Equipment in bathroom cupboard

But if the electric shaver was supplied by a 20VA shaver unit that would reduce the shock current wouldn't it?

A bit - 20VA at 230V is about 90mA - and it will probably supply a bit extra under fault conditions until the thermal overload disconnects the transformer - so likely it can supply well in excess of 100mA - that twice what can kill in normal dry conditions - and probably nearer to 50x what can kill in totally immersed conditions as skin resistance will be much reduced. So perhaps better than direct mains, but still I don't think it's the sort of thing I'd bet my life on.

   - Andy.

It is the phone on charge that people can not be parted from apparently.

What everyone already knows…

Shaver Sockets for UK Bathrooms - With Isolating Transformer - Bing video

Z.

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Perhaps we should just use 12 Volt caravan type appliances in bathrooms.

Battery toothbrushes and their chargers, and shavers are fine in a bathroom, but it's beyond me why anybody would use anything electrical whilst taking a bath. A flannel, brush, sponge, or loofah does a perfectly adequate job.

AJJewsbury: 
 

Of course if the charger had been fed via a U.K. double wound isolating transformer from a shaver outlet the deaths may not have happened. Or would they?

I suspect a separated circuit wouldn't have helped in Graham's example - the shock current flowed from L via the water and victim to N - no path to Earth involved. A 230V separated circuit (like from an isolated shaver transformer) would have been able to supply such a shock current just the same

But if the electric shaver was supplied by a 20VA shaver unit that would reduce the shock current wouldn't it? The shortest path is between the L and N at the underwater shaver, inside the shaver. When that short occurs the Voltage would be reduced substantially along with the current available.

There are though many, many recent reports of bathers being electrocuted when a phone charger falls into the bath tub. Supplied directly from a powerful source I imaging. Perhaps we should just use 12 Volt caravan type appliances in bathrooms.

Z.

Mike, Graham, thank you - I think that I have the picture.

I can visualize the current through the bath water like the flux around a bar magnet. Most of the resistance of the skin will be lost, so with a conservative figure of 1000 ohms for body resistance, 10% of mains voltage will give a 23 mA shock, which is more than enough.

I also take the point about drowning, but I would expect the autopsy to differentiate that from VF.

Of course if the charger had been fed via a U.K. double wound isolating transformer from a shaver outlet the deaths may not have happened. Or would they?

I suspect a separated circuit wouldn't have helped in Graham's example - the shock current flowed from L via the water and victim to N - no path to Earth involved. A 230V separated circuit (like from an isolated shaver transformer) would have been able to supply such a shock current just the same.

Perhaps a safer policy would be 30mA RCDs plus making all equipment deliberately class 1 with earthed parts around the live conductors (even if those live parts aren't exposed to touch) - so making a L-N shock without a L-PE residual current less likely.

   - Andy.

gkenyon: 
 

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How many official electrical  reports of fatalities do we have in the U.K. from wiring accessories being splashed in bathrooms or shower rooms? Abroad people have been killed when dropping something into an occupied bath such as a phone charger. But here in the U.K?

 

Z.

Your point being, what we do here works because there are few, if any, and those cases being where people run extension leads into their bathroom?

Ah! A question mark. What we do does indeed work for safety. But I think that these days with modern methods of construction we may be going overboard. Decades ago with iron baths, many accessible metal pipes and big metal radiators, using water pipes as the main earth electrode, and towel rails in bathrooms the electrical risks  were greater than today. Who sprays the shower rose upwards? And if they do is it really an electrical risk even with an ordinary L.E.D. light fitting. The risk of a cracked glass bulb is much reduced due to them fading away.

Many modern bathrooms and shower rooms have an all insulated tub or shower tray. The floor is covered with vinyl or a synthetic carpet, and pipes are mainly plastic or inaccessible. An upstairs bathroom is placed on an insulating wooden floor. We don't really consider many of these aspects.

I think that modern bathrooms and shower rooms are inherently safer these days due to modern construction methods.

And full R.C.D. protection affords a very good safety provision.

Perhaps a kitchen sink is a more risky place where an electric appliance like an autojug kettle/base may drop into the full bowl of water. The sad example given by Graham above is a very rare and avoidable event. Of course if the charger had been fed via a U.K. double wound isolating transformer from a shaver outlet the deaths may not have happened. Or would they?

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Z.

Chris Pearson: 
 

gkenyon: 
There is NO ‘residual current’. The OCPD will operate, but it is likely the person in the bath will be seriously injured or killed before that happens, as the electricity tracks through salt straight to the person's trunk, as it's the most conductive thing in the water, to get from Line to Neutral.

As I said, no protective conductor, no alternative path other than L-N, so an RCD is wholly ineffective. This is not a theory … it was proven in an investigation after two children died in a bath in Germany after a shaver on charge from the mains fell into the water and killed them both.

I am struggling with this. We have in the bath water a couple of electrodes. The bather is in contact with neither of them. How can the bather be a lower resistance between them than the bath water?

Electricity does not flow in ionic solutions in exactly the same way it does in solid conductors. 

AS mapj1 pointed out also, there are voltage gradients … but it is slightly more complicated than that. The presence of the body distorts the electric field in various ways, some to do with “salt” (ion) concentrations. 

Add to that, that the body resistance is lowered, and there are a lot of pathways for the current to enter the body - it's not simply hand-to-feet or hand-to-hand shock.

Finally, it may not be ventricular fibrillation that kills someone, but drowning due to muscle spasms and lack of control. 

IN fact, limitation of voltage in immersed situations is not a guarantee of protection against electric shock - a few volts is all it takes. IEC TR 60947-5 recommends that, whatever the operating voltage, current limiting (at a very few mA - strong muscular reactions occur at as little as 5 mA) is the only feasible option for equipment intended for use where people are immersed in water.

he or she is not necessarily lower res than the bath water, nor do they need to be. But if current is flowing in the water, there is a voltage gradient along the current path. Put a hand in and you can tap into that at any point along the resistance, rather in the manner of the slider of old style school rheostat.

 Now, if you have one end of your body near one electrode and the other end of your body near the other, you get a significant belt. Much like step voltages on wet ground, but larger contact areas.

As you fill more of the bath with body you displace the parallel water path, and the problem gets worse.

However if the the two electrodes are close together, and you keep well away from them, you only see a  small fraction of the terminal voltage.

M.

gkenyon: 
There is NO ‘residual current’. The OCPD will operate, but it is likely the person in the bath will be seriously injured or killed before that happens, as the electricity tracks through salt straight to the person's trunk, as it's the most conductive thing in the water, to get from Line to Neutral.

As I said, no protective conductor, no alternative path other than L-N, so an RCD is wholly ineffective. This is not a theory … it was proven in an investigation after two children died in a bath in Germany after a shaver on charge from the mains fell into the water and killed them both.

I am struggling with this. We have in the bath water a couple of electrodes. The bather is in contact with neither of them. How can the bather be a lower resistance between them than the bath water?