Live neutral reverse!

[Delboybully]

I go to a job today, a nice simple one to replace a light switch.

They have a nice 8 way board with 6 used ways, all RCBO's installed about 2 years ago. So i turn the light on that this switch controls and turn the relavent braker off and out goes the light. I then pop on my volt stick as i usually do before i check for dead and it beeps. Odd i think. So just to be sure i turn all the brakers of and the volt stick still beeps. I turn off the main switch and volt stick no longer beeps. To double check this i set my tester to volts and run through the same procedure again. Sure enough, there is a voltage at the switch until i turn the main switch off. So i think the sparky who installed the CU has made a big mistake and somehow connected live neutral reverse. So i pop the cu cover off and all looks ok (correct coloured wires in the right postions), the incoming tails look ok (the correct coloured tail in the correct terminals). I test for polarity with my AVI, and the live and neutral are reversed. So i mention to the client that this isnt good and he informs me that the meter was changed 3 months ago. I follow the live from the head and sure enough it goes into the neutral of the meter. Unbelievable, i mean these are supposed to be professionals and it isnt hard to test polarity.

So i phone the DNO and they tell me that it isnt their responsibility as they only go as far as the head and its the billing companies responsibility. So I leave telling the customer to contact their billing company ASAP to get them to sort it.

I am still fuming about this, i cant believe they screwed this up so bad!!!!! Not to mention it very dangerous!!!!!!

 

[Engineer54]

If you feel you are not competent enough to touch the DNO supply equipment that's fair enough as far as i'm concerned. What you should have done though, is contacted the DNO as your clients representative and explained the situation to them. Insisting that the required remedial work be carried out on an urgent basis, and confirming a time line.

Walking away leaving the home owner to call the DNO is a No No, as Tony first pointed out at the beginning of this thread...

 

[Des 56]

I wonder how many who have replied to this thread, absolutely adamant that he should have cut the seals and pulled the fuse,also have contributed to other threads warning of the dire consequences of pulling that fuse without proper safety gear, and how that fuse is going to one day disintegrate in his hands and blind him with the flash

Yes,more direct action informing the couldn't care less authorities would have been a better course of action,but I feel he was unfairly castigated whichever decision he made

It seems he is damned if he did and damned if he didn't

 

[Snapester]

I would like to know how his tv and other appliances are not completely fried with the L-N polarity issue?

 

[Engineer54]

I would like to know how his tv and other appliances are not completely fried with the L-N polarity issue?

??????

 

[Deleted member 26818]

I would like to know how his tv and other appliances are not completely fried with the L-N polarity issue?

In England, and also in Scotland and Wales, we use a.c.
This stands for alternating current.
The current alternates between positive and negative 50 times a second (50Hz).
If the TV and other appliances are designed to operate on a.c. they will also operate if polarity is reversed.
They won't care whether the current switches from positive to negative, or from negative to positive.

 

[Snapester]

Well isn't the Neutral flowing around the Live side and the live around the neutral? I thought that usually is what reverse polarity is?
I have been to a job before where the guy changed the CU and wired the tails the wrong way around and fried the customers laptop?

 

[Snapester]

Thanks for the i do understand the terms AC and DC and what they both do and are capable of. But i have also seen appliances and household items fried from reverse L-N issues maybe they were polarity sensitive equipment?.

 

[telectrix]

long time ago, seen loads of reverse polarity on TVs. this is back when they came without a fitted plug top and customer wired plug revered. sets worked perfectly till engineer came to work on it and the metal chassis was live.

 

[Deleted member 26818]

Well isn't the Neutral flowing around the Live side and the live around the neutral? I thought that usually is what reverse polarity is?
I have been to a job before where the guy changed the CU and wired the tails the wrong way around and fried the customers laptop?

Yes it is, but it does that 50 times a second anyway.
It's unlikely that reversing polarity would cause any damage to the lap top.
More likely that the line and earth conductors were connected before the neutral and the laptop charger was plugged in at that time.

 

[Snapester]

haha oh dear i bet that was a shock boomboom! There really are things not many its true but non the less they do exist that if the polarity on an AC supply/signal is reversed they wont work another example is computers, it will still work for a while but eventually a reversed polarity on the AC supply will cause the comptuer electronics to overheat and die.
also some hifi and stereo systems will create a voltage sometimes up to 90v or so on the chassis if the supply polarity is reversed.

 

[Deleted member 26818]

Many items of equipment suffer when there is a neutral fault.
It may be, that when the computer or Hi Fi is switched off, it is still live, as it is the neutral that has been switched off.
It may be that such devices don't like being live constantly with nowhere for the current to go.
Or it may be that it is because of the installation earthing system.
With TN-C-S, the neutral and earth are connected together.
With TN-S and TT the earth is separate, perhaps the line current flows up the neutral conductor and finds a return path through the earth conductor?

 

[i=p/u]

i.3 functional earth with electronics

 

[telectrix]

i blame this modern technology. never was a problem with valves.