UKH

Just suppose someone was daft enough to wire up an immersion tank element the wrong way round (live & neutral)...

Would it still work but not switch off on the thermostat? It's a vented tank in this thought experiment.

It will work exactly the same

Asking for a friend?🤣🤣

I'm now trying to think of anything at all that wouldn't work if you swapped live and neutral. 

Single phase of course... Seen it done with 3 phase and it definitely doesn't work ever again.

It would work as a heater but several layers of safety compromised or additional hazards introduced because fuse or circuit breaker is in neutral not live.

Fuse in neutral would not blow for short circuit live to earth so it would have to a blow a higher rated fuse for house increasing risk of fire.

Fuse in neutral would blow if heater overloads interrupting current in neutral leaving heater unexpectedly connected to live increasing risk of electrocution.

Switch in neutral rather than live turns off heater leaving heater unexpectedly connected to live increasing risk of electrocution. Although I expect (tbc) switches are double pole switching both live and neutral.

In 20 years time somebody who doesn't realise incorrectly wired could be at greater risk due to the confusion.

I am not an electrician so I may have some of the detail wrong.

Eh? Wot?  That makes no sense to me.  For clarity - I’m assuming the OP literally put the black or blue wire on the live terminal on the element and the red or brown wire on the neutral terminal.

This is a resistor, isolated from ground, connected backwards.  Elements are normally physically symmetrical in a way which means there’s no difference between L and N other than how they’re labelled.

The only consequence I can see is that the terminal marked “N” on the element with be at close to line voltage under operation and the terminal marked “L” will be close to ground voltage.  The only safety hazard I can see is that if someone was inappropriately working live on the element in the future, and they inappropriately didn’t use suitable protection when working on the terminal labelled “N”, and they didn’t notice the blue wire going to it, and they stupidly didn’t test it with a voltage detector first, they’re going to get a shock.

If it was me I’d switch them round due to OCD and knowing it was backwards.  

You may be right, that sounds more likely, cables swapped after fusing.

I was thinking live and neutral swapped somewhere after consumer unit but before fuse and switch*. Hence fuse is in the neutral rather than live.

OCD is good as a predictable colour and labelling convention is safer.

*exactly what we discovered in rented student house after kettle exploded blowing fuse in consumer unit rather than plug. We checked the rest of the house after that.

Of course😬

This isn't a question you need to ask.

If you think the tank is wired up wrongly, turn off the house supply at the main switch, use a magic wand thingy to verify that it is indeed off, disconnect the wires and use a multimeter and/or tone generator to identify how the wires are actually connected, make any corrections needed and then turn it all back on and carry on with your day.

It's a pretty simple problem to diagnose and correct and there are significant risks (as others have pointed out) to having it wired wrongly. So imo you shouldn't be thinking about whether you can ignore the problem (which does rather sound like what your question is getting at), you should just fix it.

'Significant risks' which are almost certainly outweighed by the risks of undertaking even such a simple, and arguably unnecessary, electrical DIY project if you're not completely sure you know what you're doing.

I would humbly suggest that you are doing Elsewhere a disservice. E explained the dangers of  wrong wire connection. 50 years since I studied electrics as part of my engineering , but one thing I recall is a dire warning of not getting the wires connected correctly.

240v 13A unfused live next to well earthed copper piping and HWC , what could go wrong?

I feeling really rough with my first bad cold for donkeys years , so maybe more grumpy than normal.

One thing I remember from engineering studies and work was the consequences of over confidence in your knowledge, ability and not thinking things through properly.

E saved me putting a similar post up. I would suggest you reconsider yours.

Most of what elsewhere said about switching in the neutral and safety systems only applies if the mis connection is at the source of the wiring, if had no relevance to swapping the terminals on a resistive heating element.  We discussed that and recognised the different assumptions we’d made, and I clarified that under elsewhere’s assumption I agree with them, but under my assumption of swapped wires at the heating element what they wrote does not apply.

Yes, that would be foolish.  That does not however arise from “Just suppose someone was daft enough to wire up an immersion tank element the wrong way round (live & neutral)...” as the OP says.  That would need a neutral and live to be swapped in the distribution unit!  Agree?

I suggest you re read the OP and my exchange with elsewhere.

We made very different assumptions - mine I feel is more aligned to the OP but both elsewhere and I should have stated our assumptions before posting, and neither of us did.

In my reply I recognised this and clarified my assumptions.

If the wiring from source to element is reversed somewhere that’s dangerous.

If the connections are swapped on the terminals of a resistive immersion heating element, it’s not dangerous except under the circumstance I outlined.  

Can you see the difference in the two scenarios?  It’s spelt out in my reply to elsewhere.

It’s still good practice to follow the labels on the immersion given the very narrow scenario I outlined, and just because, but I’ll hope you take the time to read the posts again.

My main point is still, that as a presumably well qualifed scientist or academic,  it is irresponsible to imply that any tom dick or harriet  can wire up domestic properties with little consequence.

KISS, usually good policy.

Edit, you state a very narrow scenario.

I bet there are a lot of malfunctions not yet experienced, and a lot in the files of building control , fire insurance and coroners.

The only people on this thread talking about wiring up domestic properties are you and elsewhere.  I assume the OP was talking about connecting an immersion element - and I made clear I was speaking about that in my post.

As it stands, although it’s not relevenat here, people can do lots of circuit wiring themselves, subject to sign off from a qualified person.  As inspection and sign off tends to cost as much as getting it done, it’s not so common.

Back to the topic, I stated the corner case risk I see with swapping the terminals on a resistive immersion element and my preference for doing it correctly so I’m not sure why you think I’m encouraging the OP to burn their house down? 

Yes, an earlier poster had said it makes no difference to function (they are correct) and I thought hard about it and identified a corner case where the OPs wiring (if it’s as per my stated assumption) could present a risk.  It took quite some time to think off to.  

I dismissed elsewhere’s concerns (and yours) not because they’re wrong, but because they don’t apply to the obvious implied details in the OP, which I also stated clearly.

I don’t really follow this.

If I was looking for risk of fire from the OPs work, it would be about the quality with which they connect the wires to the terminals rather than the polarity to a resistor with equal electrical isolation to both terminals. 

Not altering my posts.

I would humbly suggest you have not read mine properly.

I am out.

I’m not asking you to?

I have.  I’m at a loss as to how you’re jumping to the conclusions you are based on what I write.  I very clearly explained my agreement that an unfused live feed would be bad, and I’ve explained why I don’t think that applies to the OP based on their perfectly clear post.  

I repeat I’m dismissing your and elsewhere’s concerns because I don’t believe they apply to the OP’s question, and I’ve clarified the assumptions around that.  I’ve stated my agreement with those concerns if they had applied.  I’ve also identified a risk with the OPs approach that wasn’t covered by an earlier, functionally correct and well liked reply saying “it’ll work the same”

A shame you seem to have missed my point entirely.

Wow, thank goodness it's only a thought experiment. It'd turn into a real handbag fight amongst posters if it wasn't

Yes, I will be doing that, really I just wanted to know if incorrect wiring might explain the thermostat not working. I need to check the wiring anyway but if the thermostat has gone (it's quite new) then I'll just chuck it and get a new one.

Ah, then I misunderstood the question. I thought it was "can I leave this as is?", not "does this explain thermostat issues?"

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