Part P / BC question

[Stoday]

I got no further than the first page. It's rubbish! It's full of b'locks and errors.

The whole page is rubbish, it it?

Each of the 9 paragraphs are full of b'locks and errors, are they?

"Full of" does not mean "Everything". Anyway, some detail:

"on January 1st, 2003 the tolerance levels will be widened to +/- 10%." They were not.

"Supply Companies are not intending to reduce their voltages in the near future. This is hardly surprising, because such action would immediately reduce the energy used by consumers (and the income of the Companies) by more than 8%."

The author is confusing energy and power. Reducing the voltage will reduce power which is what the CEGB used to do to reduce demand (i.e. brownout) to try to avoid power cuts. Reducing the voltage will not reduce energy by anything like 8%; if it did, Vphase's energy saving con wouldn't be a con.

"In view of the fact that there will be no change to the actual voltage applied to installations, it has been decided not to make changes to the calculations in this book. All are based on the 240/415V supply voltages which have applied for many years and will continue so to do."

Here the author confuses the nominal or declared voltage with the average or typical voltage of a consumer's supply. Keeping the supply voltage for all consumers on a feeder within the tolerance based on the nominal voltage means that the average voltage must be above the nominal 230V. Indeed in theory, at the end of the feeder, where a consumer receives supply at 253V once a year and 216V once a year, his average voltage would be 243V.

Tables in BS7671 will have been based on 230V, so by using 240V instead of 230V in calculations the author will get the wrong answers.

"it is to be expected that manufacturers will supply appliances rated at 230 V for use in the UK. When they do so, there will be problems"

Why should there be problems when manufacturers should be designing equipment to operate within the voltage tolerance? (i.e. 205V to 253V for non-lighting products).

"High pressure sodium and metal halide lamps will show a significant change in colour output when run at higher voltage than their rating, and rechargeable batteries in 230V rated emergency lighting luminaires will overheat and suffer drastic life reductions when fed at 240V"

If the charging circuit for batteries can't tolerate a 4% voltage increase, it will be even worse with a 10% increase. But chargers don't work like that. They provide the correct charging parameters whatever the supply voltage providing it's within the permitted tolerance. Similarly for lighting controllers.

 

[Geps]

Can you provide a link please to the legislation?

That not meant to sound like I'm questioning your viewpoint - I am just interested in seeing what it actually says.

Cheers,

 

[JohnW2]

Can you provide a link please to the legislation?Tha t not meant to sound like I'm questioning your viewpoint - I am just interested in seeing what it actually says. Cheers,

The legislation (Part P of the Building Regs) is just a single sentence (plus notes and Schedules whoch define scope and notifiability). It can be found as the first entry in the wiki of this forum.

Kind Regards, John.

 

[ban-all-sheds]

"on January 1st, 2003 the tolerance levels will be widened to +/- 10%." They were not.

God you are pathetic, aren't you.

That was the plan, publicly stated, at the time the book was written.

Just what is so f****d up in your head that you want to tell people not to read this book because something irrelevant changed after it was written?

"Supply Companies are not intending to reduce their voltages in the near future. This is hardly surprising, because such action would immediately reduce the energy used by consumers (and the income of the Companies) by more than 8%."

The author is confusing energy and power. Reducing the voltage will reduce power which is what the CEGB used to do to reduce demand (i.e. brownout) to try to avoid power cuts. Reducing the voltage will not reduce energy by anything like 8%; if it did, Vphase's energy saving con wouldn't be a con.

Indeed.

Would you please explain why that means that what people can learn about earthing systems, cable types, the concept of correction factors, voltage drop, EFLI etc etc is of no value to them, and they should be advised against the book?

Failing that can you explain why you are being so f*****g childish?

"In view of the fact that there will be no change to the actual voltage applied to installations, it has been decided not to make changes to the calculations in this book. All are based on the 240/415V supply voltages which have applied for many years and will continue so to do."

Here the author confuses the nominal or declared voltage with the average or typical voltage of a consumer's supply. Keeping the supply voltage for all consumers on a feeder within the tolerance based on the nominal voltage means that the average voltage must be above the nominal 230V. Indeed in theory, at the end of the feeder, where a consumer receives supply at 253V once a year and 216V once a year, his average voltage would be 243V.

So calculations are not to be done using the nominal or declared voltage?

Tables in BS7671 will have been based on 230V, so by using 240V instead of 230V in calculations the author will get the wrong answers.

Are you blind as well?

I suggest you get stuck into the last link right away - it won't give you design ideas, and unfortunately it doesn't refer to the current edition of the Wiring Regulations, but it's free, and will still give you a good grounding which you can augment with more up to date publications.

