Schedules of Inspections. Clarity

[PrenticeBoyofDerry]

On the Schedules of Inspection.
Additional protection
Presence of supplementary bonding conductor
This puzzles me!
Were does this become applicable?
ie: metallic conduit containment, not being used as CPC
but metallic back boxes and face plates with a CPC pigtailed.
Is this additional protection or is it still consider part of the CPC?
Any definition in laymans terms or example would be appreciated.

 

[EFLImpudence]

On the Schedules of Inspection.
Additional protection
Presence of supplementary bonding conductor
This puzzles me!
Were does this become applicable?

To equalise potential between exposed and extraneous conductive parts by joining together but not to electrical system. E.g. water/gas pipes - not always necessary though if RCD protected.

ie: metallic conduit containment, not being used as CPC

Not the same, must be earthed so can be connected to CPC.

but metallic back boxes and face plates with a CPC pigtailed.
Is this additional protection or is it still consider part of the CPC?

CPC

One thing that confuses me is - if supplementary bonding is not required do you still tick the box or mark N/A?

 

[ricicle]

If supp. bonding is not required the it will be n/a. The additional protection in a bathroom will be afforded by the 30mA RCD. (with those installs meeting BS7671:2008)

 

[PrenticeBoyofDerry]

but as far as the bathroom is concerned on 'schedule of inspections' that would be under
Faulty protection;
(i) ADS
Presence of supplementary bonding conductors.
Would it not?
or are these the same thing?
or is
Additional protection;
something else?
I have read regulation 415.1 but still can't understand what it relates to as far as additional protection; on schedule of inspections

 

[PrenticeBoyofDerry]

One thing that confuses me is - if supplementary bonding is not required do you still tick the box or mark N/A?

If it not required it goes in as a N/A as it is not needed therefor is not unsatisfactory.

 

[EFLImpudence]

If it not required it goes in as a N/A as it is not needed therefor is not unsatisfactory.

Yes, that's what I was unsure about - whether to tick to indicate that you had checked or N/A because it's not needed.

 

[Spark123]

How about where supplementary bonding is required to provide limited touch voltages where automatic disconnection times cannot be met.
This shouldn't be applicable in domestic situations however the regs cover a whole manner of installation types.

 

[PrenticeBoyofDerry]

the installations in question is not a domestic one but one that supplies three phases to DOL that controls a motor.

 

[ricicle]

Whereabouts is the motor located ?

 

[PrenticeBoyofDerry]

This is a hyperfetical scenario!
Say, it's indoors located in a concrete factory, the DOL is about a metre in distance from the motor.

It's the check box under 'additional protection' for supp bonding. I am trying to understand were it applies?

 

[scottyboyiow]

As Spark123 I think it would apply more in a commercial/industrial circumstance, where say you cannot meet disconnection times, and it is not viable to install an RCD or an additional earth. For example a feed to a big tarmac plant. You are then allowed to bond all metal work at the end of the feed, to lessen the chance of a fault occuring and a dangerous potential developing. In 99% of cases this box would be marked N/A. Only applicable where it is actually installed.

 

[PrenticeBoyofDerry]

So the scenario is;
A three phase supply to a Motor control by DOL starter.
The cables are contained in metal trunking and metal enclosures are used, a CPC is installed.
All enclosures and lids have CPC/earth pigtails fitted.
There is no supplementary bonding evident as ADS/No RCD
There will be continuity back to the DB and to MET connecting exposed and extraneous conductive parts.
Is this purely a CPC or is it considered S.Bonding?

 

[scottyboyiow]

This is purely a CPC. Under ADS, supplementary bonding is as I described. Have a read of 411.3.2.6. So under ADS your 'presence of supplementary bonding conductors' would be marked N/A. However the pigtails linking the enclosures, would be classed as supplementary bonding under 'Additional protection'. If the pigtails were not in place this would be marked as unsatisfactory. Hope this helps.

 

[PrenticeBoyofDerry]

Is this because the links between enclosures are not directly connected to the CPC of the circuit, but just forming a bond between the metal parts of the enclosures?

 

[scottyboyiow]

Yes, that is how I interpret it anyways. People often make the mistake of marking on the test schedule under ADS that supplementary bonding is present and satisfactory, but that is not the case.