Does a stove need to be on an earth leakage?

[AndyD]

............But during my testing I tried running the oven off an extension cable from my garage DB (3 phase E/L 30mA) and it never tripped.
House DB was the old Heinemann 3 phase 20mA sensitivity type.

Is the house DB the main DB? Is the 3-phase earth leakage breaker the 'main breaker'?

So this morning some more tests.
Removed oven earth and tested earth to oven chassis voltage when hot. 115v. Touched earth wire to oven chassis and trip.

If you've got a known tripping fault on an appliance why would you disconnect the earth wire then put power on it and attempt to do live tests? This is dangerous. On top of that the tests you were doing are not relevant and their results are likely to be misleading. Firstly with a stove or oven there's highly likely to be parallel paths to earth, secondly the voltage you measured would be highly likely to vary wildly depending on the input resistance of the particular voltmeter you're using.

If you suspect you've got a faulty element why don't you just disconnect and IR test the element with a mega tester at 500v? You can't accurately localise a fault by using the earth leakage breaker instead of the correct test equipment, you're just going to run yourself around in circles...... I can state with a high degree of certainty that if there's an earth leakage fault on an element it won't make any difference to the likelihood of the earth leakage breaker tripping if the supply voltage is 220v or if it's 240v.

[Sparks]

IR test is the only way to say as Andy said, but not just the oven element. The oven itself could have a wire causing it, it could also be one of the stove plates, depending on the switches as there is a common neutral throughout the appliance.

[hislordship]

I posted my findings not for the benefit of being told how to do or not do something.
I may not be a registered electrician, but my knowledge of electricity and wiring standards is far better than what I have seen done.
I have 24 years of experience with electricity, so I know my TT from my TN-C-S (and missing neutral issues), my single phase from my three phase, my cable sizing etc. Heck, I told City Power about the voltage issue I described a week before the actual fault showed up. I told them to check their transformers etc for the cause.


In answer to the questions:

The house and the garage DBs are independent of each other. Wiring runs as follows (large property):

METER DB FEED TO MAIN DB (NEXT TO METER DB AT THE SIDE OF HOUSE)

MAIN DB [NO E/L] FEEDS
(1) SWIMMING POOL DB
(2) HOUSE DB
(3) GARAGE DB
(4) BURGLAR ALARM FLOODLIGHT SYSTEM [ONLY SINGLE PHASE BOARD]
[1-4 ABOVE ARE E/L BOARDS]

(1) FEEDS ADDITIONAL WORKSHOP D/B
(2) FEEDS ENTERTAINMENT ROOM DB AND BOREHOLE DB
(3) FEEDS STAFF ROOM DB


My use of removing the earth was to confirm 100% that the element is faulty which it has, and also to try to find why it would trip at certain voltages and not others.
I don't possess an insulation tester, as mentioned I am not an electrician as occupation.

The stove doesn't trip when using any of the plates, the warmer drawer or when using the grill option (top of oven, dual element).
Only the normal bake oven trips the power. So it must be either the new bottom bake element or the smaller of the two on the top element (around 20 years old).

As stated, the element doesn't trip consistently, so difficult to run it to see which on trips. Hence disconnecting the earth wire. This showed up the leakage to the chassis. On disconnecting the bottom element, the leakage disappeared.
PROBLEM SOLVED (also eliminates the top element as there was now NO leakage with it still connected).

I forgot to mention, on switching the oven on (without earth), the leakage shows up immediately, but at a much lower voltage (8v or so). it gradually rises as the element heats (obvious). BUT touching the earth to the chassis causes no trip 90% of the time, even when reading 115v chassis to earth. I tried touching it back 10 times, and only once did it trip. Did this mostly out of curiousity.

Yes removing the earth is not recommended, but I can tell you that the appliance was still on earth leakage, and also that no on else was allowed near the thing, even pets. I am very careful, excessively so. There was no risk to me at any point. No touching the chassis, no touching any of the wires directly.


Regardless of what you think, I can guarantee you the element NEVER trips at 220v or below. Any voltages above that and it will start tripping. If you don't believe me, you are welcome to the element to conduct tests. Collect from me in Randburg.

Why I posted this in the first place? To let everyone know that such an odd situation can arise. Not to find the problem. I've done that.
Also not to be sermonised on my methodology.
Remember, I didn't correct your incorrect use of it's (abbreviation of it is) vs its (possessive) and there's (there is) when you mean there are, i.e. as a plural.

[AndyD]

.....Why I posted this in the first place? To let everyone know that such an odd situation can arise. Not to find the problem. I've done that.
Also not to be sermonised on my methodology.

I'm afraid we're going to have to agree to disagree on several points here and I can understand why you might see it that you're a victim of sermonising or your competence is being questioned but that isn't my objective.

The problem I had was that you've posted your fault finding endeavours as a fait accomplis and as something of a tutorial or reference for future readers on a public forum. The tests you've done are inconclusive but far more importantly, the minute you disconnected the earth wire and made the appliance live, they crossed the line and bacame dangerous. On a personal level I can't and never will be able to walk on by and not offer what I'd hope is a balanced reply to highlight hazardous practices and deter future casual visitors to the forum from believing that this may be acceptable practice and from doing the same.

