Earthing steel bath
- Thread starter carl3011
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No.
You must not.
You must not.
Unless it has become "earthy" either via pipework (not in this case) or it`s in contact with say a girder or soil etc (which is unusual) then deliberately earthing it could give it a potential (earth) that it would not otherwise have.
Therefore increasing possible risk
Therefore increasing possible risk
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To expand on ebee's answer, in case it's not totally clear to you ...
The main risk of electric shock arises if someone simultaneously touches something 'live' and something earthed. The risk it therefore reduced by having as little exposed earthed metal around as possible.
Sometimes earthed metal is unavoidable ... if something metal is at risk of 'becoming live' (like the metal casing of a Class 1 electrical appliance), then it has to be be earthed (as one of the measures to reduce the risk of it resulting in a shock). However, if there is minimal risk of it becoming live (as is the case with the OPs bath - only extraordinarily unlikley happenings could result in it becoming live) then, on balance, the risk of shock is greater if the bath is earthed than if it is not.
Kind Regards, John
Well put John (I was trying to keep it simple - also not mentioning bonding for that reason too).
Yes, I realised that. However, when you just wrote "Therefore increasing possible risk", I wondered if winstom would necessarily understand 'why'. I, too, avoided mentioning bonding - hence my rather contorted/cryptic statement as to why we earth some things ("As one of the measures..."!)
Kind Regards, John
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So, suppose you had fitted a shower pump underneath the bath? Or as a plumber once suggested to me, fitted a shower pump under the bath, and plumb it so that it pumped the water into the bath as well. Earth bath?
If the pump is attached to the bath by metal (usually copper) then it is earthed but if plastic then it is not.
If you actually mean earth (i.e. attach CPC) - is the bath likely to become live?
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Well that's the thing. I buy a pump. I don't know what's inside it. It has mains going into it, and it is connected to a bath or shower plumbing. Should I trust my family members' lives to the likelihood that a piece of equipment I know nothing about the inside of, will never connect live to my pipes?
I ended up earthing the pipes.
I ended up earthing the pipes.
That is your decision if you think that is the more likely scenario.
However, the pump will already be earthed and have plastic pipe connections so unless the line conductor is going to jump out and grab the bath or pipes it will not happen.
If the pipes are already bonded then 'earthing' them will make no difference.
If they did not require bonding (not extraneous) then you have introduced a hazard.
However, the pump will already be earthed and have plastic pipe connections so unless the line conductor is going to jump out and grab the bath or pipes it will not happen.
If the pipes are already bonded then 'earthing' them will make no difference.
If they did not require bonding (not extraneous) then you have introduced a hazard.
There is no fit all answer to the question about earthing a metal bath.
Each case needs to be risk accessed and appropriate action taken.
At one extreme set of circumstances it is safer to leave the bath neither earthed nor bonded. At the other extreme it is probably safer to earth the bath.
NOT earthing appears to be the modern fit most cases answer for a metal bath on a non conductive ( when dry ) floor.
For other cases the variables need to be looked at in detail
An electric shock requires two points of contact to the human body and the points must be at different voltages to force a current through the body. Birds can perch on 11,000 volt un-insulated over head wires in perfect safely as there is no voltage difference between the two feet gripping the wire. Like wise touching a live wire when there is no other point of contact to any other conductive surface will not give an electric shock ( DO NOT TEST THAT at home, the carpet might be damp .
So if the bath is totally insulated you cannot get a shock from it (or the water in it) if it is one of the two points of contact.
Some baths are not totally insulated ( isolated ) from earth but instead have a high but variable impedance path to ground via damp floors, drain pipes, ( plastic drains lined with sludge are conductive ) or other less obvious routes.
As the second point of contact these baths will allow some current to flow hence a shock will result. The question is how much current ? A few milli amps is unlikely to be fatal ( but in some people it can be ) but might induce a fall that results in serious injury. A few milli-amps will not trip the RCD if fitted so the current will persist and the fault that caused it will still be present.
