lineset question

Ran across a 40+ yr old home-brew type lineset install for a 5 ton split system. Suction is 1-3/8 & liquid is 5/8, length is around 100'. Both liquid and suction line are touching each other the whole length, insulation if any is wrapped around both together. About 10' is underground, direct burial.
Its a fixed orifice system. In 40 yrs, its on its third condenser, which is 2-3 yrs old.
Other than requiring 3-4 times the amt of gas to charge such a system, what are the ramifications of excessive subcooling and superheat?
Is this an older style technology? (pjm should know this one..) :)
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Fish;
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.
The problems:
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 and buried.]
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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Zyp

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Well...bring the compressor up to capacity......
Add a water coil here, another one there.
Pressures go whack, depending on where you porting them from.
Logically...in your case, it's just the losses--not in friction, but temperature in having the lines in contact with one-another.
Suggest always ask yourself--where in blue blazes has it gone off to ?
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Oh other thing, cant suck it all into the condensor unless it has a huge reciever.
Probly stinks anyways and was never properly flushed and therein lies the reason for the last compressor failure and the one before that.
Personally, I suggest shouldn't touch unless both indoor an out are replaced.
Charge extra for the lineset flush, ( appears lineset replace is problemmatic ) add a good filter and come back later for a to replace it.
Good luck.
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