# Interest group forums > Electrical Contracting Industry Forum >  Maximum overcurrent protection on a plug circuit

## Dave A

What is the maximum overcurrent protection allowed in terms of the regulations for a plug circuit on a typical house or flat installation - single phase, 2.5mm wiring, 16A socket outlets?

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## Yuri

20A C/B

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## AndyD

Hmmm, am I smelling a trick question? OCPD's protect the circuit cabling that's connected to them. They would usually be sized according to the cable so for example if you have a 4mm radial socket circuit you would specify a 25A mcb regardless that the socket outlets are only rated at 15A or 16A. A 20A MCB would be used for a 2.5mm cable.

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## Dave A

> Hmmm, am I smelling a trick question?


Not really. I was wondering why so many original installations (dated about 1960's / 70's) in Durban have 30A circuit breakers on their plug circuits. It's so widespread, there must be a story.

BTW - the regs say you can only have overcurrent protection exceeding 20A (on a single phase circuit that contains only 16A socket outlets) if there is overcurrent protection on the socket that doesn't exceed the socket's current rating.

6.15.3
(I better check and edit that in the morning if my memory has let me down).

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## bergie

the regs say the overcurrent protection may not be more than 25% of the rating of the socket outlet.
16 amp plug + 4 amps = 20 amps    2,5mm
32 amp plug +8 = 40 amps             6mm
63 amp plug +15,75 = 78.75 amps ( 80 amp breaker ?)  16mm-25mm depending

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AndyD (18-Jan-14), Dave A (16-Jan-14), mikilianis (17-Jan-14)

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## Yuri

Look up on page 194  6.15.5

You my not use a bigger than 125% rated CB
So
16 x 1.25 = 20 A

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## Dave A

When it comes to 6.15.3 to 6.15.5 , I suggest you need to pick the section that applies to the actual circuit configuration.

Ultimately it's the 6.15.3 situation that has my interest piqued. I suppose what I need to do is hunt down one of our tests where this has come up and look at the wire size on record against the "offending" CB.

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## ians

Dave back in the day all plugs circuits where wired with 4 mm house wire and a 30 amp circuit breaker was installed as was the geyser, 4mm wire with a 30 amp circuit breaker. The HOB and ELO was wired with 6mm, things have changed.

The rules has since changed and not plugs nor geysers are wired using 4 mm wire anymore (speaking in general). however you need to be very careful of these older installations because the bright sparks of today don't know about 4 mm wire and 30 amp breakers. I have come across many houses which still have 30 amp breaker, the catch comes in with additions or alterations to an existing installation many "electricians" just use 2.5 mm twin+ earth and don't derate the breaker in the DB or even add an earth leakage when adding sockets. Kitchens are a bad place for this type of problem. A customer will get a kitchen company in to replace the kitchen and the shop fitters are jacks of all trades, before you can say refurbish kitchen the 2.5 mm twin +e is in, the DB is hidden away nicely right at the point where the top part of the cupboard meets the wall so you cant open the DB, the plugs are connected to an existing socket in the kitchen and bingo 1 circuit does it all, well until a real electrician comes along to do an inspection report, the 30 am is replaced with a 20 amp and for some unknown reason when ever you run the kettle, the dishwasher, the washing machine and the tumble drier together it just seems to trip and never did that before. I am sure there are a few of you smiling as you read this...been there done it.

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Dave A (22-Jan-14), Leecatt (14-Feb-14), mikilianis (23-Jan-14)

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## Dave A

Thanks Ian. I just knew there was a story there... and the hassles that go with just downgrading the breaker are exactly as you say.

Now to massage the problem for possible alternative retrofit solutions.

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## Sparks

And to crown it off, the sod got his tiler to do the plugs so all the earth wires of the T&E were cut off and they installed the cheapest plastic framed plugs they could get. Just before the place was sold!

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## Slow Blow

Back in the 70's plug circuits were wire with either 4.00mm wire (radial circuit) or 2.5mm wire (ring main), all breakers and fuses were rated 30 amps

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## Leecatt

I have heard some say that replacing an existing socket outlet is neither an addition nor an alteration and therefore the 30 amp circuit breaker can stay.
In my opinion it is an alteration and requires the correct 20 amp circuit breaker to be fitted into that circuit.
What do other think? Do you agree?

