bonding conundrum

[Engineer54]

Separate supplies with separate MET's then it will need bonding, exactly the same as in block of flats. Doesn't matter how close the 2 conection points are, you treat each individual dwelling as a separate entity!!

 

[Silly Sausage]

Separate supplies with separate MET's then it will need bonding, exactly the same as in block of flats. Doesn't matter how close the 2 conection points are, you treat each individual dwelling as a separate entity!!

But as Tel said earlier on, what if someone stuck a piece of plastic in between? It would depend how atractive the next door neighbour is.

I'd do exactly what you say.

 

[rich.250]

I have just looked at a job that fits this scenario. There is a 50mm copper riser with meters sprouting of it on each floor in the stairwell. At the moment there are two 6mm bonding cables clamped to a couple of the branches one of which goes to the power head of the flat I am concerned with. The copper pipework within the flat is being renewed and I propose fitting a 10mm bond at the kitchen stopcock back to the MET WITHIN the flat. Am I correct in this course of action.

Yes, each separate flat should be treated as separate place.
As e54 said.

Obviously you need to check that each separate flat needs bonding with your tester.
If there's no parallel path to earth no need to bring it to the Same potential.

 

[tony mc]

411.3.12 is the reg re this topic with alot more in GN8.

 

[Cazmac1]

Read some more post's and things don't seem to be adding up so I with draw my comments and advice.

 

[Engineer54]

But as Tel said earlier on, what if someone stuck a piece of plastic in between? It would depend how atractive the next door neighbour is.

I'd do exactly what you say.

This case is a little different from blocks of flats, in that the Granny flat is attached to the main building and uses an extension of the house water service, where flats would be taken individually from a main riser feed. But seeing as the two separate unit's are owned by the same homeowner the chances of a plastic pipe isolating the units is to be honest remote. You could always make the homeowner aware, that if any plastic pipe is inserted into the water service between the two units he will need an electrician to test the Granny flat. So to ascertain if the service in that unit still remains extraneous or not, (over 23Kohms) if it's not, the bonding conductor and clamp needs to be removed!!

 

[johnny999]

I have spoken to great white oracle ( who takes my money every year so I can be in their gang ) & he informed me that I should bond the water pipe where it enters the flat to the cu in the flat. So that is what I will do, many thanks for all the answers & comments.

 

[clive dobbs]

Hi
Can somebody tell me what earthing arrangments are at the origin of both supplies?, for example if the house supply earth was PME and the flat earth was TT then as things stand you could be introducing a different earth potential back into the main house as the water pipes are connected at the moment. A solution may be for earthing purposes is to install a piece of plastic pipe from the main house where it enters into the flat this would seperate bonding pipework and earth potentials, although there still could be implications within the common water.

 

[Deleted member 26818]

Hi
Can somebody tell me what earthing arrangments are at the origin of both supplies?, for example if the house supply earth was PME and the flat earth was TT then as things stand you could be introducing a different earth potential back into the main house as the water pipes are connected at the moment. A solution may be for earthing purposes is to install a piece of plastic pipe from the main house where it enters into the flat this would seperate bonding pipework and earth potentials, although there still could be implications within the common water.

Or just install bonding as per the requirements of BS7671.
There could be difference in potential even if both installations are PME, just the same as with neighbouring properties in a terrace.

 

[SimpleSimon]

Id be bonding both flats seperately. I think if you test you'll find the water could be an extrenupus part. They are two seperate supplies with two seperate earths.

Sent from my GT-I9100 using Tapatalk

 

[clive dobbs]

The trouble is not knowing the earthing arrangments, the example I gave in a fault condition like losing PME neutral main house you would be introducing a different potential TT back from the flat therefore the equpotential zone in the house now has potential earth, and bonding would not stop the risk of electric shook in the house.

 

[1shortcircuit]

Okay so what if you walked through the front door of the granny flat and had no access to next door... You found NO BONDING so tested to see if the water pipe was extraneous and found that it was not? we'd stick a bond on it anyway??? This then takes us to the long debate that has been battled out in other threads which makes out you should bond metal windows and loose change on the bedside cabinets etc (Engineer54 will remember that one I'm sure)

If it's bonded next door and that's the reason you get your test results then you won't know that BUT the bonding next door will have a clamp attaching it to a pipe which will also have a label on it saying "Electrical Earth Connection - DO NOT REMOVE"!

If you've bonded the pipework and then the supply pipe is replaced with a plastic one then you have now created a potentially lethal situation if a fault were to occur.

You cannot be accountable for what a wet head decides to do or not do when he goes in after you?

A block of flats is entirely different and as I recently was informed each one AND the main installation should ALL have their own bonding (Main installation to within 600mm of stop tap and flats to within 600mm of point of entry - Where reasonably practicable)

This is my opinion based on a lot less experience than many others that have posted the opposite in this thread but to me it makes sense. I'll stand corrected though if someone can PROVE without doubt that my actions would have the book thrown at me in a court of law.

:thumbsup

 

[rich.250]

If its under 23k ohms- bond to bring it to same potential as MET.

If over 23k ohms no need to bond

 

[1shortcircuit]

a clamp attaching it to a pipe which will also have a label on it saying "Electrical Earth Connection - DO NOT REMOVE"!

My mistake, it actually says " Electrical Safety Connection - DO NOT REMOVE" :thumbsup

Better squeeze that in before I get picked up on it