196
APPENDIX F — OPTIONAL FACTORY-INSTALLED LOW AMBIENT MOTORMASTER
®
V CONTROL
This appendix contains instructions for the start-up and service
of the optional low ambient Motormaster
®
V (MMV) control
on 48/50A020-060 units.
The Motormaster V control is a motor speed control device
which adjusts condenser fan motor speed in response to vary-
ing liquid refrigerant pressure. A properly applied Motormaster
V control extends the operating range of air-conditioning sys-
tems and permits operation at lower outdoor ambient tempera-
tures. Head pressure refers to the refrigerant pressure at the dis-
charge side of the compressor. Thus it is sometimes refers to as
'discharge pressure'. Head pressure control will be managed di-
rectly by the
Comfort
Link controls (no third party control).
The head pressure control stages fixed speed fans and modulat-
ing 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 tem-
peratures (SCTs) as the feedback information to the condenser
fans (also referred 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 Cir-
cuit B. There are a total of up to 6 condenser fans (depending
on unit size and installed options) for controlling the head pres-
sures of the 2 refrigeration circuits, of which up to 2 fans can
be controlled by VFD(s) (variable frequency drive(s)) upon in-
stallation option.
The control described in this document is also referred to as
condenser fan control. Where Motormaster control is involved,
it may also referred to as low ambient 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 field-installed Motormaster V control as found in
CESR131343-07-xx and earlier that make use of accessory part
numbers CRLOWAMB018A00 through CRLOWAMB026A00.
Please refer to page 46 and accessory documentation for those
units with field-installed accessories.
Location of Motormaster V device is shown in Fig. M-P.
Fig. M — Low Ambient MMV 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 ...