Adjust Refrigerant Charge
NOTE: Actual start-up and all refrigerant charge modifications
should be done only under supervision of a qualified refrigerant
mechanic.
With all fans operating, adjust the refrigerant charge.
Measure pressure at the liquid line service valve, being sure
Schrader depressor is used if required. Also, measure liquid line
temperature as close to the liquid service valve as possible. Add
charge until the pressure and temperature conditions of the
charging chart curve are met. If liquid pressure and temperature
point fall above curve, add charge. If liquid pressure and
temperature point fall below curve, reduce the charge until the
conditions match the curve. (± 3 ºF allowable range)
If the sight glass is cloudy, check refrigerant charge again.
Ensure all fans are operating. Also ensure maximum allowable
liquid lift has not been exceeded. If charge per chart and if the
sight glass is still cloudy, check for a plugged filter drier or a
partially closed solenoid valve. Replace or repair, as needed.
Check Compressor Oil Level – After adjusting the refrigerant
charge, allow the compressor to run fully loaded for 20 minutes.
Running oil level should be within view of the crankcase sight
glass. Stop the compressor at the field power supply disconnect
and check the crankcase oil level. Add oil only if necessary to
bring the oil into view in the sight glass. If oil is added, run the
compressor for an additional 10 minutes; then stop and check
oil level. If the level remains low, check the piping system for
proper design for oil return; also, check the system for leaks.
If the initial check shows too much oil (too high in the sight glass)
remove oil to proper level. See Preliminary Oil Charge, for proper
procedure for adding and removing oil. See Fig. 9.
When the above checks are complete, repeat the procedure
with the unit operating at minimum load conditions.
Fig. 9 – Operating Oil Levels
Final Checks – Ensure all safety controls are operating, control
panel covers are on, and the service panels are in place.
OPERATING SEQUENCE
Cooling - When the first stage (TC1) of the cooling thermostat
closes, timer starts. After 3 minutes, the timer expires, energizing
the compressor.
On demand for additional cooling capacity, the second stage (TC2)
of the cooling thermostat closes, energizing field supplied liquid
line solenoid (LLS) valve, which opens.
At shutdown, the Time Guard timer prevents the compressor from
re-starting for approximately 3 minutes.
Never charge liquid into the low-pressure side of system. Do
not overcharge. During charging or removal of refrigerant, be
sure indoor-fan system is operating.
38AKS024 – 044
38AKS016
1/8 OF SIGHT GLASS
3/8 OR 1/3 OF SIGHT GLASS
1/4 OF SIGHT GLASS
MAX.
MIN.
3/4 OF
SIGHT GLASS
(11 pages)
(286 pages)
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