AAON LC-054 - Manual (Page 15)

15
Dual Pumps
When redundant pumping is required, a
factory installed dualArm pump can be
ordered on units 15 tons and larger. A
dualArm pump is a pump with two
independent motors and pumps in a single
casing. This pump has a swing split-flapper
valve in the discharge port to prevent liquid
recirculation when only one pump is
operating. Isolation valves in the casing
allow one pump to be isolated and removed
for service while the other pump is still
operating.
The controls package will activate the pump
when the unit is given a run command. If the
controls do not recognize flow in 60
seconds, the second pump will be activated
and an alarm signal will be generated. If the
second pump does not activate, the cooling
will be locked out.
Differential Pressure Gauge and
Thermometers
A differential pressure gauge and
thermometers are available as a factory
installed option when using a factory
installed pumping package. Thermometers
are installed around the evaporator of the
unit. A differential pressure gauge is
installed at each pump. This pressure gauge
is connected in three places to the water
piping: before the suction guide/strainer,
after the suction guide and before the pump,
and after the pump. There is also a needle
valve at each of these points to isolate the
pressure. To measure the pressure at any
given point, open the needle valve at that
point and close the other two needle valves.
Instead of two pressure gauges, one pressure
gauge is used to minimize calibration and
gauge errors.
Pipe Insulation
All evaporators in the LC Series chiller are
heat traced and insulated. The water piping
and components on standard LC are not heat
traced or insulated at the factory. The
factory can install heat trace as an optional
feature. All water piping shall be leak tested
in the field prior to startup, as shipping
vibrations may have loosened connections.
Installation
Lifting the Unit
If cables or chains are used to hoist the unit
they must be the same length and care
should be taken to prevent damage to the
cabinet or injury to the installer.
Arrange spreader bars, blocking, or other
lifting devices to prevent any damage to the
coils or the cabinet of the condensing unit.
Before lifting unit, be sure that all shipping
material has been removed from the unit.
All LC Series chillers have lifting channels
in the base of the equipment to allow
moving and placement without physical
damage.
Unit may be positioned with a forklift.
Remove the harness used in hoisting. Make
sure the unit is properly seated and level.
Locating the Unit
The LC Series chiller is designed for
outdoor applications and mounting at
ground level or on a rooftop. It must be
placed on a level and solid foundation that
has been prepared to support its weight.
When installed at ground level, a one-piece
concrete slab should be used with footings
that extend below the frost line. Also with
ground level installation, care must be taken
to protect the coil fins from damage due to
vandalism or other causes. As a standard, all