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

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.

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 - 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?

"andrew_h"

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

........ Phil

--- Not necessarily.

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

View in courier:

O O O O O | | | | | | | | | | | | | | |

As you put your voltmeter across the outlets, the ones with no [R] in them cause the voltmeter to read 240V, since that's what's across the outlet. The one with the [R] (resistance) in the line will keep the amount of current your meter needs to read 240V from going into the meter, so it reads low.

If we assume that your meter's resistance looks like 10 megohms, then when there's 240V across it there'll be

E 240V I = --- = ------- = 24 microamperes R 10E6R

of current in the meter, which it adds a zero to so that it can display "240"

Now, though, if there's a high resistance in series with the meter, the circuit will look like this:

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.).

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

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 ?

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.

-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.