Excellent explanation of bonding and its increased importance should the RCD fail. Also good advice about how RCD's can have a high failure rate. Thank you.
Coming late to the discussion. One aspect not explicitly covered (as yet) was the generator 'reference' to earth and how / why that reference should be (or not) connected for (I believe) the elimination of human shock voltages (and if not connected the low currents that will/can still kill you ), rather than, as mentioned, what is considered the [lack of] power currents in the reference line, i.e. the currents would never blow a fuse or trip a circuit breaker. The aspect of creating a [mass of] earth reference protection can also be for the electromagnetic (radio) interference reduction that all the EMI/RFI filters in modern electronic equipments provide with their Y capacitors 'leaking' deliberately to their 'earth' / chassis. It also appears as it those in the US may have different views because of their own peculiar systems and operating environments with respect to protecting linesmen from back feeds from all the back up genny's in rural US.
Re Fault currents on PME systems around 20 minutes - had that same issue on jobs where measuring the Ze, calculating fault currents and using the adiabatic equations showed the 1.5 sq mm in T and E wasn't up to it for the ring circuit, and we ended up in pvc pipe and 2.5 cpc , another job where the cooker cable did not go the direct route and instead went the long way round the understair closet and then to the kitchen the other side of the wall, because even with the extra cable it was both cheaper than doing it in 10 (more of a pain to terminate).
Hi sorry if a daft question, but on an earth fault loop path for a TT system When there is an earth fault, the current must flow down to earth, back to the transformer and back to operate the fuse. Does it really take this path, how does the electricity flow through the actual ground all the way back to the transformer ? I can't understand how it flows through mud and that quick to complete the fault path. Even hard to believe it can do this on a TNCS etc
Like Robert says I would check with the manufacturer weather a dual rcd consumer unit is ok for a tt system as the inter connections between the main switch and the 2 rcd’s will not be rcd protected. Excellent videos thanks.
I do not get how an RCD could help in case of a PEN-fault as the current comes from the CPC. There is no imbalance between the phase and the neutral. There are ways to detect it but as I understand the UK they are used only with EV-chargers as bonding does not help there.
ON a TNCS system is there not a customer earth rod connected to the consumer unit . Would this not keep the neutral at 0 volts even if the supply neutral got disconnected ?
To bond, or not to bond, that is the question. Scenario. Central heating and shower, fed from the heating boiler, plastic pipes are used for most of the feeds, only copper showing above ground, including a towel rail. Do those copper pipes need bonding? if so, to what??
Big fan of your content. I have a question that I cant seem to get a solid answer for. If copper pipes from house go underground and re-enter a ultily room outbuilding as copper. Does it need additional 10mm bonding at entry at utiliy. The board in ultilty room only has 6mm twin and earth supply so can't bond from there. I'm guessing it would have to come from the main board. Thanks I can't find answer anywhere.
Technically it should be considered as a new extraneous conductive part and be provided with main bonding, this is based on the theory of why we put the main bonding in. However with the way the regulations are worded it doesn't actually tell us to do this. The fundamental outcome must be that touch potentials are less than 50V for the duration of the fault. You can carry out the exercise in regulation 415.2 and see if bonding is in fact needed.
@@SparkyNinja Thanks for your reply. Yes it's abit confusing. I IR tested between MET and and pipe in utility and it looks like additional bonding is needed. Costumer just bought the house and ECIR was completed so they're not happy it wasn't picked up.
I've just seen a house with an incoming lead water pipe. The waterboard sweated on a new fitting and then used a plastic pipe to connect to the stop cock. The earth bonding was on the copper pipe after the stop cock. The plastic pipe disconnected additional path to earth. I queried this with them and they said "that is what they do". Would you add a 10mm earth from the incoming lead pipe to the copper pipe to reconnect it?
