Kitchen nightmare

[nuelec]

To all you experienced fault finding electricians out there, any help appreciated on the below problem

A busy kitchen in a busy restaurant which is almost open 24/7 has a metal worktop. Kitchen staff occaisonally get minor shocks from worktop. Sockets in the vicinity are from 2 circuits. Both have been tested 1 is almost perfect. IR readings above 100 M.ohms
the other is a bit iffy (about 3.5 M.ohms from L/N to Earth.
Although low i dont deem this enough to present an immediate danger.

The shocks tend to happen whilst using portable kitchen appliances on the metal worktop. They have been tested all ok. I am guessing there is plenty of water splashing around but the staff are a bit low on detail which only adds to the problem

The worktop is not bonded but is earthed through other equipment as it is bolted to a series of other worktops & eventually to a splashback which has metal clad isolators & sockets fixed directly on it so i can only assume it is earthed through these. Hence i have 240v across worktop & live conductors of nearbye sockets.

Do I

A. remove all parrallel earth connections from the worktop. It is not an extraneaus item so is not required to be bonded
B. get to the bottom of the Low IR readings on the iffy circuit
C. Both
D. anything else?

I have been called to investigate this issue several times but never really get any headway as the kitchen is always so busy. I proposed spending a night in the restaurant without any kitchen staff in the way. But With Sunday night from midnight the only possibility for this restaurant the labour costs were too excessive for them. However very recently one member of staff recieved a serious shock which has prompted the restaurant management into action. So now i am under pressure to resolve it but it is difficult one & whatever option i choose its going to be expensive for them (Sunday night x 2 electricians) so i want to get it right

Thanks in advance for any idea's

 

[Lagentium]

Do the circuits have RCD protection?

 

[trev]

If someone has received a shock then the restaurant owners should, assuming they actually give a flying something about their staff, be making an effort to get this resolved not paying lip service to it by telling you to work at ridiculous hours.
If this shock was reported they might find themselves closed by the powers that be until they prove that their installation is not making the environment unsafe to work in.
I'm sorry but this just beggars belief.
As the electrician responsible for putting this right I do not envy your position.

 

[amlu]

dodgy appliance? ask the staff what they were doing/holding with their other hand when they received the shock. alternatively go there and try to find out yourself.

 

[nuelec]

No They dont!
That was my first recomendation but they refused it as they didnt want any nuisance tripping!
I will insist on it now though. & was thinking of individual RCD sockets rather than rcbo to minimise the nuisance tripping
But still need to get to the bottom of the problem

 

[uksparks]

I would do an IR reading between the worktop and the line and neutral to see if you have anything going on there, personally I'd earth it as its metal and lots of it and got power round it.

 

[uksparks]

It's pointless having rcd sockets in this setup in a way as its not going to reduce the risk if the worktop is live.

Are you sure it's not something as simple as nylon soled shoes then earthing through the worktop, getting a static shock... Just a thought.

 

[uksparks]

Just to add, I'd rcd the circuit as if it's tripping it, something is clearly wrong.

 

[amlu]

if there is a dodgy fryer/fridge/mixer around with plenty of earth leakage then parts of worktop may get some voltage on them, and if not earthed properly... continuity test between worktops and db may help

 

[Lagentium]

I'd try and get every appliance on RCD sockets, or even in pairs and the fault will show itself and you can work it out through process of elimination.

 

[trev]

These clowns need to be reminded that they have a legal responsibility to provide a workplace which is as safe as it possibly can be. If that means getting someone with a bit of clout in like Environmental Health or the HSE then so be it.
Would they be so blasé about it if a staff member were seriously hurt or killed?

 

[nuelec]

I will almost definately be fitting RCD's to all sockets & whatever is required to improve the IR readings on the iffy circuit. The worktop issue is the bit i am unsure about should it be earthed or not? The regs say not but am i putting the staff in more danger if i remove all parallel earths?

 

[nuelec]

Agreed with all the posts about the managements attitude. Money/ profit first and all that!
But to be fair to them i think they are now taking it seriously

 

[Lagentium]

I'd common everything up with an earth wire, make everything the same potential then back to the DB, aswell as RCD protection.

 

[trev]

I'd be looking to get everything I could with an electrical connection permanently off the tables. Then I'd test to see if the tables are an ECP. If they are I'd bond them, if not I wouldn't.