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1. Individual pipe runs to a maximum of 20m, including 7.5m lift, are permissible with liquid lines, 80m
with expansion lines, provided good refrigeration practice is followed.
Performance is based on 7.5m pipe runs. Correctly sized pipes for each installation will result in no
significant loss of capacity on extended pipe runs.
a) Pipe sizes are based on:-
Minimum of 3.8 m/s (750 fpm) suction gas velocity for horizontal or downflow.
Minimum of 7.6 m/s (1500 fpm) suction gas velocity for upflow.
Maximum of 15.2 m/s (3000 fpm) suction gas.
b) Where vertical risers exceed 3m, oil traps must be formed in the pipe. This will help ensure that oil
returns to the compressor. Typically fit an oil trap every 3m with a trap at the bottom of the riser.
2. In calculating equivalent lengths of pipe runs, the effect of bends and fittings must be taken into
account. The table below covers the fittings most likely to be encountered in this installation.
The equivalent lengths of all the fittings in a pipe run should be added together and the total added to
the actual pipe length in order to calculate the total equivalent length.
3. Use the shortest possible route, avoiding sharp bends.
4. Completely insulate the suction line, fully over the indoor unit drain tray.
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