mains outlet - only 80 volts!?! why ? (Australia)

Got a problem here .... just wondered what people might hypothesis could be wrong.

One of the dual power outlets in the kitchen was working fine on Friday morning. I actually charged my phone through one (the toaster and kettle are normally plugged into both). Anyway, the phone charged - and I then disconnected the transformers.....

Then later when another family member went to boil water, it wouldnt start ... same with the toaster.

Anyway when I checked it carefully with the DMM, the output at the outlet was only 80 volts?!! This is from the normal 240v (Australia).

I switched off that circuit and unscrewed it to look behind. Everything was fine... I even took the connections out of the plate and then put them back in. Put it back in,t urned the power back on - same, 80V.

The wire etc looked fine - the ONLY thing I did notice was that about

15cm (6in) up from the plug point on the wire, there was a bit of blackening. But, this flaked off a bit.

If there was a short, then wouldnt the circuit breaker have tripped ???

We have 2 safety switches installed two on all the circuits - so if there was electricity leaking to ground somewhere, wouldnt that have tripped too?

How is this staying at 80V? My thoughts were that if something had happened to the wiring somewhere in the wall, then there would be 0V. I cant understand the 80....if its working, 240V, otherwise no voltage.

ANY help/ideas would be GREATLY appreciated..... just wondering what could be causing it. I have called my electrician, but that will take some time. I'm not planning on doing anything stupid, but would like to know or have an idea why it might be like this.

Reply to
andrew_h
Loading thread data ...

--
If the circuit breaker hasn\'t tripped, My guess would be that
something in the receptacle has let go and the 80V you\'re measuring
 Click to see the full signature
Reply to
John Fields

Hypothesis. DMM too sensitive. Even the least bit of leakage could give a reading! Better to use a real lamp or at least a neon bulb? For example the apparent 80 volts is about one third of the normal 240. Assuming the DMM has an input resistance of say 10 megohms; a leakage of 20 megohms through a broken or faulty item such as a wall socket, due perhaps to burning etc. could result in a leakage current of 240 volts divided by 30 megohms. Thus 240/30 x 1000,000 = 8 microamps. And as we said that small leakage current could result in one third of the total voltage appearing across the DMM. Possible problem in the wall socket/outlet or back down the line somewhere; maybe the breaker for that circuit has/is tripped or faulty or has a slight leakage current (which may not necessarily be a faulty condition?) so that leakage current could perhaps be 'normal'? Not familiar with Australian wiring practice so can't comment further.

Reply to
Terry

All of that by John F is quite valid. But as well, a lamp plugged into this socket may prove that the 80volts is but a high impedance coupling to a DVM that is always too sensitive for mains power fault finding.

An important point for Australia is that anything behind the faceplate is the domain of a licensed electrician. No homeowner electrical work is allowed in Australia.

--
John G

Wot\'s Your Real Problem?
Reply to
John G

John G - actually no, that's not right.

Any electrical work CARRIED OUT by an electrician must be done so that it wold pass an inspection (which would.... NEVER ... happen), but there is nothing stoping any DIY person doing as much electrical work on their own house as they wish.

Thanks to all for your input and advice ... I'll wait for the electrician anyway.

Just a question - I've tested other power points on that circuit, and they are all fine (240v at outlets). If there was a fault in the wiring down to the kitchen powerpoint (that is faulty now), would all the outlets have a lower voltage, as they are all connected ??? Or not neccessarily?

Reply to
andrew_h

"andrew_h"

** Fraid it is right - d*****ad.

** Shame that last bit has been *illegal* across Australia for nearly a century.

For example: in NSW, the HOME BUILDING ACT of 1989 provides huge fines ( circa $20,000 ) for UNQUALIFIED individuals doing electrical wiring work.

formatting link

........ Phil

Reply to
Phil Allison

--
Not necessarily.

If all of the other outlets are OK, here\'s what I think is going on:
 Click to see the full signature
Reply to
John Fields

to the OP NO only the outlets past the bad connection will be 80 volts. Any on the supply side of the break will be normal voltage. You can tell if the kitchen (bad point0 is last by checking howmany wires arive at the connections. If there is only one on each connection then it is the end of the line. If there are 2 wires on each connnection then there is most likely another general purose outlet somewhere else down stream of the kitchen.

My suggestion to use a lamp overcomes trying to do calculations which at best are nebulus because of stray capacitive coupling . This discussion belongs more in alt.engineering.electrical even though most of the people there have USA experience.

On the subject of licensing. In some states (or maybe all) it is against the rules for an unlicensed person to fix an extension cord or replace a fuse. (For US readers, fuses were commonly installed only 10 or 15 years ago in household panels in Aus.).

--
John G

Wot\'s Your Real Problem?
Reply to
John G

The spelling in my previous post was terrible. I should try and only do one thing at a time.

--
John G

Wot\'s Your Real Problem?
Reply to
John G

A few weeks ago (bout 2) I charged a cordless drill battery on this outlet .... that was charging for hours (like 5+ hours). The transformer was extremely hot too (normal...but it was hot).

Could that have possibly caused some problems - i.e. heating up the outlet and then the heat moving back up the wire and burning it a bit in spots???

then this resistance slowly caused problems till friday when it all but stopped working ?

Reply to
andrew_h

A cordless drill charger would be considered a fairly light load, much lighter than a toaster or kettle so no, it should not have anything to do with the problem.

--
John G

Wot\'s Your Real Problem?
 Click to see the full signature
Reply to
John G

--
What is it that you don\'t understand about "if all the others on
that circuit work?
Reply to
John Fields

--
You should try _to_ only do one thing at a time. ;)
Reply to
John Fields

--
Yes, especially if the contacts between the wires and the socket
weren\'t good and tight.
Reply to
John Fields

-0800, "andrew_h" wrote:

that's not right.

done so that

but

work

their own house as they wish.

I'll wait for the

power points on that circuit, and

there was a fault in the

faulty now), would all the

connected ??? Or not

the other outlets are OK, here's what I think is going on:

| |

|

| | | |

| | |

you put your voltmeter across the outlets, the ones with no [R]

the voltmeter to read 240V, since that's what's across

with the [R] (resistance) in the line will keep

meter needs to read 240V from going into

we assume that your meter's resistance looks like 10 megohms,

there's 240V across it there'll be

microamperes

to so that it can

in series with the meter,

|

O | +------------+

resistance in the circuit will be greater than

meter, the current in the circuit

read lower.

it was

circuit would have to be:

I 8µA

means

flowing through your meter, must be

and the most likely place for that resistance to be is in the

isn't, then it's (scary) in the wiring to that

the last one in the daisy chain if

--

be 80 volts.

--
What is it that you don\'t understand about "if all the others on
that
 Click to see the full signature
Reply to
John Fields

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.