Can an oven be run from a fused spur on a ring final circuit?
Usually not. BS 7671 Appendix 15 lists connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit as one of the ways of satisfying Regulation 433.1.204. A 13 A fused connection unit protects the spur cable. It says nothing about whether the ring should be supplying that load at all. Those are two separate questions, and on site they get run together constantly.
What Appendix 15 says about spurs
Appendix 15 is the clearest statement in BS 7671 of what a ring final circuit may carry. It covers two arrangements.
An unfused spur. Figure 15A states that an unfused spur should feed one single or one twin socket-outlet only. One. Figure 15B, covering radial circuits, carries the same sentence with an extra qualification: an unfused spur run in 2.5 mm² cable should feed one single or one twin socket-outlet only. Both figures add that an unfused spur may be connected to the origin of the circuit in the distribution board.
A spur behind a fused connection unit. Here the number is not fixed. Both figures say the number of socket-outlets supplied from a fused connection unit is dependent upon the load characteristics, having taken diversity into account. The fuse is doing the limiting, and the maximum fuse in an FCU to BS 1363-4 is 13 A.
The two questions that get run together
“It’s on a fused spur, so it’s fine” answers only the first of two questions.
- Is the spur cable protected? Yes. That is what the 13 A fuse in the connection unit is for.
- Should the ring be supplying this load in the first place? A fuse in a connection unit has no view on that whatsoever. That question belongs to Regulation 433.1.204, and Appendix 15 handles it separately.
What Regulation 433.1.204 actually says
433.1.204 permits accessories to BS 1363 to 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 series, BS 3036, BS EN 60898, BS EN 60947-2 or BS EN 61009-1 (RCBO). The circuit is wired with copper conductors having line and neutral of at least 2.5 mm², except for two-core mineral insulated cables to BS EN 60702-1, where the minimum is 1.5 mm².
Then comes the part that bites at audit. Such circuits are deemed to meet the requirements of Regulation 433.1.1 if two conditions are both met:
- the current-carrying capacity (Iz) of the cable is not less than 20 A, and
- 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.
Two limbs, joined by “and”. Both have to hold. It is worth quoting both, because quoting only the second invites the obvious reply that half the sentence has been left out.
Note the framing as well. 433.1.204 does not say a ring final circuit is compliant. It says such circuits are deemed to meet the requirements of 433.1.1 when those conditions apply. Take the conditions away and the deeming goes with them, and the circuit falls back to being assessed against 433.1.1 on its own merits.
Where the 2 kW figure comes from, and what it is not
Appendix 15 is marked Informative. Its heading reads “APPENDIX 15 (Informative) RING AND RADIAL FINAL CIRCUIT ARRANGEMENTS, REGULATION 433.1”.
Figure 15A restates the load condition, that the load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable, and then says: “This can generally be achieved by:”
- locating socket-outlets to provide reasonable sharing of the load around the ring;
- not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit;
- connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit;
- taking account of the total floor area being served. (Historically, a limit of 100 m² has been adopted.)
Read that opening line carefully, because it changes what the list is. These are four ways of achieving the load condition. They are not four prohibitions. BS 7671 does not say an oven over 2 kW must be on its own circuit. It says putting it on its own circuit is one of the things that generally gets a ring final past 433.1.204.
The distinction matters when somebody argues the point. The requirement is the load condition in 433.1.204. The 2 kW line is guidance on how to meet it, printed in an informative appendix. Anyone defending a 2.5 kW oven on a ring has to show the load condition is satisfied some other way, which is a harder argument than it sounds but not an impossible one.
Two things in that list are widely misquoted. It is 2 kW, not 3 kW and not “anything under 13 A”. And item (b) ends “or loads of a similar profile”, which is the half that gets dropped. That catch-all is what covers EV charge points, hot tubs and heat pump controls, none of which are named anywhere on the page.
The number that explains the one twin socket rule
Appendix 15 opens with a note that is easy to skim past and explains a good deal of the rest: “The total design current for a twin 13 A socket-outlet to BS 1363-2 is assumed not to exceed 20 A.”
Twenty amps. The same twenty amps that appears in the first limb of 433.1.204’s deeming condition. That is the engineering reason an unfused spur is limited to one twin socket-outlet, and it is sitting in a note at the top of the appendix rather than in the figure everybody photographs.
What Appendix 15 does not cover
The appendix scopes itself in its first sentence. It sets out options for the design of ring and radial final circuits for household and similar premises, in accordance with Regulation 433.1, using socket-outlets and fused connection units. Anyone arguing about a commercial ring final is arguing outside the appendix’s own scope.
It also states plainly that it does not cover protection against electric shock (Chapter 41), protection against thermal effects (Chapter 42), protection against overcurrent (Chapter 43), or selection and erection of equipment (Part 5). Both figures carry a separate note that consideration must be given to the need for additional protection by an RCD in accordance with Regulation 411.3.3 and Regulation 522.6.202.
Where it shows up on an EICR
Plenty of ovens are running from 13 A fused spurs on ring finals that were certified this year. The cable is protected, the installation works, and nobody has been troubled by it. The exposure is Regulation 433.1.204’s load condition, and the awkward question is not “is the spur fused” but “was the load current in any part of that ring unlikely to exceed the cable’s capacity for long periods, under the intended conditions of use”.
BS 7671 does not code anything. What an inspector does with it is a separate judgement, and one worth having a position on before the conversation happens rather than during it.
Common questions
How many socket-outlets can go on an unfused spur?
One single or one twin socket-outlet only, per Appendix 15 Figures 15A and 15B. Figure 15B adds that the spur should be run in 2.5 mm² cable.
How many socket-outlets can go behind a fused connection unit?
Appendix 15 gives no number. It depends on the load characteristics, having taken diversity into account. The maximum fuse in an FCU to BS 1363-4 is 13 A.
Does BS 7671 ban ovens over 2 kW from ring final circuits?
No. Appendix 15 is informative, and connecting cookers, ovens and hobs above 2 kW on their own dedicated radial is listed as one of four ways of generally achieving the load condition in Regulation 433.1.204. The requirement is the load condition. The 2 kW figure is guidance on meeting it.
What size protective device can a ring final circuit have?
Regulation 433.1.204 names a 30 A or 32 A device complying with BS 88 series, BS 3036, BS EN 60898, BS EN 60947-2 or BS EN 61009-1 (RCBO).
What about immersion heaters?
Appendix 15 item (b) says not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit. The “similar profile” wording is the part that matters, because it catches loads the appendix never names.
Does Appendix 15 apply to commercial installations?
It scopes itself to household and similar premises. A commercial ring final sits outside what the appendix sets out to cover.
Every regulation quoted above was read from BS 7671:2018+A4:2026, Appendix 15 (printed pages 583 and 584) and Regulation 433.1.204 (printed page 103). Table values are not quoted from scanned text.