T-CU11-OCT22-0
Page 14
Installation
Field Piping
Pipe sizing should only be determined by qualified personnel. Correct line sizing will
minimize the pressure drop and maintain sufficient gas velocity for proper oil return.
All applicable standards must be observed in the installation of refrigerant piping.
To ensure satisfactory operation and performance, the following points should be noted:
•
Pipework routes must be as simple and as short as possible.
•
Avoid low points on pipework where oil can accumulate.
•
Suction gas velocity must be sufficient to ensure good oil return.
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Use only clean, dehydrated refrigeration grade copper tube with long radius bends.
•
Avoid flare type connections and take great care when brazing. Use only silver alloy rods.
•
Run braze without over filling to ensure there is no leakage into the tube.
•
To prevent oxidation, blow oxygen free nitrogen through pipework when brazing.
•
Install insulation on all suction lines and on all pipes penetrating walls or passing through hot areas.
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Adequately support all pipe work at a maximum of 2meter intervals.
•
Where the condensing unit is situated below the indoor unit (cold room evaporator / display case), the height
difference between the two units should be no more than 6meter.
•
In vertical pipework, the use of U-trap and double suction risers is often required. These suction risers must
always be fitted with a U-trap at the bottom and a P-trap at the top and never be higher than 4m unless a
second U-trap system is fitted.
•
Additional oil may be required if piping length exceeds 25m or multiple oil traps are fitted. Check the oil level
closely during commissioning and add oil as necessary. Add oil in small amounts.
Do not overfill the
compressor!
•
Suction pipework should slope gently back towards the unit to assist oil return to the compressor. A fall of
approximately 2 cm per meter of pipework is acceptable.
•
Liquid lines should be sized to ensure a full supply of liquid refrigerant to the expansion device. Careful
attention should be paid for sizing of liquid lines on large risers (maximum rise 6m).
•
In some circumstances, a suction accumulator (not supplied) may be required. It offers protection against
refrigerant flood back during operation and against off-cycle migration by adding internal free volume to the
low side of the system.
•
Tests must be conducted to ensure the amount of off-cycle migration to the compressor does not exceed the
compressor’s charge limit.
•
An MOP expansion valve is recommended for all low temperature installations.
•
The system should be installed to utilize a pump down configuration.
•
Maximum recommended pipe length is 25m for rotary unit LRMYS0180/250AXY1; 50m for scroll unit
LRMSS0400/500/600FXY1 from the closest indoors.
System Cleanliness
The presence of non-condensable substances and contaminants such as metal shavings, solder, and flux in the system,
have a negative impact on compressor service life. Contaminants which is small enough to pass through the mesh
screen could cause considerable damage within bearing assembly. The use pf highly hygroscopic PVE oil in the
compressor requires that the oil be exposed to the atmosphere just as little as possible.
During installation, circuit contamination can be caused by:
•
Brazing & Welding Oxides
•
Filings & Particles from de-burring pipework
•
Brazing Flux
•
Moisture & Air
One of the main factors affecting equipment reliability and compressor service life is
refrigeration circuit contamination.
