McQuay MicroTech II User Manual

OM 780-2 Page 99
5. Off: Unoccupied
The sub-state name tells you why the CSM is in the Off State.
Off: Alarm Sub-state: The Off: Alarm state indicates that a CSM Fault alarm exists. In this state, the CSM cannot start for
any reason. To get the CSM out of Off: Alarm, you must clear any Fault alarms that exist. The Off: Alarm state overrides
any On state.
Off: Manual Sub-state: The Off: Manual state indicates that the CSM’s Control Mode input (System Control screen) is
set to Manual Unoccupied. In this state, the CSM cannot start for any reason. To get the CSM out of Off: Manual, you must
set the CSM Control Mode to “Automatic” or “Manual Occupied.” The Off: Manual state overrides any On state.
Off: Ambient Sub-state: The Off: Ambient state indicates that the CSM’s low ambient lockout feature is enabled and the
outdoor air temperature is below the Low Ambient Lockout Setpoint (see the System Control screen). In this state, the CSM
cannot start for any reason. Before the CSM can leave Off: Ambient, the outdoor air temperature must rise above the
setpoint by a differential of 2°F (1.1°C). Or you could also disable the feature by setting the Low Ambient Lockout Flag to
“Off.” The Off: Ambient state overrides any On state.
Off: BACnet Network Sub-state: The Off: BACnet Network state indicates that the CSM’s Control Mode is set to
“Automatic” and the CSM has received an Off command from a BACnet device. The Off: BACnet Network state overrides
the On: Schedule, On: Optimal Start, On: Input, On: Modbus Network and On: BACnet Network states. BACnet is unique
from all other scheduling methods because it can command the CSM to Off (all other scheduling methods command the
CSM to On or AUTO). BACnet can also command to AUTO (instead of Off) to allow lower priority scheduling methods
to be used.
Off: Unoccupied Sub-state: The Off: Unoccupied state indicates that the CSM is ready to operate whenever it receives an
On command. Off: Unoccupied is different from the other Off states in that it is not caused by any one stop condition; for
example, a “Manual Off” (from the CSM Control Mode variable). Instead, it is caused by the absence of an On condition.
If the CSM Control Mode is “Automatic”, any of the following On conditions will override the Off: Unoccupied state and
start the system:
• An occupied weekly, holiday or special event schedule
• An Override Time setting other than zero
• A pre-occupancy optimal start condition
• A closed external start/stop input
• A network schedule input from BACnet or Modbus
Conversely, Off: Unoccupied can occur only when the CSM’s Control Mode is “Automatic” and none of the above
conditions exist.
Recirculate
In systems that have at least one cooling load pump, the Recirculate state is used (1) to verify cooling load water flow
during the transition between Off and On and (2) to obtain an accurate cooling load loop water temperature reading before
optimal start operation. During Recirculate, the cooling load pump system operates normally. The chillers and cooling
tower systems are disabled.
On (Occupied)
When the operating state is On, the CSM supervises chiller system operation, deciding which chillers and auxiliary
equipment should operate based on the chiller sequence order and the cooling load. The On State has six sub-states:
1. On: Manual
2. On: BACnet Network
3. On: Modbus Network
4. On: Input
5. Optimal Start
6. On: Schedule
The sub-state name tells you why the CSM is in the On State.

McQuay MicroTech II Specifications

General

Brand	McQuay
Model	MicroTech II
Category	Controller
Language	English