Circuit breakers

[Cyrus123]

My apologies for a third topic on electrics but I am lost here.

First of all, the circuit breaker protects the line right? So for a 2.5mm cable I would need a 20Amp breaker?

I only have 2.5mm and 1.5mm kabels in my room yet the breakers are 40, 32 and 20 Amps. So this can't be right, right? I mean even if I hookup 2 outlets with 2.5mm cables on 1 breaker it would still be a 20Amp breaker right?

I know the wiring is messed up and I need to do it myself but in my logics the breakers are wrong as well, or did I misunderstood the whole things?

With the help of the picture could someone please try to explain to me as simple as possible how to connect my outlets to the breakers?

Let's keep it simple:

-I have 2 breakers. Each breaker has 2 screws, 1 at the bottom and 1 at the top.

-I want to connect 2 outlets. each has a cable with a brown and a blue wire.

-The main powerline comming into the condo consists of 1 white and 1 black wire.

Where do I plugin the wires in the breakers?

[Cyrus123]

Picture in case I choose the wrong breakers for the drawing and confuse someone, this is what's up:

[Cyrus123]

Alright with the yellow arrow, whoever installed this with me didn't do it right, right? I need to plugin the white main powerline into the yellow arrow and the black arrow into the top of the circuit breakers right? All the blue wires into the yellow arrow and all the brown wires into the bottom of the breakers right?

[Cyrus123]

To me it looks like instead of using the breakers as breakers they just used them as conductors trying to get the juice flowing not knowing what the hell they were for in the first place....

And the 40Amp breakers need to go, right? 40Amp is just for 10mm cable and I only have 2.5mm in my condo so it should be 20Amps, right?

No matter how many stuff I hookup to the breaker if the cables are 2.5mm it can never be a 40Amp breaker, right?

[Forkinhades]

A very important point here is that the picture on left clearly shows an RCD, which is something you must have.

No more than a 20A breaker for a 2.5mm cable.

Take a look at the pinned threads.

Elecctricity is dangerous, and should really be left to the experts.

However if you fo understand, then make sure you isolate, and test everything is indeed dead, and beware of borrowed neutrals, that can become live.

Just sub the work to a Thai

[Cyrus123]

Yeah I'm gonna buy an RCD and some 20Amp breakers, cut it all loose and mimmick the scheme tomorrow.

Sure hope I got it right!

PS: Yuk, working in here with no fans or aircon working with the electrics cut off is gonna be like a free shower!

[yankee99]

If it was me i would toss that box and get one with a standard hot bar and neutral bar. Then your brakers will have just one wire on their output. Its not a lot of money and youll be able to have a braker for every circuit.

[yankee99]

A very important point here is that the picture on left clearly shows an RCD, which is something you must have.

No more than a 20A breaker for a 2.5mm cable.

Take a look at the pinned threads.

Elecctricity is dangerous, and should really be left to the experts.

However if you fo understand, then make sure you isolate, and test everything is indeed dead, and beware of borrowed neutrals, that can become live.

Just sub the work to a Thai

Looks like a thai did the work already.

[Cyrus123]

Yeah I was thinking the same thing about the box. There's not enough space in this one right now, it fits of course but it's gonna be a mess again.

[Crossy]

Ouch!

IF those fat wires (white and black) are the incoming supply the cowboy who installed it used a 40A and 32A breaker instead of a double pole incomer. Meaning you have just two actual circuits, one on a 20A breaker and one on a 40A.

What happens if you open the rightmost 40A breaker or the 32A breaker? (everything goes off?).

IF that is the case replacing those two with a 40A RCBO (that's an RCD with overload protection) would get you on the right track.

Neutral from the output of the RCBO to the neutral bar top left (use 10mm² for this link) all outgoing neutrals to this bar and a 20A breaker to replace the 40A on the shower and you're almost there at lowest cost. You already have a nice copper bus-bar bottom feeding the MCBs so retain that.

[Cyrus123]

You already have a nice copper bus-bar bottom feeding the MCBs so retain that

From what I see that copper bus-bar should go on top along with the fat black wire feeding all the breakers.

[Crossy]

You already have a nice copper bus-bar bottom feeding the MCBs so retain that

From what I see that copper bus-bar should go on top along with the fat black wire feeding all the breakers.

Top or bottom makes no odds MCBs work either way round, since your incoming supply will top feed the RCBO you can use the bus to bottom feed the MCBs.

If you open up a Schneider consumer unit it has a top bus, our ABB consumer units are bottom bus.

Have you determined whether the rightmost breakers are actually being used instead of a 2 pole incomer?

[Cyrus123]

Haha good one actually... It doesn't really seem to matter wether I put the bus bar with the fat black wire at the top or the bottom, does it?

I see it done both ways in various schemes and pictures.... Do the MCB's have a specific side for in and out or can they be used both ways?

They just shut off when the current becomes too high so it doesn't matter if I plug the main fat black wire into the top or the bottom end right? Haha, right?

This isn't even funny.

[Cyrus123]

You already have a nice copper bus-bar bottom feeding the MCBs so retain that

From what I see that copper bus-bar should go on top along with the fat black wire feeding all the breakers.

Top or bottom makes no odds MCBs work either way round, since your incoming supply will top feed the RCBO you can use the bus to bottom feed the MCBs.

If you open up a Schneider consumer unit it has a top bus, our ABB consumer units are bottom bus.

Have you determined whether the rightmost breakers are actually being used instead of a 2 pole incomer?

