Kitchen Cross Bonding

[Pensdown]

Nope. Supplementary in kitchens was removed in the 16th, although a heck of a lot of it is still done...

Out of interest, as this practice can introduce more problems than it solves, when you come across it under what circumstances do you guys remove it, CU change? other works in the Kitchen? PIR recommendations?

Or do you just test it to ensure it's sound?

The reason I ask is because we come across this when people start cross bonding/earthing office furniture, i.e desks, steel filing cabinets etc

 

[securespark]

FFS!

I remember in the 80's doing an office block in Leeds and YE would not connect us up until we had cross bonded all the suspended ceiling struts....

I kid you not! In the end, we had an argument with the YE inspector & called in our NIC inspector & left them to fight it out... Not sure what the exact conclusion was, though.

When I come across it, I usually put it down as NTCS.

 

[Adam_151]

Is there a reg that says you must not cross bond a kitchen? - I can't recall seeing one off hand.

BS7671 has to be regarded as a minimum standard, sockets in a bedroom on the 8th floor of a block of flats do not need to protected by 30ma RCD, but doing so is not a departure from BS7671

It would appear to be one of those things thats up to the installer to decide whether doing it would offer an increased level of safety over not doing it (or he could just 'work to rule' and say "thats not required... I'm not even going to think about it, it says its not required and thats that!")

My personal opinion is that I can see the advantage of cross bonding just hot and cold just under the sink, but taking it to the MET or any CPCs would not be as clever!

 

[chaban48699]

My personal opinion is that I can see the advantage of cross bonding just hot and cold just under the sink, but taking it to the MET or any CPCs would not be as clever!

justout of interest why would taking any bonding back to the MET or CPC a bad idea?

 

[pdcelec]

there is the possibility of introducing a potential where one did not exist before or create different potentials

 

[JohnD]

Suppose you have a typical kitchen setup, with the rising water main in one corner of the kitchen, main bonded, and in the other corner, the gas boiler, with all its water and gas pipes and the boiler frame supplementary-bonded to the CPC of (usually) the ring final, the gas pipe being main bonded a few metres away, and the kitchen sink between them.

the rising water main probably connects to the kitchen cold tap in copper pipe.

The kichen sink might have one more copper pipe going to it, for the hot tap, which (assuming not a combi boiler) is not included in all this bonding.

It seems to me, intuitively, to be sensible to tie the lot together in the kitchen

 

[CallEdsFirst]

Speaking of office bonding (and not in the "take a note, Miss Jones" type way!) I was chatting to my old man the other day about severe static problems caused by the floor covering in a supermarket. He recalled a job in a server room with the same issue and the consultant suggested that he earth all the equipment racks and enclosures! Dad said "That should really make sure people in the wrong shoes get a good wallop!, I'll get right on it!"

 

[Pensdown]

FFS!

I remember in the 80's doing an office block in Leeds and YE would not connect us up until we had cross bonded all the suspended ceiling struts....

I kid you not! In the end, we had an argument with the YE inspector & called in our NIC inspector & left them to fight it out... Not sure what the exact conclusion was, though.

When I come across it, I usually put it down as NTCS.

I believe you and do you think anything has changed?

Below is an extract from the preambles section for a project that we are currently tendering in Docklands.....

DEMOUNTABLE SUSPENDED CEILINGS ELECTRICAL CONTINUITY AND EARTH BONDING

Substantial conductive parts of the ceiling system: Electrically continuous and fully earth bonded to carry prospective earth fault currents.
- Standard: To BS 7671.

- Sequence: Complete earth bonding as soon as possible after completion of each independent area of suspension system.

- Testing: After completion of the ceiling system, associated services and fittings, test conductive parts of suspension system required to carry earth fault current, or used as bonding connections. Give notice before testing.

- Electrical continuity: Measure from various distant conductive points of ceiling system and to earth bar in distribution board serving the area.

- Test current: Sufficient to indicate probable electrical performance under fault conditions.

- Test instrument: Type providing a pulse of about 25 A at safe voltage for safe duration, and indicating resistance in ranges 0-2 Li and 0-20 LI.

- Resistance of measuring conductors: Deduce from test instrument readings.

- Test readings: Record and certify. Add results to resistance of other parts of the path forming the earth fault loop.

This spec is for the CAT A fit out but you can bet you're bottom dollar that if the same consultant writes the spec for the tenants fit out there will be green & yellow cables everywhere.