It was a poor choice of words on his part, because he was obviously talking about the rcd component, but lumped it all together as rcbo. He also stated that rcd's will only operate on earth faults, which again is wrong. RCDs are actually imbalance detection devices, meaning they will operate when they detect an imbalance up to and exceeding their rating between line and neutral, as when an earth fault occurs or, for example, in a borrowed neutral situation, which is obviously nothing to do with earth fault - so another bit of sloppy wording, I'm afraid.
@@johnhoward2104 nice one I'd just starting panicking thinking I've spent nearly ten years in the industry and didn't know the basic function of an rcbo 😂
Confused about grounding If I bond a metal sink and there is a fault to earth on a kettle for example, wouldn’t a person touching the metal sink receive a shock to the kitchen floor (tiled over concrete)? Assume the rcd has failed
This annoys me though it's law to use a rcd supply for cutting the lawn with 240v electric lawnmower, Why dont lawnmowers come with 3core flex live/neutral/earth instead of 2 core live/neutral flex which will not trip the rcd if accidently cut through by the mower, Possibly leaving the cable live because the lawnmower can cut through the cable faster than the plugs tops fuse will take to blow?
What about all the single insulated interconnections to each rcd in a split load board . It’s not just the incoming tails you need to worry about . A split load board should really not be used on a TT without atleast a 100 type s rcd as a main switch .
In a kitchen protected by RCD, the worktops are coated in a stainless sheeting. Would this need supplementary bonding? The incoming water supply to the sink side of the worktops is bonded with the sink being part of the worktop, meaning that is bonded through the water pipes it’s attached too giving the same potential as the pipes?The other worktop has no direct path back to so earth, so would earthing it cause more danger?
@@SparkyNinja the argument I’m getting against whether the worktops should be earthed or not is that if a damaged cable with a live conductor exposed were to touch the worktop that the whole worktop would become live and the rcd wouldn’t trip.
Good evening. Just catching up on this. Going back to the definition of extraneous conductive part and where it is not necessary to bond water if there is an insulating section. You mentioned the situation of having a water supply pipe to a kitchen island buried in the screed. The pipe would be in the screed which gives it that earth potential but I was wondering how far up the property this would relate to. My example would be a water pipe buried in the wall plastered in maybe a short way up from the floor in a downstairs WC. Is there any evidence available that states how far up (if at all) earth potential exists within the fabric of a brick building?
The problem here is that building fabrics have a variety of different resistivities and impacts on the pipework. One buried pipework may pick up a completely different potential than another. So the measurement method is the best way for you to know how effective a buried pipe is and whether it is to be considered an extraneous conductive part or not.
SparkyNinja it’s very difficult to know with the wondering lead method if there is any parallel paths from the boiler on the pipe work . Even if you disconnect the main earth from the met and test off that as it could be the case that the gas intake is extraneous but the water isn’t but you couldn’t verify that as the gas pipe is connected to the water pipe at the boiler . You would physically have to disconnect the water intake off the boiler to know for sure.
Sorry for catching this a couple of days late! On the subject of PME systems, I recently carried out a Ze when installing an EV charger in a domestic garage. The pfc was measured at 10kA and as you can imagine the mcb’s are all rated at 6kA. The transformer was less than 100 metres from the house. I’ve installed a Matt-e O-pen device to save putting in an earth rod, but the supply still comes off a 40A 6kA mcb. I’m now thinking if I’d installed an earth rod the pfc would be much less. What’s your thoughts?
Pfc could also be live to neutral (short circuit current ) which would still be up at 10ka even on a TT . As long as the main fuse can handle the pfc or pscc there shouldn’t be a problem.
Excellent video, question concerning supplementary bonding. No RCD, If there was only a light in the bathroom & the light was not able to be touched as out of reach. Would supplementary bonding still be required. I was taught it’s only if you could touch the electrical equipment & simultaneous exposed or extraneous conductive parts. Cheers
I'm not going to pretend to actually know the answer in the company of the type of people that would watch a sparky ninja vid, but at a guess. . . If that was the case, would there still ever be a situation where someone would take something like a vacuum cleaner into the bathroom to clean it? would doing so put them at risk if there was a fault and any metal work they may come into contact with was unbonded and at 0v ?
