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airflow across indoor coil, dirty filters, etc. It opens on a pressure
drop at about 20 psig. 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 ohm meter 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.
Step 11—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.
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 12—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.
The compressor is an electrical (as well as mechanical) device.
Exercise extreme caution when working near compressors. Power
should be shut off, if possible, for most troubleshooting techniques.
Refrigerants present additional safety hazards.
WARNING
!
EXPLOSION, FIRE, ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death and/or property damage.
Wear safety glasses and gloves when handling refrigerants.
Keep torches and other ignition sources away from
refrigerants and oils.
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 anti- -rotational
device and an internal pressure- -relief port. The anti- -rotational
device prevents the scroll from turning backwards and replaces the
need for a cycle protector. 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 psi differential
pressure.
The Copeland scroll compressor uses Mobil 3MA POE oil. This
is the only oil allowed for oil recharge.
Step 13—Refrigerant System
This step covers the refrigerant system of the 50CR, including the
compressor oil needed, servicing systems on roofs containing
synthetic materials, the filter drier, and refrigerant charging.
REFRIGERANT
CAUTION
!
PERSONAL INJURY, UNIT OPERATION HAZARD
Failure to follow this caution may result in personal injury,
equipment damage or improper operation.
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.
COMPRESSOR OIL
The compressor in this system uses a polyolester (POE) oil, Mobil
3MA POE. This oil is extremely hygroscopic, meaning it absorbs
water readily. POE oils can absorb 15 times as much water as other
oils designed for 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, and 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 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 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
cylinder in upright position and a commercial metering device in
manifold hose. Charge refrigerant into suction line.
27
®
units with
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