10
2.0 PIPING
2.1 Split Air Cooled Unit Piping
Refer to the attached line sizing chart on page
36 for a guideline for sizing refrigerant lines. The ulti-
mate responsibility for line sizing selection is that of the installing contractor or the project engineer.
Data Aire does not assume this responsibility. The chart covers distances up to 200 equivalent feet.
For installations greater than this distance, consult ASHRAE or similar references.
Standard piping practices must be used to ensure proper oil return and effi cient operation. The
interconnecting lines to the remote air cooled condenser or condensing unit must be installed by
a qualifi ed refrigeration mechanic.
2.1.1 Discharge Lines
Discharge lines, also called hot gas lines, should be trapped at the top (inverted) and bottom, as
well as every 15 to 20 feet of vertical rise. Discharge line check valves are recommended on all
installations, especially those where there are long pipe runs or cold climate. Check valves should
be installed no less than 6 feet from the compressor. The discharge, suction and liquid lines need
to be refrigerant grade copper and in accordance with local code. All refrigeration piping should be
installed with high temperature brazed joints. When brazing, a supply of nitrogen gas needs to be
fed through the refrigerant lines. Be sure to open the other end of the refrigerant line to allow the
nitrogen to bleed off and not pressurize the piping. Prevailing good refrigeration practices should
be employed for piping support, leak testing, dehydration and charging of the refrigerant circuits.
During the installation the lines should be capped off and fi lled with dry nitrogen at the end of each
day’s work or until the system is completed and sealed.
Data Aire recommends a silver/phosphorus/copper alloy with 5 to 15% silver to be used to braze
the refrigerant line sets to the indoor and outdoor units. Nitrogen needs to be fl owing through the
lines to eliminate carbon deposit build-up of the joints. Carbon could contaminate the refrigerant
and restrict the metering device.
Piping must be supported within 18” of the inlet and outlet connections. 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 6 PSIG for R-407C and 9 PSIG for R-410A.
Recommended gas velocity for proper oil return is 1,000 FPM. Slope horizontal lines downward in
the direction of refrigerant fl ow, 1/2” for every 10 feet 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 insu-
lated to protect against burns to individuals near or around the lines.
2.1.2 Liquid Lines
Liquid lines are determined by pressure drop and velocity. The liquid line pressure drop for R-407C
should not exceed 5 PSIG. For systems with R-410A, the pressure drop should not exceed 9
PSIG. The recommended velocity should be between 200 and 300 FPM. To avoid excessive liquid
line pressure drop, the air cooled condenser should be located above or at the same level as the
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