Could I possibly ask about supplementary bonding when part of plumbing is copper then plastic then copper again i.e. Hepworth pipes in bathrooms and kitchens these days thank you
14:10 -'RCBOs don't operate under short circuit or overload'? Should that be 'MCBs don't operate under earth fault...' Hey? what? Is that correct? confusing..lol
been hunting down the term touch voltage and step voltage i cant find it in definitions in bs7671 any idea where it is maybe another standard or document
It's a bigger thing in transmission (substations and pylons) where the ground currents flowing through the resistance of earth generate between leg voltages sufficient to give a shock (hence some advice to shuffle, or kangaroo jump to avoid leg-leg electrical shocks), and then the touch voltages allows for all the places and cabinets you can reach between hand and foot.
I guess it could be used for connections with exposed parts. The CPC link will both be providing the function of providing the part a route to earth and bring it to the same potential as the rest of the building. Totally with you when it is just to extraneous parts though,
Excellent explanation of bonding and its increased importance should the RCD fail. Also good advice about how RCD's can have a high failure rate. Thank you.
Coming late to the discussion. One aspect not explicitly covered (as yet) was the generator 'reference' to earth and how / why that reference should be (or not) connected for (I believe) the elimination of human shock voltages (and if not connected the low currents that will/can still kill you ), rather than, as mentioned, what is considered the [lack of] power currents in the reference line, i.e. the currents would never blow a fuse or trip a circuit breaker.
The aspect of creating a [mass of] earth reference protection can also be for the electromagnetic (radio) interference reduction that all the EMI/RFI filters in modern electronic equipments provide with their Y capacitors 'leaking' deliberately to their 'earth' / chassis.
It also appears as it those in the US may have different views because of their own peculiar systems and operating environments with respect to protecting linesmen from back feeds from all the back up genny's in rural US.
Re Fault currents on PME systems around 20 minutes - had that same issue on jobs where measuring the Ze, calculating fault currents and using the adiabatic equations showed the 1.5 sq mm in T and E wasn't up to it for the ring circuit, and we ended up in pvc pipe and 2.5 cpc , another job where the cooker cable did not go the direct route and instead went the long way round the understair closet and then to the kitchen the other side of the wall, because even with the extra cable it was both cheaper than doing it in 10 (more of a pain to terminate).
Thanks for everything mate passed my City&guilds 2382/18 6th Feb
Hi sorry if a daft question, but on an earth fault loop path for a TT system
When there is an earth fault, the current must flow down to earth, back to the transformer and back to operate the fuse. Does it really take this path, how does the electricity flow through the actual ground all the way back to the transformer ? I can't understand how it flows through mud and that quick to complete the fault path. Even hard to believe it can do this on a TNCS etc
Like Robert says I would check with the manufacturer weather a dual rcd consumer unit is ok for a tt system as the inter connections between the main switch and the 2 rcd’s will not be rcd protected. Excellent videos thanks.
I know I wouldn’t be happy putting a dual rcd board on a TT system without at least a 100ma type s upfront
I do not get how an RCD could help in case of a PEN-fault as the current comes from the CPC. There is no imbalance between the phase and the neutral. There are ways to detect it but as I understand the UK they are used only with EV-chargers as bonding does not help there.
Thanks for sharing, very nice presentation and well explained
ON a TNCS system is there not a customer earth rod connected to the consumer unit . Would this not keep the neutral at 0 volts even if the supply neutral got disconnected ?
To bond, or not to bond, that is the question.
Scenario. Central heating and shower, fed from the heating boiler, plastic pipes are used for most of the feeds, only copper showing above ground, including a towel rail. Do those copper pipes need bonding? if so, to what??
One of the best videos I've see on earthing and bonding. 👏🏻
Big fan of your content. I have a question that I cant seem to get a solid answer for.
