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APPENDIX G — OPTIONAL GREENSPEED
®
/LOW AMBIENT CONTROL
This appendix contains instructions for the start-up and service
of the optional Greenspeed/low ambient control on 48/
50A020-060 units. For Design Series number (the 13th digit of
the model number) less than 4 unit with legacy Motormaster
VFD, please refer to Appendix F.
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 prop-
erly applied Greenspeed/low ambient Option control extends
the operating range of air-conditioning systems and permits
operation at lower outdoor ambient temperatures. Head pres-
sure 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
Comfort
Link 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
condenser fan control.
The low ambient control described here will be directly imple-
mented in the
Comfort
Link 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. R-T.
Fig. R — Greenspeed/Low Ambient VFD Control Location — 48/50A020-035 Units
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 ...