Refrigerant - Daikin EWWQ-AJYNN Service Manual

Maintenance
1.6

Refrigerant

1
Refrigerant
charging
3
5 5
Procedure to
charge a
moderately
undercharged
EWWQ-AJYNN unit
Charging the
refrigerant
5–10
EWWQ-AJYNN water cooled screw chillers are shipped factory charged with a full operating charge
of refrigerant but there may be times that a unit must be recharged at the jobsite. Follow these
recommendations when field charging.
EWWQ-AJYNN water cooled screw chillers are more sensitive to under-charging than to overcharging
therefore it is preferable to be slightly overcharged rather than undercharged on a circuit. The optimum
charge is the charge which allows the unit to run with a solid stream of liquid in the liquid line at all
operating conditions. When the liquid line temperature does not drop with the addition of 2.2-4.5 Kg of
charge then the subcooler is nearly full and proper charge has been reached. If the liquid line
temperature does not drop and the discharge pressure goes up 20.7-34.5 kPa as 2.2-4.5 Kg of
refrigerant is added the correct maximum charge has been reached. Unit charging can be done at any
steady load condition, at any outdoor ambient temperature. Unit must be allowed to run 5 minutes or
longer so that the condenser fan staging is stabilized at normal operating discharge pressure.
In case moisture is noticed in the system, through the moisture indicator, the system must be
evacuated to eliminate cause of trouble. After the evacuation, the system must be dried reducing it to
an almost perfect vacuum. For this purpose, a displacement vacuum pump should be used.
Any moisture and air left in the system will be absorbed by the dry nitrogen used to break the vacuum,
and they will be almost completely removed by the three evacuations. If burnt oil or sludge are found
in the refrigerant circuit (caused by the compressor motor burn-out), before the vacuum operation it
will be necessary to carefully clean the system using the filter dryer cleaneout method; which basically
involves the use of special filter dryers incorporating a suitable desiccant in both the liquid and suction
lines.
Excessive refrigerant losses can also leak oil from the system. Check the separator oil level during
operation and ensure that oil is visible in the top sightglass.
1 If the unit is slightly undercharged the unit will show bubbles in the sightglass. Recharge the unit.
2 If the unit is moderately undercharged the unit will most likely trip on freeze protection. Recharge
the unit as described in the charging procedure below.
1 If a unit is low on refrigerant you must first determine the cause before attempting to recharge the
unit. Locate and repair any refrigerant leak. Evidence of oil is a good indicator of leakage however,
oil may not be visible at all leaks. Liquid leak detector fluids work well to show bubbles at medium
size leaks but electronic leak detector may be needed to locate small leaks.
2 Add the charge to the system through the schrader fitting on the tube entering the evaporator
between the expansion valve and the evaporator head.
3 The charge can be added at any load condition.
1 Connect the refrigerant bottle with a filling pipe to the filling valveon the evaporator head. Before
firmly tightening the refrigerant bottle valve, open it and force the air out from the filling pipe.
Tighten the charging valve connection.
2 When the refrigerant stops to enter the system, start the compressor and complete the refrigerant
charge.
3 When the exact quantity of refrigerant has been predetermined, check the liquid sight glass.
If you do not know how much refrigerant has to be added, shut off the bottle valve every 5 minutes and
continue to charge the refrigerant until the sight glass is clear and free from bubbles.
Note: Do not discharge the refrigerant into the atmosphere. To recover it, use empty, clean and dry
bottles. The liquid refrigerant recovery can be made through the valve provided on the condenser coil
subcooler outlet. To facilitate the recovery of refrigerant, put the bottle inside a container full of ice;
avoid excessive filling of the bottle (70÷80% max).
ESIE07-05
Part 5 – Maintenance