Service Ports - Mitsubishi Electric PUG18AK Technical Manual

11
REFRIGERANT SYSTEM

SERVICE PORTS

There are 4 service ports available to service technicians. One port is located at each of the two "ball valves" and two
additional ports are located directly above the ball valves. The purpose of each is:
A. Liquid Line Ball Valve Service Port. This port is used to evacuate the refrigerant line set when the ball valve is in
the closed position. It may also be used to measure the liquid line pressure or more accurately the "saturated
line" pressure during normal operation.
1) During cooling operation this service port is downstream of the metering orifice which is installed inside
of the condensing unit. While in the cooling mode this pressure is typically 25 to 40 PSI above that of the
suction ball valve pressure (usually 85 to 110 PSI).
2) During heating operation this pressure continues to be downstream of the capillary tube which is now
metering refrigerant at the outlet of the indoor unit.
B) Suction Ball Valve Service Port. This port is also used to evacuate the indoor unit and line set during installation
(the ball valve must be closed to evacuate the line set and indoor unit). During normal cooling mode operation
this pressure port indicates evaporator pressure (minus line set pressure drop). Typical cooling mode pressure
readings here are in the range of 55 to 80 PSI during summer operation.
C) Two additional service ports are located directly above the ball valves. These ports are connected to the com-
pressor discharge line and the suction line just above the accumulator. These ports always read "true" high and
low side pressures regardless of cooling or heating operating modes.
D. Both refrigerant lines must be insulated as a result of the "cooling side" metering device location (in outdoor
unit). Failure to insulate the liquid line, or more accurately the "saturation line", will result in condensate drip-
ping from the line and poor cooling performance.
E. Metering Devices. Metering of refrigerant in the cooling mode is accomplished by a "fixed orifice" that is located
in the condensing unit. If a restriction or a compressor failure occurs this orifice can be easily accessed and
cleaned after refrigerant is recovered.
SP007-39