as a warning (code w37) only.
Action: Most likely cause will be excessive heat build up in the system or a breech
between primary & secondary circuits within the plate heat exchanger. Check
for high temp alarms, relieve pressure at drain point. Remove heat exchanger
& replace.
Code: a33 – ‘EPO Shutdown’
Door Control Switch or EPO/Fire Shutdown in an open circuit condition.
Action: Check link connections from terminals 1 to 2 and 3 to 4, or check circuitry if
these facilities have been wired in.
Code: a34 – ‘Flood underfloor’ or ‘Flood underfloor’ selectable - alarm or alarm +
shutdown (engineer to clear)
Water detection tape installed under floor (if fitted – optional extra) has detected a
substantial water leak.
Action: Identify and repair leak (Note: a leak of this magnitude that does not bring up
any other alarms, will most likely be from the Primary circuit).
Code: a36 – ‘Sec low pressure’ (engineer to clear)
Pressure at PS1 has dropped to more than 0.2Bar (3PSI) below the fill pump activation
threshold for more than 1 minute (applicable when unit is running in automatic mode).
Action: Check the make-up container is full, tubes are free of airlocks, container is
properly connected and fill pumps are operational. Check system for leaks.
Code: a38 – ‘Primary water no flow’ (engineer to clear)
Becomes active under the following conditions:- Valve demand is at 100%, Secondary
High Temp alarm is active and Primary High Temp alarm is active (default 5 minute delay
applies).
Action: Check that the chiller is operational and fault free.
Other conditions (i.e. not a Warning or Alarm)
Communications error
Communications break between controller mother board & display board.
Action: Check connections between the boards.
No message displayed – unit not running/not responding to start signal
Power failure on controller mother board.
Action: Check that 24v is available on control motherboard – (review digital I/O status
on Screen ref. 3-12, page 27). End digit on top line of digital inputs should be
at ‘1’. If at ‘0’, then the 24v supply failed. Switch power off, open electrical
compartment & switch power back on, if there are no LEDs showing on
mother board then check board fuse/24v supply. If LEDs are on, then check
for wiring faults on Control Switch & EPO/Fire Shutdown circuits.
DANGER: This should only be carried out by a qualified electrician.