Main bonding

[Carlosfandango]

Sorry if this has been covered before. Went to a job today to wire a heating system and the install requires main bonding. The problem is that I can't get to the main board as its solid floors etc. There is a sub main feeding a db upstairs supplied by a 16mm twin. Can I run my 10mm earths to this sub board
? TNC-S earthing. Please be gentle!!

 

[Tim]

If its 16mm twin and earth then i would say no as the earth is not a large enough conductor size to be used as a combined earthing and bonding conductor back to the met

Tim

 

[Octopus]

Tin hat on but if you are there to wire a heating system then wire the heating system. If the FCU to supply it is existing I'd carry on!!

 

[Carlosfandango]

Need to wire a supply for heating and an immersion. Will be replacing the main db and various other works so will need to wire main bonders. Place is a bit of a shambles to be fair... No cpc's in downstairs lights , exposed parts in db's etc, might end up being there a while!

 

[Hants-Spark]

Need to wire a supply for heating and an immersion. Will be replacing the main db and various other works so will need to wire main bonders. Place is a bit of a shambles to be fair... No cpc's in downstairs lights , exposed parts in db's etc, might end up being there a while!

I'd say as it's a bit more than just wiring the heating system you should be ensuring all bonding meets current regulations along with all other work you undertake. IMO

 

[Carlosfandango]

That's why I was asking the question about the bonding!! I didn't think I would get away with running the 10mm's to the sub board but was just hoping someone would tell me otherwise!

 

[amo]

16mmn t&e? so the cpc would be 10mm. how far is it from the origin to the sub board?

 

[Hants-Spark]

16mmn t&e? so the cpc would be 10mm. how far is it from the origin to the sub board?

I'm sure the cpc in 16mm T&E is 6mm

 

[tony mc]

IMO the CPC will be 6mm with 16 mm !!

 

[tony mc]

There is something on the ESC website re being able to use 6mm as long as there are no signs of thermal damage etc etc. However IMO you are installing new circuits and replacing a DB so I would be looking at installing a new main earth and bonding conductors as per table 54 (7 or 8) can't remember due to it being TNC-S. So if the DNO neutral is 35 mm or less then Im afraid its going to have to be 10mm !! I take it there is extraneous parts where you are doing the work!

 

[Engineer54]

There is something on the ESC website re being able to use 6mm as long as there are no signs of thermal damage etc etc. However IMO you are installing new circuits and replacing a DB so I would be looking at installing a new main earth and bonding conductors as per table 54 (7 or 8) can't remember due to it being TNC-S. So if the DNO neutral is 35 mm or less then Im afraid its going to have to be 10mm !! I take it there is extraneous parts where you are doing the work!

Think you'll find that only refers to leaving ''Existing'' 6mm main bonding cables in place, not that you can install 6mm MB cables where it calls for 10mm...

 

[brucelee]

If your carrying out alterations or additions which you are then the Main bonding has to meet the requiremnts and have to be done

and 6mm can only be used if existing and no thermal damage