Undercharged Refrigerant Systems; An Undercharged System Will Result In Poor Performance (Low Pressures, Etc.) In Both The Heating And Cooling Cycle - Friedrich VERT-I-PAK VHA09K25RTQ Service Manual

R-410A SEALED SYSTEM REPAIRS

Undercharged Refrigerant Systems

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.
Figure 601 (Undercharged System)
51
WARNING
NOTE: Ensure fan is on high speed during testing.
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.
If the compressor reads low amperage and has a high
discharge line temperature at the compressor, it is an
indication of low system refrigerant.
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.