Amps

[ban-all-sheds]

But, it's a DIY forum. And sometimes people will take advice and apply it correctly. Other times, it's clear that some people are just going to go ahead regardless and you'd hope that at least some of the advice will stick.

Often the advice which needs to stick, and the only advice which should be given, is "stop fiddling with things which you do not understand".

What I find most tedious is B-A-S continuing to make the same statement over and over and over again in the same thread, which is classic troll behaviour - to continue to repeat your position in the (mistaken) belief that you will alter other people's opinion.

And I do that unprompted, do I?

Gratuitously, out of the blue?

Or do I do it in response to somebody else repeating his position in the belief that he will alter my opinion?

It would be nice if he could balance that with a good sense of perspective.

I have an excellent sense of perspective.

Many people here do not.

 

[winston1]

Can't really see how ohm's law will help. It is down to converting watts to amps not ohms and volts to amps.

Which is what the calculator does.

So 13A = 2990 watts or 3kW so add all items watts together and it needs to be less than 3kW if the fuse is not going to blow.

Damn does this mean I need a new fuse every time I boil the kettle

The mains voltage in the UK is not 230v, it is 240v. 230v is a European harmonised standard with tolerances and our 240v is within those tolerances. So 13A is 3120 W.

If you kettle is rated at 3Kw (not many are these days, it is nearer 2.5Kw) that will be the rating at 240V. If you are on a lower voltage the amps drawn and total wattage will be less. (Ohms law applies).

 

[skotl]

Without all the quotes, B-A-S, take the compliments. But it would also be useful for you to see other people's points of view and take their comments on board - you don't need to argue every point.

Genuinely best regards
Scott

 

[ban-all-sheds]

The mains voltage in the UK is not 230v, it is 240v.

Wrong.

230v is a European harmonised standard with tolerances

Which applies here - see p 294 of the current edition of the Wiring Regulations.

and our 240v is within those tolerances.

So is 230V.

So is 210V.

So is 250V.

Actually, anything between 216.2 and 253 is within the tolerances.

So 13A is 3120 W.

Or 2990W.

Or 2730W.

Or 3250W.

Or anything between 2810.6W and 3289W.

If you kettle is rated at 3Kw (not many are these days, it is nearer 2.5Kw) that will be the rating at 240V.

It might be. It might not be. Depends on what the manufacturer has decided to do.

But if it is a 240V rating then you're not to use it in calculations, because our nominal voltage is 230V.

 

[ban-all-sheds]

you don't need to argue every point.

Maybe not, but I'm quite entitled to when they are wrong and I am right.

 

[skotl]

and your response above was spot-on.

How about trying to make a given point just once per thread? The less people you annoy, the more receptive people will be to your advice.

I'm going to try to stop hijacking this thread for now!

 

[winston1]

The mains voltage in the UK is not 230v, it is 240v.

Wrong.

230v is a European harmonised standard with tolerances

Which applies here - see p 294 of the current edition of the Wiring Regulations.

and our 240v is within those tolerances.

So is 230V.

So is 210V.

So is 250V.

Actually, anything between 216.2 and 253 is within the tolerances.

So 13A is 3120 W.

Or 2990W.

Or 2730W.

Or 3250W.

Or anything between 2810.6W and 3289W.

If you kettle is rated at 3Kw (not many are these days, it is nearer 2.5Kw) that will be the rating at 240V.

It might be. It might not be. Depends on what the manufacturer has decided to do.

But if it is a 240V rating then you're not to use it in calculations, because our nominal voltage is 230V.

Have you measured the UK mains voltage recently? It is between 240v and 245v, it has never changed since harmonisation. Likewise the voltage in Europe has not changed from 220v.

To use 230v in calculations is madness when the voltage is 240v is madness. Not even the Eurocrats can change the laws of physics.

 

[JohnW2]

If you kettle is rated at 3Kw (not many are these days, it is nearer 2.5Kw) that will be the rating at 240V. If you are on a lower voltage the amps drawn and total wattage will be less. (Ohms law applies).

Since you seem keen to be precise, perhaps you should point out that "Ohm's Law applies" is not precisely true in a situation like this. If voltage, hence also current and power ('wattage'), are 'lower' for something like a kettle element, it's temperature will be lower, and hence it's resistance will also be lower, tending to make current (and power) higher. The overall effect of that is that the current and power will not be as much lower as one would have expected by simple application of Ohm's Law (assuming constant resistance).

Kind Regards, John

 

[EFLImpudence]

winston1 was not wrong.

His post was entirely valid.

 

[ban-all-sheds]

To use 230v in calculations is madness when the voltage is 240v

Go and argue with JPEL/64 at the IET. Geoff Cronshaw would be the best person to approach.

 

[JohnW2]

winston1 was not wrong. His post was entirely valid.

Everything he wrote was correct other than, as I said, (if one is being precise) "Ohms law applies".

Kind Regards, John

 

[ban-all-sheds]

winston1 was not wrong.

The mains voltage in the UK is not 230v, it is 240v.

As our voltage is allowed, and has always been allowed, to vary by a certain amount above or below a nominal value, the ONLY way that a statement of what our voltage IS can be correct is for it to quote our nominal voltage.

And our nominal voltage is 230V, not 240V.

 

[ban-all-sheds]

How about trying to make a given point just once per thread

Can you persuade eveybody else to only make theirs once?

 

[EFLImpudence]

Since you seem keen to be precise, perhaps you should point out that "Ohm's Law applies" is not precisely true in a situation like this. If voltage, hence also current and power ('wattage'), are 'lower' for something like a kettle element, it's temperature will be lower, and hence it's resistance will also be lower, tending to make current (and power) higher. The overall effect of that is that the current and power will not be as much lower as one would have expected by simple application of Ohm's Law (assuming constant resistance).

Now your stretching semantics for the sake of it.

If using 230V as the nominal then we have to determine the resistance of the load and convert it correctly to arrive at (what could be called) the nominal current, which you have argued would make the installation err on the wrong side - and if that is indeed what the authors intended.

Now we will have to also compensate for a reduced resistance while the kettle warms more slowly.


However, the water does not know any of this and will boil at the same 100°C so is the resistance of the element any different?

 

[winston1]

If you kettle is rated at 3Kw (not many are these days, it is nearer 2.5Kw) that will be the rating at 240V. If you are on a lower voltage the amps drawn and total wattage will be less. (Ohms law applies).

Since you seem keen to be precise, perhaps you should point out that "Ohm's Law applies" is not precisely true in a situation like this. If voltage, hence also current and power ('wattage'), are 'lower' for something like a kettle element, it's temperature will be lower, and hence it's resistance will also be lower, tending to make current (and power) higher. The overall effect of that is that the current and power will not be as much lower as one would have expected by simple application of Ohm's Law (assuming constant resistance).

Kind Regards, John

I suggest the temperature of the element would be the same as the temperature of the water that it is in in all cases, not more than 100C.