Checking Restricted Liquid Line; Overcharge Of Refrigerant - Daikin DAR09 Service Instructions Manual

SERVICING
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 temperature
increases, more refrigerant flows to the evaporator, increasing
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 prevent
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 equaliza-
tion 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 restrictor
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 direc-
tion of the flow.
Discharge and suction pressures will be low, giving the appear-
ance of an undercharged unit. However, the unit will have
normal to high subcooling.
Locate the restriction, replace the restricted part, replace drier,
evacuate and recharge.
S-113 OVERCHARGE OF REFRIGERANT
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 return to the compressor.
An evaporator coil, using a capillary tube metering device, could
allow refrigerant to return to the compressor under extreme
overcharge conditions. Also with a capillary tube metering
device, 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 system is observed:
1. Start the system.
2. Remove and capture 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 system
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. Com-
pare the pressure to the temperature of the coldest coil since
this is where most of the refrigerant will be. If the pressure in-
dicates a higher temperature than that of the coil temperature,
non-condensables are present.
Non-condensables are removed from the system by first remov-
ing the refrigerant charge, replacing and/or installing liquid line
drier, evacuating and recharging.
S-115 COMPRESSOR BURNOUT
When a compressor burns out, high temperature develops
causing the refrigerant, oil and motor insulation to decompose
forming acids and sludge.
If a compressor is suspected of being burned-out, attach a refrig-
erant hose to the liquid line dill valve and properly remove and
dispose of the refrigerant.
NOTICE
Violation of EPA regulations may result in fines
or other penalties.
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 clean-up is
not necessary.
If acid level is unacceptable, the system must be cleaned by
using the clean-up drier method.
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