What size breakers

[bankruatsteve]

3 minutes ago, NanLaew said:

I will have an RCBO as the main breaker in the new, bespoke CU plus I will invest in a single RCBO/CB for the external sockets.

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.

[NanLaew]

34 minutes ago, 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.

Thanks. I'll save a few bob and just have four regular CB's then.

 

I assume a 32A main RCBO will suffice?

 

Can you advise on the wire size needed to bring L/N to the RCBO?

 

There's a guava tree planted in a 1 x 1 m breakout on the yard concrete behind the building and about 4m from where the CU will be located. It is always wet and shaded so if 4m is OK, I will co-locate the ground spike there.

[bankruatsteve]

2 minutes ago, NanLaew said:

Thanks. I'll save a few bob and just have four regular CB's then.

 

I assume a 32A main RCBO will suffice?

 

Can you advise on the wire size needed to bring L/N to the RCBO?

 

There's a guava tree planted in a 1 x 1 m breakout on the yard concrete behind the building and about 4m from where the CU will be located. It is always wet and shaded so if 4m is OK, I will co-locate the ground spike there.

32A breaker requires minimum 4mm² .  Location for stake should be good.  Use conduit if the cable needs protection from accidental damage.

[NanLaew]

8 minutes ago, bankruatsteve said:

32A breaker requires minimum 4mm² .  Location for stake should be good.  Use conduit if the cable needs protection from accidental damage.

All good, thanks. There's new yellow conduit on order for the spur line and the shed will have all the internal wiring running in the white conduit.

[sometimewoodworker]

44 minutes ago, NanLaew said:

The house was wired over 15 years ago by an unsupervised, 'stupid' and usually drunk electrician before RCBO's were invented.

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

 

44 minutes ago, NanLaew said:

The whole house that has been safely inhabited by a dozen, arguably 'stupid' people all this time needs a total rewiring. That's NOT going to happen.

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)

 

44 minutes ago, NanLaew said:

This is so you understand that no RCBO has ever been seen anywhere near the whole 'stupid' installation. Ever.

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?

 

53 minutes ago, NanLaew said:

Will 32A be the correct size for the load I suggested earlier?

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.

 

1 hour ago, NanLaew said:

Where should I place the ground spike and do I need more than one?

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 

[KannikaP]

On 11/15/2021 at 1:43 PM, Orinoco said:

Hi  Bankruatsteve 

Thank you for your reply.

20A ok for air cons ?

 

Thanks again

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.

 

 

[bankruatsteve]

3 minutes ago, KannikaP said:

Why a 20

amp breaker which is  there to protect the wiring.

??  Cable used is 2.5mm².  20A breaker protects.  Could go lower, but why?

[Crossy]

21 minutes ago, sometimewoodworker said:

If your building has concrete  foundations then you may have an excellent ground by linking to the rebar, for reference see UFER grounds 

 

I'm not sure that an UFER (or concrete encased electrode) will pass a Thai inspection, adding a regular rod as well would be good insurance.

[NanLaew]

31 minutes ago, 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 

Sorry, I am in Isaan where many things that had been invented in 1961 can still be hard to find. FWIW, I have lived/rented in three houses in various parts of Thailand that were younger than my pile and two had that old-fashioned RCD thing with an adjustable knob next to the plywood panel 'CU' where the user decides what's safe or otherwise (!?). The newest one was totally bereft of any electrical safety devices but I am sure that all 50-odd houses in the village passed inspection. When building my place, I did take time to specify and purchase grounded power outlets and there's 3-wires fitted accordingly but no clue if my sparky ever tied them all to where they oughter be. All wires are either blue or black but give his drunk ass his due, the size is adequate.

 

Believe me when I say our main house needs a complete re-wire. I have had a time-served and qualified Thai sparky (who worked on the Burj-Al-Arab construction in Dubai) confirm that rather than patch and fix what's unknown in the duct work and crawl spaces, it would be a 2 to 3-week gutting and rewire exercise. It's on the to-do list but not right now.

 

I wonder how many requests the MEA/PEA get to inspect add-on garden sheds, car ports, garages, workshops and man caves?

 

I appreciate the forward-thinking to possibly install bigger supply wiring but there's no plans for my 'shop' to become anything more than a 4 x 4 m hideaway from the madding crowd. The distance from the main breaker to the new CU will be about 12 m maximum.

