# Interest group forums > Electrical Contracting Industry Forum >  Earth Leakage Breaker (RCD) Tripping

## AndyD

We get a lot of threads about earth leakage faults on the forum so I thought I’d make a thread outlining in laymen’s terms what an earth leakage breaker is, what it does, why it trips and how to go about alleviating some of the problems that can be caused when it does.

The info here is aimed at homeowners and domestic users who have a basic DIY-level understanding of electrics. I’ve attempted to avoid complex technical terms and explanations in order to keep it accessible to non-professionals.


*What is an Earth Leakage Breaker?
*
The earth leakage breaker is officially known as a Residual Current Device (RCD) and in the interests of my one-fingered typing I’m going to refer to it as an RCD from now on.

The RCD is a device that is designed to disconnect the supply to a circuit or several circuits or even the entire house installation when a hazardous fault known as an earth leakage fault occurs. It’s identifiable as a wider than normal circuit breaker, often with a double lever on the front and it also has a test button which should be pressed regularly by the home owner to ensure it operates correctly.

RCD’s come in a wide range of types, some have time delays and they come rated to operate at different leakage currents, some detect DC leakage faults as well as AC leakage and they also come as 3-phase and single phase configurations.  To keep things simple I’m only covering the general purpose 30mA single phase RCD which is widely used in standard domestic electrical installations.

   

*Various examples of earth leakage circuit breakers (RCD’s)*

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ACEsterhuizen (14-Nov-15), Justloadit (14-Nov-15), mikilianis (17-Nov-15)

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## AndyD

*What Are Earth Leakage Faults?*

Current flows through a circuit the same way water flows through pipework. With water, if 10 litres flows into one end of a pipe then 10 litres will flow out of the other end. Similarly with electricity if there’s 10Amps flowing into one side of a circuit (Live) there should be 10Amps flowing out of the other side (Neutral). Current in always equals current out.

The thing that keeps the current in the circuit is insulation. The only time current is ‘lost’ or ‘leaks’ from a circuit is when the insulation has failed. Sometimes insulation failure is spectacular and results in a flash and a bang, when this happens sufficient current ‘leaks’ to cause a normal circuit breaker to trip. Sometimes however insulation failure is more subtle and results in only a slight loss of current from the circuit, this is what the RCD is designed to detect and without an RCD the circuit would remain live in the case of this kind of fault. 

You might wonder why we’d be worried if only a few thousandths of an Amp was being lost but a few thousandths of an Amp is all it takes to kill someone if it flows through their body, hence the great importance we place on even small amounts of leakage. 

Most people have experienced a tingling feeling of a small electric shock at some stage, this tingling is caused by only 1 or 2 thousandths of an Amp flowing through them and out through their feet into the ground (earth) they’re standing on. When the current flowing through someone is greater than 5 thousandths of an Amp (5 milliamps) you get muscle reaction that causes cramp, 10-20mA will give you a violent shock and 30mA is considered the maximum shock that shouldn’t cause death. More than 30mA of current flowing through a human body causes interruption of normal heart rhythm and can lead to death.

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ACEsterhuizen (14-Nov-15), Justloadit (14-Nov-15), mikilianis (17-Nov-15)

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## AndyD

*What does an RCD do?*

The RCD in a domestic DB is designed to trip almost instantly when 30mA of current is being lost from a circuit which would be a 30mA earth leakage fault. Not only must it trip when there’s a leakage fault, it must disconnect the circuit within milliseconds and it must disconnect both the live and the neutral legs of the circuit.

To detect such small currents an RCD is almost a thousand times more sensitive than a normal circuit breaker that protects a socket circuit because *the RCD is there primarily to protect people from shocks and not to protect the circuit itself or the appliance from overload.* The RCD constantly monitors the current flowing through the live and the neutral sides of the circuits because any difference in these currents is caused by earth leakage. 

For example if there’s 10 Amps flowing on the live side of a circuit and only 9.95 Amps flowing out on the neutral side then 50mA is being lost from the circuit and the RCD will trip. 

Some RCD’s offer a combination of overload and earth leakage protection in the same device but many are not designed to give overload protection and there’s often some confusion surrounding this. If you look at an RCD it usually states 60A on the front but this doesn’t always mean it will trip when the load current exceeds 60A it just means its internal contacts can only disconnect a 60Amp load if there’s an earth leakage fault.

