gkenyon:

ProMbrooke:

mapj1:
Hang on ... in 2001 edition, Table 41C (48A) is NOT an equivalent of what we have now in Table 41.1.


My apologies - I do not have the  copies to compare here, and the notes implied it was the same.  (and given even the 1977  version is 100 CHF it will be some time before we do have all possible standards here, an up to date copy of a few of them is quite enough...) However, it is interesting to know where the figures come from, as there are clearly some assumptions hidden . I will edit my post to delete the implication that it is the same.

Mike.

There appear to be assumptions, some of which I may humbly not agree with.


IMO these values need to be revisited and discussed further. 

There is definitely no problem doing that.


The basic standards for protection against electric shock, used by product and installation standards committees, are IEC 61140 (BS EN 61140), and IEC 60479 series (BS IEC 60479 series, although two of these standards are Published Document/Technical Reports rather than full standards).


It's probably best to discuss comments/suggestions in that direction.


You are fully correct that the provisions in Chapter 41 are dry conditions only. BS 7671 then has Part 7 for locations of increased shock risk.


Hence, you will not find anything to do with humid and wet location in Chapter 41.


In terms of hazard treatment to reduce risk in Part 7, in exactly the same way that we manage other risks, we use the Hierarchy of Control, which is per the following order:

1. Eliminate

• Substitute

• Engineering controls

• Administrative controls

• PPE

Consider Section 701 example given above. The controls applied are Eliminate (no mains and limits on SELV/PELV voltages in Zone 0), and either eliminate (bonding) or engineering controls (RCD) in Zones 1 and 2. Hence, disconnection time need not enter into it.

Right, but what has me perplexed are the lack of tables in part 7. Exception being medical locations however this should apply to all kitchens, bathrooms, laundry areas, garages, unfinished basements, exterior sockets, pool circuits and the like- anywhere skin conductivity is lowered typically through moisture or large earthed surfaces.


Bonding and RCDs should not be the primary means to achieve protection in these areas. Rather a pyramid approach should be taken imo. Remote earth is impossible to avoid in all scenerios. RCDs have much higher failure rates compared to MCBs. Yet ADS remains the most simple, assured and reliable way of protecting life and property.

gkenyon:

ProMbrooke:

mapj1:
Hang on ... in 2001 edition, Table 41C (48A) is NOT an equivalent of what we have now in Table 41.1.


My apologies - I do not have the  copies to compare here, and the notes implied it was the same.  (and given even the 1977  version is 100 CHF it will be some time before we do have all possible standards here, an up to date copy of a few of them is quite enough...) However, it is interesting to know where the figures come from, as there are clearly some assumptions hidden . I will edit my post to delete the implication that it is the same.

Mike.

There appear to be assumptions, some of which I may humbly not agree with.


IMO these values need to be revisited and discussed further. 

There is definitely no problem doing that.


The basic standards for protection against electric shock, used by product and installation standards committees, are IEC 61140 (BS EN 61140), and IEC 60479 series (BS IEC 60479 series, although two of these standards are Published Document/Technical Reports rather than full standards).


It's probably best to discuss comments/suggestions in that direction.


You are fully correct that the provisions in Chapter 41 are dry conditions only. BS 7671 then has Part 7 for locations of increased shock risk.


Hence, you will not find anything to do with humid and wet location in Chapter 41.


In terms of hazard treatment to reduce risk in Part 7, in exactly the same way that we manage other risks, we use the Hierarchy of Control, which is per the following order:

1. Eliminate

• Substitute

• Engineering controls

• Administrative controls

• PPE

Consider Section 701 example given above. The controls applied are Eliminate (no mains and limits on SELV/PELV voltages in Zone 0), and either eliminate (bonding) or engineering controls (RCD) in Zones 1 and 2. Hence, disconnection time need not enter into it.

Right, but what has me perplexed are the lack of tables in part 7. Exception being medical locations however this should apply to all kitchens, bathrooms, laundry areas, garages, unfinished basements, exterior sockets, pool circuits and the like- anywhere skin conductivity is lowered typically through moisture or large earthed surfaces.


Bonding and RCDs should not be the primary means to achieve protection in these areas. Rather a pyramid approach should be taken imo. Remote earth is impossible to avoid in all scenerios. RCDs have much higher failure rates compared to MCBs. Yet ADS remains the most simple, assured and reliable way of protecting life and property.