varies on electrical appliances, lights usually fitted with 6 ~ 10A, airconditioner and fridge to 30A ...

My house MCB most of it harden already, stuck, so difficult to pull down or push up. My electrician advised me to change all even though some are still good. And he suggested all change to 32A. I have 10, 20 and 32A. I am worry about his advice to change all to 32a and if the cable/wire can take load and what is the danger of doing so.

It is time to get some advice from others like you and be sure and if I can diy or just let him do it. See picture of my DB and the 3 types of MCB.

[attachmentid=3668036]

[attachmentid=3668038]  [attachmentid=3668040]

This is not the original, he changed it 12 yrs ago when i reno my house so direct replace also may not be correct.

I will test out all how it is all connected how the MCB are shared and post the table here for your further advice. Now at night cannot test, cannot see in the dark.

Also, that is why i am asking about the wire, how to identify the wire rating.

Thanks....but how this thing look like? What is cable radial or ring circuit?

Cost is not so much of a problem. The problem is under the existing box below are a row of switches sure got wire running in the wall.

Also, the wires now terminated at the DB box and how to connect to another place without major re-wiring? Even next to it still need to connect and lengthen the wire one by one? 

This time i want to make sure i know what is to be done before getting electrician to do what he wants or easy cincai job.

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

Just to confirm one more question.

Diagram below refers:
[attachmentid=3670054]

In the radial circuit as circled in red. The circuit is protected by a 20a CB.

Question:

Am I right to say the amperage of the wire(denoted in red) it carries in the radial circuit is the sum of all the 10 power points? If each point consuming 1a, the total amperage of the "red" wire is 10a?

Similarly, The "green colour" wire is the sum of 7,8,9 and 10?

You could but its not really the right way to do it for a few reasons.

1) after cutting the old wires probably be to short by a few inches to go from Main DB to sub-Db. remember you want to cut the upstairs wires from sockets a bit longer so its easy to connect into Sub-DB and you are not trying to stretch wires.

2) joined parallel wires don't really have the same capacity in practice as they do in theory. Also its easy for 1 or 2 wires of a twisted set to come loose from the crew point, then youve got loose wires and reduced capacity and remaining wires are now free to come loose also.

3) It will be very hard to join those several wires into the DB and sub Db.

4) its just plain messy.

5) AFAIK its probably against the wiring rules/codes.

6) the 2-3 mtrs of big wire from sub to main will only cost less than RM50, so its not a bifg cost

the only real reason to do what you suggested is to save $ and time inconvenience on hacking and plaster back, but this is easly out voted by reasons 1-5 above.
Cheers

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

Not sure, I did not take notice of the old DB before the reno if there was any 32A MCB.  But during reno the electrician could have use 4 mm since he put so many 32A MCBs.

I spoke to a friend and it appears that there is more to just the amperage on the MCB vs the amount of current you need to size an MCB. If the amount of current is below the MCB's rating multiplied by the value of its type, there'll no trip. In an overcurrent situation, most likely your electrical/electronic device will get fried (it's gotta be already faulty to draw excessive current) before your wire if you're lucky.

To size it, you'll need to know all the resistance involved (wire, devices, earth loop, inrush current). Not sure how many have the equipment to perform these tests?

Anyway, just to share.

http://www.studyelectrical.com/2014/07/min...tic-curves.html
http://www.theiet.org/forums/forum/message...&threadid=32143
The reason I'm researching this is because I have a neighbor who had his concealed wire shorted permanently, something I'd rather avoid.

wise words, bro weikee. I think that's why the developer gave 4mm2 wires for room aircond despite room airconds are likely 1HP.

My neighbor's house was rented out. No one really knew how that socket was used as he only got back his house recently. It was looped alright. From MCB to 3 sockets. The last point was the one that fried.

I'm installing some new points for my own house. Will be using 4mm2 to minimize the melting problem, regardless of how long I use the current. Price does not differ a lot vs 2.5mm2 when I buy in rolls. The last time I paid for wiring, I was "convinced" that their 1.0mm2 (yes, I read it on the wire several times because I thought I misread it) 3cores is good enough for 2HP aircond. 1 month warranty woh.

BTW, I've read a lot of your useful responses here when I was searching for RCCB. Pleased to meet you, finally. Speaking of RCCB, another neighbor insisted that MCB will trip when there is a current leak when I tipped him about the 10mA RCCB for heater. I guess it would, if the leakage goes beyond the MCB rating x Type.

That's why he confidently gave 1 month warranty. I always consult my friend before agreeing to all the deals offered by contractors. When problem occurs, can make money pulling new wires again.

Referring to RCCB, yes, after so much research, that's what I learned. Also read that some will trip at 50% of the value. Didn't drill too much into that.

Let me ask you this, since you're a 高人. Which is better? 10mA RCCB between MCB and water heater, or MCB between RCCB and water heater? My friend recommended the latter, but I went for the former after some research. It's sort of whether I want the MCB to protect RCCB from potential overcurrent damages, or RCCB to protect MCB from leakages. I'm protecting the RCCB because it's much more expensive. He said RCCB will not break, though I wonder what will happen when 100A flows through a 25A RCCB.

hmmmm that's where my concern is. Or probably it's unwarranted.

Type C will only trip at 5x its rated current. If my understanding is correct, there'll be no trips below 5x. On a 20A Type C MCB, it means that 99.9999A can flow through the cable without it tripping. If it heats up the cables long enough, fire or short circuit.

Of course, knowledgeable people know not to overload any particular circuit, but we can't stop anyone from doing so.

This was the reason why my friend said there's no point protecting the RCCB with an MCB. I guess there's no harm trying though
I don't think I've much choice. Seems like it's our norm in this country to compromise safety for convenience. When I goto shops for 10mA-30mA RCCB, they'll always tell me "don't buy this, always trip". I guess the same applies to MCB, so no Type B for the wicked.

Thanks bro weikee.

Yes, I found it there and my friend is using element14 exactly as you - for rare items. These are made in Europe too Costs 8x more though.

http://my.rs-online.com/web/c/automation-c...archTerm=S201b2 seems cheaper than element14. I don't know who will do the customs clearance and not sure if SIRIM approval is needed.

Edit : Ok, my friend say all the clearance will be handled by element14.