IOMM ACZ/AGZ-1 15
The net internal area of this smaller sized line (see Table 13 or 14) should be deducted from the area of
the size selected in paragraph 1) immediately above. The remainder represents the area of the other
riser. From Table 13 or 14, select a line size with an area equal, or close, to the calculated net area. The
combination of these two risers will provide the required performance at full circuit tons. The line
selected for the minimum load should always be active; and both lines should enter the overhead
horizontal line in a manner to prevent spillage of oil back down the other riser.
Underground Refrigerant Lines
McQuay does not recommend the installation of suction lines underground. If job conditions require
that they be located below ground, a suitable sized suction accumulator must be installed ahead of the
compressor to interrupt liquid refrigerant slugs at start-up.
Long Vertical Riser Installation
Where job conditions require refrigerant gas lifts of more than 25 feet, McQuay recommends the
installation of a short trap half-way up the riser or at not more than 20 feet intervals. These traps are
required to capture and hold small quantities of oil during off cycles.
Figure 8, DX Coil Piping
Condensing Unit Above Coil Condensing Unit Below Coil
CONTROL BULB
STRAP TO LINE
SUCTION TRAP
SHORT AS
FITTINGS PERMIT
LIQUID TO
COIL
S
U
C
T
I
O
N
P
I
T
C
H
T
O
C
O
M
P
R
E
S
S
O
R
LIQUID TO
COIL
CONTROL BULB
STRAP TO LINE
A
B
DUAL RISER
SUCTION TRAP
SHORT AS
S
U
C
T
I
O
N
P
I
T
C
H
T
O
O
N
E
C
O
M
P
R
E
S
S
O
R
O
N
L
Y
LIQUID TO
COIL
S
U
C
T
I
O
N
P
I
T
C
H
T
O
O
N
E
C
O
M
P
R
E
S
S
O
R
O
N
L
Y
SUCTION TRAP
SHORT AS
FITTINGS PERMIT
EXPANSION VALVE
CONTROL BULBS
STRAP TO LINE
AND INSULATE
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