All you need to know about Copper in air conditioning

COPPER
The most widely used copper type for refridgeration systems is Copper UNS No. C12200 (Phosphorus Deoxidized Copper).
It is actually a type of Wrought Copper Alloy with 99.9% copper and some alloy elements.
Generally if u are using the same copper type as the one i mentioned above, u will be in the majority. Fear Not!

DIAMETER
What is so important abt copper pipe diameter?
CAUSED the manufacturer specified this in their catalouge!! If it is not important then why the manufacturer bothers to specific! Understand?

Generally
1) Liquid Pipe Diameter(from outdoor to indoor) is 6.35mm or 12.7mm for most brands.
2) Gas Pipe Diameter (from indoor to outdoor) is 9.52mm for 9K btu fan coil, 12.7mm for 12k & 15k btu fan coil and 15.88mm for 18k & 24k btu fan coil for most brands.
**Please refer to individual catalogues for more details.
3) Thickness of the copper pipe generally range from Gauge 25(0.51mm) to Gauge 22(0.71mm) with most of the installers using either Gauge 24(0.56mm) or Grade 23(0.61mm)
** U can try asking the salesman to provide a 12.7mm copper pipe for a 9k fan coil and expect the fan coil to blow out 12K of cold air. BUTZ! dun expect the manufacturer to warranty your air con after that. **

THICKNESS
So what is that 'Grade 23' that the salesman just mentioned?
It sounds like the quality of copper, accordding to the salesman this is actually the better grade....or is it true......

The 'Grade' ( in actual fact it is called Gauge rather than Grade. If you want to be more accurate then it is SWG or Standard Wire Gauge ) is actually an industrial term for copper thickness ( in actual fact for most metals )
** Actually i have no idea who started to use Grade......maybe mentioning Grade will sound better but some consumers might mistaken it as a measurement of quality.
Example, Grade 22 is 0.71mm, Grade 23 is 0.61mm and Grade 24 is 0.56mm
This has nothing to do with the chemical content. But generally, a thicker copper is able withstand a higher operating pressure. Surely the manufacturing process also plays a very important part.

But due to copper being the most expensive material in the air con installation, most installers will use Grade 24 if not Grade 23.
Some will even think of ways to 'downgrade' the copper pipe sizes especially with the ever increasing copper prices.