Why should there be problems when manufacturers should be designing equipment to operate within the voltage tolerance? (i.e. 205V to 253V for non-lighting products).

"High pressure sodium and metal halide lamps will show a significant change in colour output when run at higher voltage than their rating, and rechargeable batteries in 230V rated emergency lighting luminaires will overheat and suffer drastic life reductions when fed at 240V"

If the charging circuit for batteries can't tolerate a 4% voltage increase, it will be even worse with a 10% increase. But chargers don't work like that. They provide the correct charging parameters whatever the supply voltage providing it's within the permitted tolerance. Similarly for lighting controllers.

Can you explain why that means that someone who needs to learn about the Wiring Regulations and basic circuit design principles etc should not read those web pages in addition to more up-to-date material?

 

[Paul_C]

What we have here though is something where the public body (LABC in this case) has already approved the work and has publicly stated it is compliant with regulations.

There's an interesting "get out" clause in the building regulations though, my emphasis added:

17.— (1) A local authority shall give a completion certificate in accordance with this regulation

{.....}

(4) A certificate given in accordance with this regulation shall be evidence (but not conclusive evidence) that the requirements specified in the certificate have been complied with.

 

[Stoday]

The half dozen issues that I identified on the first page suggest to me that the author's competence is somewhat questionable. That casts doubt on the rest of his writings.

I think it would be better for a beginner to choose a different author than to pick up the misconceptions of this one.

So calculations are not to be done using the nominal or declared voltage?

Yep, that's what the author is incorrectly saying.

Tables in BS7671 will have been based on 230V, so by using 240V instead of 230V in calculations the author will get the wrong answers.

Are you blind as well?
unfortunately it doesn't refer to the current edition of the Wiring Regulations

The Wiring Regulations last changed edition in 2008; the nominal voltage changed in 2003. So it was wrong even for the 16th edition.

 

[Stoday]

God you are pathetic, aren't you.

Just what is so f****d up in your head

can you explain why you are being so f*****g childish?

Are you blind as well?

When you are losing the argument, don't put forward your invalid answers, slag off the opposition instead; readers might be daft enough to ignore the stronger argument.

 

[bernardgreen]

230 or 240

Design for safety requires that the most dangerous voltage is used in the calculation. 240 is ( In most cases ) more dangerous than 230 volts.

If the cable rating for example an electric shower is on the limit when calculated at 230 volt then the current will be over the limit when the incoming supply rises to 240 volts. Even more over the limit when the supply reaches 253 volts ( 230 + 10% )

So maybe when calculating ratings of devices for the protection of cables and similar safety matters the operation of the circuit and loading items at 253 volts should be the overriding factor.

 

[Stoday]

If the cable rating for example an electric shower is on the limit when calculated at 230 volt then the current will be over the limit when the incoming supply rises to 240 volts. Even more over the limit when the supply reaches 253 volts ( 230 + 10% )

No it won't. If it did, it would lead to many cables being overloaded because the supply to many houses would exceed the nominal voltage for significant periods.

If the maximum current a cable can carry is I amps, then the value in the tables would be 0.9I to allow for the voltage of supply to exceed the nominal voltage on which the tables are based. In addition there are other contingencies to allow for of course.

 

[ban-all-sheds]

The half dozen issues that I identified on the first page suggest to me that the author's competence is somewhat questionable. That casts doubt on the rest of his writings.

So if you took an exam and messed up the first question, you'd be quite happy, would you, if the examiner couldn't be bothered to read any further and gave you a fail because he thought your competence was somewhat questionable?

Or say you were a newspaper editor and you wanted to run a review of a play or a film, so you sent one of your reporters to it, and he came back with a review which said "I left after 5 minutes because the opening scenes were rubbish, so don't go and see it", you'd be happy that he'd done a proper job, would you?

I think it would be better for a beginner to choose a different author than to pick up the misconceptions of this one.

You may believe that, but please don't try to pass off that conclusion as being the result of any process which could reasonably be described as "thought".

So calculations are not to be done using the nominal or declared voltage?

Yep, that's what the author is incorrectly saying.

Actually it was my mistake to use the phrase "nominal or declared voltage".

What the author said was "In view of the fact that there will be no change to the actual voltage applied to installations, it has been decided not to make changes to the calculations in this book. All are based on the 240/415V supply voltages which have applied for many years and will continue so to do."

The Wiring Regulations last changed edition in 2008; the nominal voltage changed in 2003. So it was wrong even for the 16th edition.

