Loss Of Charge Switch; Check Defrost Thermostat; Troubleshooting; Start-Up Checklist - Carrier 50JZ Installation, Start-Up And Service Instructions Manual

LED
OFF
FLASHING
ON
When the thermostat is satisfied, its contacts open, de-engergizing
contactor and blower relay. Compressor and motors stop.
If indoor unit is equipped with an off-delay circuit, the indoor
blower can be run up to an additional 120 sec to increase the
system efficiency.

LOSS OF CHARGE SWITCH

The loss of charge switch is a protective device wired into control
circuit (low voltage). It shuts off the compressor if abnormally low
pressures are present in the refrigeration circuit.
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.

CHECK DEFROST THERMOSTAT

There is a liquid header with a brass distributor and feeder tube
going into outdoor coil. At the end of 1 of the feeder tubes, there
is a 3/8-in. (9.5 mm) OD stub tube approximately 3 in. (76.2 mm)
long. The defrost thermostat should be located on stub tube. Note
that there is only 1 stub tube used with liquid header, and on most
units it is the bottom circuit.
Fig. 25—Phase Monitor Control and LED Indicators
STATUS
No Call for compressor operation
Reversed phase
Normal
The 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 closed at 30° ± 3°F
(-1.1°C +/- 1.7°C) and open at 80° ± 5°F (26.7°C +/- 2.8°C).
NOTE: The defrost thermostat must be located on the liquid side
of the outdoor coil on the bottom circuit and as close to the coil as
possible.

TROUBLESHOOTING

Refer to the Cooling and Heating Troubleshooting Charts (Table
13 & 14) for troubleshooting information.

START-UP CHECKLIST

Use the Start-Up checklist to ensure proper start-up procedures are
followed.
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