Electric shock from kettle

[jumpjamesjump]

My girlfriend got a an electric shock off of the kettle the other day when she simultaneously came into contact with it's metal lid and the metal sink at the same time. Just to give some context I am a heating engineer so have alimited understanding of how electrical installations work.  So after the shock I decided to test the kettle with my multi-meter and found that it had 240v on the metal lid and that it had 0.1ohms resistance between the earth probe on the plug and the kettle's live lid.  The consumer unit has no RCDs and it is one of the older Wylex type consumer units with re-wirable fuses and 1, BS60898 Type B 20A MCB.  Now my limited understanding is that as soon as there was a live to earth fault on the kettle then a huge ampage should have been pulled down the earth wire thus tripping either the MCB or blowing the CU's rewireable fuse or 13a fuse in the kettle's plug.  I talked to an electrician on the phone that my landlord gave me the number for and he said that these older types of fuses/MCBs would not normally trip, he also ensured me that the installation was tested a few years ago and is all fine.  

I understand that taking an electric shock will not trip the fuse straight away and therefore isn't as effective as if it had an RCD but I think that either the earth wire has too much impedance on it or it is not connected.  Any help would be greatly appreciated.

 

[ProDave]

The current that flows if you get an electric shock will never blow a fuse, but might trip an rcd.

Where was the "240V on the metal lid" measured with respect to?

If the earth continuity from the kettles earth pin to it's case really is 0.1 ohm, then I would be suspecting a wiring fault to the socket the kettle is plugged into. I would stop using that socket for anything immediately.

Try the kettle into a different socket, preferably on a completely different circuit. Do you still get "240V on the metal lid"?

 

[jumpjamesjump]

I totally forgot to add that the fault was from water on the kitchen surface underneath the kettle managing to get into the terminal connection.  So I assume it just shorted from live to earth,  hence causing the lid to become 240v.  I measured the 240v in respect to the metal kitchen sink, the metal hob and to the metal casing of the boiler.  So do you agree that there is a lack earthing continuity between the socket and the ground?

Landlord are saying they will charge me for a call out if there's nothing wrong with the installation.  But the way I see it the MCB or fuses shouild have tripped.

 

[jumpjamesjump]

Also why does a fuse not blow when you get an electric shock?  Is the human body not capable of pulling a high enough amount of amps?

 

[Evans Electric]

A fuse  wire won't  blow when you get a shock ...thats  one of the main reasons they are not used anymore .      They'll blow  on a dead short  or if  the circuit is overloaded  they might blow after a few hours  , just before the  wiring  melts       RCD's are the lifesavers  .   Your landlord , on being told someone has received an electric shock   immediately thinks of the cost of sending an electrician  .....he should be thinking someone could be killed  in my property , its my responsibility  to ensure  it is safe ,  the bloke is a  tosser. 

What does he do if you said  your kids were in hospital suffering from carbon monoxide poisoning  from a faulty gas boiler .....Oh I'll charge you for a fitter to call!!!!

Your installation  is in effect ... out of date  by about 40 odd years   &  four  editions of the Regs   I should think ...specially as its a rented property  .   All socket circuits  on the current Regs should be protected by an RCD ...in fact that usually applies to  every circuit  for various reasons .  

They would  throw the book at  this guy in Scotland .

Was the worktop flooded  and the kettle base electrics   saturated ?    

 

[ProDave]

Who does the kettle belong to, you or the landlord?

This demonstrates why in Scotland you need a valid satisfactory EICR to let a property. The sooner England and Wales catches up the better.  The lack of RCD protection would almost certainly mean the landlord up here will have had the CU replaced.

I suspect 2 faults here, a leakage problem with the element in the kettle, and no earth on the socket it was plugged into.

Tell the landlord to get an electrician there ASAP and if he asks for payment for that, tell him to whistle.  He has a duty to provide safe electrics.

If it is your kettle, just buy a new one, they are so cheap.  If the LL provided it, get the electrician to PAT test it and if it fails the LL needs to replace it.

 

[jumpjamesjump]

Thank you for replying.

The kettle belongs to myself and I have  already replaced it with a completely plastic one.  Yes the kettle based electronics were saturated. 

The thing is guys I've spoken to the electrician on the phone and he's told me that it's probably all fine and that the installation is just old.  Is that true?  Or is there a piece of regulation that I can point to and show them that proves the earth wire or installation is not ok? 

I mean the installation is 100% not working as it should right?  240v on the earth wire for an extended period time (it was at least a couple of hours) should surely trip the MCB or fuse?  

thanks again

 

[Evans Electric]

It is an old installation ,   compared to a modern system its prehistoric  .  It was the norm back when England won the World Cup  but not now  ..Get it checked  , theres only so much we can do or say on here  without being there. 

 

[ProDave]

If you have good continuity from the earth pin of the plug to the metal case of the kettle, and the socket had a good earth connected to the earth pin, then even with leakage through a faulty element, there would not be 240V present on the case of the kettle.  Hence  I suspect the socket used might not have a good earth connection.

