A Tad More Advice On Electric Breakers, Safety.

[Formaleins]

I posted earlier regarding my Consumer Unit (Square D / Schneider) and because my old Safe-T-Cut box had finally given up the ghost, I was thinking about replacing the Square D Consumer Unit for a more modern up to date version that would be as safe as possible.

Well, after looking through catalogues and online info, I really am not that sure that I actually need to change the entire consumer unit as it is pretty good quality and could possibly be upgraded to make it a bit more up to date.

 

(I was actually told that it was as old as the hills and that no one uses these any more, but after looking online, it is clear that Schneider / Square D still make these fittings that are compatible with this old box)

 

I have posted a picture of the actual box, which appears to be made up of varying ( 10A - 5KV to 45A - 10KV) MCB's. Which I would have hoped were perfectly OK to protect the circuits.

 

The one thing I wanted to look at changing (please jump in and shout if it makes no sense) was the input breaker, it looks to be a 63A - 10KV MCB, and I was thinking of changing this to the 63A RCBO (See pic attached) which as far as I understand is basically an entire Safe-T-Cut device all in a miniature package.

 

If I am mistaken please let me know as I am not 100% on some of the electrics here in Thailand and really just want to make sure that adding this will be a benefit to the safety and not a waste of time or actually causing a problem.

 

Cheers.

 

 

This is the Square D Box, I am thinking of changing the first switch - 63A Breaker to this new, RCBO breaker from Schneider.

 

 

There was also one last thing. I noticed a lot of the newer Consumer Units have their EARTH blocks tied to the NEUTRAL Block (mine is not tied together) Is it worth tying them in or best just to leave as is? - I measured the voltages earlier and there is anywhere between 2V and 4.5Volts difference between Earth and Neutral?

\

Cheers.

Edited October 28, 2018 by Formaleins

[Crossy]

That RCBO should fit, but do verify the size before shelling your hard-earned.

 

Whether you install the the N-E (MEN) link is up to you, it would be required on a new installation, but since you are updating an existing system ...

 

Have a look at your supply poles, if you see a ground from the neutral (the top wire) on every 3rd pole or so then go ahead and install the link, if you don't then leave it separate (TT).

 

[Formaleins]

10 minutes ago, Crossy said:

That RCBO should fit, but do verify the size before shelling your hard-earned.

 

Whether you install the the N-E (MEN) link is up to you, it would be required on a new installation, but since you are updating an existing system ...

 

Have a look at your supply poles, if you see a ground from the neutral (the top wire) on every 3rd pole or so then go ahead and install the link, if you don't then leave it separate (TT).

 

Thanks Crossy, in debt to you as always. The breaker is supposed to be compatible, my Square D takes QO,QH and QE types. I just thought it would be better spending 2.4K on a good RCBO rather than spending probably twice that for a new box and really just be back where I started.

 

As far as tying the Earth and Neutral that seems pointless then, as our supply poles carry no Earth, only two bare cables (I think 22KV) down to a transformer then directly across into my land. I must admit I was a little bit worried what might happen should I get a broken Neutral cable, would that not possibly end up making the Earth possibly go hot?

[sometimewoodworker]

20 minutes ago, Formaleins said:

As far as tying the Earth and Neutral that seems pointless then, as our supply poles carry no Earth, only two bare cables (I think 22KV) 

I doubt that the cables are bare, if you can see the 3 phase poles then this is 3-phase in the Delta configuration with an overhead ground to the right.

 

AFIK this is the more common transmission format in thailand. The OHG wire is bare the others not.

[Formaleins]

13 minutes ago, sometimewoodworker said:

I doubt that the cables are bare, if you can see the 3 phase poles then this is 3-phase in the Delta configuration with an overhead ground to the right.

 

AFIK this is the more common transmission format in thailand. The OHG wire is bare the others not.

My place is the same as that, but only two bare conductors and there is no earth / third cable. (There is no insulation on the two conductors where I live. They take two cables down from there and these run into a transformer box, out of the transformer comes the two insulated 240V cables.

 

I am not 100% but I am almost sure the EGAT guys told me it was 22kv. it is a small village and this lot was installed about 6 or 7 years ago. (Pity is dark, or I would grab you a photo - We often have black outs here, snakes keep getting up the support cables and then you get a bang like a bomb going off - We are about 100M from the cable and when a snake blows you would think someone had just fired a 12 bore in your back garden.

 

We also get a lot of blackouts due to some very tall bamboo up the road from me that tends to grow so tall when the wind blows, it hits the 22KV lines. EGAT boys were out last week with chainsaws and went to town ripping out anything taller than a couple of feet.

