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problem exists, be sure that all supply--air and return--air
grilles are open and free from obstructions, and that the
air filter is clean. When necessary, refer to Indoor Airflow
and Airflow Adjustments section to check the system
airflow.
Step 7 — Metering Devices- -TXV & Piston
This unit uses 2 types of metering devices. The outdoor
metering device is a fixed orifice and is contained in the
brass hex--body in each liquid line feeding the outdoor
coils. The indoor metering device is a TXV type device.
Refrigerant Circuit
FIGURE 18
Step 8 — 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. These pressure switches are
specifically designed to operate with R--410A systems.
R--22
pressure
switches
replacements for the R--410A system.
Step 9 — Loss of Charge Switch
This switch is located on the liquid line and protects
against low suction pressures caused by such events as
loss of charge, low 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
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.
22
must
not
be
used
switches
are
attached
Step 10 — High- -Pressure Switches
The high--pressure switches are located on the discharge
line and protect against excessive condenser coil
pressure.
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 (R- -410A
Refrigerant)
The compressor used in this product is specifically
designed to operate with R--410A refrigerant and cannot
be interchanged.
WARNING
!
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.
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 psi
differential pressure.
The Copeland scroll compressor uses Mobil 3MAF POE
oil. Copeland Ultra 22 CC should be used if additional oil
as
is needed in the field. Mobil Artic EAL22CC or ICI
Emkarate RL22 or 32CF oil may be used to recharge
these compressors if Ultra 22 is not available.
Step 12 — Refrigerant System
This step covers the refrigerant system, including the
compressor oil needed, servicing systems on roofs
containing synthetic materials, the filter drier and
refrigerant charging.
Refrigerant
WARNING
!
PROPERTY HAZARD, PERSONAL INJURY OR
to
ENVIRONMENTAL HAZARD
Failure to follow this warning could result in property
damage or personal injury or death.
This system uses 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 R--410A. If you are unsure consult the
equipment manufacturer.
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