Advice on reduced live-neutral reading

[chucklepie]

Hello,
I'm not an electrician, more one of those 'competent DIYers', so probably the worst kind

My electric shower broke, the shower firm came out, he was in about 2 minutes I'd say. In that time he put his meter on the terminal block, said there was only a small 60v neutral-live, 190v on neutral-earth, 240 on live-earth, meaning a fault with my supply, said I'd be charged and left.

He never once isolated the shower, so I did some testing and recreated his fault and got the same results, disconnected the shower at the terminal block inside the shower (where supply/feed meet) and my readings were normal (240v neutral-live, 0v neutral-earth, 240 live-earth). Repeated a few times with the same working when disconnected failing with shower. So I basically went and tightened all the connections in the shower circuit, and everything now just works and has been for the past month.

So I reply back the next day saying, "you didn't isolate shower to test is there a reason? and it's now working after essentially tightening connections at the shower side not touching anything on mine, can you reconsider?" All they are saying is - what you did is irrelevant, isolating shower is irrelevant, a reduced voltage on neutral-live means it's your mains and you have an intermittent fault and it's not the shower. If relevant it's a 9.5kw shower on a straight clipped run, no insulation of about 7 metres on a dedicated RCD using 10mm cable.

Anyone care to offer advice, i.e. am I completely wrong with my testing and what they say is correct?

 

[loz2754]

If the problem was not within the shower itself, then the shower guy was within his rights to declare it to be a problem with the supply.
Had you called a competent electrician instead, he would have discovered and corrected the problem.

 

[DPG]

Who fitted the shower?

. .. ..

 

[James]

It is possible that there is a fault with the shower isolator switch or any of the cable joints.
you might have fixed it but you might have just got lucky and moving the isolator a few times made a bad connection better.

 

[chucklepie]

Thanks for the replies. Just to answer in case I wasn't clear, I never touched the DP or any side of the supply. The only thing that was touched was the removal of the load end (i.e. the shower cable inside the shower) and on doing that the bad readings disappeared.

Also, regarding getting an electrician, the DP was fitted 6 months ago by an electrician who also tested the whole circuit.

 

[DPG]

Thanks for the replies. Just to answer in case I wasn't clear, I never touched the DP or any side of the supply. The only thing that was touched was the removal of the load end (i.e. the shower cable inside the shower) and on doing that the bad readings disappeared.

Who fitted the shower?

 

[snowhead]

Was the pull switch / D.P isolator turned off then back on?

Thanks for the replies. Just to answer in case I wasn't clear, I never touched the DP or any side of the supply. The only thing that was touched was the removal of the load end (i.e. the shower cable inside the shower) and on doing that the bad readings disappeared.

If not how did you manage to safely disconnect the cable from the shower and test?
I'm tending to go down the same route as James, the shower isolator is faulty / cables loose, usually the neutral and movement has made it temporarily work again.

The fault will be back.

And as others, unless the shower company installed the wiring to the shower, their responsibility stops at the shower terminal block terminals, excluding any cable that may be attached.

 

[timhoward]

Loose connections on a shower VERY frequently result in a charred / damaged Neutral conductor in an isolator as essentially it becomes a mini-strip heater. That high resistance connection creates the exact scenario that your original post describes.

I've been called out to many shower supply problems this year, and it's probably fair to say that shower terminations are among the hardest to do well in a domestic environment. The conductors are unforgiving, and some cheaper accessories on the market are not well made and (in my view) up to the task of tightly holding large conductors, especially if not dressed well and they end up under tension.

All that to say, there's a fairly high chance of a poor connection and it would be wise to get it all checked out.

 

[chucklepie]

Was the pull switch / D.P isolator turned off then back on?



If not how did you manage to safely disconnect the cable from the shower and test?
I'm tending to go down the same route as James, the shower isolator is faulty / cables loose, usually the neutral and movement has made it temporarily work again.

The fault will be back.

And as others, unless the shower company installed the wiring to the shower, their responsibility stops at the shower terminal block terminals, excluding any cable that may be attached.

Consumer box goes to DP. DP goes to shower. Inside the shower is a terminal block joining the load/feed. To test I put the tester on the terminal block and tested live-neutral, live-earth, neutral-earth showing the bad reading. Then removed the shower side of the terminal block and re-tested and it was ok. I repeated this numerous times to be sure and every time I disconnected the shower it was fine, and on reconnecting it had the bad readings.

What I did was literally went through all the connections inside the shower, reset the joints/spades. After this it worked and has done for the past month.

Hence why I was asking my question around nothing inside the DP has been touched, nothing in my feed has been touched, the only thing touched is the removal of the shower end of the terminal block and the only thing giving the bad reading was when shower was connected to the terminal block. As above, electrician fitted the DP and did a test on the circuit.

 

[MJPD29]

Who fitted the shower? Not the circuit/isolator or anything else, the actual shower

 

[DPG]

Who fitted the shower? Not the circuit/isolator or anything else, the actual shower

I've asked that twice already, but no answer so far.

 

[MJPD29]

I've asked that twice already, but no answer so far.

Sounds like this is where the issue could be

 

[chucklepie]

Sorry, I literally didn't see it, the forum UI/layout is a little busy

If you want a full breakdown: the shower is in an extension built a few years ago, the electrician did all the wiring up to the tail, the builder built the extension, did the plumbing, fitted the shower and connected the tail. The electrician did his checks and signed it all off. The cable run couldn't be any simpler, dedicated 40amp breaker straight up the wall about 3 metres to the DP and the DP a metre to the shower. All 10mm, all without any insulation.

Everything worked just fine and had done since, until it stopped working maybe 1.5 years into the shower life.

So regardless of who, why, what, my question was really a very simple one: could the meter readings be caused by a short/fault in the shower given the verdict was the mains was at fault despite the shower still being directly connected to the terminal block he was testing. Without touching the mains, removing the shower live/neutral/earth from the terminal block the mains reading was back to normal.

Hope this helps?

 

[MJPD29]

Responsibility is with whoever made final connections at the shower. The person that tested the supply at the shower has likely got those readings because of a bad connection on the supply to the shower, therefore not their responsibility. I would be looking at whoever made that final connection.