12
RSMVQ Technical Guide
SEQUENCE OF OPERATIONS
Cooling Mode and Dehumidification Operation
Cooling Mode Operation
Cooling Mode control staging is determined by the Supply Air
Temperature. Staging is met by turning the on/off compressor on
or off and the two-step compressor to low speed or high speed.
VFD compressor modulation is determined from Saturation
Temperature and Supply Air Temperature. If the Supply and
Saturation Temperatures are above their respective Setpoints,
the compressors will modulate up. If the Supply or Saturation
Temperatures are below their Setpoints, the compressors will
modulate down. Envelope and/or current protections also affect
the VFD compressor modulation.
Staging Up
1. If the Supply Air Temperature is above the Setpoint,
Compressor 1 VFD will turn on at the recommended
manufacturer’s speed for one minute. Compressor 1
VFD will modulate anytime thereafter if it is running.
2. If the Supply Air Temperature is above the setpoint
plus window, and Compressor 1 VFD is at 100% of its
capacity, Compressor 2 will turn on at low speed and
Compressor 1 will be reset to 67% of its range (min
to max). Compressor 1 VFD will modulate anytime
thereafter if it is running.
3. If the Supply Air Temperature remains above the
Setpoint plus window, and Compressor 1 VFD is at
100% of its capacity, Compressor 2 will be set to high
speed and Compressor 1 will be reset to 67% of its
range (min to max).
Staging Down
1. If the Supply Air Temperature is below the Setpoint
plus window and Compressor 1 VFD is at minimum
capacity, Compressor 2 will be set to low speed and
Compressor 1 will be reset to 67% of its range (min
to max).
2. If the Supply Air Temperature remains below the
Setpoint plus window, and Compressor 1 VFD is at
minimum capacity, Compressor 2 will be turned off
and Compressor 1 will be reset to 67% of its range
(min to max).
3. If the Supply Air Temperature continues to remain
below the Setpoint plus window, and Compressor 1
VFD is at minimum capacity, Compressor 1 will be
turned off.
4. If the Supply Air Temperature rises above the Setpoint
and Compressor 1 VFD’s minimum off time has been
met, Compressor 1 will be turned back on.
Dehumidification Operation
Dehumidification Mode control staging/modulation is determined
by using the lowest saturation temperature from each circuit.
Circuit 1 uses Superheat Controller Saturation Temperature and
Circuit 2 uses the Saturation Coil Temperature Sensor (Temp 2
input) mounted after the TXV.
Staging Up
1. Staging begins when the RSMVQ Module obtains the
Reheat Valve position and Reheat Supply Air Error
from the AAON unit controller. Compressor 1 VFD
will turn on at the manufacturer’s recommended
speed for one minute. Compressor 1 VFD will
modulate any time thereafter based on the Saturation
Temperature (lowest of both circuit’s readings).
2. If the Saturation Temperature (lowest of both
circuits’ readings) is above the Setpoint plus window,
Compressor 2 will turn on at low speed.
3. If the Saturation Temperature (lowest of both circuits’
readings) is above the Setpoint plus window, If the
Saturation Temperature of Circuit 2 is above the
Setpoint plus window, Compressor 1 VFD is at 67%
of its range min to max, the reheat valve is at 100%,
and the Supply Air Temperature is below the Reheat
Setpoint, Compressor 2 will be set to high speed.
Staging Down
1. If the Saturation Temperature of Circuit 2 is below the
Setpoint plus window, Compressor 1 VFD is below
50% (adjustable), and the reheat valve is below 50%,
Compressor 2 will be set to low speed.
2. If the Saturation Temperature of Circuit 1 is below
the Setpoint plus window and Compressor 1 VFD is
at minimum, Compressor 1 will be staged off.
NOTE:
Compressor 2 cannot be turned off in
Dehumidification Mode unless failed on alarm
fault.
Summary of Contents for ASM02293
Page 1: ...RSMVQ Technical Guide ...