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ACEsterhuizen (14-Nov-15), Justloadit (14-Nov-15), mikilianis (17-Nov-15)

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## AndyD

*Why does the RCD cause so much inconvenience?*

 Off the bat I'll say there are some very poor quality earth leakage breakers on the market. Many of the cheaper types are very prone to nuisance tripping or not functioning as they should when there’s a fault. In my opinion it's definitely worth paying the extra for a brand name like Schneider, Merlin Gerin, ABB, or CBI depending on the type of mounting rail in the DB.

If an earth leakage breaker (RCD) trips intermittently, from my experience, 98% of the time there's a fault or a number of faults on the circuits it supplies that's causing the tripping. You do get the very occasional RCD that is too sensitive by a significant margin but it's the exception not the norm.

The RCD is unlike most other circuit breakers in your DB because it monitors both the live and the neutral. *Just switching off an appliance using its built-in switch or the switch at the socket or manually tripping a normal circuit breaker to disconnect a circuit doesn’t work if you're trying to find an earth leakage fault because the neutral is still connected and the RCD will still ‘see’ the fault.* To effectively clear (remove) an earth leakage fault appliances need to be completely unplugged and circuits need to be completely disconnected on both the live and neutral side. This makes finding earth leakage faults difficult and confusing for homeowners.

In most houses nowadays there’s electronics everywhere and every house or business has dozens of electronic power supplies (switch mode supplies). A few examples would be computers, printers, laptops, phone chargers, modems, routers, hi-fi, TV’s, X-Box, M-Net decoder......the list is endless. The problem they cause is that even under normal operating conditions they have a small amount of leakage current. It's generally one or two milliamps and we call it '_functional leakage_' to differentiate it as being acceptable, unlike earth leakage fault currents which aren't. The RCD unfortunately doesn't know this leakage current has a cute name and isn't considered a fault current so when you've got possibly a dozen of these things in your average home the RCD sees all these small leakage currents as faults. Realistically they could add up to 10-15mA which means the 30mA RCD is effectively now only allowing 15-20mA of earth leakage fault current before it trips. Add to this a few LED lighting drivers, electronic ballasts in fluorescent fittings and noise/surge suppressors in your Hi-Fi that also have standing (functional) leakage to earth and next thing you know you've got nuisance tripping even though there's actually no actual 'fault'.

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ACEsterhuizen (14-Nov-15), Justloadit (14-Nov-15), mikilianis (17-Nov-15)

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## AndyD

*How Can The Nuisance Factor Be Reduced?*

To avoid nuisance tripping the layout of domestic electrical installations needs to change. RCD’s used to be very expensive and traditionally in South Africa the RCD was used as a main breaker and monitors the entire installation so only one per installation was required. This means that as soon as the combined earth leakage fault currents and functional leakage currents for the entire installation exceeds 30mA it will trip even though no single circuit has a large enough fault that would normally warrant its disconnection. Nowadays, because of the already considerable and ever increasing 'acceptable functional leakage' that comes with electronic power supplies, a single upfront RCD should be considered poor design because the inconvenience factor is high but unfortunately it’s the cheapest way of doing things and still being compliant with the existing electrical regulations it's still common practice.

A better option is a split DB with two RCD’s. This means that there’s less inconvenience when there’s a trip and it also goes some way to accommodating the acceptable standing leakage currents as outlined above. The latest development is that every single circuit breaker is also an RCD, these circuit breakers are called RCBO’s. This system is far more preferable, it means that an earth leakage fault on any circuit will trip only that particular circuit. Obviously this system costs considerably more money but prices are still coming down and already they’re within the budget of many owners of medium to large houses.


*Tripping Faults*

As far as the homeowner is concerned there’s two main types of RCD tripping fault.  There’s the type of fault that’s occurred out of the blue where the RCD has tripped and point blank refuses to reset and there’s the type of fault where the RCD trips once in a while and resets quite easily until a few hours/days/weeks later when it trips again.

Before we go any further, from experience, if an RCD is tripping there’s a 98% probability that it’s caused by a fault or a number of faults on the circuits it’s supplying rather than it being a failure of, or problem with the RCD itself. In other words, if you have an RCD that’s tripping you should approach it as being a fault somewhere on the electrical installation or in one of the items that’s plugged in, not as it being a faulty RCD.

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ACEsterhuizen (14-Nov-15), Justloadit (14-Nov-15), mikilianis (17-Nov-15)

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## AndyD

*What You Should Be Doing*

Regardless of the type of tripping fault you have there are some things you should do as a matter of course and if they’re done properly you stand a good chance of finding the problem. 