Edited October 28, 2018 by Formaleins

[Thian]

What i don't understand is how can you have 4  45Amp breakers (plus all the rest) when the headbreaker is 63Amp? Could you use all those 4 aircons at the same time? (guess those 45A breakers are for aircons).

 

Isn't the rule that you add all the amps from the breakers together and then the headbreaker has to be the same number or higher?

[Formaleins]

No aircon here, only fans. The 45 Amp Breakers are used for the hot water  - one is for the 8KW shower upstairs, the second is for a 6KW shower downstairs, the third is for the kitchen / utility, probably be used for a cooker / washer etc. but I just have it for the well pump washing machine. The last 45A is a spare at the moment but will probably end up being used to run my 4.5 HP pump that is about 50 m outside of the house. As for adding up the total Aps and selecting a breaker to fit, well, I have never seen that done before. I understand what you are saying but even the commercially available consumer units are not sold like that,  a lot of them are double the main breaker or even more.

Edited October 28, 2018 by Formaleins

[sometimewoodworker]

15 minutes ago, Formaleins said:

No aircon here, only fans. The 45 Amp Breakers are used for the hot water  - one is for the 8KW shower upstairs, the second is for a 6KW shower downstairs, the third is for the kitchen / utility, probably be used for a cooker / washer etc. but I just have it for the well pump washing machine. The last 45A is a spare at the moment but will probably end up being used to run my 4.5 HP pump that is about 50 m outside of the house. As for adding up the total Aps and selecting a breaker to fit, well, I have never seen that done before. I understand what you are saying but even the commercially available consumer units are not sold like that,  a lot of them are double the main breaker or even more.

You really need to rethink your usage of breakers unless you are running very large cable. You probably need a 10mm2 circuit for the 45A breakers.

 

Do not forget that the breaker is there to protect the wiring. 

 

If (for example) qyou are running 2.5mm2 cable with a 45A breaker you might as well have a simple switch because the wiring is likely to catch fire without tripping the breaker.

 

A 32A is easily big enough for your 6kw unit

[Thian]

That 6kw waterheater uses 27 amps...the breaker is 45 so it's almost double...i think it's too much and this isn't safe. The heater might get issues one day and the breaker won't cut it off.

 

Also it's important to use the right breaker with the right curve...i guess you can't read this website but you'll see there are many different ones with different cut off curves..make sure you get the right one for each purpose...https://www.elektramat.nl/overige-categorieen/belgie/automatische-zekering/?gclid=CjwKCAjwvNXeBRAjEiwAjqYhFhAfAKnmJm2WVuvwQzDlWKQx5rPNjUYn97LF7H6opeQ2e0Hw3ZfYrBoC4egQAvD_BwE

 

Also i know this is thailand and safety is not important here, it's all up to you but the fact you asked about it tells me you want to have it all properly installed this time.

 

I've had a waterheater exploding when i was showering in thailand, had an extensioncord on fire (by my new electric oven), had a walloutlet smoking with flames in thailand so i know what can go wrong. Never ever had any issues in Europe where i have much more heavy electric equipment.

 

My house in Holland uses those breakers with different curves, one for the wet groups and one for dry groups iirc. we don't have electric showerheaters there though but gas.

 

We use a separate breaker for a washingmachine, dishwashingmachine, oven, workshop and so on.....not like in thailand where a whole floor can be on 1 heavy breaker.

 

I hope another user can advice you better but since you're buying a new system i would install it according european rules...might cost a little more but sure is much safer.

[Thian]

5 minutes ago, sometimewoodworker said:

If (for example) qyou are running 2.5mm2 cable with a 45A breaker you might as well have a simple switch because the wiring is likely to catch fire without tripping the breaker.

 

Also keep in mind that unless you use Thaiyazaki wire you can't rely on those numbers printed on the cables here....they all are of a lesser quality and can easy get warm....if you do use those cheaper cables than buy them extra thick....and don't put too many of them in a pipe since they can get warm...hot....smoke...flames...also don't use steel pipe or crap like that and make sure no animal can get in or bite the cables, also behind the ceilings.

[sometimewoodworker]

1 hour ago, Formaleins said:

There is no insulation on the two conductors where I live.

I would really like to see that, I've never seen any HT cable run without insulation, as corrosion protection if nothing else.

[Formaleins]

3 minutes ago, sometimewoodworker said:

You really need to rethink your usage of breakers unless you are running very large cable. You probably need a 10mm2 circuit for the 45A breakers.

 

Do not forget that the breaker is there to protect the wiring. 

 

If (for example) qyou are running 2.5mm2 cable with a 45A breaker you might as well have a simple switch because the wiring is likely to catch fire without tripping the breaker.

