Thanks for the replies.

But the problem is few socket/power point to one MCB. So, if on all together total load could be more than 20A.

Let me check one by one and post here again.

Any electrician real good and qualified one to recommend?

How man? The existing DB Box is full and I have so many power points and dont know how it was connected if one wire shares many points. 

l.

Also, the wires now terminated at the DB box and how to connect to another place without major re-wiring?

Can't understand the table. mine showing me which are for 10A, 20A and 32A from the table?

One more question comes to mind. Look like never ending...

If I get to locate the bunch of wires run up to the first floor and cut them and fix a new DB at the 1st floor, I then need to run a thick cable from the new DB to the main DB at the ground floor right?

Question:

Instead of pulling a new thick cable (live, neutral and earth), can I twist a few or all of the existing "cut" cables (become a big thick cable) that I cut (for making the new DB) which connect down to the ground floor DB, same twist them together? See drawing below:

[attachmentid=3670289]

Thanks for the input. You got me, "the only real reason to do what you suggested is to save $ and time inconvenience on hacking and plaster back"

Anyway, hacking is unavoidable for the installation of sub DB where I need to hack out the cable long enough to get all of them one by one into the MCBs in the sub DB. The problem is to hack thru the slab and beam. I do not want another hole thru the beam which is at the middle of the house, it only weaken the beam.

I just need to find two 4mm wires each and twist them together which will support 60A, right? Below is the potential load up-stair:

1 x 2 1/2 hp aircond
2 x 1 hp aircond
1 x iron
5 x fans (not on when use aircond)
30 x downlight, wall light and table lamp.
1 x vacuum cleaner (not use when ironing), my wife cannot be doing 2 things at a time
Many power sockets but seldom use other than mentioned above for ironing, vacuuming, also for charging handphone, hair dryer, no water heater (I use solar heater), TV, Audio, PS2 games.

Therefore, one 4mm for 32A could be enough, but 2 x 4mm definitely more than enough. Then need to connect 2 x 4mm wire to one 8mm wire to the sub-DB.

What do you think if I use lead soldering to join the 2 4mm wire together instead of twisting them together for terminating at the sub-DB and the down stair DB? How good is the lead joint conducting electricity compare to bear copper wire?

Cheers