Transcript Ch-15

Always Learning
CHAPTER 15
Refrigerant Service Operations
OBJECTIVES
After studying Chapter 15, the reader will be able to:
1.
2.
3.
4.
Be familiar with the preventive maintenance
operations and the adjustments necessary to
keep heating and A/C systems operating properly.
Perform basic A/C service operations, given the
operating manual for the equipment.
Be familiar with how to retrofit R-134a into an R12 system.
Be able to complete the ASE tasks related to
refrigerant handling.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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KEY TERMS
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•
•
•
•
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•
•
•
•
•
Black death
Charging cylinder
Conversion fitting
Cubic feet per minute (cfm)
Electronic scales
Evacuate
Fingerprint
Flush
Identifier
Inline filter
Live flushing
Micron
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By Thomas S. Birch
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•
4
Noncondensable gases
(NCG)
Out-gases
Partial charge
Pressure-temperature (PT)
Recover
Recycle
Retrofit
Slugging
Tank certification
Topping off
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INTRODUCTION
•
The service and repair of heating and A/C systems
consist of preventive maintenance operations; the
adjustment, repair, overhaul, or replacement of
system components; and standard A/C service
operations.
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INTRODUCTION
•
There are several important facts to keep in mind
when servicing an A/C system:
•
•
•
•
A/C systems are designed to operate using a
specific amount of a particular refrigerant.
A/C systems are designed to operate using a
specific amount of a particular refrigerant oil.
Adding any other chemical into a system can create
a chemical problem that can cause system damage
or failure.
GAUGE PRESSURES
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PREVENTIVE MAINTENANCE AND
ADJUSTMENT OPERATIONS
•
The U.S. Clean Air Act has placed a group of
requirements on A/C service.
•
•
These requirements can be viewed at
www.epa.gov/ozone .
A/C SERVICE AND THE CLEAN AIR ACT
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A/C SERVICE OPERATIONS
•
REFRIGERANT CONTAMINATION
•
•
REFRIGERANT IDENTIFICATION
•
•
SEALANT IDENTIFICATION
REFRIGERANT RECOVERY
•
•
SEALANT CONTAMINATION
RECOVERING CONTAMINATED REFRIGERANT
RECYCLING REFRIGERANT
•
AIR CONTAMINATION CHECKS
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TECH TIP
•
A special filter called the Recycle Guard is
available that can be attached to the inlet
hose of the recovery machine. The Recycle
Guard filter is designed to remove
contaminants such as sealants and dye
before they can enter the recovery unit.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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A/C SERVICE OPERATIONS
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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A/C SERVICE OPERATIONS
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A/C SERVICE OPERATIONS
•
•
•
FLUSHING AN A/C SYSTEM
INSTALLING AN INLINE FILTER
CHECKING AND CORRECTING OIL LEVELS
•
•
•
OIL INJECTION, CHARGING CHOICES
EVACUATING A SYSTEM
RECHARGING A SYSTEM
•
•
•
PARTIAL CHARGING
CHARGING FROM LARGE CONTAINERS
CHARGING FROM SMALL CANS
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TECH TIP
1.
2.
The compressor in an orifice tube system is
cooled by liquid refrigerant that passes
through the oil bleed hole in the accumulator.
An undercharged system will cause
compressor overheating and probable failure.
An overcharged system will cause higherthannormal high-side pressure, especially if
the vehicle is in stop-and-go traffic on a hot
day. Excessive pressure can cause the highpressure cutoff switch to shut down the
system.
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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TECH TIP
3.
4.
The specified charge in an orifice tube system can
produce higher duct temperatures than an
undercharge.
Professional service technicians prefer not to top off
a system because the system probably has a leak
that should be repaired. Also, the system contains an
unknown amount of refrigerant, oil, and possible
contaminants. It is a much better practice to recover
the refrigerant and see how much refrigerant and oil
come out. The refrigerant can now be recycled to
remove any air that might have been present and
then returned to the system along with additional
refrigerant to fill the system with the specified amount
of clean oil.
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TECH TIP
1.
Some technicians prefer to begin the
charging process into the high side (system
off). The highside pressure should increase
immediately as the valve is opened. There
should be a slight delay and a slower lowside pressure increase as refrigerant bleeds
through the TXV or OT. A pressure increase
that is too rapid indicates a possible
compressor internal leak; too slow an
increase indicates a possible restriction of the
TXV or OT.