 

[Doc Hudson]

The thing is guys I've spoken to the electrician on the phone and he's told me that it's probably all fine and that the installation is just old.  Is that true?  Or is there a piece of regulation that I can point to and show them that proves the earth wire or installation is not ok? 

thanks again

General guidance can be found at:  https://www.electricalsafetyfirst.org.uk/guides-and-advice/for-tenants/

Also BS7671 wiring regulation 411.3.3 states that socket outlets rated up to 20amps must have additional RCD protection.  Did you ask to see a copy of a current electrical certificate before you moved into the property?  What dates are on the periodic inspection label at the fuse box?  Regulation 514.12.1 requires that this information should be prominent and durable near the origin of the installation. (typically this is normally on the cover of the fuse box).  With rented properties inspection intervals are normal 5years, or change of occupancy

Doc H.

 

[Ardet R]

If the kettle electrics have got wet then there would be a fairly high resistance path from Live through the water and so to the body of the kettle.

A high resistance test meter might measure 240V from the kettle body to a good earth such as a sink, not usually just the water on the counter, as there would be no current flowing and so the resistance would be immaterial.

When you touch the kettle casing a small current will flow through the body and you will feel a shock but the current through both the water and the body would be very low in the 10-100 mA range as the resistance of the body and the water will then be significant.  However if you were in bare feet on a wet tiled kitchen floor laid on the earth then the current could be much higher in the 200-1000mA range enough to cause death, but never enough to blow the fuse.

The fuse is only protecting the cable from overheating and burning, not people from being electrocuted,

By now any socket circuit ought to be 30mA RCD protected for just this reason, the RCD would then trip on you touching the kettle and whilst it would still hurt it should not kill and would not happen again as the circuit would be off.

 

[jumpjamesjump]

If the kettle electrics have got wet then there would be a fairly high resistance path from Live through the water and so to the body of the kettle.

A high resistance test meter might measure 240V from the kettle body to a good earth such as a sink, not usually just the water on the counter, as there would be no current flowing and so the resistance would be immaterial.

When you touch the kettle casing a small current will flow through the body and you will feel a shock but the current through both the water and the body would be very low in the 10-100 mA range as the resistance of the body and the water will then be significant.  However if you were in bare feet on a wet tiled kitchen floor laid on the earth then the current could be much higher in the 200-1000mA range enough to cause death, but never enough to blow the fuse.

The fuse is only protecting the cable from overheating and burning, not people from being electrocuted,

By now any socket circuit ought to be 30mA RCD protected for just this reason, the RCD would then trip on you touching the kettle and whilst it would still hurt it should not kill and would not happen again as the circuit would be off.

Ok so essentially the installation could technically be fine.  But because the resistance through the water until it reaches the earth wire (the kettle was plastic with a metal lid) was probably pretty high it would not have been enough to pull high ampage and to trip anything, if however it was a direct short circuit connection between the live and earth then it still may trip accordingly.  

 

[kerching]

however it was a direct short circuit connection between the live and earth then it still may trip accordingly.  

A fault loop impedance test should show whether or not this would happen

 

[Ardet R]

Yes you have the essence in a nutshell.

Subject to satisfactory testing of the circuit, by description, the installation is compliant to a very old version of  the wiring regulations, it is not compliant with the much safer regulations now in place (though there is no requirement to update unchanged installations, it is a recommended action in general and any new work is required to comply).

In essence if the circuit is in the condition to which it was installed then a direct short live to earth would blow the fuse.

An electrical path through a small volume of water and a human body may only allow 10-100mA (very variable) to flow, and cause a shock sensation but will never blow a 32A fuse.

 

[ProDave]

Ok so essentially the installation could technically be fine.  But because the resistance through the water until it reaches the earth wire (the kettle was plastic with a metal lid) was probably pretty high it would not have been enough to pull high ampage and to trip anything, if however it was a direct short circuit connection between the live and earth then it still may trip accordingly.  

I thought you said you measured 0.1 ohm from the lid to the earth pin of the plug. Highly unlikely if the body of the kettle was plastic.  When PAT testing a plastic kettle, you clip the earth lead onto the actual element.

 

[jumpjamesjump]

I thought you said you measured 0.1 ohm from the lid to the earth pin of the plug. Highly unlikely if the body of the kettle was plastic.  When PAT testing a plastic kettle, you clip the earth lead onto the actual element.

I did.  I simply put my multi-meter to the ohms setting and put one probe to the earth terminal on the plug and the other one to the lid.  Wouldn't the metal lid be connected to the earthing terminal?  Extraneous conductive part? 

thank you everyone for replying your help is much appreciated.  

 

[Ardet R]

The metal lid would be well insulated from the electrical parts by the plastic body, if you have an autoranging multimeter you may have had a result in MΩ instead of Ω but the display would still show 0.1, but with MΩ units that would be 100,000Ω.