My use of removing the earth was to confirm 100% that the element is faulty which it has, and also to try to find why it would trip at certain voltages and not others.
I don't possess an insulation tester, as mentioned I am not an electrician as occupation.

The stove doesn't trip when using any of the plates, the warmer drawer or when using the grill option (top of oven, dual element).
Only the normal bake oven trips the power. So it must be either the new bottom bake element or the smaller of the two on the top element (around 20 years old).

As stated, the element doesn't trip consistently, so difficult to run it to see which on trips. Hence disconnecting the earth wire. This showed up the leakage to the chassis. On disconnecting the bottom element, the leakage disappeared.
PROBLEM SOLVED (also eliminates the top element as there was now NO leakage with it still connected).

I forgot to mention, on switching the oven on (without earth), the leakage shows up immediately, but at a much lower voltage (8v or so). it gradually rises as the element heats (obvious). BUT touching the earth to the chassis causes no trip 90% of the time, even when reading 115v chassis to earth. I tried touching it back 10 times, and only once did it trip. Did this mostly out of curiousity.

Yes removing the earth is not recommended, but I can tell you that the appliance was still on earth leakage, and also that no on else was allowed near the thing, even pets. I am very careful, excessively so. There was no risk to me at any point. No touching the chassis, no touching any of the wires directly.

In this post I've quoted you've spent the majority of it justifying a method of testing that is blatently dangerous and should never be done under any circumstances. There is no justification. 'Careful' isn't enough ....even someone who is trained and has the appropriate experience and equipment to work live would still identify and assess the risks for every stage of every job and then have a pre planned strategy for effectively managing them.

You've also reinforced a common misconception when you imply above that working live isn't so bad because there was still an earth leakage breaker to protect you. If you understood how an earth leakage circuit breaker works you'd know how dangerous that assumption is. It's not the first time I've seen statements like that so I'm going to give you some facts;

• The electrical supply is 50 Hz which means there's 50 complete cycles per second.
• Each cycle has full voltage twice, once in the positive and once in the negative hence the voltage is at its full value 100 times per second (every 10 milliseconds).
• An earth leakage circuit breaker is considered fully functional if it trips in 200 milliseconds for a 30mA fault.
• An earth leakage circuit breaker is considered fully functional if it trips in 40 milliseconds for a 150mA fault.
• An earth leakage circuit breaker is considered fully functional if it trips in 40 milliseconds for any leakage fault greater than 150mA.

Earth leakage circuit breakers are great for detecting potentially dangerous faults and disconnecting the circuit before someone gets a shock by tripping.
If you're the only path to earth because you've disconnected the earth wire and you've made direct contact with something that's live then a massive fault current can flow through you for 40 miliseconds meaning you get a full voltage shock 4 times before the earth leakage disconnects....and that's assuming it's working correctly. There's a very high likelihood of serious injury or death. Earth leakage breakers are only considered as supplementary protection (not primary protection) in the electrical regs for good reason.


Working on live circuits or appliances is unacceptably risky even for experienced electricians, disconnecting the earth wire first and then working live is even worse, downright reckless in fact.
Please don't do it, ever.

[Festi]

Good day

I have a strange stove EL problem. When using a certain plate on the stove, we tend to set it to max and turn it down once the cooking temp is reached.
From time to time when 'switching down', it trips the EL. Max is '9', this trip happens even if the switch is set to 8.

A good few years ago I had the same issue in another house, when I had an electrician out he said the stove earth did not need to go through the EL and made the changes. As far as I knew at the time, the stove was still earthed, just not through the EL.

Am I sitting in the same situation?

[Festi]

Just a bit more info - when the switch is on '9', the switch clicks, and clicks again when setting to '8'.

Problem does seem to be more prevalent when any other plate is also on. although not always the case.

[AndyD]

Is it the spiral type or the solid heating plates?

[Festi]

Morning Andy

Solid plates. switches turn like a volume control - click to start, smooth up to 8, then click onto 9. It's when turning from 9 down that the ELS trips. so from the MAX click.

[AndyD]

It's a bit odd, I thought the stoves with spiral plates had the type of temperature controller you describe and the stoves with solid plates click between every different setting. Also, don't the solid plate controls only have 5 or 6 temperature settings?

Can you attach a photo please?

Maybe one of the domestic sparkies can give you better info than me, it's not the kind of thing I usually work on so I'm not so familiar with it.

[Festi]

Thanks Andy

I did speak to Sparky, he suggested there could be a fault with the plate/s. I do not suspect the EL, this was replaced already, was very finicky when we had bad weather. After speaking to another electrician about this issue he suggested I get the EL changed then, the brand was a very fong kong type.

The stove we have is an AEG hob, all 4 plates work the same way - 0 clicks and then smooth up to 8, clicking to 9 (max) and then clicking when turning back to 8 and lower.

Switch are located on the oven.