Main water bond in several buildings

[coxy]

Hi Everyone,
Has anyone had this situation. The main incomming supply is pme which is in a isolated building all on its own.There are 3 different buildings all isolated from each other.The buildings all have water supplies/gas.I am installing 3 separate supplies to these buildings with swa & separate cpc,back to the main incomming supply. Does the main bond to gas/water have to go back to the incomming supply from each building ??? They are quite a distance apart.Any ideas welcome.Or can they be connected to the local board ???

 

[Spudnik]

In this situation you can run bonding back to in comming supply.

However, you can also run the SWA submain to the outbuildings but not connect the cpc in the enclosure/cu. (still bond the armour at the supply end)

You then TT the outbuilding supply for your main earth and bonding.

 

[mrloy99]

Hi Everyone,
Has anyone had this situation. The main incomming supply is pme which is in a isolated building all on its own.There are 3 different buildings all isolated from each other.The buildings all have water supplies/gas.I am installing 3 separate supplies to these buildings with swa & separate cpc,back to the main incomming supply. Does the main bond to gas/water have to go back to the incomming supply from each building ??? They are quite a distance apart.Any ideas welcome.Or can they be connected to the local board ???

Hi Coxy,
I recon that it might depend on what size is your earthing conductor/swa.If your buildings are supplied in 16mm say.I would supply a main earth terminal at each building,and take bonds to there. I don't really understand why the recomendation is to make remote buildings TT.I have problems with TT systems, zs disconnection times of mcbs cannot be met,we have to rely on rcds to disconnect the fault,and as we know
rcds are rarely tested monthly as recommended,and often go faulty.I would prefer the "sound" earth of a pme any day. But thats only me.

 

[Spudnik]

The recommendation is with regard to not having to run a separate (10mm?) bond back to the origin of the supply, which would be the case if there are services in the outbuilding.



Its only to make installation easier.


But if the supply to the outbuilding is 16mm then an MET at each board would be ok.

 

[coxy]

Hi Thanks for the help.I have looked at the nic tech manual,and it does suggest turning installations into tt systems.However i think that the best solution is because i have run separate cpc's with the swa is to install met at the db then run water bonds back to there.The only problem would be the size - am i right in thinking that it would have to be half the size of the incomming neutral ?? reg 544.1.1
Thanks.

 

[zion]

Correct, each building has to be a TT system, the earth from the incoming building must not be extended to the outbuildings. local earth rods required at each building. Page 134 of BS7671 table 54.8 will give you your bonding conductor sizes.