Find the leak, cut and join back the copper pipe.

Usually the pipe leak is at the outdoor or indoor unit.
Did he even check those first before suggesting u change the copper pipe?

Call another one for 2nd opinion.
Do not mention the other guy or leaking copper lines

Sounds like BS to me

The root cause might be correct, but the solution is dumb. Copper pipe can cut and weld back, so normally just cut the leak part and join. What for replace the entire copper pipe?

Definitely. Follow what the others have commented. Get a second opinion from another contractor, don't mention its leaking, let them figure it out, and propose a remedial measure. Good ones will be able to propose a repair which does not replacing everything.

Not every repairman is skilled. So, get more to have a look at it, and sometimes it's a matter of what tools they have, so if they can't do it, find someone who can.
Best of luck.

Last time my aircon also leaking so i bought a new aircon from Shopee and call technician for installation.
then the technician dismantled old aircon together with old piping and reinstalled new aircon with new piping set.
Installation cost at around RM250 (10 feet copper only).

bollocks, they can cut where the leak is and fit a new extension with torch gas, thats how copper pipe works. Theres also many modern tools to find the leak nowadays. Clearly this guy is trying to rob you. Move away and find a better guy. Keep in mind what i said. And use it as reference.

last time had the same problem, but we did detect the leak.
instead, reinstall the ac back to back to balcony and put condenser there with short piping requirement.

60ft = 20m, it is at the limit of of performance for fully inverter unit. The option for non-inverter unit is totally out of consideration due to distance limitation.

Some Strata, they limit the location to place the outdoor unit but they will specify what type of AC to use ( inverter or non-inverter).

This is a common issue with the newly built unit, developer want to conceal the piping in the slab. But once the piping leaks, it is almost impossible to detect / repair. Ended up, the AC contractor usually will suggest to by-pass the old pipe & run the new pipes. Just like the old plumbing pipe in old house, if you ask the plumber go to detect & repair, the plumber will ask the owner to by-pass with the new piping.

1. is your outdoor unit really that far away? who the fuk installed an outdoor unit through concrete 40-50' away from the indoor unit?
2. how did they route the drainage? if the drainage anywhere near as long as the copper piping, I would be surprised if it isnt leaking somewhere and causing damage or mold to your house.

as others have noted. just need to repair the part that is leaking. by right, you shouldnt need to replace the whole length of pipe.

You put a proper PVC casing to conceal the insulated piping, run it at the edge of the walls. That would be the cheapest & reliable option.

If you want to conceal by hacking, it would be worse.

Ugly = temporary. Use this to motivate yourself that you are going to move out to bigger house in near future.

thats crazy man. the developer might have been better off putting up more decorative metalwork on the other side.

If your pipings are concealed suggest to change whole copper piping
How old is your house?

Reason being there might be multiple leaking point
let's say if you hack your wall and found one leaking point
then you weld back
after few weeks if not cold then you need find other leaking spot
hacking + weld + conceal again
double work.. labor alone will be hefty

Not suggest to do half baked work
the technician also will tell you they will not guarantee.. after repair done
because if the pipe is old and started leaking, potentially other section have same issues or will have same issue soon (almost time)

This also depends on quality and thickness of the copper pipe used by your contractor

Even if you hack the whole pipe to inspect and weld back muitlple leaking spots
don't think the repair will be as good as brand new copper pipe

Just need to ensure your technician using good copper pipe
one time repair and you're good