Testing supplementary bonding

[jimmy_one_ball]

I wondered what you're thoughts were on this method of testing the supplementary bonding in a domestic installation. So disconnect the ten mill water bond at the board and connect one crock clip to it then connect the other crock clip to the cpc bar, Hey presto can anyone think of a reason why this would not be good enough? If the resistance is less than 0.05 Ohms then supp is either in place or not required would that be right?

Thanks in advance

 

[micknew]

What were you taught during your training?

 

[trev]

1 So all water bonds are 10mm?
2 Is this on an IV or for an EICR?
3 Do you know the difference between bonding and supplementary bonding and when and where and under what circumstances they should be applied?
4 I'll leave the rest of the questions for someone else because I'm astonished

 

[davesparks]

What exactly are you wanting to test here?

 

[Pete999]

1 So all water bonds are 10mm?
2 Is this on an IV or for an EICR?
3 Do you know the difference between bonding and supplementary bonding and when and where and under what circumstances they should be applied?
4 I'll leave the rest of the questions for someone else because I'm astonished

Astonished I'm blasted gobsmacked diss the water bond and test from the earth bar get less than 0.05 ohms what planet is this bloke on? QR code 2 -- Protective supplementary bonding test - YouTube

 

[Pete999]

Wind up innit

 

[telectrix]

if he's asked a question like this on site, it's no wonder he's only got 1 ball.

 

[trev]

Wind up innit

I bloody hope so mate.

 

[Deleted member 9648]

I wondered what you're thoughts were on this method of testing the supplementary bonding in a domestic installation. So disconnect the ten mill water bond at the board and connect one crock clip to it then connect the other crock clip to the cpc bar, Hey presto can anyone think of a reason why this would not be good enough? If the resistance is less than 0.05 Ohms then supp is either in place or not required would that be right?

Thanks in advance

I get your train of thought on this Mr half-a-set (!), you are clearly thinking that the other end of the 10mm main bond is connected to the water service and therefore if you get continuity to the MET then there must be electrical continuity through the water system to the MET.
But this ignores the fact that supplementary bonding is required only in special locations,and thus it's effectiveness can only be established by testing between conductive parts and extraneous conductive parts within that location

 

[Pete999]

I get your train of thought on this Mr half-a-set (!), you are clearly thinking that the other end of the 10mm main bond is connected to the water service and therefore if you get continuity to the MET then there must be electrical continuity through the water system to the MET.
But this ignores the fact that supplementary bonding is required only in special locations,and thus it's effectiveness can only be established by testing between conductive parts and extraneous conductive parts within that location

He's avin a laff he's winding us up surely, not you wirepuller

 

[Deleted member 9648]

He's avin a laff he's winding us up surely, not you wirepuller

Dont know whether he is mate....sounds like a typical sort of bonding related query from someone who doesnt really understand bonding. One thing I have learnt on this forum is that there are vast numbers of qualified people who dont understand bonding,the reasons for bonding,what is actually required,and how to verify it. If he's havin a laff my sides arent exactly splitting.....and if he's not well at least he's having a think about what he's doing,even if he's way off the mark.

 

[Pete999]

Dont know whether he is mate....sounds like a typical sort of bonding related query from someone who doesnt really understand bonding. One thing I have learnt on this forum is that there are vast numbers of qualified people who dont understand bonding,the reasons for bonding,what is actually required,and how to verify it. If he's havin a laff my sides arent exactly splitting.....and if he's not well at least he's having a think about what he's doing,even if he's way off the mark.

I'm not laughing either but if he isn't then lets hope he learns something

 

[happysteve]

Humour a trainee, see if I've got this right? Was going to ask this in the trainee section to avoid the abuse but I'm feeling unusually brave this evening.

According to the video quoted by Pete in post #5:

< 1667Ω (if RCD present) between a piece of metal that you're testing and something at Earth potential (usually via main equipotential bonding) is ok, as the 30mA RCD will trip if there is a fault to the metal part in question, and:

> 22kΩ (whether RCD is present or not) is ok, as in the event of a fault to the metal part this will still remain "live", but if someone touches it and summat else that is at Earth potential, <10mA will flow through them which (probably) won't kill them.