If that bath was earthed or bonded the initial shock current would be higher and therefore more likely to trip the RCD ( if fitted ). It would also be more likely to be fatal.
Depending on the fault that caused the shock there is a risk to the person who comes to the rescue of the person in the bath. If the bath and the water in it are live ( the RCD has not tripped ) then the rescuer has to avoid touching anything the is connected to earth while they are pulling the casualty out of the bath.
Each case needs to be risk accessed and appropriate action taken.
At one extreme set of circumstances it is safer to leave the bath neither earthed nor bonded. At the other extreme it is probably safer to earth the bath.
NOT earthing appears to be the modern fit most cases answer for a metal bath on a non conductive ( when dry ) floor.
For other cases the variables need to be looked at in detail
An electric shock requires two points of contact to the human body and the points must be at different voltages to force a current through the body. Birds can perch on 11,000 volt un-insulated over head wires in perfect safely as there is no voltage difference between the two feet gripping the wire. Like wise touching a live wire when there is no other point of contact to any other conductive surface will not give an electric shock ( DO NOT TEST THAT at home, the carpet might be damp .
So if the bath is totally insulated you cannot get a shock from it (or the water in it) if it is one of the two points of contact.
Some baths are not totally insulated ( isolated ) from earth but instead have a high but variable impedance path to ground via damp floors, drain pipes, ( plastic drains lined with sludge are conductive ) or other less obvious routes.
As the second point of contact these baths will allow some current to flow hence a shock will result. The question is how much current ? A few milli amps is unlikely to be fatal ( but in some people it can be ) but might induce a fall that results in serious injury. A few milli-amps will not trip the RCD if fitted so the current will persist and the fault that caused it will still be present.
If that bath was earthed or bonded the initial shock current would be higher and therefore more likely to trip the RCD ( if fitted ). It would also be more likely to be fatal.
Depending on the fault that caused the shock there is a risk to the person who comes to the rescue of the person in the bath. If the bath and the water in it are live ( the RCD has not tripped ) then the rescuer has to avoid touching anything the is connected to earth while they are pulling the casualty out of the bath.
As we've discussed countless times before, no-one can really argue with such a statement. However, I think that many of us believe that the risk assessment is nearly always going to come down in favour of not earthing the bath. Earthing the bath only has a beneficial effect on safety should the bath somehow become 'live' - and the risk of that happening would seem to be incredibly small, smaller than the (also very small) risks of a situation arising in which it would be safer for the bath to be connected to earth.
However, it is a judgement of relative risks, and others (like yourself) may come to a different conclusion.
Kind Regards, John
That is true.
However, the conditions for all are the same.
Precisely.
We are not talking extremes.
If the bath is considered to be an exposed-conductive-part (how?) then it should be earthed - i.e. have a cpc connected to the circuit on which the bath is.
If the bath is determined by measurement to be an extraneous-conductive-part then it must be supplementary bonded to the other extraneous-c-ps of the location.
Again, it is nothing to do with extremes.
It is to counteract the consequences of the greater risk.
The bath may require bonding.
Unless it is part of the electrical installation (how?) it should NEVER be earthed.
Unless the bath is part of the electrical installation, i.e an electric bath, it should NEVER be earthed
What does that mean?
I think it has been shown before that Bernard is someone who would protect from the minutest (blue moon) risk to the detriment of greater more likely risks and does not distinguish between earthing and bonding.
Earthing (applying a cpc) is to operate the opd in the event of a fault making the part live.
Bonding (main and supplementary) is to equalise potential between parts in the event of a fault (until an opd disconnects the supply).
It is often asked light-heartedly whether you should earth your spoons but it is quite a good illustration.
Whilst eating your corn flakes with a spoon in the right hand you, unfortunately, with your left hand touch a live conductor on a faulty lead to the kettle.
Would you rather the spoon were earthed or not?
Earthing (and bonding) is a necessary evil and not something to be done for its own sake.
It is done because we cannot isolate everything. It would be better if we could.
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