Checking And Trimming The Refrigerant Charge; Definitions; Checking The Refrigerant Charge During Unit Shutdown - York YVAA Installation Operation & Maintenance

SECTION 9 - MAINTENANCE

Checking and trimming the refrigerant charge

Important: The amount of chiller refrigerant
charge must be verified to meet the specified
amount as found in the chiller nameplate or chilelr
factory order form (FOF). Reference this docu-
ment of the unit Sales Order screen on the chiller
control panel to determine the amount of charge
required based on the chiller rating.
During operation, the refrigerant charge level is correct
when the evaporator approach (STD), subcooling are
at the design values for the condition. For new sales,
these design values are included as part of the FOF. For
units where they are not seen on the FOF, they can be
provided upon request from the chiller sales engineer
from the chiller rating program. These depend on tube
selection, chilled fluid type, operating head, and op-
erating conditions. For YVAA Chillers, a typical way
to verify correct charge amount in the system is when
Evap sight glass is half-full.
The following equations define these parameters.
Condenser subcooling is calculated and the condenser
drain valve is controlled to the programmed setpoint by
the chiller control logic:
• Evaporator approach = (LCHLT) -
(EST)
• Discharge superheat = (DT) - (CST)
• Subcooling =
refrigerant liquid
(from condenser outlet)
172
(CST) - condensed
temperature

Definitions

• EST = Evaporator Saturation temperature; can be
calculated from saturated suction pressure on the
panel.
• LCHLT = Leaving evaporator liquid temperature
• DT = Compressor Discharge Temperature; shown
on the chiller panel.
• CST = Condenser Saturation Temperature; can be
calculated from saturated condenser pressure on
the panel.
You can view the parameters on the chiller control cen-
ter. The chiller must be at full load design operating
conditions so that the correct refrigerant charge level
can be correctly determined, when operating. When
correct condenser level is maintaining the design
subcooling, the evaporator approach and discharge su-
perheat are a function of the amount of charge that is
now maintained in the evaporator. To lower evapora-
tor small temperature difference and compressor dis-
charge superheat, add the refrigerant charge is added
to the system. If additional details are needed, contact
product technical support (PTS) for guidance.
Checking the refrigerant charge during unit
shutdown
Because YVAA uses a hybrid falling film technology,
there are no reliable means to evaluate the refrigerant
charge when the chiller is not running.
Form 201.47-ICOM1
Issue date: 17/11/2022
JOHNSON CONTROLS