Daikin Rebel Applied DPSA - Page 71

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www.DaikinApplied.com 71 IM 1287-6 • REBEL APPLIED ROOFTOP
Dehumidication operation is disabled if circuit #1 is
disabled for any reason.
• In the reheat mode, the minimum position for the reheat
valves is 10%. The controller will modulate the reheat
valves from this starting position.
• Maximum reheat signal is 85%. This will allow for the
outdoor condenser to remain active in the circuit and
assist with condenser pressure control.
• Reheat Capacity Limiting Feature is activated if the unit
is at maximum reheat (85%) and cannot achieve DAT
setpoint (minus ½ dead band) and if any compressor(s) in
circuit #2 are active. One of the compressors in circuit #2
will be shut down in order to raise the DAT at the sacrice
of slightly less dehumidication capability.
• Upon termination of dehumidication (reheat), the
maximum ramp down or decay rate of the reheat control
valves shall be 1% per sec (or 0.1V per sec).
• The reheat valve stepper motor will require occasional
re-synchronization to assure the motor and driver remain
in step with one another. Every 24 hours, the reheat
control valve will automatically be synchronized by driving
the valve to its minimum position plus 10% over drive
closed. The reheat valve will also be synchronized if
there are unexpected system responses in relation to
valve position.
• Dehumidication status can be found under the MTIII
main system menu along with reheat capacity (valve
position) display based on percentage (0-100%).
• A solenoid (SV6) and a check valve is provided to the
reheat refrigeration circuit. The solenoid is normally
closed and removes refrigerant from the reheat portion
of the refrigerant circuit when Reheat is inactive. When
Reheat is active, the solenoid closes and isolates the
reheat portion of the refrigeration circuit. When the
solenoid is in the open position, it meters (by pulsing)
refrigerant ow as it enters the suction line. This feature
reduces the amount of refrigerant needed for reheat up to
75%, compared to a ooded system arrangement. The
bleed solenoid is also pulsed at the start of the circuit to
remove any refrigerant that may have leaked past the
stepper valve and check valve while the circuit was o󰀨.
MLSCRH+MHGRH Control &
Arrangement
• In conjunction with dehumidication, the combination
of MLSCRH & MHGRH is used to increase the gross
cooling capacity of the unit by increasing the subcooling
along with utilizing hot gas reheat to assist in controlling
the temperature of air leaving the unit. This combination
option is done with two separate reheat coils located
downstream of the dx coil in the air handling portion of
the unit.
• Operation is similar to MHGRH where compressor
staging is based on leaving dx temperature and MLSRCH
is modulated to achieve and maintain the DAT setpoint.
• If MLSCRH is at maximum signal and unable to achieve
DAT setpoint (minus ½ dead band) then MHGRH is
activated to trim the DAT to the setpoint.
• MLSCRH is installed in both circuit #1 and circuit #2.
• The minimum position for the liquid reheat valves is 15%.
The controller will modulate the reheat valves from this
starting position.
• The maximum reheat signal for the liquid reheat valves is
100%.
• Communication with the liquid valves is accomplished by
0-10Vdc signal from the unit controller with the use of an
interface board.
• The liquid subcool reheat valve stepper motor will
require occasional re-syncronization to assure the motor
and driver remain in step with one another. Every 24
hours, the reheat control valve will automatically be
synchronized by driving the valves to their maximum
position (10 Vdc) for 60 seconds and then driving the
valves to their minimum position (0%) for an additional 60
seconds. The reheat valves will also be synchronized if
there are unexpected system responses in relation to the
valves position.