Carrier 024-036, Руководство по обслуживанию

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: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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through itself to an extremely low value. This, in effect, removes the
PTC from the circuit.
After system shutdown, resistor cools and resistance value returns to
normal until next time system starts. Thermistor device is adequate for
most conditions, however, in systems where off cycle is short, device
cannot fully cool and becomes less effective as a start device. It is an
easy device to troubleshoot. Shut off all power to system.
Check thermistor with ohmmeter as described below. Shut off all power
to unit. Remove PTC from unit. Wait at least 10 minutes for PTC to cool
to ambient temperature.
Measure resistance of PTC with ohmmeter.
The cold resistance (RT) of any PTC device should be approximately
100-180 percent of device ohm rating.
12.5-ohm PTC = 12.5-22.5 ohm resistance (beige color)
If PTC resistance is appreciably less than rating or more than 200
percent higher than rating, device is defective.
A94006
Fig. 11 – Capacitors
Cycle Protector
Corporate thermostats have anti-cycle protection built in to protect the
compressor. If cycle protection is needed, consult factory authorized
aftermarket offering.
Crankcase Heater
Crankcase heater is a device for keeping compressor oil warm. By
keeping oil warm, refrigerant does not migrate to and condense in
compressor shell when the compressor is off. This prevents flooded
starts which can damage compressor.
On units that have a single-pole contactor, the crankcase heater is wired
in parallel with contactor contacts and in series with compressor. (See
Fig. 12 .) When contacts open, a circuit is completed from line side of
contactor, through crankcase heater, through run windings of
compressor, and to other side of line. When contacts are closed, there is
no circuit through crankcase heater because both leads are connected to
same side of line. This allows heater to operate when system is not
calling for cooling. The heater does not operate when system is calling
for cooling.
A10174
Fig. 12 – Wiring for Single-Pole Contactor
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
conditioners or heat pumps. R-410A pressure switches are identified by
a pink stripe down each wire.
Low-Pressure Switch
Neither of the air conditioner or heat pump units have a low pressure
switch. The heat pump models have a loss of charge switch located
downstream of the liquid line filter drier. See loss of charge for more
details.
High-Pressure Switch (AC & HP)
The high-pressure switch is located in the discharge line and protects
against excessive condenser coil pressure. It opens around 650 psig and
closes at 420 (+/- 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 psig. Never open system without breaking
vacuum with dry nitrogen.
To replace switch:
1. Apply heat with torch to solder joint and remove switch.
2. Braze in a new pressure switch.
Loss of Charge Switch (HP Only)
Located on liquid line of heat pump only, the liquid line pressure switch
functions similar to conventional low-pressure switch.
Because heat pumps experience very low suction pressures during
normal system operation, a conventional low-pressure switch cannot be
installed on suction line. This switch is installed in liquid line instead
and acts as loss-of-charge protector. The liquid-line is the low side of the
system in heating mode. It operates identically to low-pressure switch
except it opens at 20 (+/- 5) psig and closes at 45 (+/- 10) psig for
R-410A. Troubleshooting and removing this switch is identical to
procedures used on other switches. Observe same safety precautions.
Defrost Thermostats
Defrost thermostat signals heat pump that conditions are right for defrost
or that conditions have changed to terminate defrost. It is a thermally
actuated switch clamped to outdoor coil to sense its temperature. Normal
temperature range is for 13.4 SEER2 33° ± 3°F and open at 55° ± 5°F.
A94006
21 11
BLK BLK
CRANKCASE HTR
CAUTION
!
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal injury.
Wear safety glasses, protective clothing, and gloves when handling
refrigerant.
CAUTION
!
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.