Extraneous....Yes or No....

[Darkwood]

I had a customer with a commercial kitchen and she received a shock as she bridged 2 tables, now both tables past the 22k to met test but a metal appliance had earthed one of the tables and a seperate fault had put a voltage into the table which had no real path through her until she bridged the tables, the fault was on a damaged fridge flex laying in a spillage which had tracked into the table - this presents a situation like previously mentioned that although the tables met requirements not to be bonded the owner had introduced an inderict connection to the MET. I find myself questioning the relaxation of the regs especially on situations where the installation isnt covered by and rcd, by the way i replaced the fuseboard and left tables unbonded as the rcd would have seen the damaged cable and i cant see this been a potential hazard in future.

 

[Risteard]

Well I've seen the 22 and 23 but never a 25K value!
I'll stick with my 23K

Wouldn't 0.25 Megohms be 250 Kilohms?

 

[Amp David]

Yes it is

 

[tricky dick]

Dear All,

I may be a bit thick here but seems to me there is quite a lot of ignorance here. Common sense is surely the thing to use. Regs is regs but guidance notes are just that.
If you have portable equipment in an environment then bonding should be carried out where a touch risk exists. The twin metal tables make no difference to the 22Kohm rule. If one table was live then a critical shock path would exist between it and an adjacent table that had a resistance to earth below the 22kohm figure. I can see no point in bonding metal parts with any resistance to earth where no electric potential can be expected. This may include many bathrooms but not those connected to a localised earth potential through for example, pipework, existing bonding etc. To my mind bonding areas where no potential is likely to exist can introduce a dangerous shock risk. The question is can the individual sparky properly understand the risks, and then justify his actions. The guy who posted the 500V potential to earth doesn't seem to understand the nature of a 3 phase supply; ie that it is 230V to earth. It all makes me worry how little some sparks seem to understand the fundamentals of the supply and associated risks.

 

[Jimmy Boy]

A fascinating thread I am ordering GN8 we have shed loads of SS kennels at work that PIR said should be bonded, but thats for a slightly differnt reason in that they take 230v leads in to them to feed heat pads, they get damaged and could liven up the kennel it was decided after discussion that if they were bonded it assure the operation of the protecting devices, now I have my doubts..mmm

 

[leckyant]

Hi guys
My heads in bits reading this thread.
domestic sparks, stick to the regs............
designers.......stick to the regs............
Personally, I would have my CU supplied from a 300 milli amp RCD with a breaker load of say 100 amps
Then RCBO's with a 10 milli amp trip. for every final circuit.......................
Thats just me!!
Actually i'm going off grid..and **** this leccy. I'm going 12 volts with solar panels and 400 AH batteriers

 

[Engineer54]

Dear All,

I may be a bit thick here but seems to me there is quite a lot of ignorance here. Common sense is surely the thing to use. Regs is regs but guidance notes are just that.
If you have portable equipment in an environment then bonding should be carried out where a touch risk exists. The twin metal tables make no difference to the 22Kohm rule. If one table was live then a critical shock path would exist between it and an adjacent table that had a resistance to earth below the 22kohm figure. I can see no point in bonding metal parts with any resistance to earth where no electric potential can be expected. This may include many bathrooms but not those connected to a localised earth potential through for example, pipework, existing bonding etc. To my mind bonding areas where no potential is likely to exist can introduce a dangerous shock risk. The question is can the individual sparky properly understand the risks, and then justify his actions. The guy who posted the 500V potential to earth doesn't seem to understand the nature of a 3 phase supply; ie that it is 230V to earth. It all makes me worry how little some sparks seem to understand the fundamentals of the supply and associated risks.

I'm afraid the problem comes these day's with the rise of the so-called Domestic Installer, who ''at best'' only understands basic domestic installations, who then moves into working in commercial premises.

Earthing and bonding arrangements can be somewhat quite involved on multi-storey commercial buildings, as they can be, in multi-story accommodation buildings, depending on the construction method...

 

[Cbigfoot]

Ok, so what is your take on this situation.

PIR on a flat in a building that is a sheltered accomodation (within a large building with communal areas for the residents) . Each flat has its own meter, (TNCS) and CCU. The heating to the flat is supplied by plastic pipes, operated by a local valve & stat arrnagement, i could not find the incoming water, or stopcock, (behind kitchen cupboards) BUT the pipework to the taps at the sink in the kitchen & bathroom is copper.

