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Thecheckvalvewillpreventowfromthecondensertothecompressorduringthe“off”cycle.
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. Pre-
vailing good refrigeration practices should be employed for piping support, leak testing, dehydration
andchargingtherefrigerantcircuits.Duringtheinstallationthelinesshouldbecappedoffandlled
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 be used to braze the
refrigerantlinesetstotheindoorandoutdoorunits.Nitrogenneedstobeowingthroughthelines
to eliminate carbon deposit build-up on the inside of the joints. Carbon could contaminate the re-
frigerant 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.
Discharge line pressure drop should not exceed 6 PSI for R-407C and 9 PSI for R-410A. Recom-
mended gas velocity for proper oil return is 1,000 FPM. Slope horizontal lines downward in the
directionoftherefrigerantow(1/2”foreverytenfeetoflinelength).Dischargelinesdonotrequire
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 line size is determined by pressure drop and velocity. The liquid line pressure drop for R-
407C should not exceed 5 PSI or 9 PSI for R-410A. 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 evaporator. Insulation of liquid lines is not required but
canbeusefulinpreventingcondensationfromformingandtoavoidashingonlongpiperuns.
2.1.3 Suction Lines
Some applications call for the compressor to be mounted as part of the condenser (more commonly
referredtoasacondensingunit).Condensingunitsrequireeldpipingofliquidandsuctionlines.
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.
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