Bonding

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I have a steel radiator in an ensuite, with a non-electrical shower, an overhead light, a fan and a shaver socket. Those circuits are not RCD protected. The installation was new in 2003.
The radiator is fed by plastic pipes. Why does it have an earth bonding wire clamped to it and where is that wire likely to terminate?
The bathroom taps are not fitted with any bonding and are also fed by plastic pipes.
My belief is that it would be safer to remove the bonding wire.

Comments and explanation appreciated.
 
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My belief is that it would be safer to remove the bonding wire.
If things are as you say then you are correct and it would.

Comments and explanation appreciated.
Lots of electricians do not understand bonding.
They think parts require bonding just because of what they are.

If you received a shock from a live wire while leaning on the radiator, when earthed, the electricity would find a path through you to earth with very little impedance, whereas if you remove this earth (it is not bonding if the part is otherwise not earthed by some means) it will have high impedance through the floor or wall and so be much less severe.

The wire likely goes to an earth connection at one of the accessories you mention.
 
The principle is to ensure that in a location where a person may simultaneously touch two metal objects with wet hands/feet, there can be no difference in voltage between those two objects. The collection of bonded objects also should be earthed by at least one route to the supply earth, but a sturdy connection between them is more important than the earth itself. Not all metal needs to be bonded, but if the metal could conceivably be made live by a fault, OR is/could become earthed, then it should be bonded to all other such metal.

Thus taps on metal pipes definitely because the pipe is typically earthed, radiator on plastic pipes.. I would have thought best to bond it in case a fixing screw has hit a hidden live cable, or has earthed it. Don't forget the light fitting if it has exposed, earthed metal.

Bonding need not be literally on the touchable object itself provided it is attached close enough that it is unlikely to be disconnected from it, for example on a metal pipe.
 
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radiator on plastic pipes.. I would have thought best to bond it in case a fixing screw has hit a hidden live cable, or has earthed it. Don't forget the light fitting if it has exposed, earthed metal

[Sarcasm] S**T, we need to start bonding TV brackets, shelves, curtain poles, loft ladders, carpet grip strips etc just incase the fixing has hit a cable [/Sarcasm]

If the radiator is fed with plastic pipes, it does not need bonding. It's that simple. As has already been pointed out, the pipes would require bonding if they were metal, but as they're not, they don't. They may well be metal under the floor, and they may well be bonded elsewhere.

I absolutely detest those disgusting radiator bonding clamps. Worst invention ever IMO.
 
I absolutely detest those disgusting radiator bonding clamps. Worst invention ever IMO.

I don't like the either, but I bought a box of them years ago, and I'm bloody determined to find use for them. :mad:

Ummmm use them to clamp little things to the support braces in the back of your van?

Hold some business cards together?

I literally cannot think of one useful thing you could use them for.

Edit, I guess steel purlins and suspended ceilings, but you could equally just do those with a nut, bolt and ring crimp, and probably get a better connection.
 
[Sarcasm] S**T, we need to start bonding TV brackets, shelves, curtain poles, loft ladders, carpet grip strips etc just incase the fixing has hit a cable [/Sarcasm]
Well, if you're wearing any rings don't stand still too long when there's an electrician around. Seriously I thought what I said was clear enough, there is NO requirement to bond metal which is unlikely to ever have a live or earthing role for personnel. There was one newsworthy case in which a householder was electrocuted by a metal rack placed above an oven. The oven supply had been taken by a very unconventional route where no-one would have expected a cable, and had been pierced by a screw. The electrician who fitted the oven was prosecuted. Extreme bad luck, but it illustrates the point. Though in such cases an RCD is the best option. Won't prevent a belt but usually prevents a death.
 
You said "I would have thought it best to bond it in case a fixing screw has hit a live cable" that sounds like the exact opposite of saying it doesn't need bonding to me, but either way.

And yes, I remember reading about that too, a diagonal route if I remember, not that I am defending him in any way, shape or form, but very few people understand cable safe zones. On site recently I had to rectify a fault because a chippy had put two, yes TWO pins through a cable chase DIRECTLY underneath a socket. It beggars belief
 
The collection of bonded objects also should be earthed by at least one route to the supply earth
No they shouldn't.

What if the potential introduced by the e-c-ps is not earth potential? Earthing them might create a fault.


Not all metal needs to be bonded, but if the metal could conceivably be made live by a fault, OR is/could become earthed, then it should be bonded to all other such metal.
1) No it shouldn't.

2) Guarding against the former is not bonding, it is earthing.


radiator on plastic pipes.. I would have thought best to bond it in case a fixing screw has hit a hidden live cable
1) That is not bonding it is earthing.

2) If the radiator is supplied by plastic pipes it is not an e-c-p, and therefore should not be bonded. Taking a metal item which is not part of the electrical installation and making it one does not improve safety, it makes it worse.
 
Good point (y)
shake%20head.gif
 
Well, if you're wearing any rings don't stand still too long when there's an electrician around. Seriously I thought what I said was clear enough, there is NO requirement to bond metal which is unlikely to ever have a live or earthing role for personnel. There was one newsworthy case in which a householder was electrocuted by a metal rack placed above an oven. The oven supply had been taken by a very unconventional route where no-one would have expected a cable, and had been pierced by a screw. The electrician who fitted the oven was prosecuted. Extreme bad luck, but it illustrates the point. Though in such cases an RCD is the best option. Won't prevent a belt but usually prevents a death.
You really don't know what you're talking about, do you.
 
it will have high impedance through the floor or wall and so be much less severe.
If only.... 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.

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

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

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.

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.

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.
 
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