So, if RCD is present, anything between 1667Ω and 23kΩ needs bonding. Is that right? If RCD is not present, then the lower limit will be a lot lower, based on 50/Ia, where Ia is the operating current causing automatic operation in 5s of the overcurrent protective device (415.2.2).

 

[happysteve]

> 22kΩ (whether RCD is present or not) is ok, as in the event of a fault to the metal part this will still remain "live", but if someone touches it and summat else that is at Earth potential, <10mA will flow through them which (probably) won't kill them.

This isn't right, is it?

Thinking about it, what this is about, is if you touch a live (230V) part in one hand and the piece of metal in the other, then <10mA (probably) will flow. Obviously, if live is connected to the metal part, it's live, it won't trip the RCD (or OCPD) and at that point it won't matter what its resistance to Earth is. Is that any closer?

 

[Richard Burns]

This isn't right, is it?

Thinking about it, what this is about, is if you touch a live (230V) part in one hand and the piece of metal in the other, then <10mA (probably) will flow. Obviously, if live is connected to the metal part, it's live, it won't trip the RCD (or OCPD) and at that point it won't matter what its resistance to Earth is. Is that any closer?

Bonding is put in place to reduce touch voltages between exposed conductive parts and exposed conductive parts during a fault.
Once the fault has cleared there is no function for the bonding.
I have not watched the link but think I have seen it before and I do not agree with it.
Saying that the RCD will protect you is pointless (to some extent) because the bonding protective function occurs before disconnection.
(However because the RCD should disconnect before the cpc rises to dangerous voltages it may be OK)

I would say that if the resistance is <22 kΩ then it should be bonded and that is it.

Attempted description:

When a fault occurs from line to cpc or exposed conductive parts then at that point the voltage on the cpc is rising to the line voltage (230 V).

If at the time of the fault you are touching an exposed conductive part (at 230 V) and an unrelated piece of metal (an extraneous conductive part) that is at zero potential (because it is introducing another earth potential from outside) then there is the risk of an electric shock.

If that extraneous conductive part is bonded to the MET then this significantly reduces the resistance of the earth path between the two points and so reduces the potential difference (voltage). The design of bonding is such that it should reduce the touch voltage to a non dangerous level.

If the resistance of the extraneous conductive part to earth is greater than 22 kΩ then in the case of a fault the "circuit" to earth is of such high resistance that no dangerous current can flow. i.e if you touch a live part (or a cpc made live by a fault) and then touch this piece of metal there is a 22,000 Ω resistor protecting you from the current flow. effectively it is an open circuit (almost).

 

[Deleted member 9648]

Bonding is put in place to reduce touch voltages between exposed conductive parts and exposed conductive parts during a fault.
Once the fault has cleared there is no function for the bonding.
I have not watched the link but think I have seen it before and I do not agree with it.
Saying that the RCD will protect you is pointless (to some extent) because the bonding protective function occurs before disconnection.
(However because the RCD should disconnect before the cpc rises to dangerous voltages it may be OK)

I would say that if the resistance is <22 kΩ then it should be bonded and that is it.

Attempted description:

When a fault occurs from line to cpc or exposed conductive parts then at that point the voltage on the cpc is rising to the line voltage (230 V).

If at the time of the fault you are touching an exposed conductive part (at 230 V) and an unrelated piece of metal (an extraneous conductive part) that is at zero potential (because it is introducing another earth potential from outside) then there is the risk of an electric shock.

If that extraneous conductive part is bonded to the MET then this significantly reduces the resistance of the earth path between the two points and so reduces the potential difference (voltage). The design of bonding is such that it should reduce the touch voltage to a non dangerous level.

If the resistance of the extraneous conductive part to earth is greater than 22 kΩ then in the case of a fault the "circuit" to earth is of such high resistance that no dangerous current can flow. i.e if you touch a live part (or a cpc made live by a fault) and then touch this piece of metal there is a 22,000 Ω resistor protecting you from the current flow. effectively it is an open circuit (almost).

Top notch explanation. Why this issue causes more confusion than any other...(well perhaps with the exception of power to sheds)....is beyond me.It's such a basic principle.