2-55
johNSoN coNtroLS
ForM 102.20-N1 (1109)
2
DX Coil Types
There are three basic types of coil arrangements used
in field erected split systems, interlaced, row split and
face split.
interlaced
Interlaced coils are the most desirable type of coil “field
erected” designs. Interlaced coils ensure the entire face
of the coil is active with any number of compressors
operating. Interlaced circuitry interweaves coil tubing
in both circuits across the entire face of the coil assuring
uniform cooling of the air by the refrigerant. This type
of coil also allows one circuit to operate while the other
circuit is turned off. Interlaced coils provide excellent
temperature control at full and part loads as well as
good TXV superheat control. TXV control is essential
for compressor reliability.
Row Split
Row split coils arrangements place coils back to back
in the air stream. Air passes through one coil before
passing through the next. Generally, the last coil in
the air stream is activated first. Each circuit may be
controlled independently in this arrangement. When
both coils are operating, the coil closest to the leaving
air will operate at a lower temperature. This type of
coil may not permit lead lag of the circuits and it may
be difficult to balance the capacity between the coils
Face Split
On a face split coil, the circuiting is divided between
two separate coils. In field-erected systems, this
arrangement may suffer from TXV superheat control
problems and compressor reliability. At low airflow,
low load situations, the TXV may have difficulty
controlling system superheat.
Air stratification, poor humidity control and
condensation on downstream components can also
occur when using face split coils. One way to address
TXV control at part load is to provide a face damper to
shutoff airflow when a coil face is inactive.
Combined Coil types
Coil types may be combined in some systems. This
requires special care. Control sequences and piping
tying the multiple systems and coils together should
be well thought out and advice from an experienced
design engineer is necessary.
DX Coil Circuiting
On many coil banks, two, or even all three of the
methods of circuiting may be combined depending
upon the cooling capacity and the level of control
required. However, coil sections must be married or
combined so that they provide for full-face operation
(
see Fig. 2-78
).
There are numerous coil arrangements available from
the Coil Marketing group as either standard designs
or contract engineering SQ optional designs. The coil
designs fall into the two following categories.
FIG. 2-78 – DX COIL CIRCUITING TYPES
LD13319B
FACE SPLIT
ROW SPLIT
INTERLACED
LEGEND
WARM AIR
COLD AIR
REFRIGERANT IN
REFRIGERANT OUT
Summary of Contents for YORK SOLUTION LD09624
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