AAON LL-540 - Manual (Page 42)

42
Maintenance
General
Qualified technicians must perform routine
service checks and maintenance. This
includes
reading and recording the
condensing and suction pressures and
checking for normal sub-cooling and
superheat.
Air-cooled
and evaporative-cooled
condenser units require different
maintenance schedules/procedures. Unit
specific instructions for both types are
included in this manual.
Compressors
The scroll compressors are fully hermetic
and require no maintenance except keeping
the shell clean.
Refrigerant Filter Driers
Each
refrigerant circuit contains a
replaceable core filter drier. Replacement is
recommended when there is excessive
pressure drop across the assembly or
moisture is indicated in a liquid line sight
glass.
Figure 21 - Replaceable Core Filter Driers
Table 8 - Filter Drier Maximum Pressure
Drop
Circuit Loading Max. Pressure Drop
100% 10 psig
50% 5 psig
The filter driers are provided with pressure
taps and shutoff valves for isolation when
changing the core. For safety purposes a
service manifold must be attached prior to
filter maintenance.
Evaporator/Heat Exchangers
Evaporators are direct expansion type with
an electronic expansion valve or thermal
expansion valve to regulate refrigerant.
Normally no maintenance or service work
will be required.
Adjusting Refrigerant Charge
All AAON chillers are shipped with a full
factory charge. Periodically adjusting the
charge of a system may be required.
Adjusting the charge of a system in the field
must be based on determination of liquid
sub-cooling and evaporator superheat. On a
Service gauges MUST BE connected
before operating the isolation valves
for the liquid line filter drier.
WARNING
Prior to filter core service, a service
manifold MUST BE attached to in
and out pressure connections to
assure no pressure exist during filter
maintenance. No-compliance could
result in injury or violation of EPA
regulations.
WARNING