Existing Supplementary Bonding

[buzzlightyear]

one of them alterations to the bathroom circuit .

 

[Pete999]

View attachment 40158 one of them alterations to the bathroom circuit .

Could do that yes.

 

[Midwest]

I have clarified this particular point before wid' my scheme. If there are no alterations to the circuits, replacements are like for like, then there is no requirement to install additional protection.

Imagine if you replace a pull cord, sorry Madame I now have to install you an RCD FCU.

Now what about that towel radiator?

 

[Ian1981]

You could put one in front of the CU, would be easier than faffing with the bathroom circuits, I would think. Still think he is wrong to use the 30 Amps in his calculations. In the video CK is using 10ma as quoted in GN3 not a current that operates an RCD 230/.01 (10ma)= 2300ohms minus the resistance of the body ohms1000, in that calculation there is not any reference to the operating current of any OCPD, only referring to GN3.

The formula given to determine the effectiveness of supplementary bonding in bs 7671 is 50v /Ia ( or I delta N when the circuit is protected by an rcd) to effectively make sure the touch voltage will not rise above 50 volts during a fault as long as the resistance of the pipework is below in this case 1.666 ohms.
So how is it wrong?
That video is for determining pipework is an extraneous conductive part like your water and gas services to see if they require protective bonding.

 

[buzzlightyear]

NAPIT | Effectively Connected Extraneous Metalwork - http://professional-electrician.com/features/napit-effectively-connected-extraneous-metalwork/

 

[Strima]

I would use the highest rated device on the installation as a fault occurring anywhere in the property could impact the bathroom.

 

[Ian1981]

I would use the highest rated device on the installation as a fault occurring anywhere in the property could impact the bathroom.

That is not what bs 7671 says on the matter.
It’s the protective device for that particular location

 

[Midwest]

I would use the highest rated device on the installation as a fault occurring anywhere in the property could impact the bathroom.

But the test or concern is between exposed conductive parts & extraneous conductive parts in that location?

 

[Pete999]

The formula given to determine the effectiveness of supplementary bonding in bs 7671 is 50v /Ia ( or I delta N when the circuit is protected by an rcd) to effectively make sure the touch voltage will not rise above 50 volts during a fault as long as the resistance of the pipework is below in this case 1.666 ohms.
So how is it wrong?
That video is for determining pipework is an extraneous conductive part like your water and gas services to see if they require protective bonding.

No the video is explaining how to test pipework to see if they require any supplementary bonding, there are other tests to ascertain that main bonding is up to scratch.

 

[Midwest]

Now what about that towel radiator?

Hurry up, I've got to go to bed soon, and I don't want to be thinking about this all night!

 

[Midwest]

No the video is explaining how to test pipework to see if they require any supplementary bonding, there are other tests to ascertain that main bonding is up to scratch.

Pete check out one of your other favourites by John Ward.

 

[Pete999]

Hurry up, I've got to go to bed soon, and I don't want to be thinking about this all night!

No nor me, can't sleep very well as it is, That's me done said my piece I believe I am right, good night all.

 

[Strima]

That is not what bs 7671 says on the matter.
It’s the protective device for that particular location

But the test or concern is between exposed conductive parts & extraneous conductive parts in that location?

Having reread the OP I now realise the towel rail is fed from the boiler and not electric.

 

[Ian1981]

Or try reading part 5 of bs 7671 and Gn8 as it’s written in black and white how to verify that pipework has a low enough resistance to ascertain the effectiveness of the supplementary bonding

 

[buzzlightyear]

Hurry up, I've got to go to bed soon, and I don't want to be thinking about this all night!

 

[buzzlightyear]

No nor me, can't sleep very well as it is, That's me done said my piece I believe I am right, good night all.

 

[Ian1981]

reg 415.2.2

"where doubt exists regarding the effectiveness of supplementary equipotential bonding, it shall be confirmed that the resistance R between simulataneously accessible exposed-conductive-parts and extraneous-conductive-parts fufils the following condition:

R less than/equal to 50 V/Ia in a.c systems

Or in the case of an rcd
50v / I delta N

 

[Midwest]

reg 415.2.2

"where doubt exists regarding the effectiveness of supplementary equipotential bonding, it shall be confirmed that the resistance R between simulataneously accessible exposed-conductive-parts and extraneous-conductive-parts fufils the following condition:

R less than/equal to 50 V/Ia in a.c systems

Or in the case of an rcd
50v / I delta N

So towel rad pipe at 0.04ohms, doesn't require local supplementary bonding?

 

[Ian1981]

So towel rad pipe at 0.04ohms, doesn't require local supplementary bonding?

Have you taken parallel paths into account?

 

[Midwest]

That's what I look like in the morning, after ----ing & turning, thinking about electrical stuff. Gonna give it up soon, go work down the garden center, moving green stuff about, and advising Mrs Miggins on what to put in her borders