Bonding problem in restaurant

[TraineeSparkyy]

Im an apprentice spark and have been sent to look at some bonding work at a restaurant as apparently staff have occasionally been getting shocks when they touch across metal counters. The bonding has been cut in some parts but when i trace it back rather then going to the 3 phase board it has been clamped to the outside of the metal enclosure of the restaurant as well as another bonding cable clamped to a copper rod that has been put into the ground. From testing i have found no continuity between the copper rod nor the bonding, nor did i get any continuity from the outside metal enclosure to the bonding or clips that are on it. the owner wants it resolved asap but im not sure whether it would be easier to run the bonding back to the MET on the board or to try and reconnect what is already there. any advice would be appreciated as i said im still learning and this is my first experience dealing with bonding in this arrangement.

 

[DPG]

Are they just free-standing metal benches? Why do they need bonding?

 

[Lucien Nunes]

it has been clamped to the outside of the metal enclosure of the restaurant as well as another bonding cable clamped to a copper rod that has been put into the ground. From testing i have found no continuity between the copper rod nor the bonding

One definitely does not want separate earthing systems that are not connected together, as each would become an extraneous conductor relative to the other and present a shock risk in the event of a fault that raised the potential of one of them. It is less likely to be a cause of shocks under normal conditions though, and a lack of bonding to isolated tables certainly isn't going to give anyone shocks, so that needs investigating. A Zdb would be a useful start here.

 

[Electro-tech]

Exactly, type of supply would be useful.

 

[littlespark]

I know youre just a trainee.... so what does your boss think?

Earthing and bonding isnt as straight forward as many might expect...


How serious are the shocks? (static?)
is there RCD protection to the supplies?
Is this a kitchen inside a metal container?
Why has the bonding been cut off in the past and not replaced? ie... did the bonding work before when it was installed, and has it been repositioning of the tables that some parts have been disconnected from the bonding and not redone.