System Information; Time Delay Relay; Loss Of Charge Switch; Check Defrost Thermostat - Carrier 50JZ024 Installation, Start-Up And Service Instructions Manual

Exposure, even if immediately cleaned up, may cause embrittle-
ment (leading to cracking) to occur in one year or more. When
performing any service that may risk exposure of compressor oil to
the roof, take appropriate precautions to protect roofing. Proce-
dures which risk oil leakage include, but are not limited to,
compressor replacement, repairing refrigerant leaks, replacing
refrigerant components such as filter drier, pressure switch, me-
tering device, coil, accumulator, or reversing valve.
SYNTHETIC ROOF PRECAUTIONARY PROCEDURE
1. Cover extended roof working area with an impermeable
polyethylene (plastic) drip cloth or tarp. Cover an approximate
10 x 10 ft. area.
2. Cover area in front of the unit service panel with a terry cloth
shop towel to absorb lubricant spills and prevent run-offs, and
protect drop cloth from tears caused by tools or components.
3. Place terry cloth shop towel inside unit immediately under
component(s) to be serviced and prevent lubricant run-offs
through the louvered openings in the base pan.
4. Perform required service.
5. Remove and dispose of any oil contaminated material per
local codes.
LIQUID LINE FILTER DRIER — The biflow filter drier is
specifically designed to operate with Puron. Use only factory-
authorized components. Filter drier must be replaced whenever the
refrigerant system is opened. When removing a filter drier, use a
tubing cutter to cut the drier from the system. Do not unsweat a
filter drier from the system. Heat from unsweating will release
moisture and contaminants from drier into system.
PURON (R-410A) REFRIGERANT CHARGING — Refer to unit
information plate and charging chart. Some R-410A refrigerant
cylinders contain a dip tube to allow liquid refrigerant to flow
from cylinder in upright position. For cylinders equipped with a
dip tube, charge Puron units with cylinder in upright position and
a commercial metering device in manifold hose. Charge refrigerant
into suction-line.

SYSTEM INFORMATION

TIME-DELAY RELAY — The Time-Delay Relay (TDR) is a
solid-state control, recycle delay timer which keeps indoor blower
operating for 60 sec on 030-060 sizes or 30 sec on 024 size 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 60 ± 5 sec or 30 ± 5 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 on
AUTO, the TDR is probably defective and must be replaced.
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. OD stub tube
approximately 3 in. long (See Fig. 31). 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.
DEFROST THERMOSTATS — Defrost thermostat signals heat
Fig. 31—Defrost Thermostat
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 tempera-
ture range is closed at 30˚ +/- 3˚F and open at 80˚ +/- 5˚F.
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.
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FEEDER TUBE
STUB TUBE
DEFROST
THERMOSTAT
C99029