Speak EV - Electric Car Forums banner

1 - 13 of 13 Posts

·
Registered
Kia Soul EV 2020 64KWh
Joined
·
235 Posts
Discussion Starter #1
This gets more confusing I have just submitted an enquiry for an install and the pre survey questionnaire they have sent includes a request to show photographic proof of water bonding (earth cable with clamp on the pipe next to the stop cock).

First I have heard of this and looking under the sink, I can't see evidence of this.

Is this a problem? What are the implications?

Be glad when I am past this hurdle tbh.
 

·
Registered
Ioniq 38kwh 2020
Joined
·
161 Posts
I've never understood bonding, surely if your pipes are earthed and say you are holding a live wire in one hand, and touch the pipe with the other, you've just given the electricity the perfect path to flow through your body? Why isn't it more dangerous than not having any bonding at all?
 

·
Registered
Joined
·
25 Posts
I've never understood bonding, surely if your pipes are earthed and say you are holding a live wire in one hand, and touch the pipe with the other, you've just given the electricity the perfect path to flow through your body? Why isn't it more dangerous than not having any bonding at all?
because if the water pipe accidentally becomes live - say because a worn bare wire touches it - you want the pipe to be earthed, to provide a low-resistance path for the electricity to flow back to its source (the local supply point). This low resistance path means a high current flows, and the circuit breaker in your house detects this high current and disconnects the supply before you can touch the pipe and receive an electric shock.

Sent from my Pixel C using Tapatalk
 

·
Registered
Joined
·
154 Posts
The purpose of bonding is to keep everything at the same potential so you never get a potential difference between metal parts, so you can never get a shock when touching two metal parts simultaneously.

The purpose of earthing is that in the event of a fault involving said metal part, sufficient current is drawn to operate the protective device and disconnect the supply.

What you don’t want is earthing without bonding because in the event that you touch both a part that has become live but isn’t earthed so doesn’t operate the protection and an earthed part because then you become the path for the fault current.
 

·
Registered
Joined
·
2,205 Posts
To expand on Barneys point, many homes use a "TN-C-S" earthing system. In this system, the "earth" thats connected to all your appliances is derived from the neutral conductor in the supply cable, rather than a separate earth conductor. The supplier then pulls neutral down to earth at various points within their network and it should, generally, stay pretty close to true earth.

You then have a risk where an earthed appliance, say a metal bodied kettle, your washing machine or dishwasher, which is connected to this neutral derived earth, is not quite at the same 0v reference to "real" earth. Inside a house thats generally fine, as everything earthed is at the same non-zero voltage. However if you introduce an external conductive path to true earth, say a water pipe or gas pipe, which is buried in the ground in the street, you've now introduced two different potentials, and created a shock risk. If your touching the sink (which is connected to your water pipe and thus is at true earth) and also touch the metal body of your dishwasher (which is connected to the derived neutral based earth), your doing to get a zing if they're at different potentials. It might not even be a full on shock throwing you across the room or whatever, but even an uncomfortable zing from a couple of volts isnt pleasant.

As a result, any such external conductors are required to be bonded to the main earthing terminal inside the property, to ensure everything inside the house is at the same potential. If your services enter the house in plastic pipes, then i dont think they need bonded.
 

·
Registered
Kia Soul EV 2020 64KWh
Joined
·
235 Posts
Discussion Starter #7
Wow, thanks both. I certainly have a renewed respect for the skill of electricians as a result of all this - its complicated stuff ain't it!
 

·
Registered
Joined
·
2,205 Posts
I've never understood bonding, surely if your pipes are earthed and say you are holding a live wire in one hand, and touch the pipe with the other, you've just given the electricity the perfect path to flow through your body? Why isn't it more dangerous than not having any bonding at all?
Its actually the opposite of what your thinking, your bonding it because its already earthed. A copper/lead/steel etc pipe buried in the road is in effect a huge earth-rod. So the pipe is already at true earth, but other things in your house might not be as i explained above. You want the voltage of all touchable metallic parts in your house to be the same.
 

·
Registered
Joined
·
3,216 Posts
Wow, thanks both. I certainly have a renewed respect for the skill of electricians as a result of all this - its complicated stuff ain't it!
Can't be that hard if I've been winging it for 34 years.
Also your gas main, possibly oil feed pipes coming in.
If you can't see it then it needs addressing anyway so rather than thinking of it as a hurdle (not that I am suggesting you do) think of it as a good opportunity to address it.
 

·
Registered
Joined
·
154 Posts
Wow, thanks both. I certainly have a renewed respect for the skill of electricians as a result of all this - its complicated stuff ain't it!
Making it work is easy. Making it safe under all conditions is the tricky bit. Luckily the regs are there to help.
 

·
Registered
Joined
·
3,216 Posts
Making it work is easy. Making it safe under all conditions is the tricky bit. Luckily the regs are there to help.
I will never forget at 16 years old my college lecturer Mr John Byrne holding up a copy of the regs.
He said if someone dies because of your work as long as you have complied with everything in this book you will be okay.
This is your defence in law.

Talk about a sobering thought.
 
  • Like
Reactions: Trevor Larkum

·
Registered
Joined
·
154 Posts
I will never forget at 16 years old my college lecturer Mr John Byrne holding up a copy of the regs.
He said if someone dies because of your work as long as you have complied with everything in this book you will be okay.
This is your defence in law.

Talk about a sobering thought.
It is your defence but hopefully also the way to make sure nobody dies in the first place!
 

·
Registered
Joined
·
3,216 Posts
It is your defence but hopefully also the way to make sure nobody dies in the first place!
But he he never said that. I can only quote what he said.
:sneaky:
 
1 - 13 of 13 Posts
Top