House mains electricity issues

[akis]

What is the "neutral" wire connected to outside the house ? Is it connected to the earth at the nearest transformer station? What is the difference between the neutral and earth? What happens if you plug in an appliance that its neutral connects to earth?

[Zero999]

1) It depends on the earthing system. As far as I'm aware TN-C-S seems to be most common in the UK. The neutral and earth conductor surrounds the live, forming a co-axial cable, running from the substation to the property.

https://en.wikipedia.org/wiki/Earthing_system

2) In a modern property, the neutral goes through the RCD in the consumer unit and the earth does not. In an old property there's no difference, except it can often be disconnected by a double pole isolator where it enters the property.

3) A device's neutral should never connect to earth. If it does, there's a good chance it will trip the RCD, as it will detect an imbalance in currents between the live and neutral.

[akis]

I have one of those bathroom shaver sockets (with a small transformer attached). I wire it to the nearest light switch but there is no neutral in the light switch so I use the switches earth. It works fine until I try to turn the lights on. Then fireworks and fuses pop out. No RCD in the house. What happened?

[HackedFridgeMagnet]

You wired it wrong. So don't do any more house wiring till you know what you are doing.

The neutral and active are for carrying the power.
The earth is not normally meant to conduct any electricity, it is only there for safety reasons.
Neutral and earth are tied together in TN-C-S in the building and connected to an earth stake, but they have different roles.

Get your house wired with RCDs on each circuit. They are that good.

[Delta]

Pardon my french, but you are a fucking idiot.  Please don't ever do anything like that again.  In fact, PLEASE don't touch mains wiring again - that shit will kill you or someone else.

"There was no neutral so I just used the earth instead"!  If electricity doesn't kill you for doing such a thing, a mob of angry electricians will.

[james_s]

While I agree that the OP should call an electrician for this one, I'm at a loss as to why it worked until the light was turned on. While not safe, it should technically work when connected between the live in the switch box and earth and it shouldn't make any difference whether the light is on or off.

As others have already said, the earth conductor is for safety and should never be used as neutral even though they are bonded together somewhere. In the US it would be in the breaker panel but I don't recall how it's done in the UK.

[P90]

ahhh, Darwinism at work...   


LOL

[NiHaoMike]

Most likely the load side of the switch got shorted to ground by accident. Could easily happen if care is not taken to prevent the bare ground wire from making contact with exposed terminals.

And here's an explanation of why using ground as return violates code even though it's electrically equivalent:
http://www.repairfaq.org/sam/appfaq.htm#afwysncgtn
There is one exception - a device can use ground for return if its current draw is low enough to be within ground leakage limits *and* the current limiting is done by a device approved for bridging hot to ground such as a Y class capacitor. (That limit is very low like well below 1mA and therefore rarely sees actual use.) Even if safe and compliant, it is discouraged since they can contribute to false tripping of GFCIs/RCDs.

[akis]

On throwing the switch there was a shorting flash and the relevant fuse popped out at the consumer unit and fused the contacts of the light switch together so it is now permanently on.

Obviously there is a short. The question is where.  The electrical shaver socket has/is a transformer. It has a L, a N and an earth attached to the body of the transformer. It was very happy working with the ceiling lights off. The light switch connects a live to the ceiling light bulb (and then to the neutral). This is the circuit that was switched in and caused my contraption to short. With the switch in the "off" position, the shaver socket had worked fine for a few hours.

[Monkeh]

Put the screwdriver away.

[akis]

Put the screwdriver away.

Does your comment mean that you do not have a clue what's going on? Otherwise why do you not share your knowledge? Isn't this what the forum is all about? Sharing of knowledge?

[P90]

I'm all for sharing knowledge... but working on mains circuit is dangerous and should not be done by those not qualified for that sort of work. Stop before someone gets hurt...

[tggzzz]

Put the screwdriver away.

Does your comment mean that you do not have a clue what's going on? Otherwise why do you not share your knowledge? Isn't this what the forum is all about? Sharing of knowledge?

He is indicating that you do not have a clue what's going on! At least you have, belatedly, asked for advice.

I certainly won't share my knowledge in this area, since

• I haven't got time to share all the necessary knowledge
• I cannot assess whether you have understood it or need further explanations
• I haven't a clue about your specific installation, nor plans
• I don't want it on my head that I have said/done anything that might lead to someone's injury. While what you do to yourself is your business, in this case you might harm someone else

You need to get taught properly by a professional.

[SeanB]

You have some wire in there on the return to the lamp with damaged insulation. Likely you also have metal conduit joining them, and a metal box the switch is in. When you pulled the switch off you put this damaged wire in close contact with a part of the conduit, or you had a small excess of wire that cracked insulation ( especially in an older house with DCC wire or very old PVC insulation, which is easy to see for DCC it has a woven cotton cover and crumbly rubber and old PVC will drip green goo) and touched the conduit or arced over on switch on.