If copper pipes from house go underground and re-enter a ultily room outbuilding as copper. Does it need additional 10mm bonding at entry at utiliy. The board in ultilty room only has 6mm twin and earth supply so can't bond from there. I'm guessing it would have to come from the main board. Thanks I can't find answer anywhere.
Technically it should be considered as a new extraneous conductive part and be provided with main bonding, this is based on the theory of why we put the main bonding in. However with the way the regulations are worded it doesn't actually tell us to do this.
The fundamental outcome must be that touch potentials are less than 50V for the duration of the fault. You can carry out the exercise in regulation 415.2 and see if bonding is in fact needed.
@@SparkyNinja Thanks for your reply. Yes it's abit confusing.
I IR tested between MET and and pipe in utility and it looks like additional bonding is needed. Costumer just bought the house and ECIR was completed so they're not happy it wasn't picked up.
Tanks, awesome and excellent video.
Great video!! can you take a bond from a existing LVAC panel to a new earth bar then run separate bonds to isolating transformers
I've just seen a house with an incoming lead water pipe. The waterboard sweated on a new fitting and then used a plastic pipe to connect to the stop cock. The earth bonding was on the copper pipe after the stop cock. The plastic pipe disconnected additional path to earth. I queried this with them and they said "that is what they do". Would you add a 10mm earth from the incoming lead pipe to the copper pipe to reconnect it?
At 13.50 you say that rcbos are not used for overload or short circuit??
It was a poor choice of words on his part, because he was obviously talking about the rcd component, but lumped it all together as rcbo.
He also stated that rcd's will only operate on earth faults, which again is wrong. RCDs are actually imbalance detection devices, meaning they will operate when they detect an imbalance up to and exceeding their rating between line and neutral, as when an earth fault occurs or, for example, in a borrowed neutral situation, which is obviously nothing to do with earth fault - so another bit of sloppy wording, I'm afraid.
@@johnhoward2104 a canny fault the guy he does know his stuff
@@johnhoward2104 nice one I'd just starting panicking thinking I've spent nearly ten years in the industry and didn't know the basic function of an rcbo 😂
Confused about grounding
If I bond a metal sink and there is a fault to earth on a kettle for example, wouldn’t a person touching the metal sink receive a shock to the kitchen floor (tiled over concrete)?
Assume the rcd has failed
This annoys me
though it's law to use a rcd supply for cutting the lawn with 240v electric lawnmower,
Why dont lawnmowers come with 3core flex live/neutral/earth instead of 2 core live/neutral flex which will not trip the rcd if accidently cut through by the mower,
Possibly leaving the cable live because the lawnmower can cut through the cable faster than the plugs tops fuse will take to blow?
What about all the single insulated interconnections to each rcd in a split load board . It’s not just the incoming tails you need to worry about . A split load board should really not be used on a TT without atleast a 100 type s rcd as a main switch .
Those would be on the load side of an RCD..?
SparkyNinja not the ones out the bottom of the main switch to the supply side of each rcd . Even the on-site guide says not to use a dual rcd on TT.
SparkyNinja No the load side of the 100 A main switch.
Thank you so much for this video. best video hands down on earthing and bonding.
In a kitchen protected by RCD, the worktops are coated in a stainless sheeting. Would this need supplementary bonding? The incoming water supply to the sink side of the worktops is bonded with the sink being part of the worktop, meaning that is bonded through the water pipes it’s attached too giving the same potential as the pipes?The other worktop has no direct path back to so earth, so would earthing it cause more danger?
Bonding it would introduce a new touch potential, introducing additional risk.
@@SparkyNinja the argument I’m getting against whether the worktops should be earthed or not is that if a damaged cable with a live conductor exposed were to touch the worktop that the whole worktop would become live and the rcd wouldn’t trip.
???
Good evening. Just catching up on this. Going back to the definition of extraneous conductive part and where it is not necessary to bond water if there is an insulating section. You mentioned the situation of having a water supply pipe to a kitchen island buried in the screed. The pipe would be in the screed which gives it that earth potential but I was wondering how far up the property this would relate to. My example would be a water pipe buried in the wall plastered in maybe a short way up from the floor in a downstairs WC. Is there any evidence available that states how far up (if at all) earth potential exists within the fabric of a brick building?
