Condensing Unit

[marksmith970]

What would happen to the capacity of a condensing unit if you 1/2" Instead of 5/8" Suction and 3/8" instead of 1/2" for the pipe run which is about 25m? The Condensing Unit is a Maneurop MCZC054MTA02G. The units are outside about 3m high.

[coolments]

It would definetley reduce but by how much I dont know.
High discharge pressure, evap being starved of enough liquid, longer run time, poor performence and excessive wear on the plant are a few of things that will occurr. you may get it to work but not as it should.

[750 Valve]

Well assuming its not a capillary system and that the original pipe sizing is correct then you'll see a lower suction pressure and a pressure drop between evap and comp in the suction line, this will increase at higher loads. You will experience longer run times due to this PD and a lot more energy input to do the work, so if your unit is borderline on the sizing it may struggle a max design conditions. On the liquid side you may also experience a pressure drop which if you don't have a good amount of subcooling can end up flashing off liquid and decreasing your capacity as well.

[old gas bottle]

why would you even consider doing it ? its a long pipe run and if anything they need to go up a size not down and fit a oil seperator , why look for trouble.

[The MG Pony]

this is a stupid thing to even consider IMO are you qualified? Never undersize your piping, the reasons given here should be evidence enough!