AAON RSMVQ2R, Техническое руководство

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14
RSMVQ2R Technical Guide
SEQUENCE OF OPERATIONS
Electronic Expansion Valve Operation and Head Pressure Control
Electronic Expansion Valve (EXV)
Operation
EXV operation is fully integrated into the DMQ EXV controller.
The DMQ EXV controller will measure suction pressure and
temperature to determine superheat and will automatically
modulate the EXV to maintain the configured superheat. The
RSMVQ2R will communicate with the DMQ controller to set
the desired superheat setpoint and to retrieve operational data
for display and trending purposes.
Head Pressure Control
The RSMVQ2R can monitor a head pressure transducer and
control a condenser fan to maintain a head pressure setpoint.
A condenser relay is commanded on when the first compressor
is enabled. The condenser fan will be controlled with a 0-10
VDC output signal. When the condenser signal first activates, it
maintains at 100% for 10 seconds.
In the Cooling Mode, the condenser signal will modulate to
maintain the cooling head pressure setpoint. The signal can
modulate between 15% and 100%. If the head pressure exceeds
550 PSIG, the condenser control signal will immediately go to
100% and a high head pressure alarm will be generated. The
alarm will be deactivated when the head pressure drops below
540 PSIG.
In the Dehumidification Mode, the condenser output signal
controls to the reheat head pressure setpoint. High head pressure
conditions produce the same effects as in the Cooling Mode.
If no head pressure sensor is detected, the condenser output signal
will be maintained at 100%.
During condenser fan head pressure control, the head pressure
setpoint will decrease when the VFD compressor speed
decreases. See Table 3, this page.
Compressor
Speed
Head Pressure Setpoint
(340 default - adjustable)
25% or lower 260 psi
25 - 100% 260 - 340 psi
100%
340 psi
Table 3: Compressor Speed / Head Pressure