Bit of fun, Interpret the previous reg

[LastManOnline]

434.5.1.

I'll have a go and try and explain this for trainees.

Not just "trainee, s" mate. That's gone right into "saved" folder.

 

[timhoward]

Now, someone can have a punt at 433.1.204

Go on then.
433.1.204
Accessories to BS1363 may be supplied through a ring final circuit, with or without unfused spurs protected by a 30A or 32A protective device [ BS88 fuse / MCB / RCBO meeting relevant regs ]
The circuit shall be wired with copper conductors having line and neutral conductions with a minimum cross sectional area of 2.5mm sq. except for two-core mineral insulated cables complying with BS EN 6072-1 for which the minimum cross sectional area is 1.5 mm sq. Such circuits are deemed to meet the requirements of 433.1.1 if the current carrying capacity (Iz) of the cable is not less than 20A 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.

This describes the good 'ole British ring final circuit and explains several things.
In certain circumstances you can do something which would normally not be allowed - you can use a 30/32A OCPD with 2.5mm T+E cable. As the best possible current carrying capacity is only 27 amps (clipped direct, table 4D5) and this is less than 30/32A it does not meet reg 433.1.1. However the exemption is permitted if certain conditions are met:

• obviously it must be wired in a ring, allowing the load current to be balanced on the two legs.
• the circuit must supply 13 amp sockets / plugs / fused connection units (BS 1363 accessories)
• the tabulated current carrying capacity in table 4D5 for the method of installation needs to be at least 20 amps. Methods 101 and 103 do not meet this requirement, so a cable over a plasterboard ceiling in >100mm thick insulation or a cable floating inside an insulated stud wall shouldn't be used as part of a ring final circuit.
• the load current at any point in the ring (and spurs if any) shouldn't be expected to exceed the current carrying capacity of the cable used for long periods of time.

[1.5mm mineral insulated cable can be used too, refer to table 4G1A]
Improvements on this attempt welcome!

I'll throw up 411.1 for next punter.

 

[SparkyChick]

Go on then.
433.1.204
Accessories to BS1363 may be supplied through a ring final circuit, with or without unfused spurs protected by a 30A or 32A protective device [ BS88 fuse / MCB / RCBO meeting relevant regs ]
The circuit shall be wired with copper conductors having line and neutral conductions with a minimum cross sectional area of 2.5mm sq. except for two-core mineral insulated cables complying with BS EN 6072-1 for which the minimum cross sectional area is 1.5 mm sq. Such circuits are deemed to meet the requirements of 433.1.1 if the current carrying capacity (Iz) of the cable is not less than 20A 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.

This describes the good 'ole British ring final circuit and explains several things.
In certain circumstances you can do something which would normally not be allowed - you can use a 30/32A OCPD with 2.5mm T+E cable. As the best possible current carrying capacity is only 27 amps (clipped direct, table 4D5) and this is less than 30/32A it does not meet reg 433.1.1. However the exemption is permitted if certain conditions are met:

• obviously it must be wired in a ring, allowing the load current to be balanced on the two legs.
• the circuit must supply 13 amp sockets / plugs / fused connection units (BS 1363 accessories)
• the tabulated current carrying capacity in table 4D5 for the method of installation needs to be at least 20 amps. Methods 101 and 103 do not meet this requirement, so a cable over a plasterboard ceiling in >100mm thick insulation or a cable floating inside an insulated stud wall shouldn't be used as part of a ring final circuit.
• the load current at any point in the ring (and spurs if any) shouldn't be expected to exceed the current carrying capacity of the cable used for long periods of time.

[1.5mm mineral insulated cable can be used too, refer to table 4G1A]
Improvements on this attempt welcome!

I'll throw up 411.1 for next punter.

I'll just add my usual comment about this regulation... this is the only regulation that defines a what a ring final circuit can be. Based on your comments, it's acceptable to change up the cable size when running in insulation. I did one rewire where there was insulation present, so based on installation methods I upped the cable size for the segments running through insulation.

And for this one, I'm going to put my tin hat on... based on that definition of a ring final, you could in theory run a spur to more than one accessory providing the cable used was suitably sized. Whilst this is not outlined in Appendix 15, which many consider to be the de facto list of what you can and can't do with a ring circuit... if for example you spurred off a ring with 6mm (without looking at the BBB I'm reluctant to say 4mm) you could supply two double socket outlets... the cable itself would meet the requirements (installation methods aside) and whilst you could in theory connect four 13A loads to it, if you did that with any ring final circuit you would expect it to trip the breaker anyway, but the cable itself would be fine. However, this has the potential to raise all sorts of issues if someone adds to that segment thinking it's a radial... but then I would hope when they isolated to do the works they would realise. Good practice says it shouldn't be done, but the regulations don't explicitly say you can't do it. Hence the lollipop circuit is allowed.