BONDING METAL WORKTOPS

[Jonny72]

Kitchen in Care home. All metal surfaces. No bonding and no earth on test. RCBOs in DB. Does this still need bonding????

 

[7029 dave]

A lot of electricians get confused between equipotential bonding and supplementary bonding.

 

[mainline]

There is no way I would suggest that we bond all random bits of metal, in fact this never was a requirement, and the old interpretation many followed of doing something like that was as incorrect then as it is now (even though it ended up in guidelines and other supportingdocuments).

However there are circumstances where it is beneficial to bond metallic material where a particular risk may exist.

The regs actually assign a name to this (supplementary bonding), and detail how it needs to be done.

Indeed if we just take the minimum requirement from the regs as all that should be done, then the whole definition and detail of supplementary bonding needs to be removed from the regs.

The reason it is there is for circumstances such as this (in my opinion), but in doing so it doesn't follow that "by the same thought everything needs to be bonded" or similar arguments.

It is a common misconception that bonding such items won’t cause any harm so a “better to be safe than sorry” attitude is taken. However, it is important to remember that by connecting to the main earthing terminal, in some circumstances, fault currents can be exported throughout the installation which would not be there if protective bonding had not been applied. This can cause an electric shock risk for persons outside of the installation in contact with the general mass of Earth and earthed equipment such as pipework, for example an outside tap or metal (class 1) electrical equipment.

 

[cliffed]

These would most certainly NOT be extraneous conductive parts.

Unless the kitchen surfaces themselves extend externally and to the ground itself.

However I would consider them an extension of exposed conductive parts, and require supplementary bonding.

But it very much depends on circumstances, movable tables no, but if it is a complete kitchen fitted worktop with appliances resting on or adjacent to it I would add supplementary

Yea definitely a thing in days gone by we bonded everything, & agree with your last statement regarding fixed metal worktops with electrical appliances