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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TECH TIP
2. Some technicians prefer to complete the charging
process with the system operating so they can watch
the gauge pressures and temperatures normalize,
even though this is not necessary with most modern
charging stations. Normal A/C system operation
should occur about 1/4 to 1/2 lb before the system is
completely charged. This last volume becomes
reserve to be stored in the receiver–drier or
accumulator. At this point, the sight glass should
clear up or the bottom of the accumulator should
become cold. The highside pressure should not
increase as the remaining refrigerant is charged into
the system.
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TECH TIP
1.
2.
3.
The charging operation should be done with the can vertical,
charging vapor, but it can be safely speeded up by rotating the
can to horizontal and then back to vertical. This increases can
pressure by adding heat to the refrigerant.
Any refrigerant remaining in the can, sometimes called the heel
or tail, often evaporates to become a contaminant in the
atmosphere. There is also a loss from the hose as the cans are
changed.
When a can empties, allow the low-side pressure to drop as low
as it will go to pull as much refrigerant as possible from the can.
It is easy to leave as much as an ounce in the can, and this can
cause an undercharged system or one without any refrigerant
reserve.
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TECH TIP
4. Tampering has become a major concern with many
A/C service technicians; once a system has been
serviced and put in proper operating condition, they
want it to stay that way. A set of seals has been
developed so it is easy to tell if a system has been
opened. These seals are plastic sleeves that are
placed over the service fittings and heated to shrink
them to fit the fitting and cap. Another type of service
port seal is similar to an electrical tie wrap, and
installs without the need of a hot air gun. The seal
must be cut in order to remove the service cap.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
Upper Saddle River, NJ 07458 • All rights reserved.
RETROFITTING R-134A INTO AN R-12
SYSTEM
•
Retrofitting is normally a repair-driven operation; it
is not done until absolutely necessary.
•
All experts agree that if a system was designed for
R-12, R-12 should be used in it when it requires
service, even though some systems cool better after
changing to R-134a.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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RETROFITTING R-134A INTO AN R-12
SYSTEM
•
•
•
REFRIGERANT CHOICE FOR RETROFIT
POSSIBLE RETROFIT PROBLEMS
RETROFIT PROCEDURE
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USING AND INSTALLING SEALANTS AND
STOP LEAKS
•
Most HVAC technicians dislike stop leaks as they
are considered an inadequate or temporary repair
method, and the best repair is to actually fix the
leak.
•
Sealants/stop leaks might or might not work, and
they might or might not damage the system.
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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SUMMARY
1.
2.
3.
4.
5.
A major maintenance operation is to ensure the
system has a good accessory drive belt that is
properly adjusted.
The first refrigerant service operation is to identify
the refrigerant in the system and check to make
sure that it does not contain a sealant.
The refrigerant is recovered from a system so
that service operations can be performed.
A Recycle Guard filter can remove contaminants
from refrigerant being recovered.
Recycling removes foreign particles, water, and
air from refrigerant.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
Upper Saddle River, NJ 07458 • All rights reserved.
SUMMARY
6.
7.
8.
9.
10.
Sections of an A/C system can be flushed or a
filter can be installed to remove foreign particles.
Most vacuum pumps require periodic oil changes
so they can do an effective job in removing air
and other non-condensable gases.
Starting with the system in a vacuum, the
specified amount of new or recycled refrigerant is
charged into the system.
Most professional technicians do not use small
cans to charge a system.
An R-12 system can be retrofitted to R-134a
using an approved retrofit procedure.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
Upper Saddle River, NJ 07458 • All rights reserved.
REVIEW QUESTIONS
1.
2.
3.
4.
5.
6.
A dirty condenser with debris at the front can be cleaned using
______________ ______________ , ______________
______________ , or a(n) ______________ .
The first step in any refrigerant service procedure should be to
______________ what type of ______________ is in the system.
More than ______________ ______________ air in the refrigerant of
an A/C system is considered contaminated.
Refrigerant contaminated with air should be ______________ and
then ______________ .
