209
APPENDIX G — OPTIONAL GREENSPEED/LOW AMBIENT CONTROL (cont)
Outdoor VFD PI Run Rate (OV.RR)
[OV_RATE] This is the number of seconds between execution
of the Greenspeed/low ambient
Comfort
Link PD routine. This
value will have a range of 10 to 120 and a default of 5.
Outdoor VFD Proportional Gain (OV.PG)
[OV_PG] This is the proportional gain for the Greenspeed/low
ambient control PD control loop. This value will have a range
of 0.0 to 5.0 and a default of 0.5.
Outdoor VFD Integration Time (OV.TI)
[OV_TI] This is the integration time constant for the Green-
speed/low ambient control PD control loop. This value will
have a range of 0.5 to 50 and default of 50.
Greenspeed/Low Ambient Outdoor VFD Setpoint
Circuit A (O.A.SP)
[OV_A_SP] If the unit is configured for Greenspeed/low ambi-
ent control, then this is the setpoint to which the
Comfort
Link
PD routine will modulate VFD fan speed.
Greenspeed/Low Ambient Outdoor VFD Setpoint
Circuit B (O.B.SP)
[OV_B_SP] This is the setpoint of Circuit B to which the
Com-
fort
Link PD routine will modulate VFD fan speed.
Condenser Fan Control Outputs
There are two outputs (MBB Relays) provided to control head
pressure of standard non-Greenspeed/low ambient units.
CD.F.A
Condenser Fan Circuit A — CONDFANA
CD.F.B
Condenser Fan Circuit B — CONDFANB
For Greenspeed/low ambient option units, the outdoor con-
denser fans are controlled via LEN with following outputs:
OV.A
Outdoor VFD Circuit A Command% — OV_A
OV.B
Outdoor VFD Circuit B Command% — OV_B
Outputs
FANS
CD.F.A
(Condenser Fan Circuit A) (MBB
Relay 6 - OFC1,4) — For size 60 ton units with MCHX con-
densers, MBB - Relay 6 drives OFC4 and compressor contac-
tor B1 or B2 auxiliary contacts drive OFC1.
Outputs
FANS
CD.F.B
(Condenser Fan Circuit B) (MBB
Relay 5 - OFC2).
Outputs
FANS
OV.A
(Outdoor VFD Circuit A Com-
mand%) — This output will be used as the run output of circuit
A Greenspeed/low ambient VFD.
Outputs
FANS
OV.B
(Outdoor VFD Circuit B Com-
mand%) — This output will be used as the run output of the
circuit B Greenspeed/low ambient VFD.
Condenser Fan Inputs
The control loop uses the following inputs for head pressure
control:
SCT.A
Cir A Sat.Condensing Tmp — SCTA
SCT.B
Cir B Sat.Condensing Tmp — SCTB
OAT
Outside Air Temperature — OAT
SCTA and SCTB are calculated using the corresponding dis-
charge pressure transducer:
DP.A
Cir A Discharge Pressure — DP_A
DP.B
Cir B Discharge Pressure — DP_B
A description of operation during the failure of a sensor can be
found in P44 Failure Mode Operation. A description of the
thermistor and transducer alarms/alerts can be found in P.98
Alerts/Alarms.
Condenser Fan Staging
For 48/50A020-035 size units, there are two outdoor fans that
are common to both refrigerant circuits. The control cycles two
stages of outdoor fans, one fan per stage, to maintain accept-
able head pressure.
For 48/50A040 and 050 size units, there are four outdoor fans
that are common to both refrigerant circuits. The control cycles
two stages of outdoor fans, two fans per stage, to maintain ac-
ceptable head pressure.
For 48/50A060 size units, there are six outdoor fans that are
common to both refrigerant circuits (size 060 MCHX units have
4 fans, 2 on each circuit). The control cycles three stages of out-
door fans, two fans for stage one, four fans for stage two, and six
fans for stage three to maintain acceptable head pressure.
For 48/50A060 size units with MCHX condensers, there are
four outdoor fans, two for each independent refrigerant circuit.
The control cycles two stages of outdoor fans for each circuit,
one fan per stage, to maintain acceptable head pressure for
standard units.
If either of the SCT or DPT sensors fails, then the control de-
faults to head pressure control based on the OAT sensor. The
control turns on the second fan stage when the OAT is above
65°F and stages down when OAT drops below 50°F.
If the OAT sensor fails, then the control defaults to head pressure
control based on the SCT sensors. The control turns on the sec-
ond fan stage when the highest active circuit SCT is above the
HPSP and stages down when the highest active circuit SCT
drops 40°F below the HPSP for longer than 2 minutes.
If the SCT, DPT, and OAT sensors have all failed, then the con-
trol turns on the first and second fan stages when any compres-
sor is commanded on.
Compressor current sensor boards (CSB) are used on all units
and are able to diagnose a compressor stuck on (welded contac-
tor) condition. If the control commands a compressor off and the
CSB detects current flowing to the compressor, then the first fan
stage is turned on immediately. The second fan stage will turn on
when OAT rises above 75°F or the highest active circuit SCT ris-
es above the HPSP and remain on until the condition is repaired
regardless of the OAT and SCT values.
START-UP
The Greenspeed/low ambient VFD electronic control will be
powered up as long as unit voltage is present. The Greenspeed/
low ambient electronic control will start the condenser fan
when the compressor engages. The control will adjust the fan
speed to maintain head pressure setpoint.
For size 48/50A 020-060 (RTPF) units, a single controller(s) or
two Synchronized VFDs are used. For size 060 MCHX units,
two independently controlled VFDs devices are used, one for
each circuit. Please refer to Fig. Q for Greenspeed/low ambient
option wiring details. The controller is configured by jumper
wires and sensor input types. No field programming is re-
quired. If controller does not function properly, the information
provided in the Troubleshooting section can be used to pro-
gram and troubleshoot the drive.
Drive Programming
The drives of the unit are pre-programed from the factory.
When equipped with the field-installed Remote VFD Keypad
(part number CRDISKKIT001A00), parameters and settings of
the drives can be reset or adjusted. The VFD is powered during
normal operation to prevent condensation from forming on the
boards during the off mode and is stopped by driving the speed
to 0. The units use ABB ACS320 or ACH550 VFDs.
Summary of Contents for WEATHERMAKER 48A2020
Page 112: ...112 Fig 20 Typical Main Control Box Wiring Schematic 48 50A Units ...
Page 113: ...113 Fig 21 Typical Auxiliary Control Box Wiring Schematic ...
Page 114: ...114 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown ...
Page 115: ...115 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown TO NEXT PAGE ...
Page 116: ...116 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont ...
Page 117: ...117 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown ...
Page 118: ...118 Fig 25 Typical Controls Option Wiring Schematic SW1 SW2 OR DEHUMIDIFY SWITCH ...
Page 119: ...119 Fig 26 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown ...
Page 120: ...120 Fig 27 Typical Power Schematic of Greenspeed Low Ambient Option 48 50A 060 Unit Shown ...
Page 121: ...121 Fig 28 Typical Small Chassis Component Location Size 020 035 Units ...
Page 122: ...122 Fig 29 Typical Large Chassis Component Locations Size 040 060 Units ...
Page 185: ...185 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716 ...