Carrier 50JZ-A - Manual (Page 20)

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Step 10 — High--Pressure Switch
The high--pressure switch is located in the discharge line and
protects against excessive condenser coil pressure. It opens at 650
psig (4482 kPa).
High pressure may be caused by a dirty outdoor coil, failed fan
motor, or outdoor air recirculation.
To check switch:
1. Turn off all power to unit.
2. Disconnect leads on switch.
3. Apply ohm meter leads across switch. You should have
continuity on a good switch.
Step 11 — Copeland Scroll Compressor (Puron
Refrigerant)
The compressor used in this product is specifically designed to
operate with Puron (R--410A) refrigerant and cannot be
interchanged.
EXPLOSION HAZARD
Failure to follow this warning could result in personal injury,
death or property damage.
Wear safety glasses and gloves when handling refrigerants.
Keep torches and other ignition sources away from refrigerant
and oils.
! WARNING
The scroll compressor pumps refrigerant throughout the system by
the interaction of a stationary and an orbiting scroll. The scroll
compressor has no dynamic suction or discharge valves, and it is
more tolerant of stresses caused by debris, liquid slugging, and
flooded starts. The compressor is equipped with an internal
pressure relief port. The pressure relief port is a safety device,
designed to protect against extreme high pressure. The relief port
has an operating range between 550 and 625 psig differential
pressure (3792 and 4309 kPa).
Step 12 — Refrigerant System
This step covers the refrigerant system of the 50JZ--A, including
the compressor oil needed, servicing systems on roofs containing
synthetic materials, the filter drier and refrigerant charging.
Refrigerant
PROPERTY HAZARD, PERSONAL INJURY OR
ENVIRONMENTAL HAZARD
Failure to follow this warning could result in property damage
or personal injury or death.
This system uses Puron (R--410A) refrigerant which has
higher operating pressures than R--22 and other refrigerants.
No other refrigerant may be used in this system. Gauge set,
hoses, and recovery system must be designed to handle Puron.
If you are unsure consult the equipment manufacturer.
! WARNING
Compressor Oil
The Copeland scroll compressor uses 3MAF POE oil. If additional
oil is needed, use Uniqema RL32--3MAF. If this oil is not
available, use Copeland Ultra 32 CC or Mobil Arctic EAL22 CC.
This oil is extremely hygroscopic, meaning it absorbs water
readily. POE oils can absorb 15 times as much water as other oils
designed to HCFC and CFC refrigerants. Take all necessary
precautions to avoid exposure of the oil to the atmosphere.
Servicing Systems on Roofs with Synthetic Materials
POE (polyolester) compressor lubricants are known to cause long
term damage to some synthetic roofing materials. Exposure, even if
immediately cleaned up, may cause embrittlement (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. Procedures which risk
oil leakage include, but are not limited to, compressor replacement,
repairing refrigerant leaks, replacing refrigerant components such
as filter drier, pressure switch, metering 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 10x10 ft (3x3 m) 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 unit base.
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.
Step 13 — System Information
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 zero gauge. Never open system
without breaking vacuum with dry nitrogen.
Check Defrost Thermostat
The defrost thermostat is usually located on the lowest liquid
leaving circuit of the left condenser coil (see Fig. 20). The
thermostat closes at 32_F +/-- 3_F (0_C +/-- 1.7_C) and opens at
65_F +/-- 5_F (18_C +/-- 2.8_C).
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.
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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