1.	Check all trailing cables. Appliance cables are particularly prone to wear and tear, abuse and damage.  Go to every appliance and unplug it, then run your hands up and down the length of the cable and visually check the plug for any signs of strain damage. Don’t limit this procedure to the items in the house, go outside and check the pool pump and the gate motor and any other things you can think of. Get up in the loft as well and visually inspect the cabling for rodent damage etc.

2.	Check for damp patches and water leaks. Moisture is a big cause of earth leakage faults, especially intermittent ones so again, be thorough and methodical. Check for garden lights getting soaked by the irrigation. Check under the fridge and washing machine and around the pool pump for water or signs of damp. Check for roof leaks that may be causing cabling or lighting to get wet. Often, fixing a water problem will also fix an earth leakage fault.

3.	Check for general damage. Seemingly inconsequential things can cause earth leakage faults. External sockets with missing box lids, external light fittings that are badly corroded and even a broken gland where there’s a cable entry. Take a slow walk around and check the lights for internal condensation and generally use your eyes.

If I arrive at a home with an intermittent RCD tripping fault this is exactly what I do first, I’ll spend at least 20 minutes to check for the obvious before looking for the trickier hidden faults. 

Another thing I’d be looking for is poor quality workmanship. Electrical work that’s been done by the homeowner or someone who’s not an experienced sparky is far more likely to be the cause of faults. There’s a way of doing things and dozens of little tricks that an experienced installer uses and they prevent future problems. It’s a lot of little things like using the correct glands for the particular cable, leaving drip loops at outside light fittings and so on but the difference is a reliable installation verses one that may or may not be.

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ACEsterhuizen (14-Nov-15), Dave A (15-Nov-15), Justloadit (14-Nov-15), mikilianis (17-Nov-15)

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## AndyD

*Point Blank Refuses To Reset*

Let’s deal first with the type of fault where it just won’t reset no matter how much you curse at it. The chances are that this would be caused by a single earth leakage fault that’s quite large. The fault could be on the installation cabling or it could be on something connected to the circuits that are affected. 

Now is a good time to have a think about anything that may have changed recently. For example have bought any new items and recently plugged them in? If so focus on the things that changed recently and undo those changes by unplugging the new appliance and seeing if the RCD resets with it disconnected.

Next step if the fault persists is to unplug every single item and appliance on the circuits that are without power due to the tripping fault then try again to reset the RCD.

If it resets then you should be able to figure out which appliance is the problem child by plugging them back in and noting which one causes the RCD to trip again. If it doesn’t reset then it’s time to call in your favorite electrician because the fault is somewhere on one of the actual circuits so you’ve done everything you can without electrical test equipment. 


*Trips Once Every So Often*

The intermittent type tripping fault can be a lot trickier to find. There’s a high likelihood that an intermittent trip is caused by a combination of acceptable functional leakage as well as a number of small earth leakage faults on the circuits and appliances.

The thing that makes this kind of fault tricky is that any of the individual faults that are contributing to it might not be large enough to be considered as a problem under normal circumstances. From the homeowner point of view this type of fault is very confusing because unplugging or disconnecting any of the contributing faults might stop the tripping problem because the cumulative effect of the remaining faults is just under the point where the RCD would trip.

Here’s an example. In a house with a 30mA RCD there’s functional standing leakage of 15mA from all the 5 PC’s, 3 laptops, router, decoder, HiFi and other electronic items. There’s also a washing machine with 12mA leakage, a pool pump with 1mA leakage and a gate motor with 2mA leakage. 

If everything is plugged in you have 30 milliamps of earth leakage current which will cause the RCD to trip. Unplug the pool pump and the RCD will just hang in there and not trip because the leakage is now 1mA less than the amount it will allow. You now take the pool pump for repair because you think it was the cause of you tripping problems, the repair guy bench tests it and only finds 1mA of leakage, he signs it off as being in good working order, shrugs his shoulders and gives you an invoice.

You hopefully see the problem here. Even removing a small part of the overall leakage current (pool pump) has fixed the tripping but the appliance with the biggest earth leakage fault (washing machine) is still connected. The same would happen if you unplugged the gate motor first, it also would appear to be the main cause of the tripping even though the earth leakage it’s causing is actually acceptable.

