Shower switch wiring

[DrJimFranklin]

238.6v is a lot nearer 240v than 230v.

You can talk about nominal voltages and tolerances all you like but the fact is the UK voltage averages at 240v and has been since long before the 15th edition.

If a shower is rated at 9.5kw at 240v to calculate the current assuming 9.5kW at 230v is clearly wrong because if it is run on 230v the power will diminish in proportion to the square of the voltage reduction. You can of course calculate what the current and power will be at 230v (assuming constant resistance). But a pretty pointless thing to do if it run on 240v anyway.

Has it occurred to you that perhaps the regulations have made a mistake? It wouldn't be the first time.

Winston, this posts clearly shows that you do not understand electricity and as such perhaps you might care to read up on it before making foolish posts like this.

As BAS has, I am sure, pointed out on many occasions, most electric showers are a FIXED resistance and all manufacturers must ensure they are made to specific standards (BS 6340-2:1983 / BS EN 60335), those standards, especially the Harmonised ones for use in Europe, require all testing and compliance is carried out at harmonised voltages...that harmonised voltage is 230V, not 231, 225 or 240V but 230V. Now what this means is that all the calculations for this unit's installation should also be carried out assuming a nominal voltage of 230V and there is a damned good reason for doing this...which I am sure even you can figure out.

Your argument is spurious, it is like saying that "my car is capable of 150mph so I don't care what the law states, I will drive at that speed because it suites me"....Try that in front of a magistrate or Judge...I'll supply popcorn for the audience quite happily.

 

[winston1]

238.6v is a lot nearer 240v than 230v.

You can talk about nominal voltages and tolerances all you like but the fact is the UK voltage averages at 240v and has been since long before the 15th edition.

If a shower is rated at 9.5kw at 240v to calculate the current assuming 9.5kW at 230v is clearly wrong because if it is run on 230v the power will diminish in proportion to the square of the voltage reduction. You can of course calculate what the current and power will be at 230v (assuming constant resistance). But a pretty pointless thing to do if it run on 240v anyway.

Has it occurred to you that perhaps the regulations have made a mistake? It wouldn't be the first time.

Winston, this posts clearly shows that you do not understand electricity and as such perhaps you might care to read up on it before making foolish posts like this.

As BAS has, I am sure, pointed out on many occasions, most electric showers are a FIXED resistance and all manufacturers must ensure they are made to specific standards (BS 6340-2:1983 / BS EN 60335), those standards, especially the Harmonised ones for use in Europe, require all testing and compliance is carried out at harmonised voltages...that harmonised voltage is 230V, not 231, 225 or 240V but 230V. Now what this means is that all the calculations for this unit's installation should also be carried out assuming a nominal voltage of 230V and there is a damned good reason for doing this...which I am sure even you can figure out.

Your argument is spurious, it is like saying that "my car is capable of 150mph so I don't care what the law states, I will drive at that speed because it suites me"....Try that in front of a magistrate or Judge...I'll supply popcorn for the audience quite happily.

What do you think I don't understand about electricity? You clearly do not understand basic physics. No resistance is fixed. It varies with temperature. That's why tungsten light bulbs have a switch on surge as the resistance is quite low at room temperature. That said I would not expect an electric shower resistance to vary much.

The electric shower in question was quoted as 9.5kW and this was quoted at 240v which seems to imply the testing was not carried out at 230v. I repeat it is absolute madness to use a voltage that does not exist in practice for this unit's installations. Surely you can see that is common sense.

 

[DrJimFranklin]

What do you think I don't understand about electricity? You clearly do not understand basic physics. No resistance is fixed. It varies with temperature. That's why tungsten light bulbs have a switch on surge as the resistance is quite low at room temperature. That said I would not expect an electric shower resistance to vary much.

The electric shower in question was quoted as 9.5kW and this was quoted at 240v which seems to imply the testing was not carried out at 230v. I repeat it is absolute madness to use a voltage that does not exist in practice for this unit's installations. Surely you can see that is common sense.

Clearly I know more about physics than you. The temperatures at which the shower coils work at is such that the material the elements are made from has an effective fixed resistance. if the coil were simple wire then the resistance would vary much more, but the that is not the case with instantaneous water heaters, of which domestic showers are an example of.

As for common sense Winston, clearly you lack any. The common sense states that you carry out the calculations to comply with safety and regulations at the voltage they require. The simple fact is that by complying with calculations made at a lower voltage means that any unit installed on a system with a higher voltage will automatically be safe because the overall load of the unit will be lower...You see what you don't understand is that there are properties in this land whose voltage will be around the 228 - 233V volt mark, these won't be in large towns or cities, but they will be in very rural locations toward the end of DNO networks or perhaps domestic properties on a section of the local network that is shared with heavy users such as large farms, remote industrial facilities etc...Don't think it possible...clearly you're daft.

