17
Caution
Wintertime Operation:
The Marley fill system used in NC cooling towers has air entrance louvers that
are molded as an integral part of the fill. This feature makes these towers very
forgiving of cold weather operation, even at the low temperature and reduced
load conditions encountered in free cooling and other low temperature applica-
tions. Nevertheless, during operation in subfreezing weather the opportunity
exists for ice to form in the colder regions of the tower.
Slushy, transitory ice forms routinely in the colder regions of the fill
of low temperature towers, and is visible through the tower louvers.
Such ice normally has no adverse effect on tower operation, but
its appearance should be a signal to the operator to undertake ice
control procedures.
It is the operator's responsibility to prevent the formation of destruc-
tive (hard) ice on the cooling tower fill. Certain guidelines should
be followed:
1. Do not allow the tower’s leaving water temperature to drop below a mini-
mum allowable level—say 36°F to 40°F. If such low temperature operation
is necessary or beneficial to your process, establish the minimum allowable
level as follows:
During the coldest days of the first winter of operation, observe whether
any ice is forming on the louver face, particularly near the bottom part of
the louver face. If hard ice is present on the louvers, you must increase the
allowable cold water temperature. If the coldest possible water is beneficial
to your process, ice of a mushy consistency can be tolerated—but routine
periodic observation is advisable.
If the minimum allowable cold water temperature is established at or
near minimum heat load, it should be safe for all operating conditions.
Having established the minimum allowable cold water temperature, maintain-
ing that temperature can be accomplished by fan manipulation, as outlined
in Item 4 under Tower Operation. However, in towers of more than one
cell, where fans are manipulated sequentially, please realize that the water
temperature will be significantly lower in the cell or cells operating at the
highest fan speed than the net cold water temperature produced by the
Note
operation
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