Wrong pipe diameters?

[SarahSmith]

Today I've had the usual "grown man crying because of warm beer" call! The unit is short cycling like it's short on refrigerant (r404). Three months back I thought there was moisture in the system because of massive head pressures but after calling the cabinet and motor manufacturers I found out both parts was delivered to different parts of the country 10 years before the shop even opened. Now this gets better!

We have 20m3 of cabinet space connected with (unnecessary extra 15m) and a total of 30m 1/2" & 1/4" suction and discharge connected to a 3hp motor (which is 4x too big for the cabinets) and I've spoken to the manufacturer who have calculated the discharge is fine but the suction needs swapping out for 3/4"? And there's not one oil trap from beginning to end!!
Any help in untangling this birds nest would be greatly appreciated thanks!

[chemi-cool]

First thing first.
Check that the TXV capacity is OK with the compressor capacity at designed evaporating temp.
If you can get rid of that extra piping, the condensing unit will thank you.
If you keep that long run pipes, I would change the liquid to 3/8 and suction to 7/8.
That will give some "breathing" to the system.
I would collect that 404 and use another refrigerant such as 507 or any drop in .