CB for indicator light

[Dylboy]

Hello

Quick one, do we need a circuit breaker to protect the cable within the DB which goes to an indicator light? The small like panel light which indicates grid on or off for example

I feel not as it's in the DB and safe zone comes to mind, I need to check the book still and I am under the impression we don't have to as very short cable etc but I would like to double check.

Cheers
Dyl

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[GCE]

Hello

Quick one, do we need a circuit breaker to protect the cable within the DB which goes to an indicator light? The small like panel light which indicates grid on or off for example

I feel not as it's in the DB and safe zone comes to mind, I need to check the book still and I am under the impression we don't have to as very short cable etc but I would like to double check.

Cheers
Dyl

Sent from my CPH2197 using Tapatalk

What is going to protect the wiring and lamp itself in the event of a short ?
The wire size to the lamp would need to be suitable rated to withstand th efault leavel and current of th emain switch - The lamp could sort and burn rather then trip

I would say you must install a CB to protect in that all equipment must be suitable protected

[Derlyn]

Howzit brother.

Short answer. .. yes you need one.
All conductors need to have suitable over current protection.

I usually use a 5A breaker.

Cheers

[Dylboy]

Ah ok thanks gents fortunately I have used circuit breakers but it's been on my mind awhile. Also last job was short a CB so I upped the cable and used the 25A, there so that's mostly what sparked the question.

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[Isetech]

I use an inline 1 amp fuse.

Will send you a picture.

[recre8]

May I raise a conflicting opinion for discussion?

My understanding is the distribution board itself (and the first 5m of cable from it) is considered a fault-free zone and therefore indicator lamps do not require overload nor short-circuit protection.

SANS 10142-1 Definitions:

fault free
arrangement of conductors for which, under normal operating conditions, the
occurrence of a short-circuit fault between phases or between phases and
earth is only a remote possibility

6.7.2 Installation Requirements > Protection > Overload Protection

6.7.2.2 Except as allowed in 6.7.2.3, an overload protective device shall be installed ....
6.7.2.3 The overload protective device may be installed at any point in the conductor run that it protects, provided that
a) there is no branch circuit or socket-outlet between the point where there is a reduction in the conductor's current-carrying capacity and the point where the device is installed, and
b) the entire length of the conductor is protected against short-circuit, or
c) the conductor is
1) of length not exceeding 5 m,
2) so installed as to minimize the risk of overload or fault in its operating condition,
3) not near flammable materials, and
4) not likely to cause harm to a person in the event of a fault.

6.7.3 Installation Requirements > Protection > Short-circuit Protection

6.7.3.4 For the purpose of protection against short-circuit current in PVC insulated cables (of a cross-sectional area ≤ 4 mm2 ), the first 5 m length in single-phase circuits and 10 m length in multiphase circuits are regarded as being fault free, ...

Note that this requirement is not applicable when the cable is used for a plugs or lights circuit. Then a breaker MUST be used.

6.7.3.3 With particular reference to socket-outlets and luminaire supplies, the cross-sectional area of PVC insulated conductors shall comply with the calculated prospective short-circuit current requirements (see also the note to 6.7.3.2) for all points of consumption that fall within the limits of 6.7.3.4.

I can't seem to find the exact paragraph that designated the DB board as fault free, but for instance:

7.12.5.1.1 Overcurrent protection and isolation shall be located as near as possible to the output terminals of each alternative supply unit, except where the cable connecting the unit to the distribution board is mechanically protected and is regarded to be within the fault-free zone of the distribution board where protection is installed.

[GCE]

May I raise a conflicting opinion for discussion?

My understanding is the distribution board itself (and the first 5m of cable from it) is considered a fault-free zone and therefore indicator lamps do not require overload nor short-circuit protection.

SANS 10142-1 Definitions:
fault free
arrangement of conductors for which, under normal operating conditions, the
occurrence of a short-circuit fault between phases or between phases and
earth is only a remote possibility


:

Hi
By the definition that you pasted it is only fault free to the extent of a short circuit fault between phases , earth etc.

It is not fault free from overload.
Wire size needs to be suitable protected from over current

All items /components need to be suitable protected - Fundamental's section 5 is pretty clear on that.

I cannot install a 500Kva genset 5m from the D/Board and connect to the busbars of a 1000Kva supply with 16sqmm wire
I need to size the wire to handle the current and ensure that if it goes overcurrent that the wire does not melt and catch fire , so it needs to be suitable protected with the correct size CB

Same story for the indicator light

Then you also have

6.6.3.2 Small power distribution units (SPDUs or ready boards) for
single-phase 230 V service connections shall comply with SANS 1619

[recre8]

Hi
It is not fault free from overload.
Wire size needs to be suitable protected from over current

Would the quoted 6.7.2.2 and 6.7.2.3 (Overload protection heading) not negate the need for overcurrent protection? Since the indicator lamp would tick the bold sections
6.7.2.3 The overload protective device may be installed at any point in the conductor run that it protects, provided that
a) there is no branch circuit or socket-outlet between the point where there is a reduction in the conductor's current-carrying capacity and the point where the device is installed, and
b) the entire length of the conductor is protected against short-circuit, or
c) the conductor is
1) of length not exceeding 5 m,
2) so installed as to minimize the risk of overload or fault in its operating condition,
3) not near flammable materials, and
4) not likely to cause harm to a person in the event of a fault.

