Home electrical safety devices

[BobZA]

Yes he needs to add a 63a mcb before the RCD as this unit does not have overload protection if he had installed a RCD with oveload protection then it can be used as a main switch at the moment there is no overload current protecting the 16mm incoming cable except for the council kiosk.

I am not an expert on the regs but I don't see anywhere that says the main switch needs to provide overload protection. All I see is "6.6.1.1 Each distribution board shall be controlled by a switch-disconnector".

The incoming cable is protected by the council board. And all the circuits in the DB are protected by individual circuit breakers (after the RCCB).

My understanding is that the "distribution board switch-disconnector" or "main switch" is for isolation purposes so this function can be fulfilled with the RCCB device. Of course most modern circuit breakers can also be used as switch disconnectors ... but I do not see the requirement for a "distribution board - main overload device"

Or am I maybe misunderstanding this particular installation?

[Leecatt]

Read 6.8.1 together with 6.7.5.7. I think that should make it more clearer

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[Derlyn]

Each phase conductor of an installation shall have both overload and short circuit protection (6.7.1.1)

Now check out (6.7.1.3 )
These conductors may be protected by the suppliers overcurrent protective device, provided that
A) the supplier agrees
B)
C) the user has access to the device.

The supplier generally will not agree and these devices are usually in a locked kiosk, so the user does not have access to them.

Here in our valley, the supply authority prefers a circuit breaker as mains in the main db so that should there be a major short or fault on the installation, it trips on the installation instead of outside in the kiosk or on the pole.

Makes sense.

[BobZA]

Read 6.8.1 together with 6.7.5.7. I think that should make it more clearer

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Thanks Leecatt. As usual a long way around in the specs. Could really be simplified. If overload is required on main switch ... then just say it.

But thanks I see your point ...

[BobZA]

Each phase conductor of an installation shall have both overload and short circuit protection (6.7.1.1)

Now check out (6.7.1.3 )
These conductors may be protected by the suppliers overcurrent protective device, provided that
A) the supplier agrees
B)
C) the user has access to the device.

The supplier generally will not agree and these devices are usually in a locked kiosk, so the user does not have access to them.

Here in our valley, the supply authority prefers a circuit breaker as mains in the main db so that should there be a major short or fault on the installation, it trips on the installation instead of outside in the kiosk or on the pole.

Makes sense.

Thanks Derlyn. What you say makes sense from a practical point off view.

And I note what Leecat said ... but I have certainly seen some installations where the main switch is only an earth leakage switch without overload. Again makes me think the regs need rework

[GCE]

Thanks Derlyn. What you say makes sense from a practical point off view.

And I note what Leecat said ... but I have certainly seen some installations where the main switch is only an earth leakage switch without overload. Again makes me think the regs need rework

I tend to disagree that the regulations need work.
What is needed is for suitable qualified people to do the work and for users of electricity to learn that Electrical contractors need to be registered before allowing them to work on their installations.

Clause 5.4.3 under fundamentals in the beginning of the regulations is clear that equipment shall be suitable rated. If you install a 63Amp earth leakage isolator type, then there needs to be at least a 63Amp C/breaker installed before the ELU.

Same way that you keep seeing 63Amp D/Pole isolators in D/boards with 80Amp C/breakers from municipality side - COC is invalid as the isolator is not suitable protected.

To go one further , the reg states " It shall also be able to carry the current that is likely to flow under abnormal conditions and for the period that the current is likely to flow." If you have a CB manufactured by A protecting an ELU manufactured by B , how do you know that the ELU will withstand the tripping curves from a different manufacture unless it has been tested as such ?


5.4.3 Current
The equipment shall be suitable for operation at the maximum steady (r.m.s.)
current to which it is likely to be subjected. It shall also be able to carry the
current that is likely to flow under abnormal conditions and for the period that
the current is likely to flow.
NOTE The period that an abnormal current will flow is equal to the operating time of
any protective device.

[Derlyn]

I tend to disagree that the regulations need work.
What is needed is for suitable qualified people to do the work and for users of electricity to learn that Electrical contractors need to be registered before allowing them to work on their installations.

Clause 5.4.3 under fundamentals in the beginning of the regulations is clear that equipment shall be suitable rated. If you install a 63Amp earth leakage isolator type, then there needs to be at least a 63Amp C/breaker installed before the ELU.

Same way that you keep seeing 63Amp D/Pole isolators in D/boards with 80Amp C/breakers from municipality side - COC is invalid as the isolator is not suitable protected.

To go one further , the reg states " It shall also be able to carry the current that is likely to flow under abnormal conditions and for the period that the current is likely to flow." If you have a CB manufactured by A protecting an ELU manufactured by B , how do you know that the ELU will withstand the tripping curves from a different manufacture unless it has been tested as such ?


5.4.3 Current
The equipment shall be suitable for operation at the maximum steady (r.m.s.)
current to which it is likely to be subjected. It shall also be able to carry the
current that is likely to flow under abnormal conditions and for the period that
the current is likely to flow.
NOTE The period that an abnormal current will flow is equal to the operating time of
any protective device.

@ GCE

I agree 100% that the regulations are spot on as far as this subject of overcurrent and shortcircuit protection is concerned.

However

In my opinion, there are grey areas as far as earthing and bonding is concerned.

I, like our brother Dylboy, am particularly interested in understanding earthing and bonding as much as is humanly possible, but after a couple of weeks of studying same, am still scratching my coconut regarding a couple of regs especially concerning domestic installations as that is where I do and have been doing most of my work.

I will in due course, list my concerns and maybe make 1 or 2 suggestions that in my opinion should clear up these grey areas.

Edited at 17.16

[Dylboy]

I have recently learnt why we Earth to Tera, to keep voltages floating to only 230V to earth...
Now I wish we had a course or something that covers more of this.

Not only earthing but everything.

I guess could do N6 electrical engineering so perhaps I should look into that but still.

What is basic to some is not for others and plays a part in huge issues of CoC etc

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