Sorry didn't read the previous msg yet, thanx!

I guess that's what happened, they're being used as a 2 pole incomer...

[Cyrus123]

So can the RCD be used either way as well or does it have a specific in and out?

The RCD's I saw at HomePro yesterday had a little turn switch with Amps running from I think 5 to 100 (not sure about exact numbers), how much should I set this to?

[Crossy]

What you looked at was likely a Safe-T-Cut device (was it an external box?), the adjustable trip current is sometimes useful if you have an iffy circuit (there's a bypass mode to get your power on with no protection too).

You should be able to get RCBOs that will fit on the DIN rail in your box replacing the two rightmost breakers.

Like this:

Ensure that you find an RCBO with 50A capacity and 30mA leakage (most are).

Most DIN mount RCBOs are top feed, they will theoretically work either way round but have input and output marked.

EDIT So in your case, the fat black wire will go to the top left terminal and the fat white wire to the top right terminal. There must be nothing else connected to those terminals.

A link of 10mm² (you can buy it in 1m lengths from HomePro but likely in black only) goes from the bottom right terminal to the neutral bar, top left of the box. The copper bus links the bottom left terminal to the bottom terminals of the MCBs.

[Crossy]

VERY EXTREMELY INCREDIBLY IMPORTANT!!

Can you get your incoming supply turned off so you can install the RCBO?

I would be very, very, hesitant to try to do it live as an amateur, get your building odd-job man to do it for you.

[Cyrus123]

Thanx guys, this has been very helpfull!

I can have someone cut the power for me.

[Cyrus123]

I want to install 4 or 5 20Amp MCB's. They only have one brand RCD from ABB, they come in 25Amp, 40Amp and 63Amp.

They're pretty expensive, 2000thb for the 25Amp and almost 4000thb for the 63Amp RCD.

Which one do I need for my setup?

If it has anything to do with it the max amount of Amps my light and electronics would rationally ever use at the same time would be about 20Amps.

I'm just assuming I need the 25Amp RCD but trying to make sure, what do I know...

[bankruatsteve]

Your current box doesn't appear to have room for 4-5 MCB's plus main breaker. Do you have Home Pro, Global, Do Home, etc. nearby? You should be able to get a Schneider Square-D box with 40 amp RCBO for the main and 4 slots for MCB's for around B3000. Safe-T-Cut boxes seem to come only pre-loaded with MCB's ranging from 15-32a - I haven't seen any with 4 20a breakers. Note: if you get a Square-D box you can only use Schneider MCB's (your current breakers would not work). A larger DIN rail box would be another option.

You didn't mention your meter size but if it's 15/45 you could go up to 63a for the main RCBO - looks like you only 'need' 40a though.

[Cyrus123]

I'm getting the RCD, MCB's and a new box all from the brand ABB.

I remember seeing the brand Schneider but they only had ABB RCD's for sale so I'm going with that.

So how do you calculate that I need a 40Amp RCD? What does it depend on?

[Cyrus123]

And how do I find out what size meter I have?

[Crossy]

And how do I find out what size meter I have?

Look at it

It will say something like 5/15, 15/45 or 30/100, the second figure is the maximum current so your RCBO should have a rating equal to or than that.

The ABB boxes are DIN mount (we have them) so any DIN module should fit, best to stick with one brand mind.

[bankruatsteve]

It depends on meter size (just look at the meter. it should say "5/15" or "15/45"), your incoming mains wire size and length, and your anticipated maximum demand (in amps). An average home will do just fine with 40a main.

[Cyrus123]

And how do I find out what size meter I have?

Look at it

It will say something like 5/15, 15/45 or 30/100, the second figure is the maximum current so your RCBO should have a rating greater than that.

The ABB boxes are DIN mount (we have them) so any DIN module should fit, best to stick with one brand mind.

So if my meter would be 15/45A I wouldn't be allowed to use the 40Amp RCD and absolutely have had to buy the 63Amp RCD?

Anyways my meter is 5/15Amp. Does it have to be the 40Amp RCD or can I get away with the 25Amp breaker as well?

I have a 20m2 condo without aircon:

PC 500w

shower heater 3500w

cooker 1300w

fans 100w

fridge 100w

lights 100w max

drill 500w

[Crossy]

On your 5/15 you can use the ABB 25A RCBO.

No point using any breakers bigger than the incomer as all that will happen is the incomer will open rather than the breaker.

Stick a 20A on each circuit and you'll be good to go.

[Cyrus123]

Thanx a lot Crossy, to make sure were talking about the same thing I added the picture. Nearest size to my 5/15A meter would be the 25Amp RCD from ABB.

Haha am I good to go?

[bankruatsteve]

Except in your OP you said you had 1.5mm2 wire also. That should be on 15a breaker. Use 20a for the 2.5mm2 wire.

Also, if you did have a 15/45 meter, a 40a main is probably the recommended one. A 63a exceeds the meter rating but (according to those that know in this forum), it could handle no problem.

[Cyrus123]

They're combination outlets with a light button. 2.5mm cable running to the outlets from the main box but from the light switch to the lamps it's 1.5mm cable.

Still 20Amp breakers right?

[Crossy]

By rights the breaker should match the smallest cable on the circuit, so 15A.

In reality you'll be just fine on 20A breakers, the lighting part is highly unlikely to be overloaded and so long as the 1.5 isn't excessively long the 20A will provide short circuit protection.