Daikin IOM 1322-1, Installation, Operation And Maintenance Manual

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IOM 1322-1 • WATER-COOLED SCROLL COMPRESSOR 38 www.DaikinApplied.com
Unit Controller
Reset : While still running, the event will be reset if evaporator
pressure > (Low Evaporator Pressure - Hold set point + 8 psi
for R134a or 13 psi for R410A). The event is also reset if the
circuit state is no longer run.
Low Evaporator Pressure - Unload
Event description:
EvapPressLow Unload N
Trigger :
This event is triggered if all of the following are true:
• Circuit state = Run
• More than one compressor is running on the circuit
• Circuit is not currently in a low OAT start
•
Has been at least 30 seconds since a compressor has
started on the circuit.
• Evaporator pressure <= Low Evaporator Pressure -
Unload set point for a time greater than half of the current
freezestat time
Action Taken : Stage off one compressor on the circuit every
10 seconds, except the last one.
Reset : While still running, the event will be reset if evaporator
pressure > (Low Evaporator Pressure - Hold set point + 8 psi
for R134a or 13 psi for R410A). The event is also reset if the
circuit state is no longer run.
High Condenser Pressure - Unload
Event description: CondPressHighUnloadN
Trigger :
This event is triggered if all of the following are true:
• Circuit state = Run
• More than one compressor is running on the circuit
•
Condenser pressure > High Condenser Pressure –
Unload set point
Action Taken : Stage off one compressor on the circuit every
10 seconds, except the last one.
Reset : While still running, the event will be reset if condenser
pressure drops below the “Hold Clear @” value which is
displayed on that circuit’s VIEW CIRCUIT n (1) screen. The
“Hold Clear @” is calculated based on number of compressors,
refrigerant, and number of High Condenser Pressure – Unload
occurrences since the circuit has cycled off or since midnight.
See table below:
Failed Pumpdown
Event description: Pumpdown Fail Cir N
Trigger
: Circuit state = pumpdown for time > 60 seconds
Action Taken : Shutdown circuit
Reset : N/A
Condenser Freeze Event
Event description: Cond Freeze Circ N
Trigger : Cond Sat Refr Temperature < Condenser Freeze Set
Point AND Condenser Pump State = OFF
Action Taken : Start condense pump.
Reset : N/A
Condenser Freeze Event (Water Cooled = Y
Only)
Event description: Cond Freeze Circ N
Trigger : Cond Sat Refr Temp < Condenser Freeze Set Point
AND Condenser Pump State = OFF
Action Taken : Start condenser pump.
Reset : Cond Sat Refr Temp > Condenser Freeze Set Point
plus 2°F.
Suction Temperature Sensor Fail
Event description: SuctT Sensor Fail N
Trigger : Sensor shorted or open.
Action Taken : None.
Reset : N/A
Event Log
An Event Log similar to the Alarm Log stores the last 25 Event
occurrences. There must be an active password for access
to the Event Log. To navigate to the Event log press the Left
Arrow key from any Alarm Log screen. When an event occurs,
it is recorded in the first slot in the Event Log. All other entries
are moved down in the Event Log and the last entry is dropped
if 25 earlier event occurrences have been logged. Each Event
Log entry includes an event description and a time and date
stamp for the event occurrence.
Controller Operation
Calculations
The Control Band defines the temperatures around the
Controlling Leaving Water Temperature set point where
compressors will be staged on or off. The controlling leaving
water temperature set point will be Evap LWT.
In cooling mode, the Control Band is calculated as follows:
Control Band = Evap Delta Temperature Set Point * 0.3
Four compressor units
Control Band = Evap Delta Temperature Set Point * 0.2
Six compressor units