AirComm Corporation Air Conditioner R134A Service Manual

							Products, INC. 
TR-134 System Service Manual
 
 
January 8, 2010 
Page iv  
 
 
LIST OF EFFECTIVE PAGES
 
 
SECTION PAGE DATE 
   
Title  i  January 8, 2010 
Record of Revisions  ii  January 8, 2010 
  iii  January 8, 2010 
List of Effective Pages  iv  January 8, 2010 
Table of Contents   v  January 8, 2010 
Introduction  1  September 15, 1995 
Air Conditioning System Description  2  September 15, 1995 
  3  September 15, 1995 
  4  March 6, 2002 
  5  September 15, 1995 
Refrigerant Servicing  6  August 21, 2006 
  7  August 21, 2006 
  8  August 21, 2006 
  9  August 21, 2006 
  10  January 8, 2010 
  11  January 8, 2010 
  12  January 8, 2010 
General Servicing  13  August 21, 2006 
  14  August 21, 2006 
  15  January 8, 2010 
  16  August 21, 2006 
  17  August 21, 2006 
  18  August 21, 2006 
  19  August 21, 2006 
Troubleshooting  20  August 21, 2006 
  21  August 21, 2006 
  22  August 21, 2006 
  23  August 21, 2006 
  24  August 21, 2006 
  25  August 21, 2006 
Checks  26  August 21, 2006 
  27  January 8, 2010 
  28  January 8, 2010 
    
						

							Products, INC. 
TR-134 System Service Manual
 
 
January 8, 2010 
Page v  
 
TABLE OF CONTENTS 
 
 
SUBJECT  PAGE 
   
Title  i 
   
Record of Revisions    ii 
   
Table of Contents    iii 
   
Introduction   
  1 
AIR CONDITIONING SYSTEM DESCRIPTION
    
1.     Vapor Cycle System Description    2 
2.  Electrical Driven Compressor Systems    4 
3.  Engine Driven Compressor Systems    5 
   
REFRIGERANT SERVICING
   
1. General    6 
2. Discharging System    7 
3. Evacuating System    8 
4. Charging System    9 
5. Flushing System    10 
   
GENERAL SERVICING
   
1. General    13 
2. Inspection Intervals    13 
3.  Plumbing System Maintenance Procedures    14 
4.  Coil Cleaning Maintenance Procedure    16 
5.  Expansion Valve Removal & Installation    17 
6. Compressor Maintenance Procedures    19 
   
TROUBLESHOOTING
   
1. General    20 
2.  Air Conditioning System Diagnosis Chart    21 
3.  Air Conditioning System Troubleshooting    22 
4. Compressor Troubleshooting    25 
   
CHECKS
   
1. General     26 
2.  Refrigerant Level Check    26 
3.  Refrigerant System Leakage Check    27 
4.  Compressor Oil Level Check    27 
   
 
  
						

							Products, INC. 
TR-134 System Service Manual
 
 
Sep 15/95 
Page 1 
 
INTRODUCTION 
 
1. PURPOSE 
 
The purpose of this System Service Manual is to provide detailed instructions for 
the servicing, troubleshooting, checking and maintaining of the Keith Products, INC. 
air conditioning systems using R134a refrigerant.  It is intended to be used for all 
Keith Products air conditioning systems using R134a refrigerant that do not contain 
separate maintenance instructions.  The System Service Manual supplements the 
Maintenance Manual supplied by Keith Products for your particular aircraft type.  
For the latest revision of this document, please visit www.keithproducts.com. 
 
2. SCOPE 
 
The scope of the System Service Manual provides the maintenance technician with 
detailed information covering: 
 
-  Overall system level description and theory of operation. 
 
-  Component level description and theory of operation. 
 
-  System level checking and troubleshooting procedures. 
 
-  Procedures for servicing the air conditioning system refrigerant. 
 
-  The identification of special equipment to accomplish the specific tasks. 
 
3. ARRANGEMENT 
 
This  System Service Manual is arranged similar to Air Transport Association (ATA) 
Specification 100 and provides general servicing and maintenance instructions . 
 
4. GLOSSARY 
 
Nonstandard abbreviations and symbols used in the Maintenance Manual are 
described below. 
 
Abbreviations: 
A/C     - Air Conditioning 
A/R     - As Required 
Assy    - Assembly 
Comm. Avail.  -  Commercially Available 
Evap   - Evaporator 
Gnd    - Ground 
GPU    - Ground Power Unit 
SW     - Switch 
VDC    - Volts Direct Current  
						

							Products, INC. 
TR-134 System Service Manual
 
 
Sep 15/95 
Page 2 
 
 
 AIR CONDITIONING SYSTEM - SYSTEM DESCRIPTION
 
 
1.  VAPOR CYCLE SYSTEM DESCRIPTION 
 
The Keith Products vapor cycle air conditioning system uses liquid refrigerant 
R134a to cool the aircraft cabin.  The major components for the R134a air 
conditioning system consists of a receiver/dryer, expansion valve, evaporator, 
compressor and condenser to cool the aircraft cabin.   Figure 1 shows an 
operational schematic of the air conditioning system. 
 
