65
gets to the medium water level. In normal
operation, the water level should swing
between the medium and high water levels.
The maximum high water level should be 1”
below the overflow drain which occurs after
the makeup water valve shuts off when the
water level reaches the high level probe.
Figure 35 - Water Makeup Valve
Make up water supply pressure should be
maintained between 15 and 60 psig for proper
operation of the valve. The makeup water
valve assembly should be inspected monthly
and adjusted as required. Replace the valve
seat if leakage occurs when the valve is in the
closed position.
Water Treatment System
All AAON evaporative-condensed chillers
come equipped with a water treatment system
that should be maintained by a local water
treatment professional trained in the water
treatment of evaporative-condensed chillers.
This system consists of a controller, three
chemical pumps and storage tanks, a
conductivity sensor, a motorized ball valve
for water bleed and a water meter.
One chemical pump and tank is typically
used for a de-scaling chemical to prevent
scale from forming in the condenser. The
other two pumps and tanks are typically used
for two different biocides (to kill any
microorganisms that could grow in the
condenser). Two biocides are used to prevent
organisms from becoming resistant to one
chemical.
The mineral content of the water must be
controlled. All make up water has minerals in
it. As water is evaporated from the condenser,
these minerals remain. As the mineral content
of the water increases, the conductivity of the
water increases. The water treatment
controller monitors this conductivity. As the
water conductivity rises above set point, the
controller will open a motorized ball valve on
the discharge side of the condenser pump and
dumps water into the condenser drain until
conductivity is lowered. While the motorized
ball valve is opened, the controller will not
disperse chemicals.
The chemicals are dispersed by the water
treatment controller based on the scheduled
input by the water treatment professional.
The water meter measures the quantity of
makeup water used by the condenser.
Any 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)
as it will corrode stainless steel.
Sequence of Operation for LZ Series units
without Diagnostics
On a call for cooling, the condenser pump is
activated. A pressure switch in the pump
discharge is bypassed for six seconds by a
time delay relay in order for the pump to
establish recirculating water flow. If flow is
not proven within the six seconds, the
pressure switch opens, breaking the safety
Summary of Contents for LZ Series
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