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/ Freeze Prevention /
When the ambient air temperature falls below 32°F, the
water in a cooling tower can freeze. Marley Technical Report
#H-003 “Operating Cooling Towers in Freezing Weather”
describes how to prevent freezing during operation. Ask your
Marley sales representative for a copy or download from our
website.
Water collects in the cold water basin during shutdowns,
and may freeze solid. You can prevent freezing by adding heat
to the water left in the tower. Or, you can drain the tower and all
exposed piping at shutdown.
■ Electric Basin Heaters
Choose from two types of automatic basin heater systems,
based on your site conditions and preferences.
You may choose a heater system consisting of these
components (shipped separately for installation by others):
• Stainless steel electric immersion heater element(s). Thread-
ed couplings are provided for installation.
• NEMA 4 enclosure containing these components:
–Magnetic contactor to energize heater.
–Transformer to convert power supply to 24 volts for
control circuit.
– Solid state circuit board for heater control and low-water
cutoff.
Enclosure may be mounted on the side of the tower.
• Control probe to monitor water temperature and water level.
Threaded couplings are provided for installation.
Or you may prefer a pre-assembled submersible tank-type
heater which requires no tower modification and can plug into
a standard grounded 3-prong 120V outlet.
The Incoloy heater element was chosen for its long life in
submerged environments. A built-in thermostat senses water
temperature and controls the supply of electricity to maintain
proper water temperature. A built-in safety switch cuts off
power whenever the element is exposed to air. The element
mounts in the tower basin on a stainless steel plate.
Any exposed piping that is still filled with water at shutdown
—including the makeup water line—should be electrically
traced and insulated (by others).
1. Required kw is the amount of heat needed to maintain +40°F
basin water temperature at the indicated ambient air temperature.
2. Tank heaters shown are 120 volts, single-phase.
3. Component heaters shown are 480 volts, three-phase.
Options or special heater selections may add several weeks to
delivery.
4. Heaters do not operate continuously. Heaters cycle on and off
automatically as basin water temperature dictates.
5. Contact your Marley sales representative for selections
appropriate for other ambient conditions than those shown here.
■ Indoor Tank Method
In this type of system, water flows from an indoor tank,
through the load system, and back to the tower, where it is
cooled. The cooled water flows by gravity from the tower to
the tank located in a heated space. At shutdown, all exposed
water drains into the tank, where it is safe from freezing.
The table on page 9 lists typical drain-down capacities
for all Aquatower models. Although we do not produce tanks,
many of our representatives offer tanks supplied by reputable
manufacturers.
The amount of water needed to successfully operate the
system depends on the tower size, GPM and the volume of
water contained in the piping system to and from the tower. You
must select a tank large enough to contain those combined
volumes—plus a level sufficient to maintain a flooded suction
on your pump. Control makeup water according to the level
where the tank stabilizes during operation.
You should always use a bottom outlet for this type of
piping system. The following table lists the flow capacities for
bottom outlets.
Basin Heater Selection
Tower
Model
+10°F Ambient -10°F Ambient
Tank Heater
Component
Heater
Tank Heater
Component
Heater
490A 1.5 kW 3 kW 1.5 kW 3 kW
490B 1.5 kW 3 kW 1.5 kW 3 kW
492A 1.5 kW 3 kW 1.5 kW 3 kW
492B 1.5 kW 3 kW 1.5 kW 3 kW
493A 1.5 kW 3 kW 2 @ 1.5 kW 3 kW
493B 1.5 kW 3 kW 2 @ 1.5 kW 3 kW
494A 2 @ 1.5 kW 3 kW 2 @ 1.5 kW 3 kW
494B 2 @ 1.5 kW 3 kW 2 @ 1.5 kW 3 kW
494C 2 @ 1.5 kW 3 kW 2 @ 1.5 kW 3 kW
495A 2 @ 1.5 kW 3 kW 3 @ 1.5 kW 4.5 kW
495B 2 @ 1.5 kW 3 kW 3 @ 1.5 kW 4.5 kW
496A 3 @ 1.5 kW 4.5 kW 4 @ 1.5 kW 6 kW
496B 3 @ 1.5 kW 4.5 kW 4 @ 1.5 kW 6 kW