The problem here is that building fabrics have a variety of different resistivities and impacts on the pipework. One buried pipework may pick up a completely different potential than another. So the measurement method is the best way for you to know how effective a buried pipe is and whether it is to be considered an extraneous conductive part or not.
SparkyNinja it’s very difficult to know with the wondering lead method if there is any parallel paths from the boiler on the pipe work . Even if you disconnect the main earth from the met and test off that as it could be the case that the gas intake is extraneous but the water isn’t but you couldn’t verify that as the gas pipe is connected to the water pipe at the boiler . You would physically have to disconnect the water intake off the boiler to know for sure.
Sorry for catching this a couple of days late! On the subject of PME systems, I recently carried out a Ze when installing an EV charger in a domestic garage. The pfc was measured at 10kA and as you can imagine the mcb’s are all rated at 6kA. The transformer was less than 100 metres from the house. I’ve installed a Matt-e O-pen device to save putting in an earth rod, but the supply still comes off a 40A 6kA mcb. I’m now thinking if I’d installed an earth rod the pfc would be much less. What’s your thoughts?
Pfc could also be live to neutral (short circuit current ) which would still be up at 10ka even on a TT . As long as the main fuse can handle the pfc or pscc there shouldn’t be a problem.
As above as far as I’m aware domestic and similar can really on the last value of over protective device for protection.
Excellent video, question concerning supplementary bonding. No RCD, If there was only a light in the bathroom & the light was not able to be touched as out of reach. Would supplementary bonding still be required. I was taught it’s only if you could touch the electrical equipment & simultaneous exposed or extraneous conductive parts.
Cheers
I'm not going to pretend to actually know the answer in the company of the type of people that would watch a sparky ninja vid, but at a guess. . .
If that was the case, would there still ever be a situation where someone would take something like a vacuum cleaner into the bathroom to clean it? would doing so put them at risk if there was a fault and any metal work they may come into contact with was unbonded and at 0v ?
Awesome video, thank you so much. Dave, your dads got a great voice to listen too. Say thanks to him for me.
At 14:04...RCBO dont operate under short circuit/overload. Am i missing something in context?
RCBO is combination of MCB and RCD so it does operate in shortcircuit, overload and earth leakage !
Well spotted- I queried this also. Sounds like an incorrect statement to me also...
Thank you
Superb video
Thanks Gentlemen, really useful stuff watching this and being reminded of the difference between earthing and bonding
I had a domestic property that had a miniscule earth loop. But meant the PFC was approx 7500 had to fit 10k breakers instead of the usual 6k
I'd like to thank you for the sharing your experience and knowledges
Could I possibly ask about supplementary bonding when part of plumbing is copper then plastic then copper again i.e. Hepworth pipes in bathrooms and kitchens these days thank you
bump
14:10 -'RCBOs don't operate under short circuit or overload'? Should that be 'MCBs don't operate under earth fault...'
Hey? what? Is that correct? confusing..lol
Thank you 🤗
been hunting down the term touch voltage and step voltage i cant find it in definitions in bs7671 any idea where it is maybe another standard or document
It's a bigger thing in transmission (substations and pylons) where the ground currents flowing through the resistance of earth generate between leg voltages sufficient to give a shock (hence some advice to shuffle, or kangaroo jump to avoid leg-leg electrical shocks), and then the touch voltages allows for all the places and cabinets you can reach between hand and foot.
@15 min in
Great vid!! 👌 think I might have to watch it a couple times tho 🤣🤯
Cracking video, should be shown in college as 95% of sparks don't get earthing and bonding
Does anyone else really dis like it when people use the term “earth bonding” a pet hate of mine
I guess it could be used for connections with exposed parts. The CPC link will both be providing the function of providing the part a route to earth and bring it to the same potential as the rest of the building.
Totally with you when it is just to extraneous parts though,