 

A 32A is easily big enough for your 6kw unit

Cable size is not an issue, the cables were sourced for the original job. The 45A circuit was running a 10KW combination heater for the past 8 years. You also need to take into consideration Time! No one runs a 10KW water heater 24/7, which is what the cable sizes are based on. i.e. Continuous current.

 

There is no issue with cables anyway, so I have no idea why you brought it up, all I am talking about is the simple replacement of one 63A Breaker with a 63A RCBO.

[Thian]

Just now, sometimewoodworker said:

I would really like to see that, I've never seen any HT cable run without insulation, as corrosion protection if nothing else.

We had several squirrels dropping dead from the cables on poles.....don't know if they bit the cables or if they were naked...

[Formaleins]

3 minutes ago, sometimewoodworker said:

I would really like to see that, I've never seen any HT cable run without insulation, as corrosion protection if nothing else.

You are joking right? I have never seen High voltage cables WITH insulation, thry use  aluminium anyway, it oxidizes on the outside layer, providing a corrosion barrier. You can always take a train or  a flight to Chiang Mai if it interests you, they have been here for years and aren't going anywhere.

[sometimewoodworker]

26 minutes ago, Formaleins said:

Cable size is not an issue, the cables were sourced for the original job. The 45A circuit was running a 10KW combination heater for the past 8 years. You also need to take into consideration Time! No one runs a 10KW water heater 24/7, which is what the cable sizes are based on. i.e. Continuous current.

 

There is no issue with cables anyway, so I have no idea why you brought it up, all I am talking about is the simple replacement of one 63A Breaker with a 63A RCBO.

You are confused 

 

To repeat the breaker is there to protect the cable. So unless your circuit cable is big enough (10mm2 is under size) the breaker can not do its job.

 

Of course you have had no problems with the breakers.

 

But get a fault that is overloading the cable, the breaker does not trip and you have yourself a nice electrical fire.

 

From the Thaivisa Guru 

 

Quote

The following shows the cables sizes for the appropriate circuit breaker;

1.5 mm² cable - 15 amp maximum circuit breaker.
2.5 mm² cable - 20 amp maximum circuit breaker.
4 mm² cable - 25 amp maximum circuit breaker.
6 mm² cable - 32 amp maximum circuit breaker.
10 mm² cable - 40 amp maximum circuit breaker.

 

Edited October 28, 2018 by sometimewoodworker

[Thian]

21 minutes ago, Formaleins said:

No one runs a 10KW water heater 24/7, which is what the cable sizes are based on. i.e. Continuous current.

unless a drunk person, kid, leaking waterhose, person with heartattack...and so on...uses it...better be safe than sorry

[sometimewoodworker]

31 minutes ago, Formaleins said:

Cable size is not an issue, the cables were sourced for the original job.

The cable sizes are probably correct for the job. But the 45A breakers are almost certainly not correct for the cable size.

[Crossy]

5 minutes ago, Formaleins said:

I must admit I was a little bit worried what might happen should I get a broken Neutral cable, would that not possibly end up making the Earth possibly go hot?

A broken neutral is one of the negatives that goes along with using TN-C-S with MEN. It is generally outweighed by the advantage of a solid metallic path between your ground terminal and the transformer star-point.

 

The idea of having the neutral earthed at many points (should) reduces the touch voltage should the neutral go open. Also, the neutral is usually the top wire of the four on the pole, so it gets damaged last if a high vehicle hits the wires.

[Thian]

9 hours ago, sometimewoodworker said:

The cable sizes are probably correct for the job. But the 45A breakers are almost certainly not correct for the cable size.

 

In Thailand you can't think all is safe according to the cable-size...the cheap cable is very crappy even with the correct thickness...i use that in the garden for binding tree's to poles, it's almost like a rope, bends very easy, breaks easy, probably has high resistance so gets warm fast...i wouldn't trust our lives on it and pay more for quality cables. 

 

My new European kitchen has a 40A main breaker in it's own fusebox...that has a thick cable as well, not a simple 2.5 mm2 ....i let the electrician (who built the whole new moobaan here)  connect it (he could get the cable cheaper than me)  but some months later the old fusebox was on fire at night (when i was abroad). He didn't tie the screw well to connect that thick cable and it started making sparks at the connector and caught fire finally...that breaker burned out. Lucky the house is still fine.

 

 

[Formaleins]

OK, for those who were interested, no need to fly up to Chiang Mai with your EGAT Electricity Spotting Handbooks and Cameras, here is a photo that shows what I believe is the 2 conductor (22KV) supply - Notice, there is NO insulation on the main conductors and there is NO earth! The only insulation (Other than AIR)  is tagged on at the downcomers where it enters the transformer.

 

 

Edited October 31, 2018 by Formaleins