AAON SB-018 - Manual (Page 34)

34
Operation
Unit operations should be controlled with
thermostat or unit controller, never at the
main power supply, except for emergency or
complete shutdown of the unit.
Packaged DX Cooling Operation and
Control
When a call for cooling is made the supply
fan motors and compressors will energize.
Electric Heating Operation
When a call for heating (G and W1, W2,
etc.) is made the supply fan motors and
electric resistance heaters will energize.
Heating is accomplished by passing
electrical current through a specified amount
of resistance heaters which will produce the
required heat.
On a fault condition the main limit located
in the supply air or the auxiliary limit
located downstream the supply blower will
remove power from all contactors.
Steam or Hot Water Preheating
Operation
Valve control for steam and hot water
heating coils are by others. Heating is
accomplished by passing steam or hot water
through the steam or hot water coil
assembly.
Maintenance
(See back of the manual for maintenance
log.)
At least once each year, a qualified service
technician should check out the unit. Supply
fans, evaporator coils and air filters should
be inspected monthly.
Periodically during operation, it is necessary
to perform routine service checks on the
performance of the unit. This includes
checking of the air flow, the air filters,
condenser water flow and refrigerant charge.
See Startup section for information on air
flow adjustment and refrigerant charge
adjustment.
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on. Check the
fans for correct operating direction,
amperage and voltage. Check compressor
operation, rotation, amperage and voltage to
the unit nameplate (check the amperage on
the load side of the compressor contactor).
Condensate Drain Pans
Drain pans will have moisture present and
require periodic cleaning to prevent
microbial growth. Cleaning of the drain pans
will also prevent any possible plugging of
the drain lines and overflow of the pan itself.
Improper installation, adjustment,
alteration, service or maintenance
can cause property damage,
personal injury or loss of life.
Installation and service must be
performed by a qualified installer. A
copy of this IOM should be kept with
the unit.
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME
To prevent motor overheating
compressors must cycle off for a
minimum of 5 minutes.
5 MINUTE MINIMUM ON TIME
To maintain the proper oil level
compressors must cycle on for a
minimum of 5 minutes.
The cycle rate must not exceed 6
starts per hour.
WARNING