electric shock in shower

[eddielarge]

Hi can any one help.

Was called to a job where the glass shower curtain had become live (230V) .

this was caused because the person who fixed it screwed through the old 6mm shower cable which was running up the wall into the loft where it was terminated into a JB because it was no longer needed.

He had only screwed through the live cable and as the metal on the glass shower curtain was not bonded it stayed live,

So when the customer had a shower the water caused a path and livened up the shower which was not electric but water mains fed,

the new shower was piped in plastic so there was no earth path to blow the RCD.

The customer got a belt off of the shower head .

I have rung the NIC and they state there is no requirement to bond shower curtain or shower.and the the rcd was sufficient.

At the end of the day they tell me this is ok but the women got a shock and it could have been serious.

can anyone shed some light on this and tell me why bonding is not needed when obviously there is a grey area.

 

[Notsosmart]

Here lies the issue with the latest regs wherby safety is reliant upon rcd's & bonding is now deemed unnecessary; that's ok as long as there is a return path for a fault. In this case because all of the water was in plastic then the rcd will never trip unless there is a short.

The other issue is how do you bond to the shower screen? I've never done it, nor would the customer be happy with us drilling & tapping into their shiny brand new (sometimes) expensive fittings. (Neither would my liability insurers if I ruined it).

What should have been done was for the redundant cable to be properly isolated at the board.

 

[Yooj]

I agree with Notsosmart in that this is caused by very poor isolation of the redundant circuit.

Is this old shower circuit on an RCD...I ask, because there was likely an earth path to trip the RCD, however it was when the user sprayed water on the shower screen, and they were in the shower...Did the RCD trip when they got a shock? If not, then there could be a problem with the RCD, and I would suggest it is tested.

If the RCD was operating correctly, then it should have operated within 40mS limiting the touch voltage to less than 50V, i.e. below the pain threshold; and since the very fact that she recieved a jolt means that there was an earth path, or an L to N, both of which were through her. If it was an L to N, then this would not trip an RCD, but the L to E would, and should have.

Additionally, supplementary bonding can only be ommited if all the circuits in the bathroom are RCD'd and the Main Protective Bonding is in place and adequate.

Yooj

 

[Notsosmart]

You could be right that the circuit isn't on an RCD, the fact that it was in 6mm suggests that it is either quite old &/or that it hasn't been installed with too much safety in mind. However the RCD could possibly have been bypassed if the waste is connected to a cast iron soil stack.

 

[eddielarge]

Yes the shower cable that caused the fault is now disconnected.

The circuit was on an rcd that was working and the main bonding was in place.

Im not sure what sort of shock she got she just said it was a shock, im thinking it was not a full packet as she might no be here now,

i agree with the point that if the plumber had safely isolated shower circuit at the dis board then this would not have happened,

I was just concerned that there was nothing in place to make plumbers responsible for lack of bonding due to installation of plastic pipes

 

[Yooj]

You could be right that the circuit isn't on an RCD, the fact that it was in 6mm suggests that it is either quite old &/or that it hasn't been installed with too much safety in mind.

I know the OSG stipulates that 10mm should be put in, but I can rightly put in a 6mm T&E for a 7.2kW shower and prove through calculation that it is fine. Though I get your point, and i am only being pedantic.

However the RCD could possibly have been bypassed if the waste is connected to a cast iron soil stack.

Not sure that I agree with the above though...the only way to bypass the RCD is to swap it out for an MCB, or to connect a loop from the RCD supply to load for L&N. An RCD monitors the differential between live and neutral, and when a differential occurs, i.e. a fault to earth (not necessarily via a CPC or bonding), then it trips...If there was an earth path via a soil stack, then an RCD would trip.

...I was just concerned that there was nothing in place to make plumbers responsible for lack of bonding due to installation of plastic pipes

With plastic pipes, there is no more need to bond these than there is to bond a plastic bath.

Yooj

 

[mechelec]

An RCD will sence any imbalance in the phase and neutral conductor. as the client had a shock an amount of voltage from the phase must have passed to earth through the path of least resistance i suggest either the magnitude of the current flowing was either less than the rated RCD value, the RCD is faulty or the cable was not RCD protected. Earth bonding is irrelevant with RCD's in bathrooms infact it should be advantageous to not have it bonded as the current has nowere to go.

 

[Yooj]

... Earth bonding is irrelevant with RCD's in bathrooms infact it should be advantageous to not have it bonded as the current has nowere to go.

Other than down an extraneous conductive part, i.e. radiator, tap/copper pipe-work etc...

Yooj

 

[eddielarge]

thanks for the replys

 

[pmac10]

Here lies the issue with the latest regs wherby safety is reliant upon rcd's & bonding is now deemed unnecessary; that's ok as long as there is a return path for a fault. In this case because all of the water was in plastic then the rcd will never trip unless there is a short.

rcd s dont detect shorts, only fault to earth.

 

[boatnik1]

However the RCD could possibly have been bypassed if the waste is connected to a cast iron soil stack.

To anyone considering useing a cast iron soil pipe as a means of bonding they should be aware that the joints in cast pipes are usually filled with a non conducting compound (sometimes putty) and this will stop the pipe from grounding. Likewise when the pipe has been left for asthetic reasons but is terminated at ground level into plastic groundwork.

 

[hotXbun]

To anyone considering useing a cast iron soil pipe as a means of bonding they should be aware that the joints in cast pipes are usually filled with a non conducting compound (sometimes putty) and this will stop the pipe from grounding. Likewise when the pipe has been left for asthetic reasons but is terminated at ground level into plastic groundwork.

Nice one boatnik ... don't forget the cutting out of a section of the cast iron to make a space for a nice shiny plastic branch complete with two rubber seals ..... now that would most definitely be a hindrance to any earth leak....

As for taking a shower in a new installation, I intend to stick a sticker onto said shower screen which will say:

WARNING .... taking of a shower whilst naked can be dangerous ... We strongly suggest you take precautions!"

I will from now on I will include a free pair of welly boots complete with user instructions

I have received a shock from a so called RCD protected SSO and it isn't so much the voltage as the shock of it occurring! I think that irrespective of what our technical books say, till that RCD trips, you are subjected to a shock - value of shock will depend on timing ... like a good joke, if the time is correct it is a real belter

 

[Davey101]

Good point mate, anyone who thinks you wont get a nasty electric shock, just because the circuit is RCD protected, has obviously not worked on many live circuits!

 

[Had8Lives]

Don't forget that bonding in Bathrooms can only be ommited if the Earth Loop Impedance is low enough to trip the breaker/RCBO in the required time.