The larger suction and liquid lines were likely for R-500 years ago. You
might also notice the fittings were "soft solder" instead of "hard solder."
Common in the 60's.
1. Oil return. Without the correct line size the suction gas velocity may
not be up to speed to sweep the oil back to the condenser from the
evaporator. [The oversized lines may help reduce capacity losses but create
an oil return issue. It is wiser to replace an oversized suction line with
two smaller lines to overcome the distance, reduced capacity and increase
the velocity for good oil return.]
2. Buried lines cause liquid migration in the suction line and can be a
problem on start up. [In the early 60's some used a liquid line solenoid to
'pump down' the suction gas to prevent migration when the lines are lengthy
3. Suction and liquid lines tied together in a common bundle can increase
the superheat delivered to the compressor. This in turn causes unusually
high discharge temperatures associated with oil sludge.
4. Manufacturers today recommend the lines not be extended to far beyond
the 50 foot mark for today's equipment. There will be a reduction in
capacity [about 4% - 8%] and the issues I mentioned above.
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