The regulations were written by very smart people with safety at the forefront of their mind. The AVERAGE voltage across Europe is actually 229.2V (hence the 230V) but there are massive variations. I have personally measured voltages as low as 218V and as high as 256V. The voltage on the DNO network is impacted by a lot of external influences that cause fluctuations and variation in the voltage supplied, this is why most commercial buildings and certainly all Data centres run their incoming supplies via PFC and UPS equipment to smooth out and cancel variations to ensure a nice smooth supply. not only does it impact how your equipment operates, but it has a big impact on your electricity bill too.

In one of my buildings some time ago the PFC kit failed catastrophically due to a fault in a capacitor, to effect repairs and work safely it had to be taken offline. The 10 days it was out of service increased the electricity bill for that month by around £2,300 to a bill of £17,800. Clearly some fluctuations in the bill will occur, but after the repairs the monthly bill fell back to nominal levels of around £15,500.

You see Winston, there is a bigger picture out there than the spot on the end of your nose chap..it's not always about what you feel is convenient or common sense..it's about what is best for ALL.

 

[EFLImpudence]

The electric shower in question was quoted as 9.5kW and this was quoted at 240v which seems to imply the testing was not carried out at 230v. I repeat it is absolute madness to use a voltage that does not exist in practice for this unit's installations. Surely you can see that is common sense.

That is winston's view.
It is also quoted at 8.7kW @ 230V so I do not understand what that has to do with the testing of it.

The simple fact is that by complying with calculations made at a lower voltage means that any unit installed on a system with a higher voltage will automatically be safe because the overall load of the unit will be lower...

Assuming I have understood you correctly, are you sure?

You see what you don't understand is that there are properties in this land whose voltage will be around the 228 - 233V volt mark, these won't be in large towns or cities, but they will be in very rural locations toward the end of DNO networks or perhaps domestic properties on a section of the local network that is shared with heavy users such as large farms, remote industrial facilities etc...Don't think it possible...clearly you're daft.

That has nothing to do with winston's view.
He believes (and will not accept otherwise) that he should calculate with the actual voltage value and not 230V although he (presumably) does not readjust all the other relevant tables which have been calculated at 230V.


I would say that for someone who only joined on Thursday you do seem somewhat cantankerous.
On the other hand, if you have been reading for a while then you would know that arguing with winston on this matter is pointless.

 

[securespark]

These are the best if you ever redo the ceiling and need a new switch.
https://www.tlc-direct.co.uk/Products/CB2167.html?source=adwords&kw=crabtree 2167&gclid=Cj0KEQjw04qvBRC6vfKG2Pi0_8gBEiQAAJq0vUCgBMhHvI5tcmdUef3Emx6gLYp5TFbwu32X7kxKcM0aAr-38P8HAQ

Yup. Can vouch for this. I installed one in 2002 on a 10.5kW shower and it is still going strong.

 

[DrJimFranklin]

The electric shower in question was quoted as 9.5kW and this was quoted at 240v which seems to imply the testing was not carried out at 230v. I repeat it is absolute madness to use a voltage that does not exist in practice for this unit's installations. Surely you can see that is common sense.

That is winston's view.
It is also quoted at 8.7kW @ 230V so I do not understand what that has to do with the testing of it..

Winston's view and opinion is irrelevant.. the regs are what they are...

The simple fact is that by complying with calculations made at a lower voltage means that any unit installed on a system with a higher voltage will automatically be safe because the overall load (should have stated current load to make clearer) of the unit will be lower...

Assuming I have understood you correctly, are you sure?.

If the resistance is fixed...if it is a moving target then No...I was speaking specifically about a fixed resistance. See the comment I have inserted...

You see what you don't understand is that there are properties in this land whose voltage will be around the 228 - 233V volt mark, these won't be in large towns or cities, but they will be in very rural locations toward the end of DNO networks or perhaps domestic properties on a section of the local network that is shared with heavy users such as large farms, remote industrial facilities etc...Don't think it possible...clearly you're daft.

That has nothing to do with winston's view.
He believes (and will not accept otherwise) that he should calculate with the actual voltage value and not 230V although he (presumably) does not readjust all the other relevant tables which have been calculated at 230V..

I stand by my comment about DAFT!!

I would say that for someone who only joined on Thursday you do seem somewhat cantankerous.
On the other hand, if you have been reading for a while then you would know that arguing with winston on this matter is pointless.