A shop that does full refrigerant service on both older and newer A/C
systems must have ______________ sets of service
______________ .
A recycling machine has the ability to remove ______________ ,
______________ , ______________ , and solid ______________
from the refrigerant.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
Upper Saddle River, NJ 07458 • All rights reserved.
REVIEW QUESTIONS
7.
8.
9.
10.
11.
12.
Refrigerant that is contaminated with air will have a(n)
______________ that is ______________ than normal for a particular
temperature.
A(n) ______________ or ______________ should never be flushed,
and it is doubtful that a flat-tube ______________ can be cleaned by
flushing.
A(n) ______________ ______________ can be installed in the liquid
line to trap debris that can plug the OT.
Water is removed from inside an A/C system by ______________ the
system to a(n) ______________ lower than the boiling point of water.
The ______________ in most vacuum pumps must be
______________ periodically in order to keep the pump operating
properly.
Partial charging of a system is not recommended because of the
difficulty of adding the ______________ ______________ of
refrigerant.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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REVIEW QUESTIONS
13.
14.
15.
16.
17.
The proper charge amount for a vehicle can be found on
the ______________ under the vehicle’s
______________ .
It will take ______________ small (12 oz)
______________ of refrigerant to charge a system that
holds 2 1/4 lbs of refrigerant.
If retrofitting an R-12 system to R-134a, a small refrigerant
leak will become ______________ , and high-side
pressures will probably ______________ .
If retrofitting a system that contains a high-pressure relief
valve, a(n) ______________ ______________
______________ ______________ must be installed.
When retrofitting a system, new ______________
______________ must be permanently installed over the
existing ones, and a(n) ______________
______________ must be filled out and placed over the
old one.
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
1. Technician A says that eye protection should be
worn when working with refrigerants. Technician
B says to avoid skin contact with refrigerants and
their oil. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
2. Two technicians are discussing how to remove
refrigerant from a system. Technician A says that
you can vent it into the atmosphere as long as it
has moisture in it. Technician B says that all
refrigerant must be captured. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
Automotive Heating and Air Conditioning, 6/e
By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
3. Technician A says that the same recovery unit
can be used for R-12 and R-134a. Technician B
says that the service hoses from an R-134a
recovery unit must have shutoff valves within 18
inches of the end. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
4. Technician A says that high pressure in recycled
refrigerant is only caused by air contamination.
Technician B says that recycled refrigerant should
have the same purity standards as new
refrigerant. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
5. Technician A says that compressor failure sends
metal and debris through the system, so it should
be flushed using R-11. Technician B says that a
good method to solve this problem is to replace
the compressor and install an inline filter. Who is
correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
6. A system contaminated with moisture should be
evacuated for a minimum of 15 minutes.
a.
b.
True
False
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
7.
Technician A says that checking the pressure–
temperature relationship is a reliable way to
check for contaminated refrigerant. Technician B
says that refrigerant with more than 2% of a
foreign refrigerant normally should be sent off for
reclaiming or disposal. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
8. Refrigerant can be contaminated with NCG if the
______________ .
a.
b.
c.
d.
recovery unit hose is not tight
system is not thoroughly evacuated before
recharging
technician uses sloppy service procedures
All of these
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
9. Technician A says that a system should be
evacuated for twice as long if the vacuum pump
will only pull it down to 20" Hg. Technician B says
that the system might have a leak in it if it will not
pull down into a deep vacuum. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
10. Technician A says that refrigerant charge levels
are given in service manuals. Technician B says
that charge levels are printed on the under-hood
decal. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
11. Technician A says that an overcharge will cause
excessively high system pressures. Technician B
says that a small can of refrigerant holds 1 lb.
Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
12. We normally charge refrigerant into the high side
with the engine running.
a.
b.
True
False
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
13. Technician A says that retrofitting a system is
simply a matter of recovering the R-12 and
recharging it with a drop-in refrigerant. Technician
B says that the charge level specification is the
same with R-134a as with R-12. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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CHAPTER QUIZ
14. Technician A says that SNAP approval indicates a
good refrigerant that will have no problems in a
system. Technician B says that using any
refrigerant that contains R-22 requires the system
to have barrier hoses. Who is correct?
a.
b.
c.
d.
A only
B only
Both A and B
Neither A nor B
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By Thomas S. Birch
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Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson Education
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