Evacuation; Introduction; Refrigerant Service Tools; Preparation - Carrier Transport Air Conditioning Installation Procedures Manual

7.1 INTRODUCTION

The process of evacuation is an important step in the
servicing and maintenance of any air conditioning
system. The purpose of evacuation is to remove all air
and moisture from the system in preparation for adding
refrigerant and oil during the charging process. It is
imperative that all air and moisture be removed from the
system, as their presence is detrimental and will
negatively affect performance and longevity of the
systems components. Air remaining in the air
conditioning system will degrade the systems cooling
performance, while any moisture remaining in the
system is both non-condensable and a basis for acid
formation. Moisture is the deadly enemy of refrigeration
systems.

7.2 REFRIGERANT SERVICE TOOLS

The following equipment is essential when performing
an installation of or servicing of any Carrier Transport Air
Conditioning system. Refer to Figure 7-2 for service
component connections.
1 Manifold Gauge Set - Provides access to and
monitors pressures within the system. Manifold Gauge
Sets are available in different configurations and styles.
3-way or 4-way, Liquid filled, with or without a sight
glass, 3 hoses or 4 hoses, 1/4 inch or 3/8 inch manifold
connections, etc. All are acceptable for servicing a
Carrier Transport Air Conditioning system. Familiarize
yourself with the proper operation of your Manifold
Gauge Set before attempting any service.
2 R134a Low Side (Suction) Coupler - Connects
the air conditioning system Suction Access Port to the
Manifold Gauge Set.
3 Ri34a High Side (Discharge) Coupler - Connects
the air conditioning system Discharge Access Port to
the Manifold Gauge Set.
4 Vacuum Pump - 2 Stage (5 CFM Minimum) -
Removes moisture and air from the air conditioning
system in order to obtain required micron level.
5 Micron Gauge - Monitors the evacuation process
in units of microns. Micron gauges can be either digital
(electronic) or analog. When the Micron Gauge is used
as specified by the manufacturer you can be assured all
contaminants have been removed from the air
conditioning system. Proper use of the Micron Gauge
will also serve as a first indication of a leak tight system.
6 Recovery/Recycle Machine (R134a) - Recovers
and Recycles R134a refrigerant that is present within
the air conditioning system.
7 Refrigerant Scale - Accurately weighs the transfer
of refrigerant into the air conditioning system.
8 Refrigerant Cylinder - Storage tank for R134a.
9 Heat Blanket - Used to increase internal
temperature of the refrigerant cylinder, greatly
increasing the transfer of refrigerant to the air
conditioning system.
10 Oil Injector - Used to add additional amounts of oil
to a closed system.
SECTION 7

EVACUATION

11 Vacuum Pump - Air and moisture are removed
from the system by inducing a vacuum through the use
of a vacuum pump. Carrier Transport Air Conditioning
recommends a 5 CFM or larger vacuum pump for
optimum evacuation in the shortest time. A vacuum,
which is measured in microns, results when pressure is
reduced within the system. Functionally, reducing the
pressure results in reducing the boiling point of water
(moisture) that may be in the system. Through the
process of vaporization, the water (moisture) changes
state from a liquid to a vapor and is drawn off by the
vacuum pump and removed from the system. If properly
completed, the system is now ready for charging.
Using a compound gauge (Low Side Gauge) for
determination of vacum level is not recom-
mended because of its inherent inaccuracy. A
micron gauge must always be used to insure a
proper evacuation.

7.2.1 Preparation

a. Evacuate and dehydrate only after pressure leak test.
(Refer to paragraph 9.2 .)
b. Essential tools to properly evacuate and dehydrate
any system include a vacuum pump (5 cfm=8 m
volume displacement) and an electronic vacuum (mi-
cron) gauge. (The pump is available from Carrier
Transicold, P/N 07-00176-11.)
c. If possible, keep the ambient temperature above
60_F (15.6_C) to speed evaporation of moisture. If
the ambient temperature is lower than 60_F
(15.6_C), ice might form before moisture removal is
complete. Heat lamps or alternate sources of heat
may be used to raise the system temperature.

7.2.2 Procedure - Complete system

a. Remove all refrigerant using an approved refrigerant
recovery system, following manufacturers recom-
mendations.
b. The recommended method to evacuate and dehy-
drate the system is to connect two evacuation hoses
(see Figure 7-2) to the vacuum pump and refrigera-
tion system. Be sure the service hoses are suited for
evacuation purposes.
c. Test the evacuation setup for leaks by drawing a deep
vacuum through the manifold gauge set, hoses, and
service couplers with the vacuum pump. Shut off the
pump and check to see if the vacuum holds. Repair
leaks if necessary.
d. Open the vacuum pump and electronic vacuum (mi-
cron) gauge valves, if they are not already open. Start
the vacuum pump. Evacuate unit until the electronic
vacuum gauge indicates 2000 microns. Close the
electronic vacuum gauge and vacuum pump valves.
Shut off the vacuum pump. Wait a few minutes to be
sure the vacuum holds.
e. Break the vacuum with clean dry refrigerant 134a
gas. Raise system pressure to approximately 2 psig
(0.2 kg/cm@), monitoring it with the compound gauge.
f. Remove refrigerant using a refrigerant recovery sys-
tem.
7--1
NOTE
T--311
3 /hr)