Cable sizes are not always what they seem. Yeterday, before swapping out the cable, i measured what I had previously used and confirmed that cheap budget brands are straight-up smaller than advertised!

For example, if you buy standard 2.5mm² cable:

• Premium brands: Measure around 1.78mm in conductor diameter (the correct math for 2.5mm² area). BCC and Yazaki

• Cheap brands: Often measure down to 1.4mm in diameter (which is actually closer to 1.5mm² area!).

Undersized copper means higher resistance, dangerous voltage drops, and a serious fire risk under heavy loads. Don't risk your safety, grab your digital calipers and verify your copper before installing it!

Stay away from anything Chinese. Safe with BC, CYW and Yazaki.

Edited July 17Jul 17 by novacova

Yeah, it's come up a few times that the budget cables are not always quite what they claim☹️

You really do tend to get what you pay for, copper isn't cheap.

Of course, there's nothing to stop you using a smaller breaker suited to the actual measured size.

Yep. My house was built with a temp. PEA supply and the builder fitted the cable from the meter to the house. A distance of 1 km.

Seven years later I got the proper supply from PEA and was asked by the kamnan to remove my temp cable from where it adorned the trees.

No problem but I took the opportunity to measure the "25mm²" cable. It came in at a hefty 22mm²

Also the writing on the sheath was noticeably absent.

So another corner for the builder to cut....

3 minutes ago, Muhendis said:

Yep. My house was built with a temp. PEA supply and the builder fitted the cable from the meter to the house. A distance of 1 km.

Seven years later I got the proper supply from PEA and was asked by the kamnan to remove my temp cable from where it adorned the trees.

No problem but I took the opportunity to measure the "25mm²" cable. It came in at a hefty 22mm²

Also the writing on the sheath was noticeably absent.

So another corner for the builder to cut....

And what rate pr unit have you payed ?

2 hours ago, Hummin said:

And what rate pr unit have you payed ?

Nominal construction supply rate which was around 8 Baht at that time.

But that was not for long because one of the first things I did was to fit solar.

That all happened eleven years ago.

Since then I have rarely used PEA except when I use slightly more industrial equipment.

All my bits of wire are well up to the required sizes now.

I don't know if it is my eyes but it seems incredibly difficult to read all those tiny little numbers and letters on a bit of 4mm² wire.

Ask AI because I'm not the best at explaining why?

Cable sizes

1.0, 1.5, 2.5 are most common.

Wattage - Calculate for both continuous and max load

Resistance - smaller size, more Resistance

Distance - When calculating distance, the needed Wattage and distance are factored

Amps - recommended brackets for 1.0, 1.5, 2.5

Same with Volts

A well known and respected YouTuber (Will Prowess) has posted how important cleaning with alcohol the copper ends and properly crimping to reduce resistance or connecting the wire.