My house developer already installed 1hp concealed piping for 1hp air cond.
Can i install 1.5 hp aircond to my 1hp piping?
Your advise highly appreciated.

My air conditioner is LG brand model Q126J3A0

No.
Piping Connections
Liquid (mm) 6.35 <- pipe from compressor
Gas (mm) 12.7 <- return pipe to compressor

It's return (gas) pipe diameter requires a larger diameter at 1/2" (12.7mm). What's installed for 1HP gas pipe is 3/8" (9.35mm).

Smaller HP AC generally can use pipes larger than its spec. Eg 1HP on 2HP piping but never the other way round.

[Update] Useful topics:
AC general discussion v1, v2 & v3
Insulation
DIY maintenance here, here and here
AC piping
Benefits of using dry mode
Whether inverter works or which one better
Hot water from aircond
Choosing btw ceiling cassette vs wall mounted units
Concealed piping issues here, here and here.

This post has been edited by halcyon27: Jan 5 2018, 10:11 AM

very useful info thanks

Actually, all the info is floating around in the AC related threads. Many forumers have shared over there. The best tools to quickly find things are: search within a topic (posts in a specific forum thread) and search within the sub-forum.

This post has been edited by halcyon27: Jan 5 2018, 08:24 AM

TS, google Mitsubishi Electric Aircon models. their inverter 1.5hp (some) uses the same pipe as 1hp.

but make sure you have 4 wires from indoor blower to compressor for inverters.

MSY-GJ13VA to be exact.

This post has been edited by advocado: Jan 5 2018, 10:29 AM

bro do you know if copper pipe must be pulled to exact length or can we do it like wires leave some extra length just in case?

also i just read (which was not mentioned anywhere) that the suction line (i would assume return to compressor line) needs to have a downward slope of 1/4" per foot in order for the oil to flow back to the compressor as oil used for lubricating the compressor flows with the refrigerant.

i'm not sure this apply to Malaysia design or new models though. can someone check? Last time i check i don't think anyone do that only drain the do that slope.