"idiot proof" final circuit design

Sorry, "American Electrics" was getting far too OT, and rather long so here it is:

Given the opportunity (and let's ignore backwards compatibility, at least to begin with), how would you redesign our domestic final circuits to be completely idiot proof?

Although the system we have at present is probably the most recently designed in the world, are there any things about it which, with today's technology, could be seen as compromises?

Particular examples brought up on the AE thread (and elsewhere over the last few months):

  • a ring circuit with a break in one of the live conductors will overload one leg as it is fused at 30/32A and the cable is only good for 20A (27A under ideal circumstances)
  • fuses in the appliance plugs can be bypassed, while MCBs screwed into the consumer unit are less likely to be.
  • fused appliance plugs are better for isolating faults to a single appliance as (usually) the plug fuse will blow before the MCB.
  • on the other hand, in a "dead short" situation, this isn't always the case even with a 3A fuse and 32A MCB (I've proved it several times :-)
  • radials using fused plugs can be rated up to 32A, but need at least 4mm2 cable, and often 6mm2 cable which is both more expensive, and much more difficult to work with than the 2.5mm2 cable used for 32A rings.
  • unfused appliance plugs (less problem with tampering) would mandate radials with a very low MCB rating and hence a large number of radials; one per room or even more.
  • either that, or they would mandate fuse protection inside every appliance and while a lot (TV, video etc) already have this, it's going to be difficult persuading manufacturers to bung a fuse inside a £3 table lamp.
  • unfused appliance plugs will *always* take out the circuit MCB on a fault, and hence tracing the appliance which caused the fault can be tricky since there are likely to be several candidates.

Erm, I'm sure I've missed some things out.

Go on then, what's the ideal? Sub mains to each room with a mini-CU in every room, with MCBs feeding individual outlets (don't laugh, it has been suggested)? Appliance plugs with built-in MCBs rather than replaceable cartridge fuses? Sockets with built-in MCBs, or RCBOs? Talking of RCDs, what about changing the way we use these things?

Have fun :-)

Hwyl!

M.

Reply to
Martin Angove
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Given that all appliances come with fitted plugs these days, it would be easy to make the use of the wrong fuse impossible, by making the design of the fuse and fuse carrier different for the appropriate size. And you could also make the sale of '13 amp' extension leads not rated at 13 amps illegal. Unless using proprietary non 13 amp connectors like some garden tools etc, use.

The idea of having a mini CU in every room is total overkill. Just how often does an MCB trip and cause a problem in the average house?

Since this is a DIY group, when re-wiring your house, simply put in an adequate number of circuits. The extra costs in materials is pennies. Then any nuisance tripping will be more localised - if it ever happens. Makes sense to perhaps have the hall and stairs lighting on its own circuit.

Reply to
Dave Plowman (News)

In message , "Dave Plowman (News)" wrote

I'm sure that I could make my roll of aluminium foil fit any size of fuse receptacle.

Reply to
Alan

The beginning of the thread was an interesting discussion. However, there was nothing new posted for many days -- just the same misunderstandings being repeated over again. You probably just started it all over again :-(

Reply to
Andrew Gabriel

I'd say you'd find that difficult with blade type fuses as used in cars.

However, the idea was to make the system foolproof. Not c**t proof.

Reply to
Dave Plowman (News)

I don't think that's possible, or desirable. You might better ask how we can redesign motor cars to be idiot proof, as they cause far far more deaths and serious accidents than electrical wiring (or even appliances)

A current-balance MCB that trips the ring if the imbalance between the two legs exceeds a certain proportion of the total is probably feasible, and could probably be combined into a single-circuit RCBO.

Ring overloading and high point load really only occurs in kitchens, domestically. Treating all hob/ovens, washing machines, tumble driers and dishwashers as fixed heating appliances and mandating points for these to be provided with each point rated at 10A or actual load if greater (in the same way we rate lighting points at 100W) would in almost all cases provide at least 4 sockets (they could be on their own

32A ring, or radial, or multiple 15A radials) in the kitchen, and take these appliances off the general purpose ring. The gp ring should be able to cope with other loads, deep fryer, combi microwave, as these are fairly intermittent anyway.

