AAON SB-018 - Manual (Page 27)

27
The waterside economizer circuit can
operate in three modes: waterside
economizer only, waterside economizer with
mechanical cooling, and mechanical cooling
only.
During waterside economizer only mode of
operation condenser water flows through the
waterside economizer coil with modulating
valves maintaining supply air temperature
setpoint. The condenser water then passes
through water-cooled condenser.
During waterside economizer with
mechanical cooling mode of operation
condenser water flows through the waterside
economizer coil with the waterside
economizer modulating valve fully open.
The condenser water then passes through
water-cooled condenser.
During mechanical cooling only mode of
operation condenser water flows around the
waterside economizer coil with the
waterside economizer bypass valve fully
open. The condenser water then passes
through water-cooled condenser.
Waterside economizer coil condensate drain
outlet drains into evaporator coil drain pan.
See the previous section on evaporator coil
condensate drain piping.
Mineral content of the condenser water must
be controlled. All make-up water has
minerals in it and as the water is evaporated
in the cooling tower, these minerals remain.
As the mineral content of the water
increases, the conductivity of the water
increases.
Field provided and installed water treatment
program must be compatible with stainless
steel, copper, aluminum, ABS plastic, and
PVC. Batch feed processes should never be
used as concentrated chemicals can cause
corrosion. Never use hydrochloric acid
(muriatic acid) or chlorine as it will corrode
stainless steel.
Heating Coils
Factory installed one or two row hot water
and steam heating coils can be factory
mounted. These coils are supplied from a
source through separate piping from the
condenser water source. All controls for
heating operation are field supplied and field
installed.
Always connect the supply to the top of the
coil and the return to the bottom. Water coils
should not be subjected to entering air
temperatures below 38°F to prevent coil
freeze-up. If air temperature across the coil
is going to be below this value, use a glycol
solution to match the coldest air expected.
Startup
(See back of the manual for startup form)
Piping shall be in accordance with
national and local codes. Pressure
limiting devices, backflow preventers
and all other safety requirements are
the sole responsibility of the installing
contractor.
WARNING
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