by ericmark »
Tue Jul 01, 2008 10:42 am
Two issues come to mind.
1) The MCB is designed to trip automatically and if held in one position although it may still trip there would be no indication of it tripping so holding the trip leaver not a good idea.
2) Not sure how a MCB used as a switch on a regular basic would last. Looking at Table 53.2 it shows Circuit-breaker and three BS EN numbers as being OK for functional switching but personally I would not permit staff in general to go into a distribution panel.
Most panels are split into two groups and I would think you could set non essential to one side and essential to the other and designate an instructed person to isolate or much easier would be to use two panels then the non essential could be switched off with one main switch.
Up to 20 amp double pole grid switches are freely available but over 20 amp they start to grow in size and one would normally use relays and contactors.
I know in one place I worked all hot plates and anything else which if left on could cause danger were fed through active RCD’s so in the event of a power cut when the power was restored these items would not auto reset other items used starters with push buttons for same reason.
In machine shops I have seen every machine feed through one large contactor and emergency stop buttons placed so if a man at one machine saw a man at another was in trouble he could stop all machines with one button. Not sure if it was a good idea as some machines do not like being stopped mid process and it was too easy to catch button by mistake.
I like the idea or risk assessment for some reason when you write things down you can better see your errors.
All best Eric
