AAON SA-070 - Manual (Page 45)

45
Figure 23 - Securing the Band
Filters
Do not operate the unit without filters in
place. Unit should be checked for correct
filter placement during startup. Operation of
the equipment without filters will result in a
clogged evaporator coil.
Adjusting Refrigerant Charge
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 TXV liquid sub-cooling is
more representative of the charge than
evaporator superheat but both measurements
must be taken.
Before Charging
Unit being charged must be at or near full
load conditions before adjusting the charge.
Units equipped with hot gas reheat must be
charged with the hot gas reheat valves
closed while the unit is in cooling mode to
get the proper charge. After charging, unit
should
be operated in reheat
(dehumidification) mode to check for
correct operation.
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge. After charging, unit should
be operated in cooling mode to check for
correct charge. Charge may need to be
adjusted for cooling mode. If adjustments
are made in the cooling mode, heating 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.
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat. Refer to the tables below when
determining the proper sub-cooling.
Checking Liquid Sub-Cooling
Measure the temperature of the liquid line as
it leaves the condenser.
Read the gauge pressure at the liquid line
close to the point where the temperature was
taken. You must use liquid line pressure as it
Before completing startup and
leaving the unit a complete operating
cycle should be observed to verify
that all components are functioning
properly.
CAUTION
The Clean Air Act of 1990 bans the
intentional venting of refrigerant
(CF
C’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.
CAUTION