broken down in the pump in the initial
first hour causing system evacuation to
take longer than it should.
10. The minimum micron level required
by AAON is 350 microns for systems
using POE oils.
11. The system must then be isolated and
the pump turned off to check for vacuum
rise due to leaks or moisture in the
system. The micron gauge must not rise
above 500 microns after 30 minutes of
wait time.
Adjusting Refrigerant Charge
All AAON CF Series condensers and
condensing units are shipped with a factory
holding charge. The factory charge is
different depending on the unit size and
system (heat pump, modulating hot gas
reheat, LAC). The factory charge per circuit
is shown on the unit nameplate. Adjusting the
charge of the system will be required during
installation.
Adjusting the charge of a system in the field
must be based on determination of liquid sub-
cooling and evaporator superheat. On a
system with a thermostatic expansion valve
liquid sub-cooling is more representative of
the charge than evaporator superheat but both
measurements must be taken.
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system.
Unit being charged must be at or near full
load conditions before adjusting the charge.
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge.
Units equipped with hot gas reheat must be
charged with the hot gas reheat valve closed
while the unit is in cooling mode. After
charging, operate the unit in reheat
(dehumidification) mode to check for correct
operation.
Units equipped with heat pump options must
be charged in cooling mode to get the proper
charge. After charging, operate the unit in
heating mode to check for correct charge.
Charge may need to be adjusted for heating
mode. If adjustments are made in the heating
mode, cooling mode must be rerun to verify
proper operation.
After adding or removing charge, the system
must be allowed to stabilize, typically 10-15
minutes, before making any other
adjustments.
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether
(PVE) oils are two types of lubricants
used in hydrofluorocarbon (HFC)
refrigeration sy
stems. Refer to the
compressor label for the proper
compressor lubricant type.
CLEAN AIR ACT
The Clean Air Act of 1990 bans the
intentional venting of refrigerant
(CFC’s and HCFC’s) as of July 1,
1992. Approved methods of recovery,
recycling or reclaiming must be
followed. Fines and/or incarceration
may be levied for non-compliance.
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