N
NickD
Interested to hear people's thoughts on best practice for proving dead and achieving safe isolation on an Economy 7 board - the problem being, (unless you work 0000-0700 GMT :wink5
the Economy 7 supply is unenergised. So 'proving' your means of isolation achieves dead actually proves nothing, because even if you had failed to isolate it'd be dead anyway - the supply is unenergised. And the energisation of the Economy 7 is outside your control, and for life criticality it's not good enough to assume it can only ever come live during the wee small hours - accidents and errors happen.
In increasing order of derangement, my thoughts currently include
- pulling the cutout fuse (would you do it if you were being assessed though?)
- carefully (no touchee copper) removing the Economy 7 tails from the main switch and isolating them in connector block
- insulation testing supply-to-load on both the L and N side of the main switch after turning off, to prove the switch open
(tin hat on, finds parapet)
the Economy 7 supply is unenergised. So 'proving' your means of isolation achieves dead actually proves nothing, because even if you had failed to isolate it'd be dead anyway - the supply is unenergised. And the energisation of the Economy 7 is outside your control, and for life criticality it's not good enough to assume it can only ever come live during the wee small hours - accidents and errors happen.In increasing order of derangement, my thoughts currently include
- pulling the cutout fuse (would you do it if you were being assessed though?)
- carefully (no touchee copper) removing the Economy 7 tails from the main switch and isolating them in connector block
- insulation testing supply-to-load on both the L and N side of the main switch after turning off, to prove the switch open
(tin hat on, finds parapet)
