Pumpdown Procedure; Low Ambient Starts; Circuit Status; Compressor Control - Daikin AGZ 025D Operating & Maintenance Manual

Pumpdown Procedure

Pumpdown is performed as follows:

If multiple compressors are running, shut off
the appropriate compressors based on
sequencing logic and leave only one running

Turn off hot gas output and liquid line output

Keep running until evaporator pressure
reaches the pumpdown pressure, then stop
compressor

If evaporator pressure does not reach
pumpdown pressure within two minutes, stop
compressor

Low Ambient Starts

A low OAT start is initiated if the condenser
refrigerant saturated temperature is less than
29.5°C (85.1° F) when the first compressor starts.
Once the compressor starts the circuit is in a low
OAT start state for a time equal to the Low OAT
Start Time set point. During Low OAT Starts, the
freezestat logic for the low evaporator pressure
alarm as well as the low evaporator pressure hold

Circuit Status

The displayed circuit status should be determined by the conditions in the following table:
Enum Status
0 Off:Ready
1 Off:Cycle Timers
2 Off:All Comp Disable
3 Off:Keypad Disable
4 Off:Circuit Switch
5 Off:Alarm
6 Off:Test Mode
7 Preopen
8 Run:Pumpdown
9 Run:Normal
10 Run:Evap Press Low
11 Run:Cond Press High
12 Run:High OAT Limit

Compressor Control

Compressors should run only when the circuit is in a run or pumpdown state. They should not be running
when the circuit is in any other state.
OMM 1166-1
and unload alarms are disabled. The absolute limit
for low evaporator pressure is enforced and the
low evaporator pressure alarm should trigger if the
evaporator pressure drops below that limit.
When the Low OAT Start Timer has expired, if
the evaporator pressure is greater than or equal to
the Low Evaporator Pressure Unload set point, the
start is considered successful and normal alarm
and event logic is reinstated. If the evaporator
pressure is less than the Low Evaporator Pressure
Unload set point when the Low OAT Start Timer
expires, the start is unsuccessful and the
compressor will shutdown.
Multiple Low Ambient Start attempts are allowed.
On the third failed Low Ambient Start attempt the
Restart Alarm is triggered and the circuit will not
attempt to restart until the Restart alarm has been
cleared.
The restart counter should be reset when either a
startup is successful, the Low OAT Restart alarm
is triggered, or the unit time clock shows that a
new day has started.
Conditions
Circuit is ready to start when needed.
Circuit is off and cannot start due to active cycle timer on all
compressors.
Circuit is off and cannot start due to all compressors being
disabled.
Circuit is off and cannot start due to circuit enable set point.
Circuit is off and circuit switch is off.
Circuit is off and cannot start due to active circuit alarm.
Circuit is in test mode.
Circuit is in preopen state.
Circuit is in pumpdown state.
Circuit is in run state and running normally.
Circuit is running and cannot load due to low evaporator pressure.
Circuit is running and cannot load due to high condenser
pressure.
Circuit is running and cannot add more compressors due to the
high ambient limit on unit capacity. Applies only to circuit 2.
AGZ 025D through 190D 31