Where this is all going is that there’s very little you, as an electrically unskilled person and without test equipment, can do to effectively find or localise this type of fault. You’ll need an experienced electrician who has the right test equipment.

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ACEsterhuizen (14-Nov-15), Dave A (15-Nov-15), Justloadit (14-Nov-15), mikilianis (17-Nov-15)

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## AndyD

*What Should I Expect From My Electrician*

First step would be to test the RCD itself. As I previously mentioned the chances of the RCD being faulty are very slim but it should be tested as a matter of course none the less. 

To test an RCD properly you need a special RCD ramp tester (see second picture below) and it would be worth confirming in advance with the electrician that he owns one. They're generally very expensive (>R20K for a Fluke) and many electricians make do with a very basic tester shown in the first picture that is not capable of performing the full range of tests. If he doesn’t own a full ramp tester then rather find an electrician who does. 

*Not* *An RCD Tester	* 



 *RCD Ramp Tester*


If the RCD passes the barrage of tests a ramp tester throws at it then the fault is definitely on one or more of the circuits it's supplying. Second step is to insulation test (IR test or Megger test) each circuit and all the items that get plugged in to check for an insulation fault that would cause an earth leakage fault current to flow. 

 *Megger Tester*

The thing with insulation tests is that there's no 100% pass, every circuit has got an insulation value that's less than infinite so every circuit has an earth leakage fault current even though it might be very small. The problem with very small leakage currents is that the RCD sees the cumulative total so if you've got 5 or 6 circuits each with 5 or 6 mA earth leakage then it's already game over because the total is >30mA even though no individual circuit would fail as having an unacceptable leakage current. 

This is often where the lesser sparky calls it quits. If he's tested the RCD itself and insulation tested the circuits and there's no fault large enough to peak his interest, this is all too often a good time to get the invoice made out and hope for the best and head for the hills.

In the good old days you could do the insulation tests and from the results you could calculate your expected leakage current under live conditions and the calculations would usually have been pretty accurate. Zoom forward to the 21st century and you now have electronics everywhere and every house or business has dozens of electronic power supplies (switch mode supplies) and even under normal operating conditions they have a small amount of leakage current, it's generally one or two milliamps for each power supply but the RCD unfortunately views this current as a fault and a megger tester can't give any indication of how large these currents are or whether they're large enough to be problematic. 

So... the next step for me would be a live leakage test which involves another relatively expensive tester, an earth leakage clamp meter which any good electrician should also own. 

*Earth Leakage Clamp Mater*

The megger tests/insulation tests are dead tests (power is off) and whilst they provide valuable information about the condition of the circuits and appliances they don't tell you how much leakage there is in real-life. An earth leakage clamp meter around the live and neutral on the load-side of the RCD as a live test (power on) will indicate of the difference between the current flowing in the Live and the current flowing in the Neutral. This difference in currents is leakage and it's exactly what the RCD monitors. If that difference is > than 30mA then it trips, even over 25mA it's likely to cause occasional nuisance tripping. The live leakage test needs to be done over a long duration with a tester that has a 'max hold' facility so you can see the maximum level of leakage current that took place over time.

The other advantage of doing the live leakage test during actual real-live conditions is that many modern appliances have internal components that are controlled by 2-pole switching. This means that when there's no power on the appliance, any insulation fault that may be present would not be visible. Live leakage testing will find the fault even if it takes some time.

Finally the incoming supply should be inspected and tested. The incoming supply is unlikely to be causing an earth leakage tripping problem but there are certain main supply faults that possibly could, depending on earthing arrangements etc. It’s also good practice to make supply tests any time a DB is worked on just in the interest of safety, it takes about two minutes to do the tests and it’s peace of mind the earthing is good and the installation is safe.

A good electrician should be inquisitive, he should be checking in the ceiling, he should be rummaging under and around things, he should be removing lids and covers and he should be all over the installation looking for possible problems inside and outside. There are certain faults that all the test equipment in the world won’t find, the only way you discover them is by getting down and dirty and hands on and by being methodical and persistent. 

Alas, not all electricians are made of the right stuff. All too often we’ve attended a fault after several electricians have been there before, only to find a litany of bad practice and sometimes downright dangerous ‘repairs’ where the RCD has been bypassed or a faulty circuit has been removed from the RCD as a workaround rather than going to the trouble of actually repairing the root cause of the tripping. The only advice I can offer is to find an electrician who comes genuinely recommended by other people and don’t necessarily go with the guy who has the cheapest hourly rate.  

