Existing one has broken so need to get replaced. Can you recommend brand/type that I can order online. Will be located outside in ceiling recess so weather protected. Main breaker on CU is 63A so does the isolation switch also need to be 63A or can be higher ? Thanks 

Any switch/isolator rated over 63A will do the trick.

 

Many would just stick one of the 100A Chang knife switches in a suitable box but I've seen isolators in MegaHome although whether they are truly weatherproof is debateable. This sort of thing 

https://www.lazada.co.th/products/schneider-safety-switch-100a-1-240vac-d223nrb-nema-type-3r-buyucanbuys-i1887582235-s5906010129.html 

 

What's the existing one like, can you just get another the same?

This is whats there now. Any good ? Doesn't need to be weather proof since its in a covered area.

If it's not actually faulty and doesn't open under load (it's a 60A MCCB) I'd leave it alone. It should really be in a box, but if it's well out of reach it's fine.

 

What's actually "broken"?

Just now, Crossy said:

If it's not actually faulty and doesn't open under load (it's a 60A MCCB) I'd leave it alone.

The problem is that lights flicker when shower is being used and sometimes all power is cut off if I turn on the tv, but this switch stays in the open position. If I flick isolation switch off then back on, power is restored. I can see one supply cable to the house isn't fully connected to the isolation switch, it's kind of only connected by half of the threads in the 16mm cable, and I can't undo the screw in the isolation switch to make a good connection, hence the thinking to replace it. Or any ideas how to undo a stubborn screw? Connections in cu checked and all good. Thanks 

Ak, OK understood. I'd get something similar and give it a box.

 

Since this is directly on your incoming supply you would have to work live (unwise) or pull the wires at the meter. I'd get the bits and get your local sparky to connect up, then the dodgy wires and stuck screw are his problem.

 

EDIT The 63A one here would do the trick https://www.lazada.co.th/products/mitsubishi-mccb-nf63-cv-2p-20a-63a-75ka-no-fuse-breaker-i1046268355-s2330864130.html

 

Or, since you just want a switch (MCB in the consumer unit is your overload protection), you could go bigger https://www.lazada.co.th/products/2p-100a-125a-nf125-cv-mccb-100-mitsubishi-kerry-i717652840-s1378686316.html

 

Or, go with yea-original Chang switch https://www.lazada.co.th/products/2p-100a-chang-2-i2168764204-s7204388326.html