Friedrich VRP7k - Refrigerant Charging and System Diagnosis

50 PB
R-410A SEALED SYSTEM REPAIR
Refrigerant Charging
WARNING
RISK OF ELECTRIC SHOCK
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.
WARNING
RISK OF ELECTRIC SHOCK
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.
Proper refrigerant charge is essential to unit operation. Operating a unit with an improper refrigerant charge
will result in reduced performance (capacity) and/or efciency. 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 ow 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 specic type of failure will be inuenced 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 sufcient 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.