*The info above is to give you a better idea of what you should be expecting from your electrician. These tests are not within the realms of DIY, they're dangerous if you're not electrically competent and even with qualified electricians live testing should be done only after an appropriate risk assessment.*

Good luck with your tripping faults and stay safe.

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ACEsterhuizen (14-Nov-15), Justloadit (14-Nov-15), mikilianis (17-Nov-15)

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## AndyD

If there's anything I missed, anything that's inaccurate or anything that doesn't read too well grammatically please let me know.

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ACEsterhuizen (14-Nov-15), mikilianis (17-Nov-15)

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## Leecatt

> If there's anything I missed, anything that's inaccurate or anything that doesn't read too well grammatically please let me know.


Well I don't know what to say. That has to be the most comprehensive narration on earth leakages I have ever read, even I learned a few things and I've been in the game over 40 years. 
If you have no objection Andy,  I would like to plagerise your work and put it into my website. 
Well done.

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Brett Nortje (07-Dec-15)

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## ACEsterhuizen

Same here Leecatt, at 50 years old and 30 years in the business  I also tip my hat to Andy and his vast knowledge, realized again that I am not even remotely close to his (and a lot of others) level (of expertise). Respect.

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## Justloadit

Thanks @Andyd.
A well laid out post with all the loose bits of information in one place.

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## AndyD

Thanks guys for the kind comments, glad it might be useful. Leecatt, you're very welcome to use it/reproduce it freely under the Creative Commons licence terms which applies to content on the forum in general. Feel free to add info to this thread as well if you like.

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mikilianis (17-Nov-15)

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## ACEsterhuizen

Ahem, uhmm, which ramp tester would you recommend Andy and where can i buy one....? (can this text get any smalller...)  :Blushing:

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## AndyD

I stumbled across these a while back and I bought a couple of for my guys. At R1.5K they're a bargain and Uni-T testers have a decent reputation even though they're not a high-end brand. I see on the same website they also have a Major Tech 5410 which is a rebranded Kew/Kyoritsu for just over R10K. I'm guessing it can test a wider range of RCD's such as versions with time delay or S-type etc but if you're working mainly in the domestic market it probably wouldn't warrant paying the extra. 

Thing is once you're paying much more than R10K for an RCD tester nowadays you might as well look at a full MFT (multifunction tester) which is a PSC, megger, loop impedance and RCD testers all rolled into one like this one for example.

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ACEsterhuizen (17-Nov-15)

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## Houses4Rent

Question: My electrician said:

"It is optional to have the lights and/or geyser on ELU but also not a must.  This is normally left at the discretion of the tenant/owner."

Is that correct and not regulated at all?

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## Dave A

> It is optional to have the lights and/or geyser on ELU but also not a must.


Correct, with some conditions attached.

For example, if there is a ceiling fan on the light circuit, the fan must either have an isolator within arms reach, or the light circuit must be on earth leakage. (See 6.16.1.4 of SANS 10142-1)

When it comes to fixed appliances (including geysers & luminaires) in zone 1 or zone 2 in a bathroom, if it is not a class II appliance it has to be on earth leakage. (See Table 7.1 of SANS 10142-1 )

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## DieterT

> Question: My electrician said:
> 
> "It is optional to have the lights and/or geyser on ELU but also not a must.  This is normally left at the discretion of the tenant/owner."
> 
> Is that correct and not regulated at all?


If I was the tenant/owner and the electrician said to me 


> "It is optional to have the lights and/or geyser on ELU but also not a must.  This is normally left at the discretion of the tenant/owner."


I would tell him to get the  :Rant1:  out!

Of course it is regulated. Conditions has to be met as mentioned. Some parts of the installation has to be under earth leakage and some parts not, should it meet the required conditions.
Nowhere ever was a choice ever given to the tenant/owner what has and does not have to be under earth leakage.
Maybe it could be that he found the lights and geyser to be effectively earthed and thus primary protection is adhered to and then only he could recommend to you in order to avoid nuisance tripping to have them removed from earth leakage or recommend for extra protection and to avoid nuisance tripping to have multiple ELUs in the DB board. If this is not the case then this electrician is "besig om n lat vir sy gat te pluk" and I hope for every job he does for you that he gives you a CoC

