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Discuss Does anyone know the rating of this paperclip? in the UK Electrical Forum area at ElectriciansForums.net
When I was an apprentice (long time ago), the electrician I was working under accidently blew an HRC in a panel at a well known chemist stores in the city of London. As a temporary measure, as he never had a replacement at approx 16:50, he also linked the HRC out with fuse wire. Not sure what the rating was, maybe around 30 Amps or a little larger? The next day I was on my own there whilst he was at the wholesalers, when walking past the panel I noticed the outer panel covering glowing red hot! My immediate reaction was to shut the panel down clear the area and get the manager to call the fire brigade, needless to say it emptied the store. However, It was a very good lesson for me never to do this no matter how awkward the situation. Unless I see it for myself I would never have believed what effect this could have.
It should be possible to adapt the design of a standard MCB such that an indicator gives a reason for the trip, as there are two mechanisms within the MCB that disconnect the switch - the bimetal strip takes care of over current, whilst the magnetic trip unit (looking at the pictures... this is basically a solenoid, right?) takes care of faults (shorts). So one indicator for overcurrent, another indicator for short, and no indicator = "Nowt to do with me, it wor a finger wot turned it off."
I'd be surprised if no-one's patented this (if not then they're too late as this counts as disclosure). It would be useful, for fault-finding purposes. Question is, is anyone aware of an MCB that does this? And would it catch on?
Sorry, they don't work like that..
Also, I don't think energising poss faulty circuits as part of fault finding would be considered good practice!
I'm sorry, I don't understand your comment. Don't work like what? The bit about the bimetalic strip disconnecting in the event of a long duration overcurrent and the magnetic trip unit quickly disconnecting in the event of a very large current? Pretty sure that's how they work (unless things've changed since Monday when I had a look inside one). All the rest of what I was describing - that's not how they work, no, I was suggesting an MCB manufacturer could adapt/enhance the design such that an external indicator showed which situation caused the device to trip. I know this is possible to do, because if you have two different mechanisms by which an event happens (switch goes) then you can determine which mechanism affected the event.
I agree absolutely, but that's not what I'm suggesting at all. Say there is a fault, or an overcurrent (too many applianced plugged in). Your MCB trips. You go to your board, you see your MCB has tripped. At this point, you've got no idea if it's tripped do to overcurrent (possible misuse of the circuit, e.g. too many fan heaters in an RFC) or if there's a short. A little coloured dot to tell you what sort of situation caused the device to trip would be nice, don't you think? Then you'd have the same "functionality" as the old semi-enclosed fuses, as you can tell by the amount of splatter whether it blew quickly or slowly. You wouldn't be using it as a way of fault finding by energising a potentially faulty circuit ... although, isn't that what everyone (general public) does after something trips? Is your first thought, "Huh, that tripped, I don't know the cause, best phone an electrician with the proper test equipment to diagnose the fault using dead tests before I re-energise the circuit?" If they did, I'm sure you'd all be "Earning £50k+!!!" and driving Ferraris (why is it always Ferraris?)
Hope that makes sense, sorry if my explanation is/was unclear.
Reply to Does anyone know the rating of this paperclip? in the UK Electrical Forum area at ElectriciansForums.net