Can I suggest you reconsider this statement then edit.
Question about rings
- Thread starter sirocosm
- Start date
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RCDs are required for all socket outlets
The maximum leakage current in normal use for one 30mA RCD is 9mA.
Single items of equipment can have 1-2mA of leakage current each.
That eliminates any possibility of having all or most of the outlets on a single circuit.
A 20A radial can easily supply 2x 2kW heaters.
Although 3kW portable heaters can be obtained, they are not particularly common and there are no circumstances where you would require 2 of them in the same room.
If people want to design and install circuits that are supplied from 2 linked breakers using undersized cable, they are free to do so.
That has been the case for ever. Any circuit can be designed in any way, and providing the designer can prove that it's safe and appropriate for use, it can be used.
The ring final is an example of one specific circuit designed for a particular purpose which was then added into BS7671 and it's predecessors.
It is the only example of a specific circuit design to be found in BS7671, and should not be in there. BS7671 is not a design document.
Deleting 433.1.204 and other references to ring circuits would mean that they can still be used, but whoever chose to use them would have to justify the design with appropriate load calculations for each installation.
A far better approach than the far too common 'shove in rings because that's what you do' efforts.
Nothing to consider.
No doubt they could be made to physically fit, however domestic CUs are not type tested with duplex/linked breakers in them, and using such things would be outside of the scope of the type tested assembly that comprises a consumer unit.
Once again...
Ring circuits have been around for 100 years in various guises.
However after the war was the first time they were specifically listed in the wiring regs.
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and that was the mistake.
all of which were designed for specific installations, rather than being some 'one size fits all' approach to electrical installations.
Most manufacturers make double pole MCBs in the same range as their single pole versions and therefore will slot directly into type approved CU's and mate perfectly with the busbar.
However it is not a solution of any sort to any percieved problems with ring finals as a broken neutral may still carry the full load.
As already mentioned the same should not be done with RCBOs.
DP and SP devices for installation into 3 phase DBs.
Not domestic consumer units.
Not specified as such in any MI's I've looked at.
I believe this is the answer to the question.
I believe so too.
As it happens, way back in the days of 15A fuse carriers in domestic fuse boxes I frequently found 2 15A fuses feeding a ring, presumably where 2 radials had been extended and eventually ringed. Also 2 15A fuses parallelled feeding an otherwise proper ring.
Last edited:
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