Liquid Lines; Suction Lines; Recommended Line Sizing; Table 1 Line Size Metric Conversion - Data Aire DAPA-2.5 Installation, Operation & Maintenance Manual

refrigerant line sets to the indoor and outdoor units. Nitrogen needs to be flowing through the lines to
eliminate carbon deposit buildup on the inside of the joints. Carbon could contaminate the refrigerant
and restrict the metering device.
Piping must be supported within 18" (457 mm) of the inlet and outlet connections external to the unit.
Internal to the unit, the inlet connection is located on the top header of all units. The discharge outlet is
located at the bottom of the header.
The discharge line pressure drop should not exceed 9 PSI (62 kPa) for R-410A 6 PSI (41 kPa) for R-
407C. Recommended gas velocity for proper oil return is 1,000 FPM (5.1 m/sec). Slope horizontal lines
downward in the direction of the refrigerant flow. The recommended slope is 1/2" (12 mm) for every ten
(10) feet (3 m) of line length. Discharge lines do not require insulation but due to the high temperatures
of the refrigerant inside the line, the pipes may be insulated to protect against burns to individuals near
or around the lines.

Liquid Lines

Liquid line size is determined by pressure drop and velocity. The liquid line pressure drop should not
exceed 9 PSI (62 kPa) for R-410A and 5 PSI (35 kPa) for R-407C. The recommended liquid velocity
should be between 200 and 300 FPM (1 to 1.5 m/sec). To avoid excessive liquid line pressure drop,
the air-cooled condenser should be located above or at the same level as the evaporator. Condenser
installations more than 15 feet (4.6 m) below the evaporator are not recommended. Insulation of liquid
lines is not required but can be useful in preventing excessive subcooling or flashing on long exposed
pipe runs.

Suction Lines

Some applications call for the compressor to be mounted as part of the condenser, more commonly
referred to as a condensing unit. Such cases require field piping of liquid and suction lines. Suction
lines are trapped similarly to discharge lines. Common practice for suction line selection and installation
should be followed. Suction lines should always be insulated.

Recommended Line Sizing

Table 1 Line Size Metric Conversion

Inch OD mm
3/8 9 mm
1/2 12 mm
5/8 16 mm
3/4 19 mm
7/8 22 mm
NOTE: All line sizes shown in this document are Outside Diameter (OD)
unless otherwise specified.
Inch OD mm
1-1/8 29 mm
1-3/8 35 mm
1-5/8 41 mm
2-1/8 54 mm
20