is this right?

[scott1]

tncs supplied. looked at a job in a flat last night( cu change, extra circuits), in a block of 24.tncs supplied . they all have 2 60amp sub mains to them from basement (one off peak)
both sub mains are run in 16mm t+e. in the flat the water supply is in copper and is bonded in 6mm. am i right in saying that this should be 10mm? if so then is the cpc undersized in 16mm t+e?
flats built in early 80s. flat on 5th floor!

 

[johnboy6083]

the bonding in the flats is only really suppllementary bonding, as the services would be bonded as they enter the building, and they will already be at the same potential. so IMO 6mm will be fine in this situation.

at the end of the day, it comes down to your interpretation of "an installation"

 

[scott1]

just been on phone to my part p provider, the said it would be fine to do works in the flat but make a note on installation cert. thought i may need a new 10mm cpc to flat.

 

[Darkwood]

the bonding in the flats is only really suppllementary bonding, as the services would be bonded as they enter the building, and they will already be at the same potential. so IMO 6mm will be fine in this situation.

at the end of the day, it comes down to your interpretation of "an installation"

Had this scenerio before, consider the water entering ground floor then rising up to floor five, each flat is classed as a independant seperate install and thus requires bonding as such, what if flat on third floor had alterations to pipe supply running through and due to insulated plumbing parts then isolates all pipework above floors this would leave either unbonded pipework above or undersized bonding in O/P case, i had same senerio in mill/shop complex and where the water supply entered each shop then a local bonding to local disboard was required.

 

[Deleted member 9648]

As per Darkwood...each flat is a separate install and requires independant main bonding. However you can assess the current setup and if there are no obvious issues with the bonding such as heat damage....leave it alone and note on the cert that it doesnt comply with current standards but appears adequate....same applies to cpc.

 

[Darkwood]

Also to note i assume the flat dist boards are supplied in 16mm T&E the earth in this cable will be undersized as its supplying multiple circuit and needs to be the same as the line csa, so note if instructed to upgrade the bonding it will be highly likely you will need to run additional earthing to dist' board.

 

[scott1]

thats the problem really, upgrading bonding not a problem in the flat but running new cpc from the ground floor would be. thanks for your help