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## Yuri

> I have heard some say that replacing an existing socket outlet is neither an addition nor an alteration and therefore the 30 amp circuit breaker can stay.
> In my opinion it is an alteration and requires the correct 20 amp circuit breaker to be fitted into that circuit.
> What do other think? Do you agree?


I agree with you

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Leecatt (14-Feb-14)

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## AndyD

Maybe if it was a single and a double skt was installed but replacing like for like I'd be hard pushed to class it as an alteration or an addition. 

On what grounds would you class it as such? I'm open to convincing if you've got a good argument  :Smile:

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ians (25-Feb-14)

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## Leecatt

I would agree that replacing one socket outlet for another of an identical type, should not necessitate a certificate of compliance. However,
Imagine the circuit was old and had steel pipes.
The earth wire is Bonded onto the steel pipe and does not travel down the pipe to the socket outlet.
Now the circuit needs to be upgraded to accommodate the new 16 amp socket outlet.
Many times i've seen the situation where the steel socket outlet is removed and replaced with a plastic one without addition of a correct earth wire being installed.

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## AndyD

There's several separate issues though, whether like for like replacement requires a Coc and whether like for like replacement requires full testing and remedial work if it fails. TBH I'd expect even a DIY'er to plug a socket tester in after a like for like replacement.

I think there's a good arguement that regulation changes should apply retrospactively to older installations, especially with regard to the safety oriented regs. There could be a grace period of maybe five years but I'd at least like to see all domestic premises with RCD protection by now and also conforming to the later earthing and bonding regs.

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Dave A (16-Feb-14)

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## Slow Blow

> \ TBH I'd expect even a DIY'er to plug a socket tester in after a like for like replacement.


Most of the "electricians" who come to me for a job don't know what a socket tester is  :No:

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## ians

> I would agree that replacing one socket outlet for another of an identical type, should not necessitate a certificate of compliance. However,
> Imagine the circuit was old and had steel pipes.
> The earth wire is Bonded onto the steel pipe and does not travel down the pipe to the socket outlet.
> Now the circuit needs to be upgraded to accommodate the new 16 amp socket outlet.
> Many times i've seen the situation where the steel socket outlet is removed and replaced with a plastic one without addition of a correct earth wire being installed.


If I recall a while back I started a thread with this issue. I was called out to look at something to find that the 4x2 sso had been replaced with DSO and a 4x4 extension box. The steel piping was used for earthing as was done back in the day. The electricians fitted new plastic DSO with no earth for the entire house.

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## ians

> Most of the "electricians" who come to me for a job don't know what a socket tester is



You should try go on a certificate of compliance refresher course if you want to see how bad it really is  :Stick Out Tongue:

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## ELECT 1

Is a  COC is necessary if replacing a plug .?? This assuming its done by an electrician. A pvc plug fitted to an old 30 amp system where the box is the earth, you will require an earth wire from the plug to the box. Now the dilemma, some school of thoughts say you must rewire and fit a separate earth wire, as you now cant use the conduit as the earth.
Some just screw an earth wire with a lug onto the plug box and earth the plug this way. So the plug is now earthed.
Now do you need a compliance, well if you rewire, i say yes, if you made the earth loop  ( if allowed )to the box i say yes, as you have now altered the installation. 
Otherwise just a normal replacement, i cant see why a COC would be necessary. Like if you need new brakes on your car, do you need a road worthy, need a service, do you need a roadworthy.

My 2c worth :Whistling:

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## ians

A trick question while on the subject of socket outlets. 

What do you do if there is a 20 amp breaker and the customer complains it is tripping when he plugs in his old wire wound welder (for domestic sparkies) or you work in a franchise where some of the single phase heating/motor equipment (for the commercial sparkies)  draws more than 20 amps never mind 16 amps on start up.

