Can anyone explain this?

[Negita43]

I recently bought an extension lead – it’s just what I needed – 3 multinational sockets USB types A and C and it is switched – one switch

So far so good when I got it, I put a socket tester in and it showed reversed live and neutral.

I tried to open the unit to look at the wiring without success so I decided to cut the cable and rewire it with my own plug.

Inside the cable there was a Brown, Blue and the Yellow and Green sheaths. The product is made in China and I guess it was made for the American/Japanese markets and as the plug is the same in Thailand and some bright spark (forgive the pun) thought they would sell it here.

Anyway I wired my plug Brown – Live, Blue Neutral, Yellow and Green Earth – put in the socket tester and it came up with Live and Neutral reversed again (see pic 1).

Ok I thought I’ll just swap the Brown and Blue in the plug.

When I put the socket tester in it came up Live and Earth reversed! (see pic 2).

I am somewhat confused as to what is going on except to more than suspect that this extension lead has not been wired to the correct colour coding and that the earth (Yellow and Green) is being used as a Live or Neutral.

There are 6 combinations possible and if I start using the Yellow and Green as a live or neutral at some point it’s going to trip the RCB.

I did think about making up a short lead with two plugs and using this to pass current through the unit and then test the cable with a meter to see which was the live cable that would then leave only 2 possibilities for the earth and neutral – would that work?

Anyone with more electrical knowledge than me have any ideas based on the information above?

I know the simplest solution would be to dump the unit and buy another – but I hate being beaten by inanimate objects!

Pic 2 appears first I don't know why

 

 

Edited January 1, 2023 by Negita43
clarification of pic number

[steven100]

Crossy is the good electrical guy on Asia Now so when he reads your topic he'll probably give you the answer.

[OneMoreFarang]

1 hour ago, Negita43 said:

I know the simplest solution would be to dump the unit and buy another – but I hate being beaten by inanimate objects!

This thing is obviously dogy. And if you "fix" that your test plug shows it correctly what did you actually "fix"?

If someone switched the wires what can you expect from the rest of that thing?

Will you trust that the USB electronic is properly isolated? I wouldn't.

Dump it!

Or to satisfy your senses open it, if necessary with a saw and look inside. And then dump it.

 

Just in case if you need a reminder what could be wrong, watch this or any other of his USB charger videos.

 

 

[Social Media]

What do you get when you plug that tester into the wall socket thats feeding that extension ?

 

Many Thaj properties dont have 3 connections only 2. Despite having 3 pins.

[NoDisplayName]

Do you have a multimeter?

 

Check continuity to see which of the plug prongs are connected to which of your outlet holes.

 

And what about that socket tester?  Could that be dodgy?

[Negita43]

11 hours ago, NoDisplayName said:

Do you have a multimeter?

 

Check continuity to see which of the plug prongs are connected to which of your outlet holes.

 

And what about that socket tester?  Could that be dodgy?

Thanks - yes I have a multi meter

The cable has been cut so I can't test the plug to outlet socket - but I wish I had thought of that before.

I built the house maybe 10 years ago and all electrics on the socket circuits are correctly wired with an earth - all earth wires go to a copper rod in the ground outside. The socket tester works fine on all the sockets in the house. I am confident the issue is with the extension wiring.

[SomchaiDIY]

filter circuits inside product can make false reading at socket tester

best use continuity test

[degrub]

Would the AC to DC inverter silicon chip for the USB ports also cause issues with the tester ? 
And the continuity check ( resistance)  measurement ?

 

 

[terryq]

It could be that the tester is not made for Thai sockets.

 

Thai 3 pin socket outlets have the live on the left, neutral on the right and earth at the top when looking from the front.

In the UK (and most of the world} the live and neutral are transposed.

 

Live can easily be checked by neon screwdriver

 

 

[4MyEgo]

[Negita43]

Major apologies and an update

1.      The plug at the pin end was wired correctly. ( I cut the cable at the moulded plug end and tested to the pins).

2.      Continuity testing using my rig (see pic) as follows:

3.      Multimeter set to diode setting

Switch OFF.

Ground to Ground Continuity

Neutral to Neutral (Blue) Continuity

Live to Live (Brown) No Continuity

No continuity between other combinations

Switch ON

Ground to Ground Continuity

Neutral to Neutral (Blue) Continuity

Live to Live (Brown) Continuity

As a layman that’s exactly what I would expect – the switch disconnects the live feed.

I then realised that maybe I had not checked one thing.

Socket tester with unit power switch on extension lead ON shows correct wiring Live/Neutral correct.

Socket tester with power switch on extension lead OFF shows live and earth reversed.

