230v between N+E and 0v between L+E

[An Buachaillín Bán]

Hi all,

I was called out earlier today to a house where a plumber was fitting a new mains electrics shower. He wanted to know if the existing cable was of a suitable size. I am a recently registered electrical contactor, however I hadn't come across this issue before. The cable was a 6sq pvc pvc. Houses were built in the 70s but cable wasn't as old, as they were brown blue and earth. However, I'm getting 230v across N+E, and 0v across L+E. Would I be right in assuming the house may not be neutralised?

Thanks in advance for all advice

 

[nicebutdim]

@Risteard or @LastManOnline might be best placed to answer questions pertaining to Irish regulations.

 

[pc1966]

It sounds more like reversed polarity which is very dangerous as (I think) ROI is like UK in that it has OCPD only in the L path and so if L & N are swapped you have no protection against faults to E.

AFIK the "neutralised" aspect is basically a local earth rod on the TN-C-S supply but @Risteard or @LastManOnline are the best to advise.

It could be a floating CPC leaking to L, but it is something you have to get professionally checked AS SOON AS POSSIBLE!

 

[An Buachaillín Bán]

Hi all,

I was called out earlier today to a house where a plumber was fitting a new mains electrics shower. He wanted to know if the existing cable was of a suitable size. I am a recently registered electrical contactor, however I hadn't come across this issue before. The cable was a 6sq pvc pvc. Houses were built in the 70s but cable wasn't as old, as they were brown blue and earth. However, I'm getting 230v across N+E, and 0v across L+E. Would I be right in assuming the house may not be neutralised?

Thanks in advance for all advice

Apologies, I edited the previous post. I'm getting 230v across L+N and 230v across N+E. But 0v across L+E

 

[James]

The N is definitely missing.

0v from L to N means that there is a connection between the 2
but because N to E is at 230v it means that you must have a floating N

Edit,
after reading the last post, it may well be that you have a reversed polarity fault.
some proper investigation needs to be done with the house isolated from supply until you can be sure that the polarity and earth are ing god working order and the correct way round.

 

[pc1966]

Apologies, I edited the previous post. I'm getting 230v across L+N and 230v across N+E. But 0v across L+E

That is a prefect fit for reversed polarity.

It might be something slightly less serious, but until found and fixed should be treated as a very serious fault.

 

[timhoward]

Also please don't assume its safe to grab hold of the consumer unit cover and pull it off, if it's a metal CU.

 

[Risteard]

As above, it sounds like reverse polarity to me.

 

[nicebutdim]

It sounds more like reversed polarity which is very dangerous as (I think) ROI is like UK in that it has OCPD only in the L path and so if L & N are swapped you have no protection against faults to E.

AFIK the "neutralised" aspect is basically a local earth rod on the TN-C-S supply but @Risteard or @LastManOnline are the best to advise.

It could be a floating CPC leaking to L, but it is something you have to get professionally checked AS SOON AS POSSIBLE!

Caught mention of 'neutralised' and completely missed the fact that 230V was present between N&E.

 

[Lucien Nunes]

As above, but repeated to reinforce the message: If the polarity is reversed at the supply terminals or meter, no single-pole fuse or circuit breaker will offer any protection whatsoever against earth faults, and all circuits will be effectively fused at whatever the main fuse rating is. You might have 100A fusing on every single appliance and any minor fault could turn into a fireball. Hopefully it's only on that one circuit but it needs checking immediately.

 

[Dave OCD]

I'd try plugging in a simple socket tester at a convenient socket or 2 which will instantly give you an idea of whether it's just the shower circuit that's reverse polarity or the entire installation. I wonder if there's been a meter upgrade recently ?

 

[pc1966]

As @Lucien Nunes has pointed out you could see polarity reversal at any one of several places. Worst case is the supply point is reversed and so the supplier's earth/CPC permanently live. That ought to be very unlikely but should never be ruled out.

This is one case where a good non-contact voltage detector pen could be a life saver! If you find it suspiciously "volty" around the supply head, CU case (as @timhoward already warned about), etc, then call the electricity board immediately.

The whole house reversal is VERY dangerous as well, but more common and more likely to have happened when a meter was changed or CU installed and someone got the tails in the wrong way round.

Finally it might just be the one circuit that someone has managed to swap L & N, probably easier to do at a RCD/RCBO than normal CU, but still a bad thing to find.

 

[LastManOnline]

Apologies, I edited the previous post. I'm getting 230v across L+N and 230v across N+E. But 0v across L+E

Those readings are very peculiar.Even if the house was,nt neutralised (and it may not be),that still would,nt account for those readings.Have you tested at the D.B. and checked how the readings are there?

 

[LastManOnline]

. Would I be right in assuming the house may not be neutralised?

You can establish neutralising with 2 steps....

1) visually confirm the link from the ESB,s cutout to the main Neutral in your D.B.

2)Test its effectiveness by conducting a continuity test between the main Neutral and the Main earth.It should read "0.00 ohms"

I,m working in Cork today.If you want to cintact me ,feel free.

 

[An Buachaillín Bán]

Hi all,

Many thanks for the replies. Those of you who said reversed polarity were correct. After much digging in the attic under floor boards I found a junction box where the polarity was reversed on load cable coming from the pull chord, cables very badly made off too might I add.
I haven't found out how long this man is without a shower, because I don't see how the previous shower would have worked either.
Either way, shower is now operational. I have offered to inspect the house at a discounted rate, as the owner is an elderly gentleman who lives on his own with very limited social contact.

Thanks again for all your help guys!