Air PreciseAIR PCA Series, Инструкция по установке, эксплуатации и обслуживанию

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IOM-PreciseAIR
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3.2. Sequence of Operation
1. To start the unit, turn the LOCAL‐OFF‐REMOTE switch to "Local" position for system local
control. "Remote" position is for remote start from a Building Management System or
remote panel via a relay contacts. In the "Off" position the compressors shut down. Some
units are furnished with START-STOP sw
itches. Turn to “Start” position to start unit.
2. The blower(s) will start and run continuously. The compressor(s) will start based on
temperature reading and set point and/or relative humidity and set point. Also, all system
safety controls must be in a “no fault” state (e.g. voltage phase monitor, overloads, E -
stop). The compressor(s) contactor coil energizes, starting the compressor and opening
an auxiliary contact removing the 120V from the crankcase heater. The controller
manages the refrigerant line solenoid/shutoff valve. The HMI screen indicates status.
3. (WATER COOLED SYSTEM MODELS ONLY)
The system will control/regulate the water regulating valve to maintain the discharge
pressure set point.
4. ( AIR‐COOLED SYSTEM MODELS ONLY)
Condenser fans are immediately engaged when the compressor contactor closes.
Depending on the size, type and destination of the condensing unit, fans may be
energized individually or in pairs. The first fan starts with signal from compressor
contactor auxiliary contact.
5. Temperature Control:
A PLC will control system capacity by cycling the compressor(s) and lead compressor
VFD. As space/room air temperature rises above set point, the system demand
increases and the first compressor starts. As temperature continues to rise and the
calculated system demand increases, the first compressor loads and eventually the
second compressors is started. As temperature continues to rise, the system demand
reaches 100%, bringing compressor(s) to 100% capacity. As temperature falls, this
sequence is reversed until the compressor(s) cycles off.
6. DX systems are provided with a VFD controlled lead compressor. The capacity control is
done by varying the compressor motor frequency for improved leaving air temperature
stability .
7. If the temperature falls below the space/room heating set point, the system will use the
duct mounted heater to warm-up the room.
8. Relative Humidity Control:
The upper humidity limit is controlled by the cooling coil. It results from the inherent de-
humidification that occurs with mechanical cooling (condensate forming on the cooling
coil surface due to coil temperature below the air dew point).