SPX MARLEY LLC, User Manual

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7
operation
A water level control system can be configured to meet various combination
requirements. Since one individual circuit card is responsible for each func-
tion, the size and circuitry varies in proportion to the number of operations
desired. For example, a water level makeup control will require a control panel
with one circuit relay card and three probes. A system configured for water
makeup that includes a high alarm and a low alarm, will require three circuit
cards and five probes—one circuit card for the water makeup option, one for
high operation and one for low.
Water Makeup Function
A system is designed for alarms and/or cutoff indication only would not be
equipped with the water makeup function.
The circuitry for water makeup in the LLC control panel provides an indepen-
dent circuit breaker for direct connection to a 110-120VAC water solenoid
valve. This added feature allows customer installation without having to
provide an additional power circuit to energize the solenoid. The solenoid is
connected to terminals 2A and 4A as represented on the control’s specific
wiring diagram.
Purpose and Function of the HAND-OFF-AUTO Switch
Located on the right side of the control’s enclo-
sure is a HAND-OFF-AUTO switch. This switch
is used primarily at cooling tower startup and in
maintenance procedures where the tower basin
is empty or has been drained. When the tower’s
basin needs to be manually filled, the switch is
placed in the HAND position. This selection
bypasses the probe assembly’s feedback and
directly energizes the solenoid valve connected
to the water supply. Once the cooling tower basin
is filled, the switch is placed in the AUTO position to allow the adjusted probe
assembly to monitor and sustain the proper operating level. Placing the switch
in the OFF position completely interrupts any monitoring or fill action normally
provided by the LLC control panel. Normal tower operation depends upon the
HAND-OFF-AUTO switch being positioned in the AUTO mode at all times.