IIRC, faults were mainly due to build up of dust and dirt in the RCD. This would not happen if the test button were used on a regular basis (ie not each blue moon).
Removal of supplementary bonding in bathroom?
- Thread starter JohnnyG
- Start date
Sadly test buttons do not get pressed from one year till next.
I know this happens and agree if they did get pressed regularly the fails would reduce, perhaps significantly
I know this happens and agree if they did get pressed regularly the fails would reduce, perhaps significantly
OK I thought I knew but now I'm confused. and very curious.
Page 24 definitions:
"Extraneous-conductive-part. A conductive part liable to introduce a potential, generally Earth potential, and not forming part of the electrical installation."
Are you saying that 'a conductive part NOT liable to introduce a potential' is still called an extraneous conductive part - although not needing bonding? If so, what is the definition of a metal object that is not an e.c.p.?
Regards.
That's it. That's all there is to it.
No. I never even came close to suggesting that this might be the case - this is obviously where you're confused.
Examples of metallic parts that are NOT extraneous conductive parts:
A metal door handle, or hinge, or bolt.
The handle on your toilet cistern.
Metallic threshold strips
The zip on your jeans.
Your belt buckle
(But you could always try bonding these if you absolutely must!
)
OK - so how do you decide if a conductive part is liable to introduce a potential, generally Earth potential, or not?
I'm surprised you ask this, Bas. There's an excellent book on the subject*: here
*To anybody unfamiliar with Mr Cockburn's opus, please deploy sarcasm detectors now.
Ha ha.
A radiator plumbed into a 100% copper CH system is a e-c-p, yes?
What if the pipework is all plastic - is the rad still an e-c-p?
A radiator plumbed into a 100% copper CH system is a e-c-p, yes?
What if the pipework is all plastic - is the rad still an e-c-p?
nope it's just a floating chunk of metal
Probably
Probably not.
In each case it is easy enough to verify by reference to your known earth datum at the MET. GN5 suggests anything over 22,000 Ohms can be regarded as not being an extraneous conductive part, but, as always, it is up to the installation designer to make that decision. (This is the hard bit for jobbing sparks; do they understand this well enough to be able to make such decisions?)
Better hope they do, because applying bonding to something which is not an e-c-p makes things less safe, not more.
Quite correct, which is why Mr Cockburn's efforts are definitely NOT part of the solution.
This is something I do not understand UNLESS it is that a lump of un-earthed metal ( such as a central heating radiator connected by plastic pipes ) is "safer" as it will not provide a circuit to earth for a person touching both the radiator and a live conductor. That would make sense if there was no chance of the water in the plastic pipes being conductive enough ( inhibitors added, it is not pure water ) to carry a lethal current from the radiator to the earthed / bondded metal work of the boiler.
Then there is the radiator that has metal pipes for some of the route but plastic sections meaning there is no metallic galvanic ( low impedance ) connection to the radiator. If any of the metal pipework connected to this radiator becomes live due to being squashed against damaged cables in a shared notch in a joist then the radiator can become live. Holding an earthed metal appliance and touching this radiator would be a potentially lethal shock hazard. In practise the conductivity of the water might be sufficient to trip an RCD when the pipe work and radiator became live but that is not 100% certain to happen.
I have 'read' the suggested 'book' and now 'know' everything about 'hazardous earths'.
Thanks, dingbat for the replies.
I appreciate your philosophy of getting me to work it out for myself rather than just telling me the answer but I still can't see anything fundamentally wrong with my first post - other than being the wrong way round. Am I missing something really simple?
However, is this not just chicken and egg? An object is an e.c.p. therefore must be bonded or an object must be bonded therefore is an e.c.p.
I have seen elsewhere a metal object that is not an e.c.p. referred to as an isolated conductive part.
As an aside - I think the experts now generally accept that the egg came first and need not be bonded.
Thanks, dingbat for the replies.
I appreciate your philosophy of getting me to work it out for myself rather than just telling me the answer but I still can't see anything fundamentally wrong with my first post - other than being the wrong way round. Am I missing something really simple?
However, is this not just chicken and egg? An object is an e.c.p. therefore must be bonded or an object must be bonded therefore is an e.c.p.
I have seen elsewhere a metal object that is not an e.c.p. referred to as an isolated conductive part.
As an aside - I think the experts now generally accept that the egg came first and need not be bonded.
Right - understood.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
