Cross bonding

[jon090]

Hi,
A customer of mine (a restaurant owner) received a letter from the electrical distributors saying that because the building was once two separate premises and they have now been knocked together to form one open plan room, there is an issue with having two separate electrical meters and isolation points - should the fire services need to shut off power.

They explain that to meet minimum requirements each meter must be clearly identified and point out where the other meter is. In addition to this, there must be "cross bonding between the earth and neutral conductors" - I'm struggling to work out exactly what that means?

 

[KAS1]

That sounds self explanatory does it not, seems it is as clear as mud to some lol

 

[44ALLAN]

Live and Neutral into 1st unit...................TNS Brown phase.
Live and Neutral into 2nd unit .................TNC-S Black phase lol

Highly unlikely but good luck

 

[jon090]

Its not 3 phase. 2 seperate single phase meters on different supplies.

 

[44ALLAN]

Its not 3 phase. 2 seperate single phase meters on different supplies.

I didn't say it was ?

Street cable outside probably is tho

 

[jon090]

Na i checked that.. Its bell wire

 

[44ALLAN]

Na i checked that.. Its bell wire

lol.
Wasn't being critical mate I was just making up a scenario where each of these 'previous rooms' were fed from a different phase with different earthing arrangement but now their both in the same room.

 

[jon090]

I still dont understand whats required? What needs cross bonding? (It was 2 seperate houses initially - its now an open plan room and hes paying 2 seperate elec bills one for each meter yet its one property)

 

[MDJ]

- I'm struggling to work out exactly what that means?

Why's that then? sounds perfectly straight forward to me.

 

[jon090]

It wasnt a trick question, was just looking for some clarity on the matter to make sure i was doing things correctly as i havnt come across this before. apreciate the help

 

[MDJ]

I'm suprised that they allow 2 supplies in one room TBH, if the load in that room could be handled by one meter I would have thought they would disconnect one and make you connect the supplies from it to the other board, I'm not suprised they want the earthing linked, imagine if there were a bit of plastic pipe in the plumbing somewhere and the earths from the 2 sides were either side of the plastic bit and there was a fault and you touched either side of the plastic, potential problem for sure, hypothetically disasterous although also possibly no issue, not worth the risk though hence them suggesting the earths are linked, at least there are trying to cover any problem that could arise.

 

[jon090]

I hear, thanks for that i just wanted to make sure. Dyou rekon 10mm bonding between each earth blocks? The run is about 20meters.

 

[Phillcbr400]

Do you know which phases each supply is on? And also what earthing arrangements are in place for each supply.

 

[jon090]

How do i check to know what each supplys phases is? Will go back and look at the earthing arrangements. I think they were both TNCS but ill double check.

 

[Phillcbr400]

Double Check with the dno, give them a ring and get clarification of what they what. It could be that you will end up with a parallel feed as such if on the same phases or maybe a touch potential of 415v if on different. If you get the scope of the works from the dno the onus doesn't solely lie with yourself.

 

[44ALLAN]

Do you know which phases each supply is on? And also what earthing arrangements are in place for each supply.

Post 3 and 7

 

[44ALLAN]

How do i check to know what each supplys phases is? Will go back and look at the earthing arrangements. I think they were both TNCS but ill double check.

Do a voltage check between a live from each circuit............
0 volts = same phase.
415v = different phase.

 

[jon090]

Ok thanks for the help mate!

 

[jon090]

44allan - the two meters are about 20 meters away from each other which would make that test difficult to do.

 

[R G]

44allan - the two meters are about 20 meters away from each other which would make that test difficult to do.

Oh dear!!!!