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## Sparks

Maitenance does not require certification. Earthing or providing an earth where there is one does not require certification. Where an earth is not available, you are obligated to provide one. If it means from the DB, so be it, the client must be made aware of the danger and legal requirement which will make him prepared to pay for it. This need not be certified. Should the client require a COC for your work he must be prepared to pay for it as it is your time compiling it. You are only obligated to certify your own work unless commissioned to certify the entire installation. Doing maintenance correctly is not changing/altering an installation. By putting an earth in from the DB you have not altered the amount of circuits nor the amount of points. These details are recorded on the COC. If you have the correct earth continuity reading for your circuit I find no fault in using the metal box for your earth. I would however inform the client that the 30A CB must be downgraded in order for the maintenance to be carried out legally and correctly.

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## Sparks

I would inform him that his welder draws too much power for the circuit and he needs to put in a new, stronger circuit or get a smaller welder if it is not justified by the amount of welding he does.

Unless of course he wants to do what we did as kids with the overhead wires which I will not explain here.




> A trick question while on the subject of socket outlets. 
> 
> What do you do if there is a 20 amp breaker and the customer complains it is tripping when he plugs in his old wire wound welder (for domestic sparkies) or you work in a franchise where some of the single phase heating/motor equipment (for the commercial sparkies)  draws more than 20 amps never mind 16 amps on start up.

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## gobbleteller

Overload protection, like circuit breakers is primarily to protect the cable that it supplies and not the individual equipment attached to it.

In an industrial setting, provided the circuit conductors allow for it, I would up the rating of the circuit breaker: If the conductors of the circuit are 2.5mm2, I'd up it to a 25A CB, if 4mm2 the maximum you would be able to go is 43A.

For the domestic installation, there may be several circuits being fed from that CB. I'd determine the maximum current that would be drawn by the welder from the nameplate, and provided this doesn't exceed the socket outlet rating and assuming the circuit is wired with 2.5mm2 and more, I'd bump up the CB to a 25A 




> A trick question while on the subject of socket outlets. 
> 
> What do you do if there is a 20 amp breaker and the customer complains it is tripping when he plugs in his old wire wound welder (for domestic sparkies) or you work in a franchise where some of the single phase heating/motor equipment (for the commercial sparkies)  draws more than 20 amps never mind 16 amps on start up.

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## ians

The answers i expected, and the plug socket and plug top which os only rated at 16 amp?

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## Sparks

Which is why after my welder, which I installed a 4mm circuit with a welding plug for, was stolen, I replaced with an inverter. Nice and light to work on a ladder with too. No need for long heavy cables.

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## Leecatt

> Maitenance does not require certification. Earthing or providing an earth where there is one does not require certification. Where an earth is not available, you are obligated to provide one. If it means from the DB, so be it, the client must be made aware of the danger and legal requirement which will make him prepared to pay for it. This need not be certified. Should the client require a COC for your work he must be prepared to pay for it as it is your time compiling it. You are only obligated to certify your own work unless commissioned to certify the entire installation. Doing maintenance correctly is not changing/altering an installation. By putting an earth in from the DB you have not altered the amount of circuits nor the amount of points. These details are recorded on the COC. If you have the correct earth continuity reading for your circuit I find no fault in using the metal box for your earth. I would however inform the client that the 30A CB must be downgraded in order for the maintenance to be carried out legally and correctly.


1./ "Earthing or providing an earth where there is one does not require certification. "
The earth wire is your most important part of your electrical circuit and *installing* one constitutes an alteration to that circuit and as such requires a COC issued.

2./ "You are only obligated to certify your own work unless commissioned to certify the entire installation"
I disagree here as well for the following highlighted reasons

*OCCUPATIONAL HEALTH AND SAFETY ACT, 1993 ELECTRICAL INSTALLATION REGULATIONS*
*Issuing of certificate of compliance*
9. (1) No person other than a registered person may issue a certificate of compliance.
(2) *A registered person may issue a certificate of compliance accompanied by the required test report only after having satisfied himself or herself by means of an inspection and test that*
(a)a new electrical installation complies with the provisions of regulation 5(1) and was carried out under his or her general control; or
(b)an electrical installation which existed prior to the publication of the current edition of the health and safety standard incorporated into these Regulations in terms of regulation 5(1), complies with the general safety principles of such standard; or
(c)an electrical installation referred to in paragraph (b), to which extensions or alterations have been effected, that
*(i) the existing part of the electrical installation complies with the general safety principles of such standard and is reasonably safe,* and
(ii) the extensions or alterations effected comply with the provisions of regulation 5(1) and were carried out under his or her general control.
*(3)If at any time prior to the issuing of a certificate of compliance any fault or defect is detected in any part of the electrical installation, the registered person shall refuse to issue such certificate until that fault or defect has been rectified*: Provided that if such fault or defect in the opinion of the registered person constitutes an immediate danger to persons in a case where electricity is already supplied, he or she shall forthwith take steps to disconnect the supply to the circuit in which the fault or defect was detected and notify the chief inspector thereof.
*(4)Any person who undertakes to do electrical installation work shall ensure that a valid certificate of compliance is issued for that work.
*