 

As mentioned in the previous post, I have the ideal wet spot 8 m from the main breaker and 4 m from the new CU.

 

My shopping list is almost complete so many thanks to @bankruatsteve and @sometimewoodworker for quick and salient advice and apologies to the OP for the wee hijack.

[Orinoco]

17 minutes ago, 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.

 

 

All ready on order., air-con getting 20A Breakers.

[bankruatsteve]

Inspections vary by PEA.  Other than verifying cable size from meter to CU (sometimes), I have never heard of any further inspection around here (Amphoe Ban Dung, UT).

[sometimewoodworker]

1 hour ago, NanLaew said:

I appreciate the forward-thinking to possibly install bigger supply wiring but there's no plans for my 'shop' to become anything more than a 4 x 4 m hideaway from the madding crowd. The distance from the main breaker to the new CU will be about 12 m maximum.

 

As mentioned in the previous post, I have the ideal wet spot 8 m from the main breaker and 4 m from the new CU.

Given those distances I would install 6mm but 4mm is plenty big enough as long as it’s not buried. The wet spot is also close enough and a single ground rod will do the job.

[sometimewoodworker]

1 hour ago, Crossy said:

 

I'm not sure that an UFER (or concrete encased electrode) will pass a Thai inspection, adding a regular rod as well would be good insurance.

It almost certainly won’t pass a real inspection, but how often is their a real inspection ???? ?

 

I know our inspection involved the head of the local PEA office chatting to SWMBO about life and drinking whisky, sitting about 50 metres away from the house.

 

TIT YMMV 5555555

[Crossy]

26 minutes ago, sometimewoodworker said:

It almost certainly won’t pass a real inspection, but how often is their a real inspection ???? ?

 

Our man actually looked at the top of the rod, complained that the inter-pole drops on the incoming supply weren't equal (installed by his men moonlighting - they were fixed the next day) and then spent 30 minutes gassing with Madam.

 

He also asked us to change the 63A incomer for a 50A but never inspected it, 63A is now re-installed ???? 

[Orinoco]

3 hours ago, Crossy said:

 

I'm not sure that an UFER (or concrete encased electrode) will pass a Thai inspection, adding a regular rod as well would be good insurance.

This is exactly what the spark did on our new build 3 weeks ago.

( they did 2 days work, not been back since )

Got them to run new wire to a new rod, near gray water tank at side of house.,

Only a clamp type of connection at present, but has easy excess to it.

3 inch  blue water pipe over the top with a cap on now.

[Crossy]

5 minutes ago, Orinoco said:

This is exactly what the spark did on our new build 3 weeks ago.

( they did 2 days work, not been back since )

Got them to run new wire to a new rod, near gray water tank at side of house.,

Only a clamp type of connection at present, but has easy excess to it.

3 inch  blue water pipe over the top with a cap on now.

 

Our roof steel actually measures rather better than our rod! It wasn't intended to be that way but the steel is contiguous from the roof right down to our 16m driven piles (we are on Bangkok clay) and the ground is never dry being right next to a ruddy great river.

 

We had a direct lightning hit to the roof not long after we moved in, structural damage limited to two ridge tiles! It did kill a bit of electronics but that was before we installed surge protection. Got SPDs up to the eyeballs now.

 

[Cardano]

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.

[Cardano]

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.

[Cardano]

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.

[bankruatsteve]

29 minutes ago, Cardano said:

Where as a combined main breaker with RCD is at a much higher current time setting usually 300 to 500mA and 300 to 500mS

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.

[bankruatsteve]

2 minutes ago, Cardano said:

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

Again, not so. 

[Cardano]

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.

[Cardano]

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.

[bankruatsteve]

3 minutes ago, Cardano said:

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.

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

[Crossy]

7 minutes ago, Cardano said:

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.

 

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 ...

 

[bankruatsteve]

2 minutes ago, Cardano said:

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.

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

[Cardano]

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.")

[Crossy]

3 minutes ago, Cardano said:

International Electrotechnical Commission: An "organization that prepares and publishes international standards for all electrical, electronic and related technologies."

 

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

 

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

 

 

 

[Cardano]

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. 

[Cardano]

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.