All those appliances are plumbed in or otherwise non-portable anyway, so there is no disadvantage to restricting their use, unlike a toastie-maker or microwave whcih might be used in a teenager's room. Such provision is also more easily enforced because these appliances are usually *fitted* by tradesmen and in kitchens comes under (or can be brought under) Part P for the fixed wiring.

Yesm that is a step back to the 'good old days'

Is an alternative, but the difficulty with removing the plug fuse is backwards compatbility, which cannot be ignored. We can't have new unfused appliances being plugged into old high-current rings, and any use of adapters or requiring householders to change plugs is going to send the death rate shooting up.

Like, using them correctly instead of whole-house?

Owain

Reply to
Owain

"The problem with designing something completely foolproof is to under estimate the ingenuity of a complete fool." - Douglas Adams

Adam

Reply to
ARWadsworth

Or find a nail, bolt or bit of wire that will fit, the final protection needs to be taken away from the idiots who can and have done such things.

Reply to
:::Jerry::::

I'm with Alan and ARWadsworth on this one. Anyone stupid enough to try doing unnatural things with stuff that's there to protect them, that they don't understand, deserves everything that they get. Even if its ultimately a Darwin Award :(

At the end of the day any system that depends for its safety on measures that are accessible to "idiots" is going to be compromised, for the reasons articulated by Mr Adams. Personally my view is that we need to do our best to make the system totally safe for the average user who follows the rules, and make it very difficult for the average DIYer to mess up.

However, we are unlikely to ever be able to cope with the lunatic fringe who are actively trying to circumvent the safety systems, and we probably shouldn't even try ...

Cheers Richard

Reply to
Richard Appleby

Every US set of Xmas lights has a fuse inside the connecting plugs, and some of these sell for $2! Doesn't seem like a problem to me, but if the fuse is inside the appliance, then replacing it may give access problems, as it already does in TVs.

Regards Capitol

Reply to
Capitol

that

measures

The point is, it doesn't need a lunatic, let the person who has never put the wrong fuse in a BS1363 plug just get things working cast the first stone, let the person who then remembers to replace it A.S.A.P cast the second...

Nothing can be made completely foolproof, but requiring more than a cheap tea-spoon to access the fuse in a moulded on BS1363 plug is not even trying. There are people changing fuses in plugs who know nothing about electrics and are clueless as to the importance of the fuse or it's rating.

Reply to
:::Jerry::::

every

Does it? IMO what it does means is that those who are with clue can and those without don't...

Reply to
:::Jerry::::

Making things idiot proof is trivial.

Making things proof against intelligent beings is impossible.

Reply to
Peter Parry

In message , ":::Jerry::::" wrote

Make it more difficult and it will be easier to cut off the plug and hold the bare wires into the socket with a couple of match sticks - or preferably with a couple of nails..

For something to be safe you don't make it impossible to fix without special tools. Having to take something apart to replace a fuse isn't safe. People are going to see if the fix works before reassembling the item.

While I guess everyone on this group may have a set of screwdrivers and/or security bit readily to hand many households don't have these items.

Reply to
Alan

You should work in government! That sounds like just the sort of attitude the ODPM would love ;-)

The problem with such nannyism, is that in any many cases you can't take the facilities away from the "few idiots" without causing major irritation to the majority of (competant) people in the process.

Reply to
John Rumm

I can only remember having to replace one or two fuses, and those were 13 amp types. Most appliances which are fused at less than 13 amp will be things like AV equipment and have internal fuses which will blow first anyway.

If you're continually replacing fuses, as you say, then you need to look into the reasons for this.

Reply to
Dave Plowman (News)

As pointed out already, you can't put a wrong fuse in a 13A plug. All appliance cords and appliancs are required to remain safe when protected at 16A nowadays, so all* BS1362 fuse values are OK.

*Minor exception, but strictly 1A BS1362 fuses should not be used in BS1363 plugs because they are not ASTA approved and would therefore result in a PAT test failure of the appliance.
Reply to
Andrew Gabriel

The Hell it is.

Idiots are far too cunning to be easily defeated.

Reply to
Huge

,

A.S.A.P

You live a sheltered life then...

No one has said anything about having to continually replace fuses.

Reply to
:::Jerry::::

,

A.S.A.P

So if fuse rating of below 13A are irrelivant, why are they still advalible...

Reply to
:::Jerry::::

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