BS 1363 in cooker isolator and 40A MCB/RCBO

[ericmark]

Simple question is it permitted to have a BS 1363 socket when the circuit is protected by a over current device larger than 32A?

433.1.5 Accessories to BS 1363 may be supplied through a ring final circuit. With or without unfused spurs, protected by a 30 A or 32 A protective device complying with BS 88-2.2. BS 88-6. BS 1361. BS 3036, BS EN 60898, BS EN 60947-2 or BS EN 61009-1 (RCBO). The circuit shall be wired with copper conductors having line and neutral conductors with a minimum cross-sectional area of 2.5 mm² except for two-core mineral insulated cables complying with BS EN 60702-1, for which the minimum cross-sectional area is 1.5 mm². Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying, capacity (Iz) of the cable is not less than 20 A and if. under the intended conditions of use, the load current in any part of the circuit is unlikely to exceed for long periods the current-carrying capacity (Iz) of the cable.

For farms I know the protective device was reduced in size to 20A (705.553.1) but if some one wanted to run a ring final with 4 mm² cable could they protect it with a 40A MCB or is 32A maximum for any circuits with BS 1363 devices fitted?

 

[JohnW2]

Simple question is it permitted to have a BS 1363 socket when the circuit is protected by a over current device larger than 32A?

You seem to be confusing things a bit, by talking about a circuit protected by an OPD >32A but then quoting the regulation which allows cable in a ring final circuit with a CCC which may be as low as 20A to be protected by a 30/32A OPD - whereas I suspect (particularly given the title of this thread) you are actually thinking about a socket in the 'cooker control unit' of a dedicated cooker radial circuit.

In that latter case, I can see absolutely no reason why the socket (invariably single) should not be allowed. I presume that the design of cooker control units with sockets is such that the current to the cooker does not go through the terminals of the socket, which, in terms of loads plugged into the socket, is protected by a downstream OPD (plug fuse) no greater than 13A.

What was your concern?

Kind Regards, John

 

[ban-all-sheds]

Simple question is it permitted to have a BS 1363 socket when the circuit is protected by a over current device larger than 32A?

The reg you quote is a bit of a red herring - it prescribes what may be connected to a ring final - it doesn't impose any requirements "in the other direction", i.e. it does not say that those accessories may only be served by a ring.

For farms I know the protective device was reduced in size to 20A (705.553.1) but if some one wanted to run a ring final with 4 mm² cable could they protect it with a 40A MCB

Not and be compliant with the regulations - the only ring circuit allowed where In > Iz is a 32A one. Wrt cable size you could do as you suggest, document it as a departure, and show that you had designed it in a way that it wouldn't be overloaded, and be guided by the same In:Iz ratio as a 32A ring, and the way the reg used to be worded with a 3:2 ratio.

or is 32A maximum for any circuits with BS 1363 devices fitted?

That's a second, separate issue.

BS 1363 does not guarantee that a socket can cope with >20A on the supply cable, so IMO 20A becomes the CCC of the circuit. Which is fine for a 32A ring, but for a ring over that, or a radial > 20A, you should probably connect the sockets on drops from the main circuit cable.