Dodgy power outlet?

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nickb800

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#112511 11-Dec-2012 15:44

Just moved into a new flat, and after getting a little buzz from my macbook case (not as dodgy as it sounds, well documented as occurring when using non-earthed duckbill style power adaptors), I went around the place with my outlet checker (same as this, but Hamer branded http://www.jaycar.co.nz/productView.asp?ID=QP2000). Most outlets came out fine, except for a couple which indicated 'earth not connected' (L-E light up, but not L-N).

Can someone put this in perspective for me - how bad is this? How reliable are such testers, given that it did indicate most outlets in the house were fine?

One outlet is a shaver outlet in the bathroom that is rarely used, the other is in the middle of the kitchen and heavily used with phone/laptop chargers, microwave, router, phone.

Landlord is really good, will get them to book a sparky if it is indeed a problem, but would like to know how hard to push if you know what I mean.

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#730559 11-Dec-2012 15:55

I'd push pretty hard. It's not a difficult fix either, odds are the earth wire's just come disconnected from the back of the socket. Seen it pretty often in old places. Got a shock a few times from my old PowerBook case when connected to a socket missing earth.

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hellonearthisman

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#730561 11-Dec-2012 15:55

Bathroom power should have an RCD built into the power socket. Try and get that upgraded if you can as I think there are rules about power outlets in wet areas.

Your 'Power Point and Leakage Tester' sounds ok, it's reliable on all but one socket and it's seems to be always wrong on the other two.

If you getting a sparky in then you could also them to test the other power sockets, pointing out the kitchen one and ask why? Maybe they have RCD's on the fuse box. That would be sweet.

dontpanic42

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#730574 11-Dec-2012 16:00

Sounds like those outlets might be RCD protected outlets.
The Neutral and Earth conductors are always separated from each other in an RCD situation, as the RCD has to be measuring the difference in current between all terminals/conductors.
In most home distribution boards that are not protected by RCDs, the Earth and Neutral bars are usually connected.

I suspect your plug checker is determining if Earth is connected by doing a loop test through earth and neutral.

That being said, if you still feel unsure about it, by all means, get a registered electrician in to check it out.

nickb800

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#730581 11-Dec-2012 16:07

Great, just the kind of advice that I was looking for.

Its a 1970s place, so no sign of an RCD anywhere, and about half of the circuits are still on old school circuit breakers or fuses. Clearly a previous owner had a hankering for DIY, theres some pretty creative stuff around, not just electrical.

Will flick the landlord a text, and make sure I'm home when the sparky comes.

On a related question, since I've had a closer look at the electrics: my bedroom is in a sleepout which has one 1.5mm^2 TPS cable running at least 10m to feed a sub-board in the sleepout, which in turn feeds four double powerpoints and a couple of light circuits. For those that know the electrical code, would four double outlets be too much for a single cable run of that diameter and length? Intuitively it would be too much if all outlets were loaded to their max (i.e. 80A !) but I'm not sure what sort of margin is allowed for in the code

nickb800

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#730584 11-Dec-2012 16:10

dontpanic42: Sounds like those outlets might be RCD protected outlets.
The Neutral and Earth conductors are always separated from each other in an RCD situation, as the RCD has to be measuring the difference in current between all terminals/conductors.
In most home distribution boards that are not protected by RCDs, the Earth and Neutral bars are usually connected.

I suspect your plug checker is determining if Earth is connected by doing a loop test through earth and neutral.

That being said, if you still feel unsure about it, by all means, get a registered electrician in to check it out.

Cant see any sign of an RCD anywhere in the house, including the switchboard. The socket tester also tests RCDs, and when the 'trip' button is pressed, the circuit doesnt trip, even on a 100mA test

Bung

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#730611 11-Dec-2012 16:28

nickb800: Just moved into a new flat, and after getting a little buzz from my macbook case (not as dodgy as it sounds, well documented as occurring when using non-earthed duckbill style power adaptors), I went around the place with my outlet checker (same as this, but Hamer branded http://www.jaycar.co.nz/productView.asp?ID=QP2000). Most outlets came out fine, except for a couple which indicated 'earth not connected' (L-E light up, but not L-N).

Can someone put this in perspective for me - how bad is this? How reliable are such testers, given that it did indicate most outlets in the house were fine?

One outlet is a shaver outlet in the bathroom that is rarely used, the other is in the middle of the kitchen and heavily used with phone/laptop chargers, microwave, router, phone.

If it's an old style shaver outlet there won't be an earth as it is an isolating transformer.

That tester may be same as this recall? http://www.jaycar.com.au/news.asp?ID=1281

Your circuit should only have around 16A as a breaker so forget 80A load.

gregmcc

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#730619 11-Dec-2012 16:37

nickb800: Great, just the kind of advice that I was looking for.

Its a 1970s place, so no sign of an RCD anywhere, and about half of the circuits are still on old school circuit breakers or fuses. Clearly a previous owner had a hankering for DIY, theres some pretty creative stuff around, not just electrical.

Will flick the landlord a text, and make sure I'm home when the sparky comes.

