Electrical Help Please

[MichaelJohn]

We built a house, almost a year ago, and used what I considered to be a very competant electrician. He used 3 pin sockets everywhere and earthed everything as standard. Very neat, consciencious etc.......

We had a storm the other day and according to my wife (as I didn't see it) there was a "flash" from the fuse box (8 chanel RCD consumer unit) and the power went off. (There was none of that electrical wire burning smell). When the electricity came back on there was no adverse effects.

However, the next day one of the showers didn't work. I tested it and it was getting electricity so I took it off, returned it to HomePro, who tested it and (as I saw) it was working just fine!!!

On returning the unit to the bathroom and testing the electricity I noticed that both the live AND the neutral were "live".

At the consumer unit, there's no returns which are live, isolating the shower circuit cuts the power correctly (but to both live and neutral).

Both showers are on seperate circuits; which do nothing else but the shower.

Although I will try any DIY I'm not confident with electricty (as i don't fully understand it) and would appreciate any helpful comments.

Many thanks.

PS we're near Sikhio (Korat) if anyone can recomend a (very) good electrician :-)

[phoneguy702]

How did you determine that both the line and neutral were live? If you tested the wires while they were all connected to the water heater then you may have made an error. The line and neutral both carry current and voltage when connected so you need to disconnect them from the heater to do the checking. Did the RCD trip open when your wife saw the flash, did it need to be "reset"?

When they tested the shower at homepro did it actually heat water or did they just look at the lights?

The storm may have sent a spike thru the electrical system which fried your water heater, which caused the flash. I suspect that once the heater is replaced your problem will be solved.

Others should be along shortly to either agree or disagree with me, you may pm me anytime if you have questions.

[Ticketmaster]

In addition, I have noticed that during a storm, the power will very often go off where I live right after a big lightening flash. I suspect that your wife saw a reflection of a lightening flash. I seriously doubt that there could possibly have been a flash from the consumer panel.

As says Phoneguy, you probably did not disconnect the wires before testing and you probably got a surge that fried a board in the water heater. You might want to install a Schneider SPD225 to protect against this. You can Google it.

[Crossy]

I'll put money on you having an open circuit neutral to your heater. Time to look for the dodgy taped joint hidden in the attic.

Only way to find it is to trace the wires back from the heater to the board (but do check all the connections are tight in the board first).

[MichaelJohn]

Thanks for all you comments. If I can reply to some of your points if may help more to determine the problem?

Phoneguy - I tested the live and neutral feed whilst disconnected from the shower and they both lit up the tester.

No, the RCD did not trip when there was a "flash" so no need for a reset - I question the "flash" too Ticketmaster??!

When I took the unit to HomePro I saw them connect electricity from a socket (live and neutral), they turned it on and the lights came on and hot water came out - so I'm reasonably confident that there's nothing wrong with the unit.

Crossy, what exactly do you mean by "open circuit neutral" - do you mean one that's mistakenly connected with a live?

Look forward to all you thoughts.

Many thanks.

[XINLOI]

What the local electrical rules don't tell you is that the neutral wire here, is actually L2 and it just as hot as L1. Don't know why they did this but we are stuck with it. If your system is truly grounded, take a voltmeter and test the heater feed to see if both legs have voltage on them. If not, look in the attic for a broken connection because they only twist and tape, which is poor at best for a connection, especially a high amperage one. Use a multimeter, not one of those LED devices that light up!

Edited April 28, 2013 by XINLOI

[Crossy]

What the local electrical rules don't tell you is that the neutral wire here, is actually L2 and it just as hot as L1. Don't know why they did this but we are stuck with it. If your system is truly grounded, take a voltmeter and test the heater feed to see if both legs have voltage on them. If not, look in the attic for a broken connection because they only twist and tape, which is poor at best for a connection, especially a high amperage one. Use a multimeter, not one of those LED devices that light up!

NO! Thailand is 3-phase 4-wire with a grounded neutral, single-phase supplies are taken from the neutral and one phase.

New installations should be wired TN-C-S with MEN (Multiple Earthed Neutral) and have a link between N and E in the distribution board, coupled with a local 1.8m ground rod.

I have seen reports of some small villages being 3-phase 3-wire (as XINLOI is describing) but they are the exception rather than the rule.

[Crossy]

Crossy, what exactly do you mean by "open circuit neutral" - do you mean one that's mistakenly connected with a live?

An 'open circuit' is just that, a break between one end and the other, as others have noted, time to look for the break.

You could be seeing what looks like a hot neutral if you are using a high-impedance measuring device (digital meter) by capacitive coupling to an unconnected wire or feed through the heater.

It shouldn't be beyond a local sparks to find and fix this fault.

[MichaelJohn]

Well guys, thanks for all you comments and advice; I've fixed it!

As you all suggested I went in the roof and hunted round for the connections - actually only one connection despite the wire passing through 3 junction boxes.

The neutral was live at this connection too so I disconnected from the shower etc to find the problem.

The bottom line was that the cable from the junction box to the shower was faulty - with only the live (black) connected both neutral ends (white) were live so there must be a short in the wire somewhere.

Having removed the wire from it's channel and tested it does indeed have a problem - push the black wire in a socket and the white is live!!!!

So, replacing the wire makes the shower function correctly :-)

It would have been a good test for trainee electricians about taking things for granted as I was scratching my head at times not believing the unbelievable.

Many thanks again for all your help.