Cardano

6 hours ago, toofarnorth said:

Isn't that Cornish for a weekend hobby ?

No, it's when someone smacks you with a fish!

9 minutes ago, Crossy said:

 

Oddly enough we are in Thailand, Thai regs apply.

 

Do you actually have a 100A ISOLATOR? Where is your installation over-current protection, there's no DNO fuse here.

 

Do you also have UK style ring-finals on 32A MCBs?

Installation exceeds Thai regs requirement. Yes actually have 100A isolator with 80A kWh meter. You are correct there is no supply authority fuse here, so no protection up to DB. My DB is imported Schneider Iso-Bar fully encapsulated so is classified as fault free zone hence do not need protection on incomer. Yes my ring circuits are 32A, 30mA, 30mS RCBO's.

4 minutes ago, Crossy said:

 

Which are then "massaged" by the local regulatory authorities!

 

You may wish to consult the TIS standards for wiring in sunny Thailand.

 

 

 

no thanks.

15 minutes ago, bankruatsteve said:

RCD devices measure current between L and N. Earth is desired but not necessary for the device to function properly. 

Twaddle, earth is part of the neutral system on TNC-S system.

9 minutes ago, Crossy said:

 

To ensure no confusion please indicate which country's regulations you are using.

 

Thailand has very simplistic requirements, basically a 30mA RCBO on the incomer with any sub units likely being 10mA. Discrimination is unfortunately marginal.

 

Now of course there's nothing to stop you using higher current and/or time delayed units but the MEA/PEA inspector may will not understand what you have and fail the installation.

 

When in Rome Thailand ...

 

I am using IEC standards and UK 17th Edition of wiring regulations, if you want to use Thai standards that's your choice. I have 18 way DB fully fitted with SP RCBO's and MCB's with incoming 100A isolator all conforming to the above standards and regs, PEA approved no problem. 

9 minutes ago, bankruatsteve said:

I don't know where you are getting your information from, but it is incorrect.  BTW, a main breaker is double pole. 

I am fully aware of what a mains breaker is, 2 pole, 3 pole or 4 pole. As to where I am getting my info from; apart from being an electrical engineer for 40+ years try the IEC standards (International Electrotechnical Commission: An "organization that prepares and publishes international standards for all electrical, electronic and related technologies.")

7 minutes ago, bankruatsteve said:

Again, not so. 

To comply with IEC 61947 earth fault disconnection time must be maximum 0.4 seconds to achieve this is earth fault loop impedance must be 5 ohms or less. Please explain why you disagree.

2 minutes ago, bankruatsteve said:

Not so, in Thailand anyway. Outside of Safe-T-Cut which has selectable from 5-30mA, all double and single pole RCBO that I have seen are set to 30mA.

That's exactly what I said; all RCBO's and RCD' designed for single circuit protection are 30mA / 30mS rating to provide the closest personal protection for human life. Forget the stupid Thai device called Safe-T-Cut it doesn't comply with IEC 60898 (the industry standard). If you want to fit a combined MCB/RCD incomer then it will need to be rated as I said at 300 to 500mA and 300 to 500mS otherwise you will get spurious tripping and no selectivity if you have downstream RCBO's.

On 11/17/2021 at 10:23 AM, sometimewoodworker said:

Since they were invented in 1961 (RCD) that is a little while before your house was wired. No?

 

I didn’t suggest that it should. It isn’t as safe as it could be, adding RCBO whole house protection doesn’t require a complete rewire (safer if earthed sockets are introduced but not essential)

 

I don’t doubt that.
I did not categorise the installation as stupid.

 

I did, and do, categorise not installing safety equipment because it will not be inspected as idiotic and incredibly stupid. However since you are going to install RCBO/s that doesn’t apply to you, does it?

 

I would suggest going for a 6mm or 10mm supply to the building. 10mm is way over what is currently suggested but if you ever want more stuff then you have the capacity for it. Depending on the distance for the feed 4mm will work if the distance is short but allows for little expansion.

 

It should be placed in ground that never dries up completely and is a close as is practical to the CU. The structure of your soil governs the requirement. If your building has concrete  foundations then you may have an excellent ground by linking to the rebar, for reference see UFER grounds 

you need to get your earth loop impedance tested to ensure less than 5 ohms, otherwise any earth fault protection equipment is useless.

On 11/17/2021 at 10:40 AM, KannikaP said:

I have just hada 12k btu aircon fitted in a bedroom, mitsubishi Happy Inverter, max current 7 amps. Why a 20

amp breaker which is  there to protect the wiring.

 

 

Correct, breaker is to protect cable not the appliance. for 7 amp 1.5mm cable with 10A MCB is fine.

On 11/17/2021 at 9:25 AM, bankruatsteve said:

There is no exceptional reason to have single circuit RCBO when the main breaker is RCBO.  The ground stake is normally within short distance from the CU and not covered by concrete.

There is one very important reason; and that is the sensitivity level of a single pole RCBO or 2 pole RCD are set at 30mA / 30mS to provide the safest protection for human life and that is why manufacturers make these units, to protect human life . Where as a combined main breaker with RCD is at a much higher current time setting usually 300 to 500mA and 300 to 500mS as it is designed for general system ground fault protection for circuits without dedicated RCBO protection (lighting, fixed equipment etc. but not personal protection). The reason for such a high setting is to provide selectivity with downstream dedicated RCBO's and to prevent spurious tripping caused by lighting circuits containing filament bulbs and equipment with inherent earth leakage.

Electricity is extremely dangerous, especially here in Thailand, don't try and do it on the cheap! always put safety before cost as it could cost you a lot more than money in the end.

Ok, first some fundamentals;

1. Cable is sized to provide the required full load current at rated voltage for the end consumer.

2. MCB is sized to protect the cable (not the end consumer)

3. All cables have a maximum current carrying capacity based on voltage divided by resistance per Km (R1+R2). Cables are then derated based on ambient temperature (typically standard ratings are based on 20 degs C), type of insulation and installation method.

So for your 1.5mm 2 core PVC insulated cable recommended maximum load after derating for temperature at 30 degs C (because we're in Thailand) PVC insulation and installation in conduit enclosed in a wall is 12.64A. As stated above the MCB needs to protect the cable so MCB should be either 10A or less.

Similarly your 2.5mm cable maximum load should not exceed 20.6A and be protected by 16A MCB or less.

Maximum load for 1.5mm circuit = 220V*10A= 2.2kW 

Max load for 2.5mm circuit = 220V*16A= 3.52kW

All MCBs are designed to operate without trip up to 1.15% of their rating

Hence all your loads that you have stated will be okay based on 10A and 16A MCBs.

As for earth fault/leakage protection this is another ball game in Thailand, first you need to ensure you have installed a functional earth system with enough earth rods to achieve a earth loop impedance of less than 5 ohms to enable your RCDs or RCBOs to trip in less than 0.4 seconds when installed in circuits requiring personnel protection (showers, hand held appliances etc.). Suggest you get a reputable sparky who knows what their doing to check this for you otherwise consequences could be.......well not good. 

My advice would be to buy consumer unit with enough capacity for all consumer circuits plus 25% spare. Fit all socket, shower and water heater circuits with dedicated RCBOs, all other circuits standard MCBs. Alternative is split phase board with RCD protection and standard MCBs.

DO NOT buy one of those Safe-T boards, use only good quality reputable branded products.

Hope the above is some help.