230V between N-E and L-E with breaker off

[Dwight]

Hi guys,

 

I have a similar problem as mentioned in this thread . At any socket outlet in the house, if I turn the breaker off I measure 0V between L-N, 230V between L-E and 230V between N-E. With the breakers on, all measurements are normal. I was only able to take a quick look in the CU today (will investigate further tomorrow), and it sure looks like L-N is reversed from the meter since I have 230V between the Neutral bar and the earth cable that connects to the earth rod and 0V between earth and the MCB busbar. No MEN-link done inside the CU.

 

In the thread I linked to it seems like the OP solved the issue by reversing L-N in the CU. Problem is I don't understand how a reversed L-N can give these measurements? Could someone help me understand please?

 

Dwight

[BritManToo]

My house was the same when they built it.

L and N reversed coming out of the meter.

After I complained and the guy fixed it, I watched him sneaking down the road testing everyone else's meters.

[sometimewoodworker]

2 hours ago, Dwight said:

 

Hi guys,

 

I have a similar problem as mentioned in this thread . At any socket outlet in the house, if I turn the breaker off I measure 0V between L-N, 230V between L-E and 230V between N-E. With the breakers on, all measurements are normal. I was only able to take a quick look in the CU today (will investigate further tomorrow), and it sure looks like L-N is reversed from the meter since I have 230V between the Neutral bar and the earth cable that connects to the earth rod and 0V between earth and the MCB busbar. No MEN-link done inside the CU.

 

The first thing I would do is to check on the supply poles to see if you have every 3rd pole earthed.

2) the next thing is to change your main disconnect breaker/switch to a two pole one so that when it’s off it isn’t so important that the supply is connected the wrong way round and you are isolated from the grid,

3) change the supply so the connection is correct.

4) if every 3rd pole is earthed bond the earth and neutral MEN-link.

[Dwight]

Thank you for your replies. Sorry if I was not being clear, but the breaker I referred to was the circuit breakers for the individual circuits. The main breaker is a 2-pole breaker and works properly.  When I turn the circuit breaker for any circuit off, it still shows 230V between both N-E and L-E. I just don't understand how a reversed L-N on the supply could possibly cause that?

 

[bankruatsteve]

Please post photo of your CU (breaker box) with the cover off.

[Crossy]

9 hours ago, Dwight said:

I just don't understand how a reversed L-N on the supply could possibly cause that?

 

Any load on the circuit (even a neon indicator) will let enough current through for your meter to read. It does sound like a L-N swap.

 

Easy to check at your incoming supply, preferably to a known earth (my now famous screwdriver in the lawn).

[sometimewoodworker]

13 hours ago, Dwight said:

Thank you for your replies. Sorry if I was not being clear, but the breaker I referred to was the circuit breakers for the individual circuits. The main breaker is a 2-pole breaker and works properly.  When I turn the circuit breaker for any circuit off, it still shows 230V between both N-E and L-E. I just don't understand how a reversed L-N on the supply could possibly cause that?

 

As @Crossy said any load will show a current if line is not disconnected. 

So in the case of a line neutral swap if your individual breakers are only breaking the neutral connection it is potentially very dangerous if a fault happens as everything is still live.

 

Even if the circuit is correct and there is TNC-S in your area without a MEN link in the CU there could be enough induced voltage in the neutral to give a reading. The good news is that if this is the situation it isn’t very dangerous as the current available would be tiny.

 

[Dwight]

Thank you all for explaining. I am at work at the moment so have not had time to look into it further yet. I will try to find a known earth to confirm that the incoming supply indeed is reversed. If they are, I will begin with swapping them in the CU after the main breaker. After that I will check the power poles to see if I can see any of them being earthed or not. My plan is then to install a new CU with new breakers and an RCD and perhaps even the MEN link if implemented in my area.

