AAON LL-540 - Manual (Page 52)

52
If the water in the sump is below the low
probe, it will not allow the condenser pump
or the sump heater to operate. It will activate
the make-up water solenoid to try to fill the
sump assuming water is flowing to the unit.
Once water is above the low probe, it will
allow the condenser pump and sump heater
(if ordered and the ambient temperature is
below 40°F) to operate. The make-up water
solenoid will remain activated until water
gets to the high water level. The make-up
water solenoid will deactivate until water
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 make-up water valve shuts off when the
water level reaches the high level probe.
Figure 24 - Water Makeup Valve
Make up water supply pressure should be
maintained between 15 and 60 psig for
proper operation of the valve. The make-up
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-cooled condensers
come equipped with a water treatment
system that should be maintained by a local
water treatment professional trained in the
water
treatment of evaporative-cooled
condensers. 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,