On a related question, since I've had a closer look at the electrics: my bedroom is in a sleepout which has one 1.5mm^2 TPS cable running at least 10m to feed a sub-board in the sleepout, which in turn feeds four double powerpoints and a couple of light circuits. For those that know the electrical code, would four double outlets be too much for a single cable run of that diameter and length? Intuitively it would be too much if all outlets were loaded to their max (i.e. 80A !) but I'm not sure what sort of margin is allowed for in the code

First problem, minimum size of a submain is 4mm2, so 1.5mm2 is not right.

gregmcc

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#730623 11-Dec-2012 16:42

nickb800: Just moved into a new flat, and after getting a little buzz from my macbook case (not as dodgy as it sounds, well documented as occurring when using non-earthed duckbill style power adaptors), I went around the place with my outlet checker (same as this, but Hamer branded http://www.jaycar.co.nz/productView.asp?ID=QP2000). Most outlets came out fine, except for a couple which indicated 'earth not connected' (L-E light up, but not L-N).

Can someone put this in perspective for me - how bad is this? How reliable are such testers, given that it did indicate most outlets in the house were fine?

One outlet is a shaver outlet in the bathroom that is rarely used, the other is in the middle of the kitchen and heavily used with phone/laptop chargers, microwave, router, phone.

Landlord is really good, will get them to book a sparky if it is indeed a problem, but would like to know how hard to push if you know what I mean.

if L-E lights up, but L-N doesn't then that tells me that the netural is not connected. (and that this tester is a bit dodgy)

As far as the shaver outlet goes, that would be a correct test as the outlet is fed thru a really small isolating transformer that's why there is nothing from L-E or N-E

The other socket, most likely the pins on the outlet have spread apart over time, been 1970's vintage that is no surprise.

nickb800

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#730639 11-Dec-2012 16:56

Okay, slightly ambiguous results, but sounds like a visit from the sparky is definitely in order.

Thanks everyone for their collective wisdom. The effect of an isolating transformer on the shaver outlet's test makes sense to me.

Off the dodgy point in the kitchen is a multiboard feeding several non-earthed devices (chargers etc), so unless the near new multiboard is connecting earth and neutral, I guess we can infer that neutral is connected, and thus the tester is doing something funny?

dontpanic42

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#730755 11-Dec-2012 19:14

gregmcc:
First problem, minimum size of a submain is 4mm2, so 1.5mm2 is not right.

Agreed. If it is in fact 1.5mm2 TPS, that's some seriously dodgy stuff there for a sub-main.
Get that checked ASAP.

nickb800

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#731987 13-Dec-2012 12:39

Bung:
That tester may be same as this recall? http://www.jaycar.com.au/news.asp?ID=1281

Your circuit should only have around 16A as a breaker so forget 80A load.

Thanks for pointing that recall out, I got in touch with Hamer and they affirmed that their model is unaffected, its only that specific Digitec branded model that is affected

richms

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#732211 13-Dec-2012 19:00

If it is showing nothing on L-N and connected 2 pin devices are working in the outlet, the tester is is defiantly wrong.

And 1.5mm to an outbuilding is fine if it is breakered appropriately. There were also some changes in one of the revisions that allowed for stepped wiring sizes that eliminated the need for breakers in the outbuilding in some situations, but I know there was massive confusion about at the time it came in and both sparkys I know are still putting in breakers in outbuildings because they feel its the "right" thing to do.

Richard rich.ms

mjb

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#732221 13-Dec-2012 19:22

dontpanic42: Sounds like those outlets might be RCD protected outlets.
The Neutral and Earth conductors are always separated from each other in an RCD situation, as the RCD has to be measuring the difference in current between all terminals/conductors.

No, they're not separated any differently than a "normal" non-RCD protected circuit - E-N are still bonded at the distribution board, but not *after* the RCD, or the RCD would always be tripping.

an RCD only measures the difference between Phase and Neutral - if that differs by more than the rated limit, it'll trip.

dontpanic42: In most home distribution boards that are not protected by RCDs, the Earth and Neutral bars are usually connected.

I suspect your plug checker is determining if Earth is connected by doing a loop test through earth and neutral.

No - E-N should be bonded on *any* mains distribution board (in NZ), and if it's not, that's a serious problem.

That would be the correct test for the tester to do - even through an RCD, as long as the loop check doesn't exceed the current limit of the RCD, or it'd trip ;)

dontpanic42: That being said, if you still feel unsure about it, by all means, get a registered electrician in to check it out.

Absolutely - never gamble with potential mains problems..

(always happy to be corrected - especially by a registered sparky!)

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gregmcc

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#732235 13-Dec-2012 19:41

And 1.5mm to an outbuilding is fine if it is breakered appropriately. There were also some changes in one of the revisions that allowed for stepped wiring sizes that eliminated the need for breakers in the outbuilding in some situations, but I know there was massive confusion about at the time it came in and both sparkys I know are still putting in breakers in outbuildings because they feel its the "right" thing to do.

Only if it is one circuit, but as soon as you put a splitter box the end then it's a sub main, the minimum size must then be 4mm2, the OP has quite clearly said there is a sub board on the end of the 1.5mm2 so the minimum size must be 4mm2

richms

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#732236 13-Dec-2012 19:42

Unless the building is transportable or some other loophole I cant remember to get away with being cheap with cable.

Richard rich.ms

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