Removal of old main bond

[jimmymac]

Good afternoon folks,
i was helping out a fellow spark today as i often do and he often helps me when needed. We were doing a CU change on a certain property and it involved upgrading the main bonds from 4mm to 10mm. We could get to the incomers easily but the problem is that since the old 4mm bond was installed there has been quite alot of modernisation and it would mean lifting alot of laminate flooring or removing some kitchen cupboards to gain acces to the old bond/clamps for removal. I suggested leaving it in-place and just installing the the new 10 mm but my pal said he wasn't comfortable with that, i couldn't see a problem, what about you??

In the the past i've seen people use a seperate CPC along side SWA so as to get the circuit to comply, i know it probably looks more proffesional to have a single piece of bonding but there will be less resistance if there more bonding in place or am i missing something?? your thoughts please people??

 

[telectrix]

all depends. if you can get the new 10mm as near as practicable to the entry points, then that's what i would do, unless the customer is prepared to rip out cupboards.

 

[Spazz]

In this case I would cut back tidy where it enters the wall at both sides and leave the res in place (same as in roof)

If the home owner wants it removed the they are paying so you do what they ask.


Your mate might be doing it for some extra cash - longer on a job more money (if by the hour and not per install)

 

[Farmelectrics]

Can you not do an adiabatic calculation you might not need to upgrade it

 

[Dave 85]

Bit of a pointless question this Im afraid. Why on earth (excuse the pun) would he feel uncomfortable about leaving an earth bond and clamp in place. What exactly is he worried is gonna happen?

 

[londonlec]

I would have cut it off flush/left it in situ. No point in ripping the gaff apart to rip out an old bond.

 

[Farmelectrics]

Totally agree just leave it

 

[Guest55]

Can you not do an adiabatic calculation you might not need to upgrade it

Unfortunatley not.
Adiabatic can be used for cpc's , bonds have got to be as per regs table of minimum sizes.

 

[IQ Electrical]

Unfortunatley not.
Adiabatic can be used for cpc's , bonds have got to be as per regs table of minimum sizes.

On a TN-S system, you can size the earthing conductor by using the adiabatic equation, the main protective bonding conductors are then sized in accordance (not less than half) with the earthing conductor so technically, depending on the system type, farmelectrics is right in one respect BUT there is a minimum size requirement of 6mm copper!

 

[Guest55]

.......... BUT there is a minimum size requirement of 6mm copper!

Er , isnt that what i said 10mins ago ? :-/

 

[IQ Electrical]

Er , isnt that what i said 10mins ago ? :-/

Er no, unless you've edited it.....

 

[Guest55]

So this requirement to use at least 6mm that you speak of , is it in a table within BS7671 ?

......bonds have got to be as per regs table of minimum sizes.

 

[jimmymac]

all depends. if you can get the new 10mm as near as practicable to the entry points, then that's what i would do, unless the customer is prepared to rip out cupboards.

Hi Tel, yes, we can get to the entry points easily. The original bond was installed quite a way from the entry points which is what makes it such a pig to get to, i think the house must have been gutted and the whole floor lifted when it was originally bonded.

It's good to here that you agree with me, i guess this would be within the regs then??

 

[IQ Electrical]

So this requirement to use at least 6mm that you speak of , is it in a table within BS7671 ?

It's all in post #9 I simply enlarged on what you said regarding 'cpcs' and the adiabatic equation, explaining how indirectly, the adiabatic can be used and the circumstances when it can be used.

 

[Guest55]

Ahh , my mistake.