I’m still confused but maybe this extra information will help others who know more give me an explanation

[Crossy]

Your problem is those "universal" outlets.

 

The UK has the L&N transposed with respect to Thailand, so whichever way round you wire it will be "wrong" for one or other.

 

Hook up your new plug so that it's "right" for the plugs you use most with the extension.

 

Note that Thailand should be "Live on the Left" when you look into the outlet with earth at the top. It's not totally clear but is your new plug actually correct? (I also see rather more bare-copper than I'd like)

 

Most (all) modern appliances don't really care about L-N polarity but it's best to be correct.

[NoDisplayName]

1 hour ago, Negita43 said:

Socket tester with unit power switch on extension lead ON shows correct wiring Live/Neutral correct.

Socket tester with power switch on extension lead OFF shows live and earth reversed.

I'm not an expert at this.....but I do recall reading somewhere that some power strips may be capable of automatically switching N/L if reversed.

[Sophon]

1 hour ago, Crossy said:

Your problem is those "universal" outlets.

 

The UK has the L&N transposed with respect to Thailand, so whichever way round you wire it will be "wrong" for one or other.

 

Hook up your new plug so that it's "right" for the plugs you use most with the extension.

 

Note that Thailand should be "Live on the Left" when you look into the outlet with earth at the top. It's not totally clear but is your new plug actually correct? (I also see rather more bare-copper than I'd like)

 

Most (all) modern appliances don't really care about L-N polarity but it's best to be correct.

To me it looks like neutral is on the left

[Crossy]

3 minutes ago, Sophon said:

To me it looks like neutral is on the left

 

Yeah, I was being slightly more diplomatic ???? 

 

'Tis incorrect.

[Crossy]

7 minutes ago, NoDisplayName said:

I'm not an expert at this.....but I do recall reading somewhere that some power strips may be capable of automatically switching N/L if reversed.

 

That's not something I've ever come across, it would be awfully expensive to implement with really little added value.

 

[Crossy]

1 hour ago, Negita43 said:

Socket tester with unit power switch on extension lead ON shows correct wiring Live/Neutral correct.

Socket tester with power switch on extension lead OFF shows live and earth reversed.

 

These little testers are easily confused so really should be considered a quick check, if they show something awry start checking.

 

The question is, are you going to plug in Thai appliances (leave it as it is - but please tidy up the wiring in your plug) or UK appliances (swap Land N in your plug).

 

EDIT I'm assuming that the wall outlet does test as "Correct" of course.

 

[unheard]

1 hour ago, NoDisplayName said:

I'm not an expert at this.....but I do recall reading somewhere that some power strips may be capable of automatically switching N/L if reversed.

You probably think of the Ethernet NICs crossover detection feature.

All modern switches detect and apply an internal crossover when necessary.

[Negita43]

Crossy - I take your point about the bare wire - it was a quick wire up to test only.

The live and neutral are correct (brown to the left, blue to the right - and the socket tester confirms this) what worries me more is that when the extesion lead's switch is OFF and certainly the plug sockets do go off - tested with a lamp - the socket tester shows Live and Earth reversed yet when I continuity test just  the cable switching off the switch removes continuity on the live - which is what I would expect. 

Now take a look at these two videos - one with the switch on the unit ON and one with it OFF - Notice with the switch ON the Desk Lamp is ON, the socket tester is correct and the charger lights are solid green

With the unit's switch OFF the Desk lamp is OFF (although it flashes for about 20 seconds when I switch the unit off) and all the lights for the USB charger are flashing and  how even the unit's blue indicator light keeps flashing.

My feeling is that there must be someting not quite right inside the extension leads casing

 

 

  Sorry can't get rid of this grey area

 

[Crossy]

That your tester is still showing "something" when you open the switch means you are possibly not opening the "real" live. You may really be opening the real neutral which can certainly confuse some testers (particularly if you have other stuff plugged in - even the internal electronics of the USB outlets), an open neutral may also explain the flickering of the desk lamp as it turns off.

 

Please re-test with nothing else plugged in to your strip.

 

Not that I don't believe you, but please post a better photo of your plug wiring.

 

In reality, if it's reading right with the swich on then you are good to go. The switch may be opening the neutral but it's not really a hazard unless you start poking your fingers around and relying on the switch as isolation (unwise).

 

This is what looking into the outlet (or at the back of the plug) should be like (US terminology - Hot = Live).

 

[Negita43]

Thanks Crossy really apprecioate your help now (and over the years), Here is a picture of the plug - the bare metal will be rectified IF (no longer considering when!) I can get the unit sorted.  - more info - the blue indicator light on the unit stays on even with the  unit switched OFF  and the socket tester shows Live/Earth reversed. With the unit switched ON the socket tester shows correct wiring. Don't you think that this indicates something amiss inside the unit? And I have just realised it's showing 225 Volts even with the unit switched off BUT the desk lamp if plugged in goes OFF!

