I'm having some new Mitsu Slim 9000 and 13,000 BTU units installed and I want to make sure the installers run the correct sized wire from the main electric board to the condenser and wall units. I have had experiences in the past in Thailand where the incorrect gauge of wire was used and the electrical system would short out. [When I investigated the problem, there was actually about a half-meter section of wire where the plastic wire covering had actually melted off.]

So what is the proper wire size for standard home air-con units?

All AC units sold include install booklets even if you the owner never see them. But in these books the manufacturer will spec the proper wire and breakers for their units.

Most people never read these as the installers are supposed to be trained to know these specs but this is Thailand so take it upon yourself to look at the install book. It may be printed in Thai but if lucky an English version also.

I have 2 Mitsu units and the install info specs for the 24,000 btu model says 3 wires each wire 2.5 sqmm to a 20 amp breaker, the second 9,000 btu unit specs 3 wire-1.0 sqmm wire to a 10 amp breaker

Check your book for you're units spec

Here is a handy chart. http://www.simetric.co.uk/siwire_elect.htm For normal house wireing in THailand i would use 3.3mm2 or 12 AWG for your size ac I would use 5.2 mm2 or 10 AWG.

10 awg would be much bigger than needed for his 13,000 btu unit and for sure too big for the 9,000.. Copper cable here is not cheap so buy what is needed. Again I suggest using the install manual from the manufacturer

Thanks for the input...I will be sure to grab the manuals from the installers when they open the boxes and check the specs with the cabling the installers plan to use.

According to this online installation manual I found, AWG14 is the specification for both the cabling to the power-supply and between the wall-unit and the condensor.

Is Thai wiring graded using the AWG specification...I don't recall seeing wires referred to them like this? What would be the Thai specification for AWG14 wire?

Mitsubishi Mr. Slim Installation Manual.PDF

There's no exact equivalent, 2.5mm² is the next size bigger than AWG14

There's no exact equivalent, 2.5mm² is the next size bigger than AWG14

As said, no standard size matches in mm2 from AWG. Reference table with nearest sizes.

AWG to mm2 table

Thanks again...will be sure to check that the wire being used is 2.5mm thickness. Will be interesting to see if they try to skimp a bit and use something thinner.

My unofficial guess is they will use a lighter awg cable and it will be 2 core.

Make sure they pull 3 wires one of which should be the earth(ground) connection and hopefully this earth will be close to a green color to distinguish it from the hot and neutral.

My wager is on them installing the 2.5mm2 as it is a small unit and small wire already. If it was a bigger unit I could see them undersizing the wire. Please don't ask me to explain my rationale. I'll even double down and say that they will check the panel for grounding and then run 3 wires without it having to be mentioned. I know, way out on a limb here, but I have a good feeling about this one.... And the winner is..........?

Americans remember we are using 230v here not 115v. The wire does not need to be anything like the size used in the US.