Does a stove need to be on an earth leakage?

[kosmonooit]

As long at the external conductive surfaces are earthed on a stove, isn't that the major safety base covered? just asking ...

Also still wondering why you don't have a stove on EL if that specific plug/socket is used as per the regs? Why would that change anything to do with safety as far as EL / Residual Current is concerned?

Can't see any point in putting lights on EL, but if it makes one or the client feel safer, then why not, but using multiple units per sub circuit might make this less trouble.

[AndyD]

As long at the external conductive surfaces are earthed on a stove, isn't that the major safety base covered? just asking ...

People getting electric shocks is an extremely serious matter because a few milliamps traveling though some poor soul can cause their death. Electrical installations have a belt and braces approach to stopping people getting shocked. For someone to get shocked under normal circumstances requires that there's two serious faults happening simultaneously and either of these faults must, according to the regs, be repaired immediately upon being discovered.

Firstly we have the earth wiring which should prevent the chassis of any item or appliance from becoming at a voltage that can give someone a shock (touch voltage). There's a few problems with this, corrosion, poor connections and terminations, trailing cable damage and even missing connections often make the earthing inadequate or even ineffective. Add to this the fact that when it's tested by an electrician the tester being used actually passes a few miliamps through it during the test; even the best tester will only use a few Amps whereas under fault condition the earth wiring may need to carry hundreds or even thousands of Amps momentarily and invariably that's when any weaknesses show themselves. As soon as a single earth is missing or inadequate, the surrounding equipotential zone that was providing user safety then becomes your worst enemy.

Under normal conditions a missing or inadequate earth won't cause injury, it does however mean that if there's another fault on the same circuit it can be lethal.

Secondly we have insulation. This is the medium that separates the current carrying parts of the circuit from the other parts of the installation that can be touched by a user. It ensures that current stays withing the circuit and doesn't 'leak' out and find it's way to earth through unauthorized paths. Failure of the insulation and the potentially dangerous condition it can cause would be detected firstly by the earth leakage breaker which would usually trip when around 25(ish) miliamps is leaking. If there's a complete failure of the insulation then a much larger current will flow which will cause the normal circuit breaker that's supplying that particular circuit to trip. This only protects the circuit wiring from overload, it won't protect someone who gets a massive shock, they'll be long dead by the time a 10 or 20A circuit breaker has disconnected by tripping. Insulation faults are also deemed by the regs to require immediate remedy.

As with the earth fault, an insulation fault on its own won't cause injury or give a shock because the earth is preventing the faulty item developing a 'touch voltage'.

So no single fault will cause a shock but ignoring an insulation fault puts all the eggs in one basket leaving the earth as the only protection. Not acceptable. A circuit tripping an earth leakage breaker and being removed from the earth leakage protection...not acceptable.

Don't treat the symptoms, treat the actual cause. Find the damn fault and fix it.

Also still wondering why you don't have a stove on EL if that specific plug/socket is used as per the regs? Why would that change anything to do with safety as far as EL / Residual Current is concerned?

Can't see any point in putting lights on EL, but if it makes one or the client feel safer, then why not, but using multiple units per sub circuit might make this less trouble.

I'd suggest nowadays we should actually be using domestic DB's with dual e/leakage protection as a minimum with one E/L for the sockets and one for the remainder of the installation. There's no reason not to, the cost has reduced to such a point where it's no longer an issue and using two E/L breakers gives a safer installation without the annoyance of the entire power going off every time there's tripping. We should in fact be using RCBO's giving earth leakage protection on every single circuit individually but whilst they've been the norm overseas link1 link2 link3 link4 for the last few years they don't even sell them in any of the major SA wholesalers yet .

[Didditmiself]

Andy, what are RCBO's? Maybe someone else mentioned it but I missed it.

[AndyD]

An RCBO is similar to a normal circuit breaker but it also provides 30mA earth leakage protection as well as the standard overload protection on a circuit by circuit basis.

The average domestic installation has a single earth leakage breaker that protects the entire installation which introduces a few problems. For example a single earth leakage fault on only one of the circuits causes the entire installation to trip in most cases which certainly isn't ideal. Also many electronic appliances have an acceptable amount of background earth leakage during their normal operation. This background leakage can accumulate to a substantial amount if there's several PC's, TV's and fluorescent lights or LED drivers being supplied and it can cause annoyance tripping of the earth leakage breaker even though there's not actually a fault present.

Using RCBO's means that every individual circuit has it's own 30mA earth leakage protection so if there's an earth leakage fault on any one circuit, only that circuit trips.

This is a single pole RCBO, it only interrupts the live of the circuit, the neutral connection you can see is just for reference.



The problem with just interrupting the neutral with an earth leakage fault is that whilst the circuit will become dead the fault won't actually be cleared if it's N-E leakage. That's why it's better to use the type below which is 2-pole, it disconnects the live and the neutral together if there's a fault. (It's actually an SP+N type circuit breaker because it only provides overload protection monitoring on the live wire, not the neutral.)

[Justloadit]

I arrived recently from an overseas trip, and took note of the DB in the apartment I used. Interestingly, in this 2 bedroom apartment, two toilet, and lounge, there was 8 RCBO's separating lights in rooms, plugs in rooms, appliances. Each circuit breaker was numbered, and a table on the door indicated exactly what each circuit breaker was protecting. Any laymen by identifying the tripped breaker number would immediately be able to identify the fault location.

On second thought, I should have taken a picture when I looked.

I thionk we got a long way to go to follow this route. In my mind this is the way it should be done.

