Bonding

[seasickstevie]

Bernard, you're obviously far more knowledgeable on the subject, but likewise I've always thought ...

There is no clear fits all answer to the question bond or not bond.

 

[EFLImpudence]

There is also a path through the liquid in the pipe. If that liquid were pure water then the impedance over a few feet woud be high enough to limit the current to a few milliamps. But it isn't pure water, it has ( should have ) various chemicals added to reduce the corrosion and other effects of water on metal. It has metal salt and oxide particles which make it conductive.

We do not earth or bond water.
If you are concerned then you can measure it and consider the best way.

There is no clear fits all answer to the question bond or not bond.

No but there are the accepted compromises.

What current through the body is fatal. ? What duration of mild shock can be fatal ? Which route through the body is the current taking ?.

You're point?
That we should earth (not bond) for hand to hand contact but not hand to foot?

Would a high impedance route to ground ( no bonding ) always ensure the current was low enough to cause no harm to the person even if they were unable to break the contact ? 10 milliamps for a few seconds can do more harm than 40 milli-amps for 50 milli-seconds.

No, but the reverse would always ensure the opposite.

Would it be better to ensure the fault impedance to ground was low enough to ensure the RCD would trip if a person was receiving a shock.

Not in the way you suggest - by earthing isolated parts.

A short duration but massive shock seldom kills. It will, as with a defibrillator, stun the heart and stop it. The heart then re-starts by itself. A much lesser shock but of prolonged duration will keep the heart stunned and unable to pump blood and it is the damage to body tissue, brain cells and heart muscles from lack of blood flow that leads to death.

That is why we try to cater for the most likely at the expense of the remote.

It would be safer to have no electricity or water in a bathroom.