186CNV / 284ANV: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
3
ELECTRICAL
Aluminum Wire
Whenever aluminum wire is used in branch circuit wiring with this unit,
adhere to the following recommendations.
Connections must be made in accordance with the National Electrical
Code (NEC), using connectors approved for aluminum wire. The
connectors must be UL approved (marked Al/Cu with the UL symbol)
for the application and wire size. The wire size selected must have a
current capacity not less than that of the copper wire specified, and must
not create a voltage drop between service panel and unit in excess of 2 of
unit rated voltage. To prepare wire before installing connector, all
aluminum wire must be “brush-scratched” and coated with a corrosion
inhibitor such as Pentrox A. When it is suspected that connection will be
exposed to moisture, it is very important to cover entire connection
completely to prevent an electrochemical action that will cause
connection to fail very quickly. Do not reduce effective size of wire,
such as cutting off strands so that wire will fit a connector. Proper size
connectors should be used. Check all factory and field electrical
connections for tightness. This should also be done after unit has reached
operating temperatures, especially if aluminum conductors are used.
ELECTRICAL SYSTEM OVERVIEW
The electrical system consists of four main primary components and
sub-systems as listed below and shown in Fig. 1.
• Terminal Block
• Transformer
• Compressor and Fan Sub-System
• Control Sub-System
A200232
Fig. 1 – ELECTRICAL SYSTEM OVERVIEW
Terminal Block
The terminal block provides the connection point for high voltage field
power wiring
Transformer
IMPORTANT:
The 24VAC power (Rc) in the PCM comes from the
transformer in the equipment. The phase of this transformer connection
is not controlled relative to the phase of the power provided by the
transformer in the indoor equipment (Rh). Wiring requirements in this
manual do not connect Rc and Rh together. For any non-standard
wiring, care should be taken to make sure that Rc and Rh are not
connected together. Doing so may result in destroying one or both of the
transformers in this and the indoor equipment.
The transformer converts line voltage power to low voltage power
required by the control system. The transformer also provides isolation
between the line voltage and low voltage systems.
Compressor / Fan Sub-System
The compressor / fan subsystem consists of the following components:
• Variable speed compressor
• Variable speed fan
• Variable Frequency Drive (VFD) sub-system for driving the
compressor and fan
The VFD sub-system consists of several components that are shown
conceptually in Fig. 2 with detailed wiring shown in
. The
function of each component is described in further detail in the following
section.
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or death.
Exercise extreme caution when working on any electrical components.
Shut off all power to system prior to troubleshooting. Some
troubleshooting techniques require power to remain on. In these
instances, exercise extreme caution to avoid danger of electrical shock.
ONLY TRAINED SERVICE PERSONNEL SHOULD PERFORM
ELECTRICAL TROUBLESHOOTING.
CAUTION
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
Aluminum wire may be used in the branch circuit (such as the circuit
between the main and unit disconnect), but only copper wire may be
used between the unit disconnect and the unit.
CAUTION
!
Equipment Damage Hazard
Failure to follow this caution may result in equipment damage or
improper operation.
Do not connect the equipment 24VAC supply (Rc) to the indoor
equipment 24VAC supply (Rh).
TERMINAL
BLOCK
TRANSFORMER
COMPRESSOR &
FAN SUB-SYSTEM
CONTROL
SUB-SYSTEM
Line Voltage
Field Wiring
(Power)
Low Voltage
Field Wiring
(Communicaon
/ Control)