[AndyD]

That's pretty much the way we label as well. We number each circuit breaker and we provide a card in the door of the DB which states the current and curve of the breaker and exactly what each one is protecting. We keep a pdf copy of every legend card we make so we can easily provide a replacement if the original grows legs. Also we label the individual sockets, isolators and light switches with the number of the circuit breaker that supplies them.

The worst labeling I come across is usually in domestic premises, there seems to be a trend of just calling each circuit breaker either 'plugs' or 'lights' which isn't much use when there's numerous socket and light circuits. Also the adhesive labels should be outlawed, they always come adrift over time. All labeling should be traffolyte in my opinion.

[kosmonooit]

The requirements for labelling are quite clear in the regs, each circuit should be identified but it really depends on the effort & care that the installer is prepared to put in. Most of the time I see those stickers you get on sheets that just say "Plugs" "Lights" as you say but I agree indexing them to circuit descriptions, a sheet in the back of the db cover is a good idea, or even printed longer labels on the cover. For other labelling I use a Brother printer, it produces a durable label, perhaps in commercial installations when one has the means and the time to engrave labels, that would preferable.

What I do see often is the popular bad habit is gluing cut plastic sheet to cover gaps between circuit breakers, that definitely does not stand the test of time and falls of in a few years.

"Best Practices" ... seems lacking in the industry. And lets no go to what one sees in ceilings

[Justloadit]

Nice way Andy.

My current house has no door, but a crappy cover over the circuit breakers. The 2 screws holding the cover have stripped the thread from the DB side, so everything stands scew and at an angle. Over the years I have labelled a few of the circuit breakers, such as the geysers, out buildings and pool pump. Fortunately it is in the garage, so no one sees it. But darn what a crappy way of doing things.

[ians]

Just a note, a brand new stove plate out the box can trip an earth due to moisture. Stoves connected to earth leakage units are an expensive waste of time. Make sure earth is up to standard and you can go home and sleep without worrying.

[ians]

Having light circuits on earth leakage is another silly idea. Earth leakage trips, now you have to try find a torch or phone etc. The new south Africa load shedding has resolved this issue to an extent. How ever introduced a new pile of problems generator connections, inverters and solar power.

[AndyD]

........What I do see often is the popular bad habit is gluing cut plastic sheet to cover gaps between circuit breakers, that definitely does not stand the test of time and falls of in a few years.

"Best Practices" ... seems lacking in the industry. And lets no go to what one sees in ceilings

I don't think it's possible to compensate for shoddy workmanship with legislation. You can make as many rules and regs as you like, if a tradesman has no care and pride in their work you're always going to end up with a shoddy job outcome.

Nice way Andy.

My current house has no door, but a crappy cover over the circuit breakers. The 2 screws holding the cover have stripped the thread from the DB side, so everything stands scew and at an angle. Over the years I have labelled a few of the circuit breakers, such as the geysers, out buildings and pool pump. Fortunately it is in the garage, so no one sees it. But darn what a crappy way of doing things.

Some labels is always better than no labels but it should have been fully labelled when it was installed and also if the property has ever changed hands the labelling would need to be complete for the CoC to be issued.

Domestic DB's are notorious for stripped screws, they just have about two turns of thread in a piece of 0.9mm plate. We usually use a clinchnut tool (sometimes called rivnut) to put proper thread inserts in, it looks a bit like a pop riveter and it inserts a proper threaded bush that will never strip. You get a nice small portable version like this which will work up to an 8mm thread and it won't break the bank. We have also use a fancy hydraulic one in the workshop that can insert up to 12mm threads.

Having light circuits on earth leakage is another silly idea. Earth leakage trips, now you have to try find a torch or phone etc. The new south Africa load shedding has resolved this issue to an extent. How ever introduced a new pile of problems generator connections, inverters and solar power.

I think if a light circuit is on an RCBO it will only trip if there's a good and proper leakage fault on that actual circuit in which case it's a good thing to have it trip even if it is an inconvenience. You're right though if there's a single upfront earth leakage breaker for the entire installation it is a right royal pain if there's a tripping problem somewhere else that's causing the lights to go off as well.

[Justloadit]

Having light circuits on earth leakage is another silly idea. Earth leakage trips, now you have to try find a torch or phone etc.

One concern I have about the lights not being on a ELB, is when the glass part of an E28 screw globe comes unstuck from the base, and when you turn breaks off. Now one needs to get a long nose pliers to dig and catch the metal base to unscrew. I am always concerned that the wall switch, actually switches off the Live circuit. When this happens I do switch off the main switch for safety, but what about other people? I suppose with the new LED and CFL versions this may not happen.

[AndyD]

I think lighting, especially in domestic installations should be considered high shock risk. Light fittings are often replaced as fashion accessories by DIY'ers so poor terminations and missing CPC's are likely as well as DIY relocations where the entire fitting gets moved and the cabling extended. Light fittings have notoriously poor cable strain relief and it's not uncommon to see the screw in lamp holders connected the wrong way around where the body of the lamp cap (threaded part) is live and the center pin is neutral. Also as Justloadit says many people rely on the single pole light switch for safe isolation....which it isn't. There's numerous other reasons I'd consider them high risk including the fact that many cheaper electrical testers can't give a reliable voltage reading if the circuit is live and supplied by a dimmer.

[ians]

When the lamp breaks, you shouldnt be messing with a long nose pliers in it unless you have isolated the system.

We cant start fitting earth units to everything because people negligent. Then we might as well enforce a law that machine in factories should all be on earth leakage.

[ians]

This why it is so important that a real electrician carries out the work and a qualified tester does the testing properly.