S-111 Fixed Orifice Restriction Devices; S-112 Checking Restricted Liquid Line; S-113 Overcharge Of Refrigerant; S-114 Non-Condensables - Amana PHB**C Service Instructions Manual

SERVICING

S-111 FIXED ORIFICE RESTRICTION DEVICES

The fixed orifice restriction device (flowrator) used in conjunc-
tion with the indoor and outdoor coils are a predetermined
bore (I.D.).
It is designed to control the rate of liquid refrigerant flow into
an evaporator coil.
The amount of refrigerant that flows through the fixed orifice
restriction device is regulated by the pressure difference be-
tween the high and low sides of the system.
In the cooling cycle when the outdoor air temperature rises,
the high side condensing pressure rises. At the same time,
the cooling load on the indoor coil increases, causing the low
side pressure to rise, but at a slower rate.
Since the high side pressure rises faster when the tempera-
ture increases, more refrigerant flows to the evaporator, in-
creasing the cooling capacity of the system.
When the outdoor temperature falls, the reverse takes place.
The condensing pressure falls, and the cooling loads on the
indoor coil decreases, causing less refrigerant flow.
A strainer is placed on the entering side of the tube to pre-
vent any foreign material from becoming lodged inside the
fixed orifice restriction device.
If a restriction should become evident, proceed as follows:
1. Recover refrigerant charge.
2. Remove the orifice or tube strainer assembly and 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 re-
striction 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 OVERCHARGE OF REFRIGERANT

An overcharge of refrigerant is normally indicated by an ex-
cessively high head pressure.
An evaporator coil, using an expansion valve metering de-
vice, will basically modulate and control a flooded evaporator
and prevent liquid return to the compressor.
An evaporator coil, using a fixed orifice metering device, could
allow refrigerant to return to the compressor under extreme
overcharge conditions. Also with a fixed orifice metering de-
vice, extreme cases of insufficient indoor air can cause icing
of the indoor coil and liquid return to the compressor, 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 is observed:
1. Start the system.
2. Remove small quantities of gas from the suction line dill
valve 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 min-
utes. Compare the pressure, to the temperature of the cold-
est coil since this is where most of the refrigerant will be. If
the pressure indicates a higher temperature than that of the
coil temperature, non-condensables are present.
Non-condensables are removed from the system by first re-
moving the refrigerant charge, replacing and/or installing liq-
uid line drier, evacuate and recharging.

S-115 COMPRESSOR BURNOUT

When a compressor burns out, high temperature develops
causing the refrigerant, oil and motor insulation to decom-
pose forming acids and sludge.
If a compressor is suspected of being burned-out, attach a
refrigerant hose to the liquid line dill valve and properly re-
move and dispose of the refrigerant.
Now determine if a burn out has actually occurred. Confirm
by analyzing an oil sample using a Sporlan Acid Test Kit,
AK-3 or its equivalent.
Remove the compressor and obtain an oil sample from the
suction stub. If the oil is not acidic, either a burnout has not
occurred or the burnout is so mild that a complete cleanup is
not necessary.
If acid level is unacceptable the system must be cleaned by
using the cleanup drier method.
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