Circuit breakers

[bankruatsteve]

Technically no - if you use different size wires on the same circuit the breaker should be sized to the smallest wire. BUT - since the 1.5 only feeding lights it is very unlikely you would overload 15 amps. So, go ahead with the 20amp.

[Cyrus123]

Ok, thanx for the quick help!

[Cyrus123]

So uhm.... There's also a shower heater on 1.5mm cable. Same thing drawing power from behind one of those combi outlets. So 2.5mm from the box to the outlet and from there 1.5mm to the light and the heater.

Should I make an exception for this one and place a 15Amp breaker?

[bankruatsteve]

So uhm.... There's also a shower heater on 1.5mm cable. Same thing drawing power from behind one of those combi outlets. So 2.5mm from the box to the outlet and from there 1.5mm to the light and the heater.

Should I make an exception for this one and place a 15Amp breaker?

Yah - I would. Better to re-wire with 2.5 to the shower. Crossy?

[Cyrus123]

Ok, one more perhaps really stupid question but for example my fans are plugged into the outlets with 2x0.5mm cable. Fridge runs on 2x1mm cable. My cheap extension cords go up to 5 meter on 2x0.5mm as well.

So what protects those? Perhaps the cables are too short to matter?

Edited September 26, 2014 by Cyrus123

[Crossy]

So uhm.... There's also a shower heater on 1.5mm cable. Same thing drawing power from behind one of those combi outlets. So 2.5mm from the box to the outlet and from there 1.5mm to the light and the heater.

Should I make an exception for this one and place a 15Amp breaker?

Yah - I would. Better to re-wire with 2.5 to the shower. Crossy?

Yes, a 3.5kw shower on 1.5mm² is marginal but not dangerous, unless you're in to 3 hour showers. As a fixed load I would leave it on a 20A, a 15A may open when you're half way through.

[bankruatsteve]

You don't need to worry about the cable from appliance to plug - assume the mfg. has safely sized to requirement.

BTW: if your shower is the normal 3.5KW, you may pop a 15a breaker on full heat and especially if something also drawing from the same-circuit receptacle. You really should re-wire if you can.

[Crossy]

All your appliances are effectively fixed loads on the end of the flex. Most have some form of internal protection against overload (a fuse, or impedance protection on a fan motor) they will be fine.

[Cyrus123]

So those short pieces of wire running from the RCB to the MCB's and the neutral wire mounting point, does this have to be 10mm cable? I mean I bought a meter of it but it's more easy using some leftover 2.5mm cable.

[Crossy]

So those short pieces of wire running from the RCB to the MCB's and the neutral wire mounting point, does this have to be 10mm cable? I mean I bought a meter of it but it's more easy using some leftover 2.5mm cable.

Yes, you should use the 10mm² to the neutral bar, your consumer unit should have come with a nice copper bus bar to connect the MCBs.

[Cyrus123]

And the new box, couldn't have done it without you guys!

PS: Still need to change the 16A for a 20A though, was a bit too enthusiastic installing today

Edited September 26, 2014 by Cyrus123

[yankee99]

Looks good if the smaller breaker carries the load no need to change.

[Crossy]

Has Cyrus got the guts to post a photo with the lid off??

Seriously, looks 100000000 times better than the original.

If the others in the building are of the same standard could be a little earner Cyrus

[bankruatsteve]

Yeah - looks good. I wouldn't change out the breaker unless no cost though. At least not until it starts tripping - which may never happen.

[Cyrus123]

Haha I'm on a tourist visa and I like it here so no jobs on the side

Sure I can post a pic with the lid off, will have to wait till monday though when I change the breaker.

Thanx again!

I was kinda wondering though if the RCD couldn't have been a bit cheaper, is this normal 2000thb for a 25Amp? Everything was labeled breaker or safety breaker but this was the only thing they had with the little test button and single switch I recognised...

[Crossy]

Yeah, that's about the right price, they're about 30-35 Quid in the UK (inc VAT).

You probably could have got the stuff cheaper and an electric wholesaler, but without the luxury of spotting what you need, have to ask (I'm lucky, our wholesaler speaks better English than I do Thai).

[Cyrus123]

I just read there's no more than 4 MCB's allowed on 1 RCD so I'd have to remove one since I installed 5 of them, is that right? I don't know, these seem to be Dutch regulations but I can't find any of this on english pages...

What I kind of forgot to mention is that I'm a tenant and had the aircon removed since it was in the way and I don't use it. However the next will probably have it installed back again, is this still possible on this 25Amp RCD?

Edited September 26, 2014 by Cyrus123

[Crossy]

No such reg in Thailand don't worry. It's probably to prevent all the lights going out in the event of a trip, the UK has something similar in the IEE Regs (17th edition) which requires the lighting to be split between two or more RCDs.

Adding a small aircon won't cause any issues, a 9000 BTU will draw about 900W = 4A.

[Cyrus123]

So does the meter have some kind of build in main safety/RCD? With this setup what will trip first, the meter or my 25A RCD?

Edited September 27, 2014 by Cyrus123

[yankee99]

So does the meter have some kind of build in main safety/RCD? With this setup what will trip first, the meter or my 25A RCD?

I doubt you will ever draw enough amps to trip your 25a.If you have a short in your condo unit then the breaker in your box will trip first.

Edited September 27, 2014 by yankee99

[Cyrus123]

Ok, another stupid question but I used these white connector strips to add some length to some of the 2.5mm wires in the box that were too short.

