electrical.theiet.org/.../
Personally I think Rotary Isolator would be far better than 20 amp Double-pole switch shown Fig 2 as this allows for isolation and LockOff/LockOut
The cost of the Rotary Isolator is still quite low see URL below. (Other brands and other Wholesalers are available).
www.superlecdirect.com/.../
As always please be polite and respectful in this purely academic debate.
Come on everybody let’s help inspire the future
However the dual pole switch shown in the example lacks a lock off/isolation mechanism.
I hear this, but I'm not sure I fully agree there's an issue for the 'local switch' or 'local isolator' situation.
BS 7671 does not fully agree with the perspective that locking off is a requirement either, and therefore it would not be appropriate to produce a requirement from thin air when it's specifically covered in BS 7671. Specifically, there is not always a need to 'lock off' for EAWR (for example, if you are in control of the point of 'isolation' for equipment made dead throughout the work activity ... BS 7671 also acknowledges this, see Regulation 462.3 (3rd bullet example).
Of course, you can apply more than one bullet of the note of Regulation 462.3 ... and they are only examples.
If the switch conforms to another part of BS EN 60669 in addition to BS EN 60669-2-4, it will be suitable for isolation, BUT it should be marked as above.
Which in hindsight could/should have been included in the original article. The suggested replacement SHOULD BE NO LESS SAFE THAN THE ORIGINAL. The original had 3 functions, act as a switch, contained a fuse for safety and was a point of isolation and lock off/out. I can understand losing one of the 3 functions/features but removing 2 is unreasonable.
Why? See above regarding BS 7671 requirements and why this is acceptable. The article could have said a lot of things about product standards for isolators, but that wasn't the purpose of the article.
Furthermore it would probably be beneficial if this is added to BS7671 and also the OnSite guide. Thus helping future electricians who MAY encounter this in NEW installs or in installs that are 30 plus years OLD. The UK nominal mains voltage was officially changed from 240V to 230V in 1994 to harmonize with European standards, though in practice the supply voltage often remains closer to the old 240V standard.
Agreed regarding the On-Site Guide and other guidance ... watch this space 
. I'm not sure it would be seen as "too much detail" for BS 7671, and there'd perhaps be a question as to where it goes.
I'm very aware it was common practice 'back in the day' (i.e. up to 1980s) to use a 'robust' FCU ... but those old FCUs were not made to BS 1363! BS 1363 didn't include requirements for FCUs until 1995. (Perhaps that could have been stated in the article?)
(For nostalgia's sake, there are some images of the older products on the 'on-line museum' at this web-site: https://flameport.com/electric_museum/index.cs4)
The purpose of these discussions/debates is to make the industry safer for the benefit of everyone. In my eyes healthy debate amongst engineers is a way of making things better. This is akin to having a peer review.
Agreed. Good discussion/debate.
However the dual pole switch shown in the example lacks a lock off/isolation mechanism.
I hear this, but I'm not sure I fully agree there's an issue for the 'local switch' or 'local isolator' situation.
BS 7671 does not fully agree with the perspective that locking off is a requirement either, and therefore it would not be appropriate to produce a requirement from thin air when it's specifically covered in BS 7671. Specifically, there is not always a need to 'lock off' for EAWR (for example, if you are in control of the point of 'isolation' for equipment made dead throughout the work activity ... BS 7671 also acknowledges this, see Regulation 462.3 (3rd bullet example).
Of course, you can apply more than one bullet of the note of Regulation 462.3 ... and they are only examples.
If the switch conforms to another part of BS EN 60669 in addition to BS EN 60669-2-4, it will be suitable for isolation, BUT it should be marked as above.
Which in hindsight could/should have been included in the original article. The suggested replacement SHOULD BE NO LESS SAFE THAN THE ORIGINAL. The original had 3 functions, act as a switch, contained a fuse for safety and was a point of isolation and lock off/out. I can understand losing one of the 3 functions/features but removing 2 is unreasonable.
Why? See above regarding BS 7671 requirements and why this is acceptable. The article could have said a lot of things about product standards for isolators, but that wasn't the purpose of the article.
Furthermore it would probably be beneficial if this is added to BS7671 and also the OnSite guide. Thus helping future electricians who MAY encounter this in NEW installs or in installs that are 30 plus years OLD. The UK nominal mains voltage was officially changed from 240V to 230V in 1994 to harmonize with European standards, though in practice the supply voltage often remains closer to the old 240V standard.
Agreed regarding the On-Site Guide and other guidance ... watch this space . I'm not sure it would be seen as "too much detail" for BS 7671, and there'd perhaps be a question as to where it goes.
I'm very aware it was common practice 'back in the day' (i.e. up to 1980s) to use a 'robust' FCU ... but those old FCUs were not made to BS 1363! BS 1363 didn't include requirements for FCUs until 1995. (Perhaps that could have been stated in the article?)
(For nostalgia's sake, there are some images of the older products on the 'on-line museum' at this web-site: https://flameport.com/electric_museum/index.cs4)
The purpose of these discussions/debates is to make the industry safer for the benefit of everyone. In my eyes healthy debate amongst engineers is a way of making things better. This is akin to having a peer review.
Agreed. Good discussion/debate.