The receiver/drier stores liquid R134a refrigerant under pressure.  The drier portion 
of the assembly removes any traces of moisture that may have accumulated in the 
system.  Liquid refrigerant flows from the receiver drier through the expansion valve 
where the refrigerant pressure is reduced, allowing it to spray into the evaporator.  
At the same time, a blower driven by an electric motor passes air over the 
evaporator.  This air is cooled since heat is removed from the air by the evaporation 
of the refrigerant in the evaporator.  The evaporator produces water due to 
condensation.  This water drains overboard through a line attached to the 
evaporator cover. 
 
The refrigerant leaves the evaporator as a gas.  This gas is pumped by the 
compressor, raising its pressure and temperature.  This high temperature gas then 
flows to the condenser.  Cooling air, driven by another electric blower motor, 
passes over the condenser, cooling and therefore condensing the refrigerant to a 
liquid.  The liquid refrigerant then enters the receiver/drier, repeating the process. 
 
The plumbing which connects the compressor, condenser and the evaporators, 
consists of rubber based hoses with a nylon barrier.  The fittings are permanently 
swaged onto the hoses. Some systems that have been converted from R12 to 
R134a refrigerant use Barb Lok hose fittings.  Fittings are either o-ring type or 
use flared connections.  Sealant is used on the fitting mating surfaces to prevent 
refrigerant leaks.  Two R134a service valves are sized differently to avoid incorrect 
cross-connecting when gaining access to the plumbing for system recharging. 
 
The compressor on Keith Products air conditioning systems is driven either by an 
electrical motor, or by the engine.  Listed below is a more detailed description of 
electric and engine driven compressor systems.  
						

							Products, INC. 
TR-134 System Service Manual
 
 
Sep 15/95 
Page 3 
 
 
 
Figure 1.  Air Conditioning Vapor Cycle System  
						

							Products, INC. 
TR-134 System Service Manual
 
 
March 6/02 
Page 4 
 
2. ELECTRICAL DRIVEN COMPRESSOR SYSTEMS 
 
Electrically operated systems use the aircraft electrical system and are operable in 
most normal flight modes.  Air conditioning may be operated with ground external 
power or the aircraft electrical system providing voltage to the proper buss. 
 
The compressor and condenser are manufactured on an assembly pallet. In most 
cases, the compressor drive and condenser fan drive are both driven by a 
common, double shafted motor.  The compressor is belt driven from the shortest 
shaft while the condenser fan is attached directly to the longer motor shaft.  
Condenser cooling air (ambient air) is drawn over the compressor and drive motor 
to provide cooling airflow for those components prior to passing through the 
condenser coil to remove heat from the system.  Some electrically driven systems 
have separate compressor drive and condenser fan motors.  After passing through 
the condenser coil, the air is exhausted to the outside.  The compressor takes low 
pressure refrigerant gas and compresses it to a higher pressure and temperature.    
    
On the ground, the electrical system allows operation of the air conditioning system 
from either aircraft generator or from an active GPU prior to engine start. Some 
system safety features include electrical interlocking and load shedding.  In flight, 
the air conditioning system can be operated from the aircraft electrical system only 
with aircraft generators on line.  Loss of aircraft generator power will automatically 
shed the air conditioning system electrical loads except for the minimal loads of the 
evaporator fans. 
 
The entire air conditioning refrigerant loop is protected against over pressure and 
over temperature conditions by two separate safety devices.  The first device is a 
binary high/low pressure switch that activates in the event of an overpressure and 
is on the compressor discharge port.  This switch will open at approximately 350 
PSIG and will interrupt power to the compressor control circuit.  This in turn will de-
energize the compressor motor relay and remove power to the compressor motor.  
The refrigerant system pressures will then drop. The switch will also interrupt 
power to the compressor control circuit under low pressure conditions.   The 
second safety overpressure device is a fuse plug which will vent the system 
refrigerant safely overboard in the event of a system pressure in excess of 425 
psig.  It is located on the receiver/drier.    
						

							Products, INC. 
TR-134 System Service Manual
 
 
Sep 15/06 
Page 5 
 
3.  ENGINE DRIVEN COMPRESSOR SYSTEMS 
 
Engine driven systems use compressors that are engine mounted; or on some 
rotorcraft, driven off the tail rotor drive shaft.  A pulley via a V type belt turns the 
compressor.    A clutch mounted on the compressor engages the compressor 
when the air conditioning system is selected ON. 
 
The condenser uses a separate fan with electrical motor to supply cooling air.  The 
condenser cooling air (ambient air) is drawn in through a cutout in the fuselage 
skin of the aircraft and passes through the condenser coil to remove heat from the 
system.  After passing through the condenser coil and blower, the air is exhausted 
to the outside of the aircraft.  
 
The entire air conditioning refrigerant loop is protected against over pressure 
conditions by two separate safety devices.  The first device is a binary high/low 
pressure switch.  This switch will open at approximately 350 PSIG and will interrupt 
power to the compressor clutch at which point the system pressures will drop. The 
switch will also interrupt power to the compressor clutch under low pressure 
conditions.   The second overpressure safety device is a fuse plug which will vent 
the system refrigerant in the event of a system pressure in excess of 425 PSIG.  It 
is located on the receiver/drier.