Heatcraft Refrigeration Products 4346B001 - Manual (Page 6)

6
Water Coils Exposed
to Freezing Temperature
Water coils exposed to freezing temperatures must be
protected from freeze-up by either adding anti-freeze
solution to coils or proper draining of the coils.
The coils are circuited so that there are no trapped
circuits. However, because of the serpentine nature of
the circuiting, it is almost impossible to adequately drain
the coils by gravity alone. Particularly on longer coils,
even a fraction of a degree deviation from a horizontal
plane can lead to water being trapped within the
serpentine.
Water that failed to drain from a single tube,
or even part of a tube, can cause the tube to
rapture upon freezing.
Draining Coils Using Supplemental
Air Blower
Ideally, a blower capable of delivering 150 CFM of air
at approximately 40-50 inches of water or more should
be used. Some small air compressors, while delivering
higher pressures, probably will not deliver sufficient
volume of air and this is equally as important.
1. Drain the coils by gravity after opening the
supply, return, vent and drain connection.
2. Connect the blower to large connection that
is at the greatest elevation. The small vent or
drain connection on the header to which the
blower is connected should be closed.
Refer to Figure 1 for typical hook -up during the
blow-out operation.
It is helpful to tap the coil causing along the
length of the coil during the draining process.
The blower should be operated until no moisture
can be detected leaving the coil. Then, shut the
blower off and permit the coil to stand for a few
minutes. This will permit the moisture that has
adhered to the walls to accumulate. Then the
blowing out operation should be repeated.
Ideally, the coil should be permitted to stand
twenty-four (24) hours and blown out again.
3. Leave all connections open until coil is put into
operation.
Installation of Anti-Freeze Solution
A second way to prevent a coil freeze-up is to add an
anti-freeze to the coil, such as industry inhibited glycol.
The coil should be valved off so that only the coil would
have anti-freeze added to it. The most positive way to
assure the mixing of the anti-freeze is to make a run-
around loop with a circulating pump.
1. Open all connections and drain the coil as
thoroughly as possible.
2. The anti-freeze solution should be added to the
coil and circulated through the coil until the
solution is thoroughly mixed and all air is purged
from the coil. The air vent should be opened
during the filling operation and cracked during the
pumping operation to accomplish this. When
the solution has circulated for 15-20 minutes,
the concentration of the solution should be
checked with suitable hydrometer. If the
concentration is low, add more glycol and
operate the pump again. A typical piping diagram
is shown in Figure 2.
3. The anti-freeze solution may then be left in
the coils or drained and used to flush another
coil. The concentration must be checked for each
coil flushed.
The adding of anti-freeze to a system exposed to
freezing conditions may be necessary if the system
must be operation at a moment’s notice. This affects
the chiller and coil performance and must be taken into
consideration when selection the components.
Note: Most anti-freeze solution will be furnished with
a chart of concentration at freezing point. It is also
important to be certain that the anti-freeze solution
used is not corrosive to the tubing.