There is NO bonding of any kind, main or supplementary within the flat from the CCU or MET.

Bathroom circuits are NOT on RCD, with a shaver point by the sink.

IR reading on 500v between local socket & kitchen pipework is 0.18Mohm, same reading between shaver socket & bath pipes.

All other readings etc in the PIR are good & normal, building was new fabrication in 2009.

How would you report & code it, cos i am really in two minds about it. Fortunately the flat is currently empty & off supply. But there are 50 other flats in the building.

 

[IQ Electrical]

Ok, so what is your take on this situation.

PIR on a flat in a building that is a sheltered accomodation (within a large building with communal areas for the residents) . Each flat has its own meter, (TNCS) and CCU. The heating to the flat is supplied by plastic pipes, operated by a local valve & stat arrnagement, i could not find the incoming water, or stopcock, (behind kitchen cupboards) BUT the pipework to the taps at the sink in the kitchen & bathroom is copper.

There is NO bonding of any kind, main or supplementary within the flat from the CCU or MET.

Bathroom circuits are NOT on RCD, with a shaver point by the sink.

IR reading on 500v between local socket & kitchen pipework is 0.18Mohm, same reading between shaver socket & bath pipes.

All other readings etc in the PIR are good & normal, building was new fabrication in 2009.

How would you report & code it, cos i am really in two minds about it. Fortunately the flat is currently empty & off supply. But there are 50 other flats in the building.

You really need sight of the incoming water-my guess is that in a communal installation from 2009 the supply will be in Alkathene pipe and therefore there will be no main protective bonding requirement.

 

[Cbigfoot]

You really need sight of the incoming water-my guess is that in a communal installation from 2009 the supply will be in Alkathene pipe and therefore there will be no main protective bonding requirement

Yes i really did try, but it just disappears, my best guess is it is in poly as the heating is supplied in plastic Hep.

I have to go back next week, i am goiung to check the main buildings supply, as i think that will be Poly as well.

 

[IQ Electrical]

You really need sight of the incoming water-my guess is that in a communal installation from 2009 the supply will be in Alkathene pipe and therefore there will be no main protective bonding requirement

Yes i really did try, but it just disappears, my best guess is it is in poly as the heating is supplied in plastic Hep.

I have to go back next week, i am goiung to check the main buildings supply, as i think that will be Poly as well.

Yes, you might find a manifold arrangement in the plant room or even the EIC in the 'as fitted' manuals to help you determine the installation methods.

 

[tricky dick]

Would seem to me that bonding should be carried out to the copper pipe source and supplementary bonding as per a normal installation. The shaver socket is incidentally, an isolating device, an earth leak from a plugged in shaver etc would not trigger an RCD. If the consumer units aren't fitted with RCD protection then I would replace or fit RCBO to all circuits. Earthing in flats can be problematical and an RCD should be the first line of defence against electrical shock.

 

[somersetsparks]

Would seem to me that bonding should be carried out to the copper pipe source and supplementary bonding as per a normal installation. The shaver socket is incidentally, an isolating device, an earth leak from a plugged in shaver etc would not trigger an RCD. If the consumer units aren't fitted with RCD protection then I would replace or fit RCBO to all circuits. Earthing in flats can be problematical and an RCD should be the first line of defence against electrical shock.

Would seem that piping could be all plastic with copper facings, verey common now.
The flat may have been wired to the 16th as it was designed before the change, so maybe no RCD's required by the regs.

 

[IQ Electrical]

Would seem to me that bonding should be carried out to the copper pipe source and supplementary bonding as per a normal installation. The shaver socket is incidentally, an isolating device, an earth leak from a plugged in shaver etc would not trigger an RCD. If the consumer units aren't fitted with RCD protection then I would replace or fit RCBO to all circuits. Earthing in flats can be problematical and an RCD should be the first line of defence against electrical shock.

The 'source' is likely to be PVC and the OP is carrying out a periodic inspection!

 

[tricky dick]

The poster said the bathroom was plumbed in copper. He needs to find the source of that. (may be from the DHW cylinder etc or Boiler) and put a main bonding to it IMHO