If they have buttons I think they would be the single phase plus in types not the 3 phase ones. My big Tupperware box of lock off has a suitable device for every device I have come across. I would need to check my ancient copy of BS 3871 to see if the meet the 3mm requirement of isolation.

JP 

John Peckham said:

I would need to check my ancient copy of BS 3871 to see if the meet the 3mm requirement of isolation.

I can save you the time of doing that, John ... it's not there.

But than again, BS 5419, the old standard for LV isolators, also doesn't have a stated minimum gap , just "in development" rather than a table.

There are some interesting observations:

• BS 3871 Appendix D contains the statement "Complete isolation of the circuit in which a fault has been present usually occurs at the first or second instant of zero current following initiation of the fault". Meaning of course, that "back in the day" they thought that BS 3871 breakers provided isolation ...
• BS 5419 Appendix B has some advice on creepage and clearance distances, without providing tables of actual minimum distances.
• Both standards use a 2 kV "withstand" test across open contacts

So, it's clear that "back in the day" these products may well have been considered OK for providing isolation ... but they definitely don't meet the requirements for isolation of BS EN 61140 today (5 kV impulse withstand for CAT III, typically 3 mm gap).

John Peckham said:

I would need to check my ancient copy of BS 3871 to see if the meet the 3mm requirement of isolation.

I can save you the time of doing that, John ... it's not there.

But than again, BS 5419, the old standard for LV isolators, also doesn't have a stated minimum gap , just "in development" rather than a table.

There are some interesting observations:

• BS 3871 Appendix D contains the statement "Complete isolation of the circuit in which a fault has been present usually occurs at the first or second instant of zero current following initiation of the fault". Meaning of course, that "back in the day" they thought that BS 3871 breakers provided isolation ...
• BS 5419 Appendix B has some advice on creepage and clearance distances, without providing tables of actual minimum distances.
• Both standards use a 2 kV "withstand" test across open contacts

So, it's clear that "back in the day" these products may well have been considered OK for providing isolation ... but they definitely don't meet the requirements for isolation of BS EN 61140 today (5 kV impulse withstand for CAT III, typically 3 mm gap).