Edited January 2, 2023 by Negita43
added something

[Crossy]

Well task A. would be to correct your plug wiring. Live (brown) goes on the Left looking at the back of the plug when the earth is at the top. 

 

That may well cause a L-N reverse on your tester but it should then go off when you open the switch (which will then be in the real live).

 

The problem with these little testers is they are very simple and easily confused. You are giving it a L-N reverse AND an open neutral. With two faults the indication could be almost anything. As noted earlier, they are a guide only, anything they tell you is wrong should be taken with a pinch of salt.

 

The L-N being swapped at the outlets is incredibly common on these units with "universal" outlets (as explained in my earlier post).

 

Have you checked the wall outlet with your tester, just in case?

 

Personally, I'd fix your plug wiring, make sure the switch really opens the actual live so everything goes off when you open it, and leave it alone, it will be fine.

[OneMoreFarang]

Whoever did this, even if it is temporary, shouldn't work with main voltage!

[Mavideol]

21 hours ago, Negita43 said:

The product is made in China

there is your answer

[Negita43]

Thanks Crossy But I am confused - The socket tester shows correct wiring on every socket I have tested in the house - I know the wiring is correct on these circuits because I have inspected a couple.

So I wired the plug to conform with the socket tester showing  correct wiring. Now I have changed it to to your recommendation the socket tester shows Live and Neutral reversed (which is why I changed it in the first place).  I bow to your superior knowledge and will leave the plug as you say. However it is definitely switching OFF the neutral not the live. I am not comfortable with this and I am going to dump it. Thanks again for your constructive and sensitive help.

[Crossy]

13 minutes ago, Negita43 said:

However it is definitely switching OFF the neutral not the live. I am not comfortable with this and I am going to dump it.

 

Does the tester actually go off completely when you turn off the switch now?

 

If it does, then I suspect you are mistaken, but no harm done if you ditch the beast (or just don't turn off the switch).

 

I no longer buy extensions; I prefer to make my own then I know they are wired correctly and have sensibly sized wiring.

[Sophon]

19 minutes ago, Negita43 said:

Thanks Crossy But I am confused - The socket tester shows correct wiring on every socket I have tested in the house - I know the wiring is correct on these circuits because I have inspected a couple.

So I wired the plug to conform with the socket tester showing  correct wiring. Now I have changed it to to your recommendation the socket tester shows Live and Neutral reversed (which is why I changed it in the first place).  I bow to your superior knowledge and will leave the plug as you say. However it is definitely switching OFF the neutral not the live. I am not comfortable with this and I am going to dump it. Thanks again for your constructive and sensitive help.

A pic of a Chang socket, which conveniently have indications for L/N/E:

[Negita43]

1 minute ago, Crossy said:

 

Does the tester actually go off completely when you turn off the switch now?

 

If it does, then I suspect you are mistaken, but no harm done if you ditch the beast.

 

I no longer buy extensions; I prefer to make my own then i know they are wired correctly and have sensibly sized wiring.

1. The tester does not show a voltage but the Live/Earth reversed lights come on.

2. The reason I know it's switching the neutral is that this extension was bought to power a small project outside with a socket (all the testing till now was not using this) if I plug the socket tester into the outside socket connected to different old extension lead it shows correct wiring - as soon as I change to the new extension it shows reversed live/neutral.

If I then use one of these "Mains tester screwdrivers" (not recommended I know) on this outside plug  with the old extension lead it shows live in the live hole (technical term) as marked on the socket - if i use it with this new extension lead it shows the neutral  hole as live! (I couldn't use the mains tester directly on the new lead as it is shuttered).

Crossy, have a SPARKsling New Year and thanks again.

[Negita43]

11 minutes ago, Sophon said:

A pic of a Chang socket, which conveniently have indications for L/N/E:

Yes thank you - I have 2 of these in my kitchen bought from HomePro although I think you will find most of the standard unswitched

Thai plugs also show the same indications after you prize off the cover.

Edited January 2, 2023 by Negita43
word added

[Negita43]

EPITAPH

Finally got the unit open (2 screws under the label as well as the 4 under the feet)

It's not easy to see but it looks like the live which goes through the switch then links to the right hand side of the socket and the blue goes to the left hand side when viewed from the front I think this is the opposite of what Crossy says  it should be based on the plug wiring.  I might try re-make correctly then I guess that the two red wires that go to the pcb will also need to be reversed to correct the issues I was having when I reversed the plug  to get the socket tester to show a correct connection.