I have seen this way too many times. Earth leakage tripping, get to the house and find everything is wired under earth leakage (most of the time because it was some MnT job and they do so to cover themselves)
Sparky then goes and rewires the DB so it's just the plugs under earth leakage and the rest above....you ask what is wrong with this picture? The sparky never gone to check the primary form of protection. In effect taking secondary form of protection away, there is no more protection. But you say I can see the earth connected to the appliance/geyser/lights, but is it really, is the earth resistance such that should a fault occur and you are touching the conductive surface that, that fault condition will dissipate to earth via the earth connection, or through you as person to earth? and or is the earth resistance as such should a fault occur the circuit breaker would trip (yes a poor earth influences the CB from tripping as per designed curve)

Did the sparky check that before rewiring the DB in order to stop the nuisance tripping? I tell you most probably not, cause most of them can't even get it right on the CoC.
Do yourself a favour and watch next time someone does a CoC if they are testing the earth resistance from incoming earth to each point of consumption and conductive surfaces for earth continuity and earth resistance.

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## Houses4Rent

Thanks, that is all a bit too high for laymen like me. The EL tripped without any apparent reason. That is when sparky removed lights from EL.

"We took the lights off from earth leakage which could be the cause of the power tripping. The hot water cylinder was not on Earth leakage. "

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## AndyD

> Thanks, that is all a bit too high for laymen like me. The EL tripped without any apparent reason. That is when sparky removed lights from EL.
> 
> "We took the lights off from earth leakage which could be the cause of the power tripping. The hot water cylinder was not on Earth leakage. "


I would personally say a circuit should not be removed from the earth leakage for 2 reasons;
Firstly the level of protection on that circuit has been reduced to overload only meaning it's now less safe than it was originally.
Secondly if it's causing the earth leakage to trip then there's nearly always a fault that needs actually finding and remedying rather than a half-assed workaround.

The earth leakage offers a fair to good level of fire protection, if there's a poor termination that's overheating or burning or some kind of arcing fault the earth leakage will almost always by the protective device that trips long in advanced of the 10A or 20A circuit breaker. Removing circuits from the earth leakage breaker because of a tripping problem is something I'd expect from a DIY'er but I hold electricians to higher standards and hope it's something they wouldn't do regardless of whether the regs specifically forbid it or not. The regs are the absolute minimum permissible standard and not to be considered pinnacle of electrical good practice. 

The fact is however that probably in the majority of cases that a circuit is removed from the RCD because it's causing tripping it would be against the regs because the circuit itself or the fixed appliance has a fault or intermittent fault such as low insulation which would be below the allowed value stated in the regs.  

There's many options available other than removing a circuit from an earth leakage breaker such as;
Find the fault.Redesign the circuit if there's high standing/functional leakage.Find the damn fault.Install an RCBO for that circuit.Install a second RCD an split the DB circuits accordingly.Did I mention find the fault?

Earth leakage faults are often caused by;
Rodent damage.Insect infestation.Water ingressPhysical damage or excessive wear and tear to cables or a part of an appliance.Poor terminations or other types of arcing faults.In all of these cases just removing the circuit from the earth leakage is asking for trouble.

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mikilianis (23-Dec-15)

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## Leecatt

I agree, so many times I have found that the earth leakage is tripping due to BURNING WIRES inside of a light fitting or connection box. Removing the light circuit from the earth leakage does  not resolve the problem, it exacerbates it.

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## Brett Nortje

> I agree, so many times I have found that the earth leakage is tripping due to BURNING WIRES inside of a light fitting or connection box. Removing the light circuit from the earth leakage does  not resolve the problem, it exacerbates it.


The only reason those wires are burning is because there is 'too much heat per capita,' or, not enough area for electrons. think, now, if you were to have heat 'enveloping an area,' the more area there is, the more the heat spreads - like a hot spring where there is much more heat than a kettle, yet, there is so much less steam, yes?

If you really know your stuff, you might want to make fancy wires! these wires could be made out of something denser, or, a better conductor. you could make money with the people that take care of their stuff, but builders will always use the cheapest stuff.

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## AndyD

Most of the burning connections or terminations I come across are plain old poor installation techniques. It's little things like not using end ferrules on fine stranded wires when terminating, incorrectly sized connector blocks, too many wires in a termination, wires that are twisted too tight and they don't spread in the MCB cage clamp, even wires that have completely missed the cage clamp on MCB's and were just trapped behind it. Poor crimping technique on lugs is another....... the number of times I see lugs crimped using a pair of side cutters or hammer and screwdriver, I swear there must be a nationwide shortage of indent crimpers, oh yeah and over-tightened screws in plugs is another.