Now, you can fix this by using the old wire as a pull, to get a new set of 4 wires ( line in, neutral, return and a PE connection ) back to the likely source of the wire, in the lamp fitting. This then will get rid of the damaged wire, and give a neutral for the socket outlet, plus a better ground connection.

In the light you will have to join the line to the existing and insulate it, either with a Wago connector or a ceramic wire nut and tape it up ( wire nut local code determines if you can use it, here it is an approved method with a ceramic nut) The neutral in the light will need to join 3 wires, one the neutral to the board, one the short stub to the light and the third the neutral to the switch. This also needs to be insulated as if it i live conductor, as it is one. The return wire can go straight to the lamp socket. The ground wire must be connected to the metal case of the ceiling rose using a screw, picking up the conduit there. Reason for separate ground is that the use of conduit as ground is no longer allowed, as there can be PVC conduit in there, which is not conductive, and which might have been put in during renovation, ideally the ground should be all the way back to the consumer unit and connect there to the earth busbar, but you will have to pull all the cabling along the way and replace all of it to do so, YMMV.

Then you just replace the ceiling rose with the light socket attached to the new wires ( old one likely you will buy a new one), replace the lamp and cover. Switch side you connect the new switch, with the shaver socket cable fed out through a cable gland ( so as not to cut the sheath with time) and put the light switch back, turn on the circuit and check light works and shaver does as well.

[akis]

You have some wire in there on the return to the lamp with damaged insulation.

Spot on! I took the strongest torch I have and examined the return wire and sure enough the insulation has been chewed on the retaining screw that holds the light switch into its metal casing! By coincindence the electrical shaver was connected to the same circuit and I assumed the design was faulty somehow, when in fact it was the action of removing and then reinstalling the light switch that caused the problem. Or the wire had been damaged before and was looking for an excuse to make contact with the retaining screws/chassis!

[RGB255_0_0]

I just hope you don't kill anyone but yourself 

[P90]

I just hope you don't kill anyone 

FIFY

[Mechatrommer]

Does your comment mean that you do not have a clue what's going on? Otherwise why do you not share your knowledge? Isn't this what the forum is all about? Sharing of knowledge?

yeah so do most of us here with lack and confusing information you provided. transformer shaver to what? can you at least draw some schematics? you tried to tap a light switch to earth, light outlet only contains live wire, a switch and a wire that goes back to the light appliance, up there, only there is a neutral line for the current to go back to the source. you turn on the switch at the outlet, both wire that you saw will be a live wires. tapping switch outlet is just as good as tapping a life line. you need to find the proper neutral path for it to go back after passing appliances.

i dont agree with anyone who say put away the screwdriver or such, its a learning process. i was once there, electric shock as early as 10yrs old. but i do agree you need a guidance from experienced personnel so you'll have less chance of being a roasted turkey. please do install an RCD / ELCB, its between life or death choice, its alot lot more important than getting a proper expensive fuse for your DMM. just to get the idea, imagine a live wire accidentally touches your body during home improvement attempt, current run through the earth through your body to the leg, you are stuck there due to paralysis, and there is no other way to stop this... a proper RCD / ELCB installation will prohibit this. trust me been there. and burning house down to the ashes ground have occured from time to time around here due to improper wiring practice, the latest occurence is few days ago just few meters from where i work..

before making further mod attempt, make sure RCD / ELCB is in place in fully and proper operation, otherwise.... put away the screwdriver

[RGB255_0_0]

I just hope you don't kill anyone 

FIFY

Let's be frank. If it wasn't for the RCD/over current protection, there could well have been a serious incident. He got protected because of the efforts of people who knew what they were doing by making and/or enforcing the rules.

[Zero999]

Put the screwdriver away.

Does your comment mean that you do not have a clue what's going on? Otherwise why do you not share your knowledge? Isn't this what the forum is all about? Sharing of knowledge?

As mentioned above, we can only guess what's going on, in the absence of all the information required to figure it out.

If you're offended by any of the flaming, then tough shit



People here care far more about your personal safety and that of others than your hurt feelings, which is a very good thing, whether you realise it or not.

Now I don't want to discourage anyone from learning electronics, just not on mains wiring, where a mistake could kill someone. Get yourself some AA batteries, a battery holder, a cheap multimeter (don't use it on mains though) some LEDs, resistors and switches and experiment with them. Even that's not perfectly safe, since the short circuit current from some batteries can be high enough to burn you but the limited energy in a small battery means no harm will result. You can then think about things you can do to make it even safer, such as adding a fuse or a PTC resistor if you want something resettable.

[tggzzz]

People here care far more about your personal safety and that of others than your hurt feelings, which is a very good thing, whether you realise it or not.

