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Marley
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Sigma F Series Cooling Tower
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Specifications: Options
24
Specification Value
Control Options
Control System:
5.7 Add the following paragraphs in
the Mechanical Equipment sec-
tion: Each cell of the cooling tower
shall be equipped with a UL listed
control system in a NEMA 3R or 4X
outdoor enclosure capable of control-
ling single-speed or two-speed motors
as required, and designed specifically
for cooling tower applications. The
panel shall include a main fused dis-
connect with an external operating
handle, lockable in the off position for
safety. Across-the-line magnetic start-
ers or solid state soft-start starters
as required shall be controlled with a
thermostatic or solid state tempera-
ture controller. Door mounted selector
switches shall be provided to enable
automatic or manual control and wired
for 120VAC control. Control circuit to
be wired out to terminal blocks for
field connection to a remote vibration
switch and for access to extra 120VAC
50VA control power, overload trip
alarms and remote temperature control
devices. The temperature controller
shall be adjustable for the required cold
water temperature. If a thermostatic
controller is used it shall be mounted
on the side of the tower with the tem-
perature sensing bulb installed in the
cold water basin using a suspension
mounting bracket. If a solid state tem-
perature controller is used the control-
ler will be door mounted on the control
panel. The temperature controller will
display two temperatures, one for
outgoing water and the other for set
point. Water temperature input shall be
obtained using a three-wire RTD with
dry well in the outlet water piping and
wired back to the solid state tempera-
ture controller in the control panel.
■ If it is your opinion that the control system for the cooling tower
should be part of the tower manufacturer’s responsibility, we are
in wholehearted agreement with you. Who better to determine
the most efficient mode and manner of a tower’s operation—and
to apply a system most compatible with it—than the designer
and manufacturer of the cooling tower?