McQuay AWS User Manual

32 KOMAC00607-09EN
Rapid Shutdown
A rapid shutdown requires the compressor to stop and the circuit to go to the Off state
immediately.
The circuit will do a rapid shutdown if either of these conditions occurs at any time:
• Unit State is Off
• A rapid stop alarm occurs on the circuit
Circuit Status
The displayed circuit status is determined by the conditions in the following table:
Enum Status Conditions
0 Off:Ready Circuit is ready to start when needed.
1 Off:Stage Up Delay Circuit is off and cannot start due to stage up delay.
2 Off:Cycle Timer Circuit is off and cannot start due to active cycle timer.
3 Off:Keypad Disable Circuit is off and cannot start due to keypad disable.
4 Off:Circuit Switch Circuit is off and circuit switch is off.
5 Off:Refr In Oil Sump
Circuit is off and Discharge Temperature – Oil
Saturated Temperature at gas pressure <= 5°C
6 Off:Alarm Circuit is off and cannot start due to active circuit alarm.
7 Off:Test Mode Circuit is in test mode.
8 EXV Preopen Circuit is in preopen state.
9 Run:Pumpdown Circuit is in pumpdown state.
10 Run:Normal Circuit is in run state and running normally.
11 Run:Disc SH Low
Circuit is running and cannot load due to low discharge
superheat.
12 Run:Evap Press Low
Circuit is running and cannot load due to low evaporator
pressure.
13 Run:Cond Press High
Circuit is running and cannot load due to high
condenser pressure.
Compressor Control
The compressor will run only when the circuit is in a run or pumpdown state. This
means the compressor should not be running any time the circuit is off or during
preopening the EXV.
Cycle Timers
A minimum time between starts of the compressor and a minimum time between
shutdown and start of the compressor will be enforced. The time values are set by
global circuit set points.
These cycle timers are enforced even through cycling of power to the chiller.
These timers may be cleared via a setting on the controller.
Compressor Run Timer
When a compressor starts, a timer will start and run as long as the compressor runs.
This timer is used in the alarm log.
Compressor Capacity Control
After starting, the compressor will be unloaded to the minimum physical capacity and
no attempt to increase compressor capacity is made until the differential between
evaporator pressure and oil pressure meets a minimum value.
After the minimum differential pressure is met, compressor capacity is controlled to
25%.
Compressor capacity will always be limited to a minimum of 25% while it is running,
except for the time after compressor start when the differential pressure is being built
and except when changes to capacity are performed as needed to meet unit capacity
requirements (see unit capacity control section).

McQuay AWS Specifications

General

Brand	McQuay
Model	AWS
Category	Chiller
Language	English