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Dave A (26-Feb-14)

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## Dave A

Well argued on the interpretation of this section of the regs, Leecatt.

It's something of a Catch 22 though when you can't issue the COC on the part of the installation you worked on, because some other part of the installation (which you didn't work on) isn't up to standard. And now you're responsible to ensure that magically this other part is brought up to standard?

What do you do? Hold a gun to the user/lessor's head?
Do the fix for free?
Not exactly what the contractor signed up for when they were contracted to add a plug point (or replace a faulty one for that matter)  :Mad: 

I'm starting to think there's scope for a change in the regs here. Perhaps something that allows the registered person to report non-compliance to the supply authority?

Dunno for sure - just thinking out loud here.

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## gobbleteller

Ians, to tell you the honest truth, I have no domestic installation knowledge. I work on the mine and thus have no exposure to the domestic side of our industry. All I'm saying is that as long as amperage drawn by the welder isn't higher than the rating of the socket outlet supplying it, I would up the circuit overload protection. Being a domestic welding machine I'd assume it would be fitted with a 16A plug, in other words the welding machine must be rated at less than 16A. If you can't read the nameplate, test the current drawn by the welding machine. If the current drawn by the welding machine is higher than the 16A of the socket outlet and plug, then a separate circuit and male-and-female welding plug will be needed as Sparks mentioned. 


> The answers i expected, and the plug socket and plug top which is only rated at 16 amp?

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ians (26-Feb-14)

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## ians

" then a separate circuit and male-and-female welding plug will be need"

That was the answer I was looking for, plug and socket rated correctly.

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## Sparks

> 1./ "Earthing or providing an earth where there is one does not require certification. "
> The earth wire is your most important part of your electrical circuit and *installing* one constitutes an alteration to that circuit and as such requires a COC issued.
> 
> [/B]


I must still disagree here, installing an earth wire from the DB because of a breakdown in continuity has not changed the installation. It has merely brought the existing circuitry up to standard with requirements. Neither the amount of circuits nor the amount of points have changed. The circuit has only been made safe. If there is an earth from the DB available and it is too short to connect you must extend it with a pigtail, without having to certify it.

Regarding the obligation to certify, well your point 3 states certification must be refused where a fault is detected and point 4 states that your work be certified. 

When you are called out to change a socket outlet, you do not inspect the whole house to see if there are faults, you are shown to the faulty socket outlet and you work on that point. If you discover something like the earth is a problem you inform the client of what it could mean for the rest of the installation, but it remains his choice as to when and by whom it be attended. This is where you get the opportunity to sell your business and could end up with a nice commission if handled properly. Should the client be under financial constraints there is no reason why any corrective work cannot be done in stages as a gradual upgrade. You would still however be expected to repair the faulty socket outlet as requested.

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## Dave A

Perhaps this comes down to the definition of a "change to the electrical installation"?

Is there a definition on this in the code?
(I don't have a copy handy here at home right now).

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## Slow Blow

A "change to the installation" means that there extra points added i.e. as in an extension to the premises or extra lights or sockets added to the existing installation (new kitchen maybe), then the CoC can state the extra work has been tested and found to be compliant.

When I have installed a pay as you go meter in an existing house I have only given a CoC to cover the work carried out, this should be kept with the original CoC for insurance purposes.

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## Dave A

There is no definition of what constitutes a change to the installation in SANS 10142-1

The closest the regulation comes to dealing with this is under 7.4 -




> Where any addition or alteration has been effected to an electrical installation for which a certificate of compliance was previously issued, the user or lessor of such electrical installation shall obtain a certificate of compliance for at least the addition or alteration.

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Gtfast (30-Mar-17)

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