Poor installation technique still remains the most common cause of burning or arcing problems I come across but poor quality manufacturing is more recently becoming a serious contender for the title. Neutral bars with only a single screw per termination are quite common to see failures on, in the good old days where there were double screwed connections failures were pretty rare. Poor clamp terminals on MCB's are more common nowadays as well, I've come across a few MCB's in the last year or two where no matter how the wire is inserted it doesn't get firmly clamped by the termination, either that or the screws strip....and before someone suggests it, yes I do use a calibrated torque driver for wiring up panels.

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mikilianis (23-Dec-15)

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## Justloadit

The screws strip or the thread strips because they have reduced the thickness of the termination material, so that they can save a few cents. Thinner material means there is less area to cut the thread on.

Another issue I have found, especially with high current terminations, and areas in which there are high swings in temperature, is that the terminal screw unloosens, or more likely is that the copper in time with the high current flow, changes shape, aggravated by the pressure of the screw force on the copper. Over time the electrical contact degrades, whcih cause more temperature due to contact resistance, and the copper becomes annealed, and the start of a burning point.

Part of maintenance in panels is to check the terminations points every 6 months to ensure that they remain tight.

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## AndyD

Yep the copper settles over time but if the wire was correctly prepared it's usually minimised. It's a habit of some to use linesman's pliers to twist the wire strands tight before putting the wire into the lug or cage clamp or if there's two wires they twist both wires together tightly. This just means the wires don't settle into the shape of the clamp as it's tightened and the contact area between the clamp and the wire is a lot less..... leading to higher resistance...... leading to heat.

Molex have a nice beginners guide to crimping, it's biased toward production line crimping but it's an interesting read and good info.

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Justloadit (08-Dec-15), mikilianis (23-Dec-15)

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## Justloadit

The issue is rather the electrician in most instances. How perfectionist is he, or is he simply trying to make a quick buck.

I love tools, and in many instances, I have tools which I may only use once or twice a year.The fact remains, that when I have used that tool, I am confident that what I have done will stand the test of time.I am a believer of doing your best at what ever I do, even if it is digging a hole in the garden. I like to get the right tool for the job.

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AndyD (08-Dec-15)

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## AndyD

Tools are important especially with processes like crimping, there's no substitute for using the correct crimper for the type and size of crimp you're using. I think your first point might be even more important though, the attitude of the person doing the work invariably reflects heavily on the quality of the finished job. I also used to think shoddy workmanship was about people trying to make a 'quick buck', I'm sure that's the motivation for some of the corner cutting I encounter almost daily but over the years I've started leaning more toward thinking it's a general personality deficit and simply a lack of pride or concern.

Maybe in the past there was an education angle as well, bad habits like old wives tales or urban myths get passed on from generation to generation. I know a few of the things I was taught by the journeymen and masters who were my mentors when I was an apprentice were not the best practices. In those days you just did what you were taught and there were very few ways to improve or verify your inherited knowledge but nowadays with the internet there's no excuse for not constantly checking and learning and keeping your knowledge accurate and up to date.

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mikilianis (23-Dec-15)

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## jkamuz

Just a quick question,  is the use of porcelain screw connectors compliant.  I prefer crimped joints.

Sent from my GT-I9100 using Tapatalk

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## AndyD

They're most commonly used internally in appliances like stoves, autoclaves, kilns and ovens where there's high temperatures. As far as I know there's nothing in the regs that would mean you can't use them but they wouldn't be the best or most appropriate connector for most applications.

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jkamuz (10-Dec-15), mikilianis (23-Dec-15)

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## Dave A

> Just a quick question,  is the use of porcelain screw connectors compliant.  I prefer crimped joints.


per SANS 10142-1
It's definitely not compliant with SANS 10142-1 for earth connections (a joint must require a tool to disconnect). When it comes to phase and neutral conductors, it is cable type dependant as I recall.

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jkamuz (10-Dec-15)

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## Ippi591

Thanks for that info AndyD, very informative (even 5 years later). I have a question though, is there a limit on how many milliseconds the RCD should take to trip? I did a check across 37 installed RCD's and the time range from 9 to 203 milliseconds.

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## Ippi591

I found a document, VC8035 From 1987, Compulsory Specification for Earth leakage protection units.

It lists the following times:



Are they still relevant?

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