All RCBOs?

[JohnW2]

And the NEC says that breakers should not be loaded to more than 80% of their rating.

... and Wylex say ...

All sorts of people/organisations/companies 'say' all sorts of things

Kind Regards, John

 

[EFLImpudence]

Would that not be the opposite/reverse of what we normally mean by diversity?

 

[JohnW2]

Would that not be the opposite/reverse of what we normally mean by diversity?

It is a rather odd use of the word - but, don't forget that what "we normally mean" (in electrical circles) by the word "diversity" does not, itself, correspond with (ordinary) dictionary definitions of the word, or everyday use of the word.

However, I agree that they could, and probably should, have worded it differently.

Kind Regards, John

 

[He who knows]

they took the (initial) paucity of evidence that there was not any problem to mean that there was a problem?

Ah - the old absence of evidence Ξ evidence of absence conflation

 

[JohnW2]

Ah - the old absence of evidence Ξ evidence of absence conflation

Exactly.

Kind Regards, John

 

[Risteard]

And the NEC says that breakers should not be loaded to more than 80% of their rating.

And it's a sensible requirement.

 

[Risteard]

As I said, some EU Member States take different views from the UK about various things. For example ...
As I half-expected. So the Irish take the same view as the Germans and others did (although I believe they are now 'rethinking their position') that, despite the absence of any evidence of any 'problem', they took the (initial) paucity of evidence that there was not any problem to mean that there was a problem?

It's for the over-70s in the south though I think, rather than the over-65s. It could be said that there's a paucity of evidence that any of these vaccines are safe in medium to long term, of course, however, owing to the expedited nature of the approvals.

 

[JohnW2]

It's for the over-70s in the south though I think, rather than the over-65s. It could be said that there's a paucity of evidence that any of these vaccines are safe in medium to long term, of course, however, owing to the expedited nature of the approvals.

Sure, there are inevitably uncertainties about the longer term safety of any of the vaccines, but we have no sensible alternative but to accept that. On the positive side, the short-term safety data (of which we now have far more than one could normally even dream of at such an early stage) is at least as good as for any other vaccine.

Beyond those theoretical 'risks' which we have to accept (for people of all ages), the only uncertainty which seems to have concerned such as the Germans (and apparently also the Irish) is how efficacious the vaccines are in older people, simply because the initial clinical trials did not involve many such people (and despite their being no reason to think that they wouldn't be at least reasonably efficacious in older people, in the same way that 'flu vaccines are). The 'worst' they would therefore be risking would be to 'waste' vaccine on people to whom it did not give much benefit but, given that they are the group most at risk of serious illness and death, that seems to be a very reasonable 'risk' to take (as the UK did).

In any event, we are now starting to see increasing amounts of evidence of very useful efficacy in older people - so, hopefully, those nations who have previously been hesitant/cautious will soon start changing their view.

 

[JohnW2]

And it's a sensible requirement.

If there is a 'requirement', or even just a recommendation, that something should never be loaded to more than 80% "of it's rating", doesn't that mean that "the rating" really should be reduced by 20% ?

What is the point in having, say, a switch "rated at 100A" which comes with a recommendation/requirement that it should not be used to switch more than 80A?

 

[EFLImpudence]

It would also mean that the same 'restriction' would, in consequence, apply to cables (if overload possible).

Ring circuit conundrum - what to do?

 

[JohnW2]

It would also mean that the same 'restriction' would, in consequence, apply to cables (if overload possible).

Indeed - nd I think that probabl;y gives insight into why "do not load beyond 20% of rating" is silly. As we've often discussed, it's pretty apparent that the CCC 'ratings' of cables we work with have substantial built-in 'safety margins' already.

With cables, for example, we know that they are deemed to be able to carry 1.45 times their "rated" CCC for an hour without coming to harm, and I strongly suspect that the 'built-in margin' is even greater than that ... and hence, I suspect, similarly for most electrical items/devices (at least, those deriving from half-reputable manufacturers!).

Kind Regards, John

 

[He who knows]

If there is a 'requirement', or even just a recommendation, that something should never be loaded to more than 80% "of it's rating", doesn't that mean that "the rating" really should be reduced by 20% ?

Sloppy work there.

Me, I mean.

Pretty sure (but didn't check and didn't clarify) the NEC requirement isn't "never", it applies to "constant" loads. Which I assume must mean "for more than X minutes/hours/whatever".

My point was that different countries have different rules, and what they want in the USA is as relevant to the UK as what they want in the ROI.

 

[JohnW2]

Sloppy work there. .... Me, I mean. .... Pretty sure (but didn't check and didn't clarify) the NEC requirement isn't "never", it applies to "constant" loads. Which I assume must mean "for more than X minutes/hours/whatever".

Fair enough. In that case it would be similar to what Wylex say about 'adjacent' MCBs in what I quoted in post #61 - namely that (if I understand them correctly) that adjacent MCBs should be not loaded to more than 66% of their 'rating' (In) for periods in excess of 1 hour.

My point was that different countries have different rules, and what they want in the USA is as relevant to the UK as what they want in the ROI.

Indeed so. I don't think it particularly useful to take much notice of rules/regulations/practices (in relation to anything) in other countries - the domestic ones can be confusing enough!

Kind Regards, John

 

[securespark]

Type F will become the go-to type as they are suitable for all types of equipment.
Once enough are made, like everything the price will plummet.

EG, 5G phones were 4 figures when 5G was first available.
Now the cheapest 5G phone is around 200 quid.

 

[ericmark]

I will admit when opening some distribution units the heat from the MCB's is staggering, however in domestic we have a consumer unit with 14 MCB's and total supply of in my case 60 amp, so one MCB/RCBO helps cool the next, we do have using which are set to the maximum motor overloads

for example, and I remember arguments as to if you needed a MCB and a motor overload, as the motor overload did not have the magnetic release so may not switch in the time permitted.

But one is moving into the risk assessment area, and the same with the RCBO if you have all RCBO what is the risk that any item will stop it tripping at the same time as there is a fault where it needs to trip? If we look at a shaver socket they are safe without an earth because only one item is supplied from that isolated supply.

The odd one out is the charging of a vehicle too close to premises to allow the safe use of a TT supply, but not inside the premises. This is a special case, and the regulations seem to have lumped together items which are special cases and those which were covered by existing regulations, so we have mobility scooters, e-bikes, milk floats, fork lifts which have been captured by the new electric car regulations which in the main do not require to be charged outside the building and the charger is not built into the vehicle so there is an isolation transformer of some type between the mains supply and the electric vehicle.

In my old house plugging in an electric car could have removed the protection from half the house, as only two RCD's but this house there is a dedicated RCBO for supply to outside, so it would only affect the electric car supply. And the car could be parked in this house a good 10 meters from the house, but old house would be likely within on meter, which is a very different situation.

I know where a garage is converted into a room, and a window is put in, there is a limit to how close to that window a parking space for a car can be, but can't find it, I know the car parking bay must be able to be widened to 3.3 meters wide but not what the clearance needs to be to any window. For a caravan it is 5.25 meters but hard to find for a car, which seems odd as clearly anyone fitting a car charging unit must fit it where a car can be legally parked, having a charging point which you can't park a car close enough is clearly not going to be much use.

But the whole reason for the B type RCD and the 6 mA DC detection etc is all about charging an electric car.