Service Manual

22
REFRIGERATION SYSTEM
Refrigerant
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could result in personal
injury or equipment damage.
R- 410A refrigerant which has higher 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.
!
WARNING
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage or improper operation.
The compressor in a R- 410A system uses a polyol
ester (POE) oil. 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.
CAUTION
!
In an air conditioning and heat pump system, refrigerant
transfers heat from one place to another. The condenser is
the outdoor coil in the cooling mode and the evaporator is
the indoor coil.
In a heat pump, the condenser is the indoor coil in the
heating mode and the evaporator is the outdoor coil.
In the typical air conditioning mode, compressed hot gas
leaves the compressor and enters the condensing coil. As
gas passes through the condenser coil, it rejects heat and
condenses into liquid. The liquid leaves condensing unit
through liquid line and enters metering device at evaporator
coil. As it passes through metering device, it becomes a
gas- liquid mixture. As it passes through indoor coil, it
absorbs heat and the refrigerant moves to the compressor
and is again compressed to hot gas, and cycle repeats.
Servicing Systems on Roofs With Synthetic
Materials
POE (polyol ester) 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 which 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 refrigerants 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) drop 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.
Brazing
This section on brazing is not intended to teach a technician
how to braze. There are books and classes which teach and
refine brazing techniques. The basic points below are listed
only as a reminder.
Definition: The joining and sealing of metals using a
nonferrous metal having a melting point over
800_F/426.6_C.
Flux: A cleaning solution applied to tubing or wire before it
is brazed. Flux improves the strength of the brazed
connection.
When brazing is required in the refrigeration system, certain
basics should be remembered. The following are a few of
the basic rules.
1. Clean joints make the best joints. To clean:
 Remove all oxidation from surfaces to a shiny
finish before brazing.
 Remove all flux residue with brush and water
while material is still hot.
2. Silver brazing alloy is used on copper- to- brass,
copper- to- steel, or copper- to- copper. Flux is
required when using silver brazing alloy. Do not use
low temperature solder.
3. Fluxes should be used carefully. Avoid excessive
application and do not allow fluxes to enter into the
system.
4. Brazing temperature of copper is proper when it is
heated to a minimum temperature of 800_F and it is a
dull red color in appearance.
Service Valves and Pumpdown
PERSONAL INJURY AND UNIT DAMAGE HAZARD
Failure to follow this warning could result in personal
injury or equipment damage.
Never attempt to make repairs to existing service
valves. Unit operates under high pressure. Damaged
seats and o- rings should not be replaced. Replacement
of entire service valve is required. Service valve must be
replaced by properly trained service technician.
!
WARNING
Service valves provide a means for holding original factory
charge in outdoor unit prior to hookup to indoor coil. They
also contain gauge ports for measuring system pressures
and provide shutoff convenience for certain types of repairs.
(See Fig. 15.)
Front- seating service valves are used in outdoor residential
equipment. This valve has a service port that contains a
Schrader fitting. The service port is always pressurized after
the valve is moved off the front- seat position.
The service valves used in the outdoor units come from the
factory front- seated. This means that the refrigerant charge
is isolated from the line- set connection ports. All heat
pumps that are equipped with and AccuRater piston
heating metering device are shipped with an adapter stub