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APPENDIX F — OPTIONAL FACTORY-INSTALLED LOW AMBIENT MOTORMASTER
®
V CONTROL (cont)
Unit size (Configuration
UNIT
SIZE), refrigerant type
(Configuration
UNIT
RFG.T), and condenser heat ex-
changer type (Configuration
UNIT
CND.T) are used to
determine if the second stage fans are configured to respond to
a particular refrigerant circuit (independent control) or both re-
frigerant circuits (common control). The 48/50A2, A3, A4, A5
060 units with microchannel (MCHX) condenser heat ex-
changers are the only units that utilize independent fan
controls.
There are configurations provided for head pressure and motor
master control that can be found at the local display under
Configuration
COOL.
Motormaster Control (M.M.)
[MOTRMAST] The condenser fan staging control for the unit
will be managed directly by the ComfortLink controls through
the use of VFDs. There will be no VFDs installed in the stan-
dard unit. This configuration must be set to YES if the optional
condenser fan VFDs are installed on the unit. Setting this con-
figuration to YES alters the condenser fan staging sequence to
accommodate the Motormaster control algorithm.
The standard unit is capable of mechanical cooling operation
down to 32°F outdoor temperature. With the addition of acces-
sory Motormaster V speed control on the stage 1 condenser
fan(s), mechanical cooling operation down to –20°F outdoor
temperature is possible.
This configuration will have a range of NO/YES and will de-
fault to NO.
NOTE: Setting Motormaster control to YES will automatically
enable the SCB2 PCB at LEN address 0x62 and the 4 to 20 mA
outputs to control the VFDs.
Head Pressure Setpoint (HPSP)
[HPSP] This is the head pressure setpoint used by the Com-
fortLink control during condenser fan, head pressure control.
This configuration will have a range of 80 to 150°F and a de-
fault of 110°F.
Compressor Lockout Temperature (MC.LO)
[OATLCOMP] This configuration defines the outdoor air tem-
perature below which mechanical cooling is locked out. To
make proper use of Motormaster control, it will be necessary
for an operator to manually change this setting. This configura-
tion will have a range of –20 to 55°F and a default of 40°F.
Motormaster Setpoint Offset (MM.OF)
[MMSPOFST] This value is added to HPSP in order to calcu-
late the Motormaster Setpoint MM_SP. This value will have a
range of –20 to 20 and a default of –10.
Motormaster PD Run Rate (MM.RR)
[MM_RATE] This is the number of seconds between execution
of the Motormaster ComfortLink PD routine. This value will
have a range of 10 to 120 and a default of 5.
Motormaster Proportional Gain (MM.PG)
[MM_PG] This is the proportional gain for the Motormaster
control PD control loop. This value will have a range of 0.0 to
5.0 and a default of 1.0.
Motormaster Integration Time (MM.TI)
[MM_TI] This is the integration time constant for the Motor-
master control PD control loop. This value will have a range of
0.5 to 50 and default of 30.
Motormaster Setpoint (MM.SP)
[MM_SP] If the unit is configured for Motormaster control, then
this is the setpoint to which the ComfortLink PD routine will mod-
ulate VFD fan speed. The Motormaster setpoint is calculated as
HPSP+MMSPFOST. This setpoint will be used by both the A and
B circuits.
Condenser Fan Control Outputs
There are two outputs (MBB Relays) provided to control head
pressure:
CD.F.A Condenser Fan Circuit A — CONDFANA
CD.F.B Condenser Fan Circuit B — CONDFANB
MM.F.A Motormastr Fan Circuit A — MM_A_RUN
MM.F.B Motormastr Fan Circuit B — MM_B_RUN
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
MM.F.A (Motormastr Fan Circuit A) (SCB
Relay 1) — This output will be used as the run enable of circuit
A Motormaster VFD.
Outputs
FANS
MM.F.B (Motormastr Fan Circuit B) (SCB
Relay 2) — This output will be used as the run enable of the
circuit B Motormaster VFD.
In addition, if Motormaster control is enabled, there will be
two 4 to 20 mA analog outputs to modulate fan speed for Mo-
tormaster operation:
A.VFD MtrMaster A Commanded % — MM_A_VFD
B.VFD MtrMaster B Commanded % — MM_B_VFD
For Motormaster fan of Circuit A to modulate, MM_A_RUN
must be ON.
For Motormaster fan of Circuit B to modulate, MM_B_RUN
must be ON.
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). The control cycles three stages of outdoor fans,
two fans for stage one, four fans for stage two, and six fans for
stage three to maintain acceptable head pressure.
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