I used the smallest size while I have bigger ones as well, didn't really think about it at the time. They come in 3 sizes @ HomePro. still have the package of the biggest size, what I can read in non-thai is 2.1 x 12.8 x 1.4 PVC-10MM.

Did it matter which ones I used?

[Cyrus123]

Ok, another stupid question but I used these white connector strips to add some length to some of the 2.5mm wires in the box that were too short.

I used the smallest size while I have bigger ones as well, didn't really think about it at the time. They come in 3 sizes @ HomePro. still have the package of the biggest size, what I can read in non-thai is 2.1 x 12.8 x 1.4 PVC-10MM.

Did it matter which ones I used?

Picture in case it's unclear what I mean:

[Crossy]

Choc-blocs (those white connectors) are, at least theoretically, made in various current ratings, which ought to be moulded into the plastic (yes, I know this is Thailand).

Failing that a good guide is that you should be able to get two of the wires you're joining into one end. I take this a step further by stripping the wire so it goes under both screws, feed one wire from each end (you need to have both screws loose of course), when you tighten everything up you end up with twice the effective contact area. Should reduce the chances of things getting warm.

[Forkinhades]

^ totally concur, but I like to feed both wires from one end.

[Cyrus123]

Sticking in the wires the entire way and tighten with both screws seems like a good idea, they have a way of getting loose sometimes. I suppose twisting and taping is better but I didn't have much length left in the box.

I'm going to replace the 1.5mm shower heater cable as well monday with a 2.5mm cable but have a little issue I'd like to ask. I connected a TL light with a 1.5mm cable to the cable of the shower heater, they also share the same 1.5mm earthing wire.

So if I give the shower heater a 2.5mm cable, can I still connect the 1.5mm TL light cable to it and use a 20Amp breaker for the circuit just like with the ceiling lights or is this a bad thing?

[Forkinhades]

I would suggest using at least 4mm for your shower, a little extra cost, but handy for upgrades.

The lighting should be protected by 10 amp MCB

[Cyrus123]

I would suggest using at least 4mm for your shower, a little extra cost, but handy for upgrades.

The lighting should be protected by 10 amp MCB

If I would upgrade the shower heater it would get it's own circuit and MCB, right now it draws power from the outlet outside the bathroom on 2.5mm so a 4mm cable wouldn't be usefull yet.

The lights don't have their own circuits, they all run from behind an outlet which is itself fed by 2.5mm cable.

I'll scetch the situation better, my mistake:

From a 20Amp MCB runs a 2.5mm cable towards an outlet next to the bathroom. This outlet is combined with a light switch and 1.5mm cable to the lamp. From behind the outlet runs a 1.5mm cable into the bathroom towards the shower heater, halfway the cable I cut it and attached a 1.5mm cable for the TL light.

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.

We decided 20Amp MCB's were fine for the outlet's on 2.5mm with a light button and 1.5mm cable to the lamps. Does a TL light make any difference? Should I run a 2.5mm cable to the TL light as well or do I simply change the shower heater cable and keep the 1.5mm for the TL?

I don't know wether a simple ceiling lamp or a TL light make any difference, I mean the TL does require a earthing wire unlike the lightbulbs for example.

I suppose the best decision is to feed all the lamps with 2.5mm cable but it's ridiculously thick for 24W of lightbulbs so I'm fishing if I can get away with the TL on 1.5mm as well

Edited September 27, 2014 by Cyrus123

[Crossy]

OK let's take a pragmatic approach, Cyrus is in a rental on a 5/15 meter with a 25A incomer.

Forky is absolutely correct and what you suggest / have would not be permitted in the UK, we're not in the UK (or Kansas).

If you look at most Thai installations where the lights are on the power circuit, the power is wired in 2.5 and the spurs to the lights in 1.5 all on a 20A breaker. In reality, that bit of 1.5 is never going to be over loaded (it has a light bulb on the end) and if it does develop a short it will easily open the 20A breaker.

Personally, I would put the shower on its own breaker and pull 4mm as the cost is a marginal increase over 2.5 (but you are renting, 2.5 will be more than adequate), but nothing else on that circuit.

Find an alternative source for the TL.

[Forkinhades]

You can get an individual MCB with enclosure, and 'fuse' down.

Important thing to remember is your current carrying capacity of your cables.

Xy has a link to these, but remember the values given are for a perfect environment, and perfect installation. In practice this is never going to happen, and everything little thing you do will derate the cable together with thermal effects (Ambient temperature)

So whatever figures are given you should derate by about 0.7 ie: if the current suggested for a 2.5mm cable is 21Amps, you should multiply this by 0.7 to give a more accurate value of what your cable can carry.

there are many different types of cable with quite a large 'swing' of the CCC.

[Cyrus123]

Alright I'll give the shower heater a 4mm cable and personal 25A MCB.

Now I still have an outlet on a 20A MCB with a lightswitch and 1.5mm cable towards the bathroom lightbulb, since I can no longer connect the TL light to the shower heater cable I have to run a cable outside the bathroom to this outlet as well. Do I need to use 2.5mm for this or is 1.5mm fine like the lightbulb?

Or perhaps since I'm now ripping of all the cables towards the bathroom anyway perhaps it's better to give both the lightbulb AND the TL light a 2.5mm cable like the outlet from which they draw power? It's just that those fat 2.5mm cables are an ugly sight compared to 1.5mm.

Edited September 27, 2014 by Cyrus123