Perhaps you'd care to get out your copy of the 16th Edition and tell us what Appendix 3 says.

When you are losing the argument, don't put forward your invalid answers, slag off the opposition instead; readers might be daft enough to ignore the stronger argument.

I'm not losing any argument, because you aren't engaging in anything which could be treated as such, you are just coming up with one pathetic ad hominem-esque reason after another why people should not visit that website.

I would ask what your motives are, but your opinions are clearly so ill-informed that I really don't give a **** about them.

To say, for example, that someone new to all of this cannot learn anything useful about earthing systems, what EFLI is and why it is important, etc, from these pages: http://www.tlc-direct.co.uk/Book/5.1.1.htm is barmy.


And incredibly irresponsible - I urge anybody reading this to ignore Stoday - http://www.tlc-direct.co.uk/Book/1.1.htm is a useful free resource which, even though it doesn't refer to the current edition of the Wiring Regulations, will still give you a good grounding which you can augment with more up to date publications.

 

[JohnW2]

No it won't. If it did, it would lead to many cables being overloaded because the supply to many houses would exceed the nominal voltage for significant periods. If the maximum current a cable can carry is I amps, then the value in the tables would be 0.9I to allow for the voltage of supply to exceed the nominal voltage on which the tables are based. In addition there are other contingencies to allow for of course.

I can believe that, even though I can't find anything in the regs which actually says so. It certainly does appear that the tabulated CCCs in Appendix 4 of the regs 'take into account' a number of factors (e.g.the I2/In ratio for Type B MCBs), without actually saying so explicitly.

However, following Bernard's line of thought, it does seem that, in many other contexts relating to safety, there may be no 'taking into account' that real-world currents may be up to 10% higher (and are very likely to be at least a few percent higher) than those calculated on the basis of the nominal supply voltage of 230V. For example, taking Bernard's shower, if it consumes 40A at 230V, and given that the regs require In of the OPD to be no less than the design current (I presume on the assumption on nominal voltage calculations?) , can we assume that those who manufacture 40A MCBs have 'taken into account' the fact that it may actually draw 44A.

Bernard is obviously right that safety provisions/requirements should be on the basis of 'worst case scenarios' - in this case, highest permitted supply voltage. The question to which the answer is often less than obvious (at least, to me), is the extent to which those who produce Tables, products etc. have made 'adjustments' to enable one to calculate on the basis of nominal voltage, yet end up with answers that are applicable to maximum permitted voltage. It would certainly be helpful (and hopefully reassuring) if we were told about what such 'adjustments' had been applied.

Kind Regards, John.

 

[ban-all-sheds]

can we assume that those who manufacture 40A MCBs have 'taken into account' the fact that it may actually draw 44A.

Well, we all know about assumptions.

But since BS EN 60898 requires a B40 to pass 45.2A indefinitely without operating it does not seem unreasonable to assume that it would also require it not to suffer any damage whilst doing so.

Ditto 58A for up to an hour.

 

[JohnW2]

can we assume that those who manufacture 40A MCBs have 'taken into account' the fact that it may actually draw 44A.

Well, we all know about assumptions. But since BS EN 60898 requires a B40 to pass 45.2A indefinitely without operating it does not seem unreasonable to assume that it would also require it not to suffer any damage whilst doing so. Ditto 58A for up to an hour.

As you say, they are not unreasonable assumptions, but it is not very satisfactory that we have to rely on assumptions when determining whether or not a circuit complies with the regulations.

Furthermore, whilst I agree that the assumptions you state are reasonable in terms of damage (or lack of it) to the MCB, that may not have been the primary consideration which resulted in the reg's requirement that the MCB's In must be no less than the design current.

Having said all that, the reason for the 'I1 factor' being 1.13 does not appear to be clear (unless BS EN 60898 gives an explanation?) - so maybe that is largely to take into account the supply voltage variations we're discussing - I1 would have to be at least 1.10In to ensure that a load which drew exaxtly In at 230V didn't result in operation of the device if the supply voltage rose to 253V.

However, my point remains that it would be far more satisfactory if all of this was explicit in the regs, rather than relying on assumptions!

Kind Regards, John.

 

[ban-all-sheds]

Maybe it's explicit in BS EN 60898, which is not a banned or restricted publication.

 

[JohnW2]

Maybe it's explicit in BS EN 60898, which is not a banned or restricted publication.

It's restricted access as far as I'm concerned! However, even if it does contain 'all the answers', I still think the regs themselves ought to explain what's going on - otherwise designers who, like Bernard, are conscientious are bound to have these concerns.

Kind Regards,John.