Service Manual

11
21
C terminal of
ID low voltage
harness
R terminal of
ID low voltage
harness
11
BLK
BLK
RED
R
RED
RED
RED
CCH
SWITCH
BLK
Relay
R
e
l
a
y
R
E
D
RED
Relay
RED RED
A170102
Fig. 6 – Wiring for 3- Phase 460 Volt
The crankcase heater is powered by high- voltage power of
unit. Use extreme caution troubleshooting this device with
power on. The easiest method of troubleshooting is to apply
voltmeter across crankcase heater leads to see if heater
has power. Do not touch heater. Carefully feel area around
crankcase heater. If warm, crankcase heater is probably
functioning. Do not rely on this method as absolute
evidence heater is functioning. If compressor has been
running, the area will still be warm.
With power off and heater leads disconnected, check across
leads with ohmmeter. Do not look for a specific resistance
reading. Check for resistance or an open circuit. Change
heater if an open circuit is detected.
Time- Delay Relay (TDR)
The TDR is a solid- state control, recycle delay timer which
keeps indoor blower operating for 90 sec after thermostat is
satisfied. This delay enables blower to remove residual
cooling in coil after compression shutdown, thereby
improving efficiency of system. The sequence of operation
is that on closure of wall thermostat and at end of a fixed on
delay of 1 sec, fan relay is energized. When thermostat is
satisfied, an off delay is initiated. When fixed delay of 90 
20 sec is completed, fan relay is de- energized and fan
motor stops. If wall thermostat closes during this delay, TDR
is reset and fan relay remains energized. TDR is a 24v
device that operates within a range of 15v to 30v and draws
about 0.5 amps. If the blower runs continuously instead of
cycling off when the fan switch is set to AUTO, the TDR is
probably defective and must be replaced.
Pressure Switches
Pressure switches are protective devices wired into control
circuit (low voltage). They shut off compressor if abnormally
high or low pressures are present in the refrigeration circuit.
R- 410A pressure switches are specifically designed to
operate with R- 410A systems. R- 22 pressure switches
must not be used as replacements for the R- 410A air
conditioner or heat pump. R- 410A pressure switches are
identified by a pink stripe down each wire.
Low- Pressure Switch (AC
Only)
The low- pressure switch is located on suction line and
protects against low suction pressures caused by such
events as loss of charge, low airflow across indoor coil, dirty
filters, etc. It opens on a pressure drop at about 50 psig for
R- 410A and about 27 for R- 22. If system pressure is above
this, switch should be closed. To check switch:
1. Turn off all power to unit.
2. Disconnect leads on switch.
3. Apply ohmmeter leads across switch. You should
have continuity on a good switch.
NOTE: Because these switches are attached to refrigeration
system under pressure, it is not advisable to remove this
device for troubleshooting unless you are reasonably
certain that a problem exists. If switch must be removed,
remove and recover all system charge so that pressure
gauges read 0 psi. Never open system without breaking
vacuum with dry nitrogen.
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal
injury.
Wear safety glasses, protective clothing, and gloves
when handling refrigerant.
CAUTION
!
To replace switch:
1. Apply heat with torch to solder joint and remove
switch.
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal
injury.
Wear safety glasses when using torch. Have quenching
cloth available. Oil vapor in line may ignite when switch
is removed.
CAUTION
!
2. Braze in 1/4- in. flare fitting and screw on replacement
pressure switch.
High - Pressure Switch (AC &
HP)
The high- pressure switch is located in liquid line and
protects against excessive condenser coil pressure. It
opens around 610 to 670 psig for R- 410A and 400 psig for
R- 22 (+/- 10 for both). Switches close at 298 (+/- 20) psig
for R- 22 and 420 or 470 (+/- 25) psig for R- 410A. High
pressure may be caused by a dirty condenser coil, failed fan
motor, or condenser air re- circulation.
To check switch:
1. Turn off all power to unit.
2. Disconnect leads on switch.
3. Apply ohmmeter leads across switch. You should
have continuity on a good switch.
NOTE: Because these switches are attached to refrigeration
system under pressure, it is not advisable to remove this
device for troubleshooting unless you are reasonably
certain that a problem exists. If switch must be removed,
remove and recover all system charge so that pressure
gauges read 0 psi. Never open system without breaking
vacuum with dry nitrogen.
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal
injury.
Wear safety glasses, protective clothing, and gloves
when handling refrigerant.
CAUTION
!