Accumulator; Contaminant Removal; System Charging; Checking Charge - Bryant R-22 Application Manual And Service Manual

If the strainer must be replaced, shut off all power to the unit. See
Fig. 49 for strainer location.
XI. ACCUMULATOR
The accumulator is a device always found in heat pumps and found
in some condensing-unit models. Under some light-load condi-
tions on indoor coils and on outdoor coil with heat pump in heating
mode, some liquid refrigerant is present in suction gas returning to
compressor. The accumulator stores liquid and allows it to boil off
into a vapor so it can be safely returned to compressor. Since a
compressor is designed to pump refrigerant in its gaseous state,
introduction of liquid into it could cause severe damage or total
failure of compressor.
The accumulator is a passive device which seldom needs replac-
ing. Occasionally, its internal oil-return orifice or bleed hole may
become plugged. Some oil is contained in refrigerant returning to
compressor. It cannot boil off in accumulator with liquid refriger-
ant. The bleed hole allows a small amount of oil and refrigerant to
enter the return line where velocity of refrigerant returns it to
compressor. If bleed hole plugs, oil is trapped in accumulator, and
compressor will eventually fail from lack of lubrication. If bleed
hole is plugged, accumulator must be changed. Bleed hole is so
tiny that cleaning efforts are usually not successful. The accumu-
lator has a fusible element located in the bottom-end bell. (See Fig.
51.) This fusible element melts at 430°F and vents the refrigerant,
if this temperature is reached either internal or external to the
system. If fuse melts, the accumulator must be replaced.
To change accumulator:
1. Shut off all power to unit.
2. Remove and reclaim all refrigerant from system.
NOTE: Coil may be removed for access to accumulator. Refer to
appropriate sections of service manual for instructions.
CAUTION: Wear safety glasses and gloves when work-
ing on refrigerants and when using brazing torch.
3. When accumulator is exposed, remove it from system with
tubing cutter.
4. Scratch matching marks on tubing stubs and old accumu-
lator. Scratch matching marks on new accumulator. Un-
braze stubs from old accumulator and braze into new

accumulator.

5. Thoroughly rinse any flux residue from joints and paint
with corrosion-resistant coating such as zinc-rich paint.
6. Reinstall accumulator into system with copper-slip cou-
plings.
7. Evacuate and charge system.
8. Pour and measure oil quantity (if any) from old accumula-
tor. If more than 20 percent of oil charge is trapped in
accumulator, add oil to compressor to make up for this loss.
XII. CONTAMINANT REMOVAL
Proper evacuation of a unit removes non-condensibles and assures
a tight, dry system before charging. The 2 methods used to
evacuate a system are the deep-vacuum method and the triple-
evacuation method.
DEEP-VACUUM METHOD
The deep-vacuum method requires a vacuum pump capable of
pulling a vacuum of 1000 microns and a vacuum gage capable of
accurately measuring this vacuum depth. The deep-vacuum
method is the most positive way of assuring a system is free of air
and liquid water.
TRIPLE-EVACUATION METHOD
The triple-evacuation method can be used where the vacuum pump
is capable of pumping down to only 28 in. of mercury vacuum, and
the system does not contain any liquid water. The procedure is as
follows.
1. Pump the system down to 28 in. of mercury vacuum and
allow pump to continue to operate for additional 15
minutes.
2. Close service valves and shut off vacuum pump.
3. Connect a refrigerant cylinder to the system and open until
system pressure is 2 psig.
4. Close the service valve.
5. Allow system to stand for 1 hr, during which time the dry
refrigerant will be able to diffuse throughout the system,
absorbing moisture.
This procedure is repeated 3 times, after which the system will be
free of any contaminants and water vapor.
XIII. SYSTEM CHARGING
For all approved combinations, system must be charged correctly
for normal system operation and reliable operation of components.
CAUTION: Always wear safety glasses and gloves
when handling refrigerants.
If system has lost all charge, weigh in charge using dial-a-charge
or digital scale.
System charge should be fine-tuned by using the superheat or
subcooling method, whichever is appropriate. These methods are
covered in the Checking Charge section below.
NOTE: Heat-pump check charts are for checking charge and
performance and for adding a small amount of charge. During
heating mode, correct method of charging is the weight method. In
heating mode, check should be made approximately 15 minutes
after a defrost with unit running with a clean coil. In cooling cycle,
system should run at least 10 minutes for temperatures and
pressures to stabilize. All charts assume there are no system
abnormalities and indoor coil airflows are correct. If system
abnormalities exist, correct them before checking system charge.
XIV. CHECKING CHARGE
Superheat charging is the process of charging refrigerant into a
system until the temperature (superheat) of the suction gas entering
the compressor reaches a prescribed value. Small variations of
charge affect suction-gas superheat temperatures greatly. There-
fore, this method of charging is very accurate. This method can be
used only on split-system condensing units and heat pumps
(operating in the cooling mode) with fixed-restrictor-type metering
devices such as Check-Flo-Rater™, cap tube, etc. For units using
—43—
430 FUSE
ELEMENT
Fig. 51—Accumulator
A88410