: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
9
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.
Contactor
The contactor provides a means of applying power to unit using low
voltage (24v) from transformer in order to power contactor coil.
Depending on unit model, you may encounter single- or double-pole
contactors. Exercise extreme caution when troubleshooting as 1 side of
line may be electrically energized. The contactor coil is powered by
24vac. If contactor does not operate:
1. With power off, check whether contacts are free to move. Check
for severe burning or arcing on contact points.
2. With power off, use ohmmeter to check for continuity of coil.
Disconnect leads before checking. A low resistance reading is
normal. Do not look for a specific value, as different part numbers
will have different resistance values.
3. Reconnect leads and apply low-voltage power to contactor coil.
This may be done by leaving high-voltage power to outdoor unit off
and turning thermostat to cooling. Check voltage at coil with
voltmeter. Reading should be between 20v and 30v. Contactor
should pull in if voltage is correct and coil is good. If contactor does
not pull in, replace contactor.
4. With high-voltage power off and contacts pulled in, check for
continuity across contacts with ohmmeter. A very low or 0
resistance should be read. Higher readings could indicate burned or
pitted contacts which may cause future failures.
Capacitor
Capacitors are used as a phase-shifting device to aid in starting certain
single-phase motors. Check capacitors as follows:
1. With power off, discharge capacitors as outlined above. Disconnect
capacitor from circuit. Put ohmmeter on R X 10k scale. Using an
analog ohmmeter, check each terminal to ground (use capacitor
case). Discard any capacitor which measures 1/2 scale deflection or
less. Place ohmmeter leads across capacitor and place on R X 10k
scale. Meter should jump to a low resistance value and slowly
climb to higher value. Failure of meter to do this indicates an open
capacitor. If resistance stays at 0 or a low value, capacitor is
internally shorted.
2. Capacitance testers are available which will read value of capacitor.
If value is not within ±10 percent value stated on capacitor, it
should be replaced. If capacitor is not open or shorted, the
capacitance value is calculated by measuring voltage across
capacitor and current it draws.
Use following formula to calculate capacitance:
Capacitance (mfd)= (2650 X amps)/volts
3. Remove any capacitor that shows signs of bulging, dents, or
leaking. Do not apply power to a defective capacitor as it may
explode.
Sometimes under adverse conditions, a standard run capacitor in a
system is inadequate to start compressor. In these instances, a start assist
device is used to provide an extra starting boost to compressor motor.
This device is called a positive temperature coefficient (PTCR or PTC)
or start thermistor. It is a resistor wired in parallel with the run capacitor.
As current flows through the PTC at start-up, it heats up. As PTC heats
up, its resistance increases greatly until it effectively lowers the current
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.
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or
equipment damage.
Capacitors can store electrical energy when power is off. Electrical
shock can result if you touch the capacitor terminals and discharge the
stored energy. Exercise extreme caution when working near capacitors.
With power off, discharge stored energy by shorting across the
capacitor terminals with a 15,000-ohm, 2-watt resistor.
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or
equipment damage.
Always check capacitors with power off. Attempting to troubleshoot a
capacitor with power on can be dangerous. Defective capacitors may
explode when power is applied. Insulating fluid inside is combustible
and may ignite, causing burns.
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or death.
Exercise extreme caution when taking readings while power is on.