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5 - DIAGNOSTICS - TROUBLESHOOTING
5.1 - General
The PRO-DIALOG Plus control system has many fault tracing
functions. If an operating fault is detected, an alarm is activated
and an alarm code is generated.
5.2 - Displaying alarms
The alarm LED on the unit gives an immediate display of the
alarm. It is followed by a flashing sequence that describes the
alarm code: the first for the alarm code number, and the second
for the units.
Example:
Alarm 36 is detected by the Pro-Dialog Plus control, the LED
is on continuously for 5 seconds, then flashes 3 times, goes off
and flashes 6 times, goes off and restarts the cycle.
The Pro-Dialog control permits the display of up to 5 fault
codes that are active on the unit.
5.3 - Resetting alarms
When the cause of the alarm has been corrected the alarm can
be reset, depending on the type, either automatically on return
to normal, or manually when action has been taken on the unit.
Manual resetting must always be made at the unit and the
folllowing procedure must be followed: Press the alarm reset
button, until the LED showing the alarm codes lights up. Press
it a second time to reset the alarms.
Alarms can be reset even if the unit is running. This means that
alarms can be reset without stopping the machine. In the event
of a power supply interrupt, the unit restarts automatically
without the need for an external command. However, any faults
active when the supply is interrupted are saved and may in
certain cases prevent a circuit or the unit from restarting.
4 - PRO-DIALOG PLUS CONTROL OPERATION
4.1 - Safety loop
This contact checks the status of a customer safety loop. It
prevents the unit from starting if it is open. If this contact
opens, while the unit is running, this will immediately shut
down the faulty unit.
4.2 - Capacity control
The control activates the compressors, based on the thermostat
cooling stage demand.
NOTE: Pro-Dialog imposes a minimum delay of 4 minutes,
before adding an additional cooling stage, and a minimum
delay of 3 minutes before cutting out a stage.
4.3 - Compressor start-up sequence
The compressors are started and stopped in a sequence
designed to equalise their run times (value weighted by the
number of compressor start-ups).
4.4 - Head pressure control
Condensing pressure control is automatically ensured by a two-
speed fan (no adjustment).
4.5 - High pressure load shedding function
This function does not require an additional board. It prevents
high pressure breaks on a circuit by the following means:
• Preventing any capacity increase on the circuit once the
high pressure value has reached an initial threshold.
• Shedding one compressor once a second protection
threshold has been reached.
In the event of a compressor being unloaded, no capacity
increase will be authorised on the circuit concerned for a period
of 10 minutes.
4.6 - Pumpdown
If a circuit is shut down or started after more than 15 minutes
of being shut-down, it is subjected to a pumpdown cycle in
order to purge the refrigerant from the evaporator and the
suction line. The maximum duration of the pumpdown cycle is
2 minutes.
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