Quite right too

Personally I care far more that he might hurt the next person to use/investigate one of his "installations". If he kills himself, then the consequences is merely to have improved the species.

[Ian.M]

The O.P. cannot legally do this sort of electrical installation work in the UK.
To summarise: under Part P of the Building Regulations, all electrical work other than like for like replacement of fittings and wiring on protected circuits, 'downstream' of the protection, not in restricted zones (e.g wet areas), requires notification to the local building authority, and if notifiable, has to be performed by a registered competent person or fully inspected by a registered qualified electrician.   

If the shaver socket is in a bathroom, it is likely to fall in a restricted zone, the regulations for which are quite complex, and it is obvious that the O.P. has no hope of passing the competent person certification without extensive formal training. 

The UK Wiring Regulations aren't quite as draconian as the Australian ones, but they are headed in that direction.  The wiring colour code changed when the regulations were changed to restrict D.I.Y, and wire to the old colours is no longer sold, so any subsequent spot check can easily see if you have replaced or added circuits, and unless they are not notifiable or you have the right paperwork showing they were performed legally, at the minimum you will have to have a full electrical inspection, and at worst there could be considerable fines.

As such the only advice we can legally and ethically give is:

DON'T MESS WITH IT YOURSELF
EMPLOY A REGISTERED QUALIFIED ELECTRICIAN

[james_s]

Yeah that's ridiculous. I'm perfectly ok with requiring an inspection, but damned if I'm going to hire an electrician to do electrical work in my own home. It's something that I personally am proficient at, I've been trained by a family member who spent his career as a licensed electrician and I've got a good understanding and a lot of experience. It just isn't something I chose as a career path.

I think that while the intent is good, in practice requirements like this don't do anything to stop people who know just enough to be dangerous, they will still attempt to do it, only they will not have access to proper supplies, books and knowledgeable advice or an inspection. I've certainly seen plenty of examples of people who should not have tried to do electrical work. My house was originally built with an unfinished basement which was finished by the original owner. I had to redo much of the wiring because it was so badly done. All the light switches were on the neutral, all of the receptacles had been installed with the wires trimmed so short they would just barely reach to those horrid spring loaded backstab terminals. The receptacles were all the cheapest crap available and they were so loose plugs wouldn't stay in. When I pulled them out of the boxes several of them fell apart.

[akis]

Many thanks for all the comments of caution and others.

To summarise :

1) A fixing screw on a light switch cut into the insulation of a return wire making contact, and when the light was turned on it shorted live (L) against the casing/screw which was earthed (E). The light switch fused. The fixing screw has had a chunk taken off. That was a sloppy work on my part forcing a screw in like this when I clearly felt that the switch was not fitting in properly but it was very late at night and was too tired having worked all day.

2) At the same time I had also connected a bathroom shaver socket to that light switch. When the main fuse tripped I thought it was something related to the shaver socket and I asked here. But it was simply a fixing screw grinding on a live wire.

3) Someone asked why did I chose that light switch as a source of power. Because it is the nearest and only source of power in that location. The light switch lacked a N and so I wired the shaver socket's N to the E of the light switch. In future I will attempt to draw a new line into the light switch. Please note I have not connected the house's N to E.

4) In this very large and unnecessarily hostile thread, there are, I think, just two messages referring to what might actually be wrong in connecting N to E inside the house, and I think there is only one message, posted late on the thread, on why it should not be done. To explain it for anyone that wonders, if you or an appliance connects N to E, inside the house, and if you then somehow remove/disconnect the E from the consumer unit and from all the other places that the house might be earthed at (eg water pipes etc) then you are in danger since the house is no longer earthed and your earth becomes live (through this appliance) thereby killing you when you say try to turn the tap on in your kitchen. Something like that. Just to make it clear, I did not connect N to E and there is no N at that location.

5) There are PSUs and other gadgets and appliances, that do legitimately (?) connect L to E, so long as the leakage is very small - obviously smaller than the 15mA, or so, that would trip the RCD.

6) In Germany there is at least two places (hotels) I have visited that have power sockets inside the bathroom, next to the sink, and I have used them to boil my kettle and my coffee maker which was resting on the sink. Either those hotels have illegal installations or they just do not care. Similar power sockets found in other EU countries I have visited, most modern hotels, above and below the sink in the bathroom.  There are also other power sockets so you can plug in your washing machine in the bathroom. My bathroom (in UK), which is larger than a small bedroom, has no power sockets.

[Monkeh]

Please note I have not connected the house's N to E.

That doesn't matter, you've still created the potential for a dangerous fault. You are passing current through a non-current-carrying conductor with only the primary winding of a transformer to limit the current.

Sorry, but I'm not going to coddle you: You should not be doing mains wiring. You don't know the regulations or, quite clearly, the reason behind them, and your installation is sufficiently out of date to not make any attempt to protect you from yourself, let alone others.