 

I'm sorry for all questions, but I just really want to make sure that I understand this fully. Hope you don't mind. I've made a little drawing of how I understand your explanation for the reason to the measurements I am seeing. Is this what is going on in my circuits? With the neutral open (MCB off), and the live side still energized any load in the circuit is letting current pass so that I essentially get the same potential at both L and N in the socket where I am connecting my meter?????

 

 

 

[lom]

Your L is going through the lamp and down to the socket, open the lamp switch and it won't go there.

I agree with others here, you have L and N reversed and in a lamp circuit the switch should always break L.

[bankruatsteve]

If it were me, I would be taking the measurements in the CU versus the outlet.  Using the screws in the main breaker and the ground bar (or if you want to keep the same using neutral bar, ground bar, and screw for the MCB with MCB on), it should be obvious if your lines are switched.  Most CU configurations would not allow a safe change over unless there is external isolator.  That's why I thought a photo would help.  

[Crossy]

If you have a neon screwdriver that's a very quick and easy way to check polarity.

 

Put it on the incoming "Live" and it should light up, on the incoming "Neutral" it shouldn't. Do it with the main breaker OFF just to avoid any unexpected effects.

 

If you don't have a neon go and buy one ???? 

 

For a known earth stick a big screwdriver in the lawn, then you KNOW that's ground and not some weird voltage being induced in your house wiring.

 

Known earth to live should be 220V, same to neutral should be close to zero.

[Dwight]

Thanks all. Sorry to keep confusing you... My sketch was only a way for me to try to understand why a reversed neutral would give me these readings at the socket, nothing else. I already opened the CU and it was by measuring L-E there (incoming screws on main breaker to earth rod) that made me realize that my supply probably is reversed. I will do as Crossy said and confirm this by using his famous screwdriver method. I might have a neon screwdriver too, just have to find it. 

 

[Dwight]

Ok guys, sorry for the delay but here are some photos from todays testing. I don't really have a lawn, but managed to find a crack in the concrete and stick my screwdriver down in the ground there. Poured some water in there too, hoping to get a decent earth. One of the photos is measuring between screwdriver in ground and the THW wire connecting to my earth rod. The other photo is measuring between screwdriver in ground and incoming neutral from meter. I assume that we can conclude that the incoming supply is indeed reversed? 

 

I am thinking to swap them around by simply disconnect the busbar and cut off the part that runs between the main breaker and first MCB. Then use some THW 10mm2 to connect the first MCB to L-out (left side) from the main breaker. And of course move the 2 green ones over to the right side of the main breaker instead. Sounds ok?

 

Regarding the MEN-link I can't see the power poles on our street having an earth connection with regular intervals. Definitely not as often as every 2-3 poles for sure. I see a plastic pipe running down the side on 1 or 2 of them but hard to tell if it has do to with MEN since a few of the houses have their supply going under ground from the meter on the pole to the house. So I am thinking of leaving it as it is without the MEN connection in my CU for now. I will probably install a new CU with an RCD though. Just need to climb up and take a peak above the ceiling first to see what the situation is like with borrowed neutrals etc.

 

In my CU the earth connections are being done behind the CU in the plastic wall box so you can't see the connection between the earth rod and the circuits earth in my photos. Also some neutrals are connected back there as well, I can't see any link between earth and neutral though.

[Crossy]

Due to the photos not really showing the meter reading properly can you post your measurements please?

 

If you are getting 220V between the incoming "neutral" and your known earth then things are reversed.

 

Why not pay a local sparks to come and swap the wires either in your box or at the meter, has to be better the cutting the bus-bar etc?

 

 

[Dwight]

Sorry Crossy, it's 230V between "neutral" (left side of Main breaker that connects to the neutral bar) and known earth. 0V between incoming "live" (right side of Main breaker that connects to the MCB busbar) and known earth. I could find a local spark to come swap it at the meter, but I got the tools, the time and since my CU is not one of those newer plug-on systems it seems easy enough to swap it on the outgoing side with the Main Breaker turned off. Thank you all for your help so far. 

[Crossy]

Definitely a**e backwards then, go for it.