Bonding loophole (hopefully!)

[tatty]

If main equipotential bonding to gas and water supply on a TNC or TNC-S system is less than 10mm does it need to be upgraded?

For example if existing bonding is 4mm does this need to be upgraded, at additional decorating cost to the customer, or is there a way around it?

Mat

 

[cozycats]

They haven't invented wireless earthing yet so yes it needs to be upgraded if tncs, I don't think we have tnc, (in houses anyway) that sounds like a tncs system without any main eq bonding, strictly a nono in domestic. If TNS the main eq would best be 10mm but could be less depending on size of main fuse. 4mm sounds too small though, ok for tt.

 

[Spark123]

They haven't invented wireless earthing yet so yes it needs to be upgraded if tncs, I don't think we have tnc, (in houses anyway)

Yes, it is prohibited by the ESQCR for a consumer to use tn-c. (p.s. were you reading the iee site on 1st April )
For a TN-CS the DNO should be consulted for the correct size cable for main equipotential bonding,
(for info, a TN-S the main eq bonding needs to be at least half the size of earthing conductor of the installation i.e. if is 16mm², the main eq bonding will need to be 10mm².)

 

[cozycats]

Hi spark 123 I think that is the main earhting conductor nt main eq bonding otherwise all main eq ought to be 16mm!!!!!!

 

[Spark123]

(TN-S) "Main earthing conductor" of the building nom 16mm² is the cable from cutout or DNO cable to MET, "main equipotential bonding conductors" from the MET to the Gas/Water pipes etc need to be at least half that of the 16mm² "main earthing conductor", which will require the "main equipotential bonding conductors" to be 10mm².
PME/TN-CS is a different ball game and the DNO needs to be consulted as they can have a different requirement for main equipotential bonding than BS7671.

 

[cozycats]

sorry didn't read your post properly!!

 

[Spark123]

Don't worry, no problem with clarifying things, gets the grey matter working

 

[securespark]

There's no way round it.

A bonding conductor of <10mm2 is not to current standards. Regs say you must ensure that before you make alterations or additions, the bonding arrangements must be adequate. Make of that what you will, but in my mind that means ensuring the bonding is to 10mm2 at least.

Generally, DNO's ask for max 16mm2 on PME.