At 10x rated current a type C can trip in as little as 0.0015 seconds. I doubt it would do. A wire fuse is closer to a D type, which is orders of magnitude slower at 10x rated current.
NT
Sounds like an urban myth. Switching of E7 and similar loads is controlled by a phase modulation of 198KHz radio 4. If you have a big radio, try tuning into R4 with the BFO switched on...
James
/Some/ E7 is teleswitched. A lot isn't. timeswitches are still widely used. Some suppliers offer industrial tarrifs of variable hours which are teleswitched. You (and the supplier) get what is paid for.
snipped-for-privacy@care2.com coughed up some electrons that declared:
I don't have my books to hand, so I'll not argue. But if that is correct, then the conditions for putting in a Type D breaker or something with a similar trip curve are considerably more onerous in terms of having a low loop impedance on the local circuit *and* on the supply (ie in the event of a dead short L-E fault, would the breaker or fuse clear before the cable damages itself through overheating?).
It would be quite possible to have a perfectly ordinary and good installation where adding a type D to a random circuit would make it both non compliant and dangerous (particularly from risk of fire, but also shock if the breaker/fuse cannot reliably clear a fault.
However, this does change if there is RCD protection (don't think that was mentioned) - but even so, personally, I would want to then ensure that a L-N fault would clear in the expected times, which is an easier target to meet, but not necessarily a forgon conclusion.
I'd be cautious about jumping straight to something with that sort of characteristic without risking a few quid on the middle option first (there's always ebay if a Type C doesn't work out).
IIRC (memory poor, open to correction) a Type C is several times less sensitive on the instantaneous trip part of the curve compared to a Type B, so there's a good chance it would buy enough margin.
I'm happy to come back tomorrow and reel off some numbers, or I think if one digs into Hager's literature, the trip curves for most of their devices are in there somewhere. Might have a rummage later...
Cheers
Tim
You put the dimmer after the switches and leave it on full. A soft start dimmer will just limit the current when you switch on and do sod all once on.
10x rated i is a reasonable ballpark for a toroidal startup surge. That's 12.5A in this case, which is only just over 2x the MCB's rated i - I was thinking 10x MCB rated i, so you may well be right with a type C.
NT
snipped-for-privacy@care2.com coughed up some electrons that declared:
Aye - I was more concerned about randoming banging Type D's - or something equally thick skinned - in without a more detailed test of the installation (loop impedances mainly), which is why I was discouraging it.
There are dimmers with two way switches - so assuming you leave it full up should be ok. But I'm not even going to suggest this to them.
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