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APPENDIX I — OPTIONAL GREENSPEED
This appendix contains instructions for the start-up and service
of the optional Greenspeed/low ambient control on 48/50P020-
060 units. For Design Series number (the 13th digit of the model
number) less than 4 unit with legacy Motormaster VFD, please
refer to OPTIONAL MOTORMASTER® V CONTROL.
The Greenspeed/low ambient Option utilizes varied frequency
drives (VFDs) which adjust condenser fan motor speed in re-
sponse to varying saturated refrigerant head pressure. A properly
applied Greenspeed/low ambient Option control extends the oper-
ating range of air-conditioning systems and permits operation at
lower outdoor ambient temperatures. Head pressure refers to the
refrigerant pressure at the discharge side of the compressor. Thus
it is sometimes refers to as "discharge pressure." Head pressure
control will be managed directly by the ComfortLink controls (no
third-party control).
The head pressure control stages fixed speed fans and modulating
fans, if available, to maintain the head pressures of circuit A and
circuit B within acceptable ranges. For controls purpose, the head
pressures are converted to saturated condensing temperatures
(SCTs) as the feedback information to the condenser fans (also re-
ferred to as "outdoor fans"). SCT.A is the saturated condensing
temperature for refrigeration Circuit A, and SCT.B is the saturated
condensing temperature for refrigeration Circuit B. There are a to-
tal of up to 6 condenser fans (depending on unit size and installed
options) for controlling the head pressures of the 2 refrigeration
circuits. The Greenspeed Option can further optimize the energy
efficiency of the units by varying the speeds of condenser fans to
achieve optimal head pressures during normal operations.
The control described in this document is also referred to as con-
denser fan control.
The low ambient control described here will be directly imple-
mented in the ComfortLink software. It will not be compatible
with the existing Motormaster V control as found in
CESR131343-07-xx and earlier that make use of accessory part
numbers CRLOWAMB018A00 through CRLOWAMB026A00.
The location of Greenspeed/low ambient VFD device is shown in
Fig. AL-AN.
Configure Greenspeed/Low Ambient Control
The Greenspeed/low ambient control is configured for proportion-
al integral (PI) control mode. The VFDs control varies the con-
denser fan motor speed to maintain a setpoint of discharging head
pressure.
The following ComfortLink control configurations must be set
when using a Greenspeed/low ambient device:
•
Configuration
COOL
Test Greenspeed/Low Ambient Control
To test the control and motor in the test mode, run compressor
no. 1. The Greenspeed/low ambient electronic control adjusts
the fan speed based on the discharge line pressure input. Ensure
that fans are rotating clockwise (as viewed from above). If rota-
tion is backward, lock out all power then swap 2 leads AFTER
the VFDs control.
For P series units, fan stages react to discharge pressure transduc-
ers (DPT) (Pressures
REF.P
nected to the compressor discharge piping in circuit A and B. The
control converts the pressures to the corresponding saturated con-
densing temperatures (Temperatures
SCT.B).
OV.EN = YES
DP.A and DP.B) which are con-
REF.T
SCT.A and
®
/LOW AMBIENT CONTROL
Unit size (Configuration
if the second stage fans are configured to respond to a particular
refrigerant circuit (independent control) or both refrigerant cir-
cuits (common control). The 48/50P070 and 075 units are the
only units that utilize independent fan controls.
There are configurations provided for head pressure and low am-
bient control that can be found at the local display under Configu-
ration
COOL.
Greenspeed/Low Ambient (OV)
[OUTDOOR_VFD] 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
standard unit. This configuration must be set to YES if the option-
al condenser fan VFDs are installed on the unit. Setting this con-
figuration to YES alters the condenser fan staging sequence to ac-
commodate the Greenspeed/low ambient control algorithm.
The standard unit is capable of mechanical cooling operation
down to 32°F outdoor temperature. With the addition of optional
Greenspeed/low ambient speed control on the stage 1 condenser
fans, mechanical cooling operation down to –20°F outdoor tem-
perature is possible.
This configuration will have a range of NO/YES and will default
to NO.
Low Ambient Setpoint (LASP)
[LASP] This is the head pressure setpoint used by the
ComfortLink control of condenser fans for head pressure control
under low ambient conditions. This configuration will have a
range of 80 to 150°F and a default of 100°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 GreenSpeed/low ambient control, it will be neces-
sary for an operator to manually change this setting. This configu-
ration will have a range of –20 to 55°F and a default of 53°F.
Outdoor VFD PI Run Rate (OV.RR)
[OV_RATE] This is the number of seconds between execution of
the Greenspeed/low ambient ComfortLink 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 Greenspeed/
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 ambient
control, then this is the setpoint to which the ComfortLink PD rou-
tine 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
ComfortLink PD routine will modulate VFD fan speed.
259
UNIT
SIZE) is used to determine
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