I don't mean to be combative, I just want to approach from a strictly minimum requirement with the regs (as opposed to the right and safe thing to do)

[Derlyn]

In the above context, replace the word "may" with "is allowed to be" and read it again.

Its allowed to be anywhere along the length of the wire, but it must be there.

[recre8]

In the above context, replace the word "may" with "is allowed to be" and read it again.

Its allowed to be anywhere along the length of the wire, but it must be there.

Hmm now that is an interesting twist to the interpretation. My intepretation was in that 6.7.2.2 "Except as allowed in 6.7.2.3, an overload protective device SHALL be installed ..." - making the conditions in 6.7.2.3 override the "shall" to a "may".
Question is though, if you interpret the "may" as "still required but placement is relaxed"... then for instance the following path of reading becomes nonsensical.

6.7.2.3 The overload protective device may be installed at any point in the conductor run that it protects provided that
> c) the conductor is
> 4) not likely to cause harm to a person in the event of a fault.

Forming the sentence out of the clauses like that leans more towards the requirement of the device vs the positioning of it. The regs really are waaaay to ambiguously written.

[Dave A]

6.7.2.3 The overload protective device may be installed at any point in the conductor run that it protects provided that
> c) the conductor is
> 4) not likely to cause harm to a person in the event of a fault.

Forming the sentence out of the clauses like that leans more towards the requirement of the device vs the positioning of it. The regs really are waaaay to ambiguously written.

Have you perhaps missed the "and" at the end of subclause 3?
All four subclauses must be met, not just subclause 4. So it can't be read in isolation (as would have been the case if the "and" was an "or").

[recre8]

Have you perhaps missed the "and" at the end of subclause 3?
All four subclauses must be met, not just subclause 4. So it can't be read in isolation (as would have been the case if the "and" was an "or").

I read it the following way:
6.7.2.3 (a AND b) OR (a AND c1 AND c2 AND c3 AND c4)

The given senctence was more to question whether the "MAY" in 6.7.2.3 refers to the position of the protective device or whether it refers to the requirement of it.

My initial understanding of the paragraph was that overload protection is not required when an indicator LED lamp (which fails open-circuit) connected via a PVC cable of 4mm2 or less AND less than 5m run from the DB AND and with no plug or light socket, and correctly and safely installed in the DB Board. If the lamp is installed after any breaker (mains for instance) then it would be short-circuit protected too and comply with all the requirements of 6.7.2.3.

[Derlyn]

The mains might be an isolator which offers no short circuit or overload protection.

[Isetech]

However the circuit breaker feeding the DB will have overload and short circuit protection. We dont use circuit breakers before the main switch, or a circuit breaker in place of a main switch, unless as per the example.

One of the challenges I have noticed in large 3 phase DB's. When people run a wire from a busbar fed from a 250 amp breaker, to an earth leakage with no overload protection, lets say with a 6 or 10 mm , then add 10 x 20 amp breakers. In a case like this, the earth leakage would have overload protection or there would be a circuit before the earth leakage.

When we work in large industrial applications, you realize how little people understand fault levels and when to use the correct ka rated breakers.

I have fund that people dont understand that the cable size, distance from the transformer, and the busbar dimensions all contribute to the fault level calculations.

A long time ago I learnt to put my blinkers on and focus on the task at hand, people dont like it when you point out issue with their electrical installation. The only time I make a fuss about incorrect installations is when on of my customers purchase or rent a building and I become responsible for the electrical installation once the previous owner has issued a COC, no matter how illegal. So longer as I have a copy of the document. I point out the issues, then leave it up to the customer to ecide if they want to bring the installation up to standard. If renting a building we dont bother unless there are some seriously dangerous parts.

I have one right now where I can see the electrician who signed the COC never even visited the site, there is a socket outlet literally in the bath. There are many other issues but not as dangerous.

The mains might be an isolator which offers no short circuit or overload protection.

[Isetech]

I am going to request a copy of the COC, so that I can find out who signed it, I need one of those COC's for a mate, I can't sign off the property he is selling because there is too much illegal stuff.

Do as the electricians do in SA, we all know the chance of getting caught is almost zero, why try be the hero and waste your mates money doing it right

We were discussing paying bribes, when back in the day when it was seen as a bad thing, now you request the figure so that you can add it to the quote