--- Q. Is a 27/25 amp MCB suitable to protect 10 amp socket outlets in final subcircuits?
A. Yes, provided that maximum voltage drop and the cable maximum current rating (when de-rated for thermal insulation) is not exceeded, a 27/25 amp MCB is permitted. The requirement for the protective device rating to not exceed twice the socket outlet rating has been deleted from the Electricity Regulations 1997. ----
It's a valid point Andy. With the multiple adapters that were common here in BS546 days, it would have been quite easy for someone to load a 5A outlet up to 15A, although in the case of BS546 the 5A connectors would probably carry 15A without any problems anyway.
By the way, a few manufacturers here (e.g. MK) now opffer a 3A MCB as well, for separate smoke alarm circuits, bell chime transformers, etc.
Re: 27A MCB?#140272 02/25/0409:54 AM02/25/0409:54 AM
Wow!. I don't know what they've been smoking at the Electrical Safety Service these days!. But, let's just get one thing straight here, There is no way that any Electrician here would run a 10A socket-outlet on a 25A breaker, that's for sure. Even though a circuit like this would be run in 1.5mm(16A) or 2.5mm cable(20A), the loss of the rule mentioned above, opens the whole subject up to a dangerous situation with cables being overloaded beyond their design loadings. BTW, the 27A MCB was used for 4mm before we changed over to (ahem) International fusing sizes. And 25A, is still only allowed for 4mm and very short runs of 2.5mm to permanently connected appliances.
[This message has been edited by Trumpy (edited 02-26-2004).]
Re: 27A MCB?#140275 02/27/0406:17 AM02/27/0406:17 AM
I think Ireland had it's own slightly strange implementation of BS546. I've never seen a multiple adaptor for anything other than the 15A socket outlets.
Did you not have the adapters to allow multiple 5A BS546 plugs to be connected to a 15A outlet? They were pretty common here. as were the ones which were all 5A, i.e. a 5A 3-pin plug to a 5A 3-pin socket plus two 5A 2-pin sockets, or a multiple 5A 2-pin.
BTW, the 27A MCB was used for 4mm before we changed over to (ahem) International fusing sizes.
Although for radial circuits 20A is the most usual here, at least in residential work, the Regs. allow a 30A cartridge fuse or 30/32A MCB to be used for a radial circuit wired in 4 sq. mm. Rewireable 30A fuses are not permitted for such radials however.
[This message has been edited by pauluk (edited 02-27-2004).]