Service Manual

SERVICING
37
If a restriction should become evident, proceed as follows:
1. Recover refrigerant charge.
2. Remove the orifice assembly and clean or replace.
3. Replace liquid line drier, evacuate and recharge.
CHECKING EQUALIZATION TIME
During the "OFF" cycle, the high side pressure bleeds to the
low side through the fixed orifice restriction device. Check
equalization time as follows:
1. Attach a gauge manifold to the suction and liquid line dill
valves
2. Start the system and allow the pressures to stabilize.
3. Stop the system and check the time it takes for the high
and low pressure gauge readings to equalize.
If it takes more than seven (7) minutes to equalize, the restric-
tion device is inoperative. Replace, install a liquid line drier,
evacuate and recharge.
S-112 CHECKING RESTRICTED LIQUID LINE
When the system is operating, the liquid line is warm to the
touch. If the liquid line is restricted, a definite temperature
drop will be noticed at the point of restriction. In severe cases,
frost will form at the restriction and extend down the line in the
direction of the flow.
Discharge and suction pressures will be low, giving the ap-
pearance of an undercharged unit. However, the unit will have
normal to high subcooling.
If a restriction is located, replace the restricted part, replace
drier, evacuate and recharge.
S-113 REFRIGERANT OVERCHARGE
An overcharge of refrigerant is normally indicated by an exces-
sively high head pressure.
An evaporator coil, using an expansion valve metering device,
will basically modulate and control a flooded evaporator and
prevent liquid refrigerant from returning to the compressor.
An evaporator coil, using a fixed orifice restrictor device
(flowrator) metering device, could allow liquid refrigerant to re-
turn to the compressor under extreme overcharge conditions.
Also with a fixed orifice restrictor device (flowrator) metering
device, extreme cases of insufficient indoor air can cause icing
of the indoor coil and liquid refrigerant to return to the compres-
sor, but the head pressure would be lower.
There are other causes for high head pressure which may be
found in the "Service Problem Analysis Guide."
If other causes check out normal, an overcharge or a system
containing non-condensables would be indicated.
If this system is observed:
1. Start the system.
2. Remove and capture small quantities of refrigerant as from
the suction line access fitting until the head pressure is
reduced to normal.
3. Observe the system while running a cooling performance
test. If a shortage of refrigerant is indicated, then the sys-
tem contains non-condensables.
S-114 NON-CONDENSABLES
If non-condensables are suspected, shut down the system and
allow the pressures to equalize. Wait at least 15 minutes.
Compare the pressure to the temperature of the coldest coil
since this is where most of the refrigerant will be. If the pres-
sure indicates a higher temperature than that of the coil tem-
perature, non-condensables are present.
Non-condensables are removed from the system by first re-
moving the refrigerant charge, replacing and/or installing liquid
line drier, evacuating and recharging.