Piping; Discharge Lines; Liquid Lines - Data Aire DARC 03 Installation, Operation & Maintenance Manual

2.0

Piping

Refer to the Line Size chart (7.0 LINE SIZES) for a guideline to sizing refrigerant lines. The ultimate
responsibility for line size selection is that of the installing contractor or project engineer. Data Aire
does not assume this responsibility. The chart covers distances up to 200 equivalent feet. For in-
stallations greater than this distance refer to ASHRAE or similar references.
Note: Standard piping practice must be used to ensure proper oil return and efficient
operation. The interconnecting lines to the remote air-cooled condenser must be in-
stalled by a qualified refrigeration mechanic.
• Only use refrigerant grade copper tubing (ACR
• Soft solder joints are not acceptable
• Purge dry nitrogen through the lines while brazing
• Do not leave dehydrated piping or components open to atmosphere any longer than is re-
quired
Welded or sweat joints should be used. Piping must be supported within 18 inches of the inlet and
outlet connections on the units.
2.1

Discharge Lines

Discharge lines (also called hot gas lines) should be trapped at the top (inverted) and the bottom.
In addition, a trap should be installed for every 15 to 20 feet of vertical rise. Discharge line check
valves are highly recommended on all installations. Check valves should be installed 6 to 10 feet
from the compressor. See Figure 3
Proper design will minimize refrigerant pressure drop and will maintain sufficient gas velocity to
carry oil through the condenser. Discharge line pressure drop should not exceed 6 PSI. Recom-
mended gas velocity for proper oil return is 1,000 FPM. Slope horizontal lines downward in the
direction of refrigerant flow (1/2" for every 10 feet of line length).
2.2

Liquid Lines

Liquid line size is determined by pressure drop and velocity. The liquid line pressure drop for R-407C
should not exceed 5 PSI (35 kPa) or 9 PSI (62 kPa) for R-410A. 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 below the evaporator are not recommended. Insulation of liquid lines
is not required but can be useful in preventing excessive sub-cooling or flashing on long exposed
pipe runs.
1 The American refrigeration industry uses different copper pipe call ACR (air conditioning and refrigeration field services) pipe, which is
sized directly by its outside diameter (OD) and a type letter indicating wall thickness. ACR pipe is manufactured without processing oils that would
be incompatible with the oils used to lubricate the compressors in the HVAC system
10 Air Cooled Condenser User Manual
•
preferred)
1