Liebert CHALLENGER 3000 Operation And Maintenance Manual page 63

Operation
1. During start-up, when the humidity control calls for humidification, the fill valve opens and
allows water to enter the canister. When the water level reaches the electrodes, current flows and
the water begins to warm. The canister fills until the amperage reaches the setpoint and the fill
valve closes. As the water warms, its conductivity increases and the current flow, in turn, rises. If
the amperage reaches 115% of the normal operating amperage, the drain valve opens and flushes
some of the water out of the canister. This reduces electrode contact with the water and lowers
the current flow to the amperage setpoint. Boiling soon commences, and the canister operates
normally.
2. If the conductivity of the water is low, the canister fills and the water level reaches the canister
full electrode before the amperage setpoint is reached. The humidifier stops filling to prevent
overflow. Boiling should commence in time. As water is boiled off, the mineral concentration in
the canister increases and current flow also increases. The canister eventually reaches full output
and goes to normal operation. No drain is permitted until then.
3. When full output is reached the circuit board starts a time cycle which is factory set at 60 seconds.
During this repeating time cycle, the fill valve will open periodically to replenish the water being
boiled off and maintain a "steady state" output at the set point. The amperage variance will
depend on the conductivity of the water.
4. After a period of time, the mineral concentration in the canister becomes too high. When this
occurs, the water boils too quickly. As the water quickly boils off and less of the electrode is
exposed, the current flow decreases. When the current crosses the low threshold point (factory set
at 90%) before the end of the time cycle, the drain valve opens, draining the mineral laden water
out and replacing it with fresh water. This lowers the mineral concentration and returns the
canister to "steady state" operation and prolongs canister life. The frequency of drains depends on
water conductivity.
5. Over a period of time, the electrode surface will become coated with a layer of insulating material,
which causes a drop in current flow. As this happens, the water level in the canister will slowly
rise exposing new electrode surface to the water to maintain normal output. Eventually, the
steady state water level will reach the canister full electrode and indicate so by activating the
canister full alarm. At this point, all of electrode surface has been used up and the canister should
be replaced.
6. After the entire electrode surface has been coated, the output will slowly begin to fall off. This
usually occurs in the last several hours of electrode life and should allow enough time to schedule
maintenance. During these last hours, the mineral concentration can increase. If the mineral
concentration is too high, arcing can occur. If the electrodes start to arc, turn off the humidifier
immediately and replace the canister with the identical part.
Controls
The humidifier RUN/DRAIN switch is located at the upper right of the humidifier assembly. This
switch should be in the RUN position when the humidifier is in normal operation, and in the DRAIN
position when a manual drain sequence is required. The electronic control board for the humidifier is
located on the right side of the humidifier assembly. When the main unit is energized, power is avail-
able to the humidifier circuits.
Component Operation and Maintenance
55