Friedrich 2008 - Manual (Page 16)

Refrigerant Charging
NOTE: Because The RAC System Is A Sealed System,
Service Process Tubes Will Have To Be Installed. First
Install A Line Tap And Remove Refrigerant From System.
Make Necessary Sealed System Repairs And Vacuum
System. Crimp Process Tube Line And Solder End Shut.
Do Not Leave A Service Valve In The Sealed System.
Proper refrigerant charge is essential to proper unit
operation. Operating a unit with an improper refrigerant
charge will result in reduced performance (capacity) and/or
efficiency. Accordingly, the use of proper charging methods
during servicing will insure that the unit is functioning as
designed and that its compressor will not be damaged.
Too much refrigerant (overcharge) in the system is just as bad
(if not worse) than not enough refrigerant (undercharge). They
both can be the source of certain compressor failures if they
remain uncorrected for any period of time. Quite often, other
problems (such as low air flow across evaporator, etc.) are
misdiagnosed as refrigerant charge problems. The refrigerant
circuit diagnosis chart will assist you in properly diagnosing
these systems.
An overcharged unit will at times return liquid refrigerant
(slugging) back to the suction side of the compressor eventually
causing a mechanical failure within the compressor. This
mechanical failure can manifest itself as valve failure, bearing
failure, and/or other mechanical failure. The specific type of
failure will be influenced by the amount of liquid being returned,
and the length of time the slugging continues.
Not enough refrigerant (undercharge) on the other hand, will
cause the temperature of the suction gas to increase to the point
where it does not provide sufficient cooling for the compressor
motor. When this occurs, the motor winding temperature will
increase causing the motor to overheat and possibly cycle open
the compressor overload protector. Continued overheating of
the motor windings and/or cycling of the overload will eventually
lead to compressor motor or overload failure.
Unplug and/or disconnect all electrical power
to the unit before performing inspections,
maintenances or service.
Failure to do so could result in electric shock,
serious injury or death.
Sealed Refrigeration System contains refrigerant
and oil under high pressure.
Proper safety procedures must be followed,
and proper protective clothing must be worn
when working with refrigerants.
Failure to follow these procedures could
result in serious injury or death.
WARNING
WARNING
RISK OF ELECTRIC SHOCK
HIGH PRESSURE HAZARD
SeAleD RefRIGeRATION SYSTeM RePAIRS
ANY SEALED SYSTEM REPAIRS TO COOL-ONLY MODELS REQUIRE THE INSTALLATION OF A LIQUID LINE DRIER.
ALSO, ANY SEALED SYSTEM REPAIRS TO HEAT PUMP MODELS REQUIRE THE INSTALLATION OF A SUCTION LINE DRIER.
IMPORTANT
EQUIPMENT REQUIRED:
1. Voltmeter
2. Ammeter
3. Ohmmeter
4. E.P.A. Approved Refrigerant Recovery System
5. Vacuum Pump (capable of 200 microns or less
vacuum.)
6. Acetylene Welder
7. Electronic Halogen Leak Detector (G.E. Type H-6 or
equivalent.)
8. Accurate refrigerant charge measuring device such
as:
a. Balance Scales - 1/2 oz. accuracy
b. Charging Board - 1/2 oz. accuracy
9. High Pressure Gauge - (0 - 400 lbs.)
10. Low Pressure Gauge - (30 - 150 lbs.)
11. Vacuum Gauge - (0 - 1000 microns)
EQUIPMENT MUST BE CAPABLE OF:
1. Recovery CFC’s as low as 5%.
2. Evacuation from both the high side and low side of the
system simultaneously.
3. Introducing refrigerant charge into high side of the
system.
4. Accurately weighing the refrigerant charge actually
introduced into the system.
5. Facilities for flowing nitrogen through refrigeration tubing
during all brazing processes.
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