79
PB
R-410A SEALED SYSTEM REPAIRS
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
HIGH PRESSURE HAZARD
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.
Undercharged Refrigerant Systems
An undercharged system will result in poor
performance (low pressures, etc.) in both the heating
and cooling cycle.
Whenever you service a unit with an undercharge of
refrigerant, always suspect a leak. The leak must be
repaired before charging the unit.
To check for an undercharged system, turn the unit
on, allow the compressor to run long enough to
establish working pressures in the system (15 to 20
minutes).
During the cooling cycle you can listen carefully at
the exit of the metering device into the evaporator;
an intermittent hissing and gurgling sound indicates
a low refrigerant charge. Intermittent frosting and
thawing of the evaporator is another indication of a
low charge, however, frosting and thawing can also
be caused by insufficient air over the evaporator or
partial restriction in the refrigeration system besides
the metering device..
Checks for an undercharged system can be made at
the compressor. If the compressor seems quieter
than normal, it is an indication of a low refrigerant
charge.
A check of the amperage drawn by the compressor
motor should show a lower reading. (Check the
Unit Specification.) After the unit has run 10 to
15 minutes, check the gauge pressures. Gauges
connected to system with an undercharge will have
low head pressures and substantially low suction
pressures.
Figure 601 (Undercharged System)