I have not been on the forum for a very long time, Winston was not about then to my recollection. As for cantankerous...been called worse. But as an Electrical Engineer with 33 years experience I suppose I am slightly short with people who talk *******s because they REFUSE to understand. Those who simply don't know and are willing to learn is another matter.

 

[DrJimFranklin]

These are the best if you ever redo the ceiling and need a new switch.
https://www.tlc-direct.co.uk/Products/CB2167.html?source=adwords&kw=crabtree 2167&gclid=Cj0KEQjw04qvBRC6vfKG2Pi0_8gBEiQAAJq0vUCgBMhHvI5tcmdUef3Emx6gLYp5TFbwu32X7kxKcM0aAr-38P8HAQ

Yup. Can vouch for this. I installed one in 2002 on a 10.5kW shower and it is still going strong.

I would agree with Simon. Crabtree do not get the recognition they deserve. When I was new to the industry back in the very early 1980's it was always a choice between Crabtree or MK... MK stole a march for a long time and Crabtree seemed to go into the doldrums, but the quality of their wiring accessories has never diminished... good value for your hard earned.

 

[securespark]

I would say that for someone who only joined on Thursday you do seem somewhat cantankerous.

No, although he joined recently, Jim's been here before under two other monikers.

Welcome back FWL_Engineer / Big_Spark / DrJimFranklin.

Looking good, if your avatar is anything to go by!

 

[EFLImpudence]

The simple fact is that by complying with calculations made at a lower voltage means that any unit installed on a system with a higher voltage will automatically be safe because the overall load (should have stated current load to make clearer) of the unit will be lower...

Assuming I have understood you correctly, are you sure?.

If the resistance is fixed...if it is a moving target then No...I was speaking specifically about a fixed resistance. See the comment I have inserted...

The current will rise with the voltage.

You see what you don't understand is that there are properties in this land whose voltage will be around the 228 - 233V volt mark, these won't be in large towns or cities, but they will be in very rural locations toward the end of DNO networks or perhaps domestic properties on a section of the local network that is shared with heavy users such as large farms, remote industrial facilities etc...Don't think it possible...clearly you're daft.

That has nothing to do with winston's view.
He believes (and will not accept otherwise) that he should calculate with the actual voltage value and not 230V although he (presumably) does not readjust all the other relevant tables which have been calculated at 230V..

I stand by my comment about DAFT!!

Everyone agrees. I was merely trying to explain.

 

[DrJimFranklin]

I would say that for someone who only joined on Thursday you do seem somewhat cantankerous.

No, although he joined recently, Jim's been here before under two other monikers.

Welcome back FWL_Engineer / Big_Spark / DrJimFranklin.

Looking good, if your avatar is anything to go by!

Thanks Simon.. I write passwords down now to avoid forgetting them...

 

[DrJimFranklin]

The current will rise with the voltage.

Which Universe does that apply too?

Here is an example..

9.5kW / 220V = 9500/220 = 43.18A

9.5kW / 230V = 9500/230 = 41.3A

9.5kW / 240V = 9500/240 = 39.58A

9.5kW / 250V = 9500/250 = 38A

 

[EFLImpudence]

Which Universe does that apply too?

This one.

The simple fact is that by complying with calculations made at a lower voltage means that any unit installed on a system with a higher voltage will automatically be safe because the overall load (should have stated current load to make clearer) of the unit will be lower...

 

[flameport]

9.5kW / 220V = 9500/220 = 43.18A
9.5kW / 230V = 9500/230 = 41.3A
9.5kW / 240V = 9500/240 = 39.58A
9.5kW / 250V = 9500/250 = 38A

Correct but only if they are four different showers, each rated 9.5kW at different voltages.

 

[DrJimFranklin]

9.5kW / 220V = 9500/220 = 43.18A
9.5kW / 230V = 9500/230 = 41.3A
9.5kW / 240V = 9500/240 = 39.58A
9.5kW / 250V = 9500/250 = 38A

Correct but only if they are four different showers, each rated 9.5kW at different voltages.

In this instance we were not discussing showers, but his idea that current increases with voltage, which is does not.

 

[winston1]

What do you think I don't understand about electricity? You clearly do not understand basic physics. No resistance is fixed. It varies with temperature. That's why tungsten light bulbs have a switch on surge as the resistance is quite low at room temperature. That said I would not expect an electric shower resistance to vary much.

The electric shower in question was quoted as 9.5kW and this was quoted at 240v which seems to imply the testing was not carried out at 230v. I repeat it is absolute madness to use a voltage that does not exist in practice for this unit's installations. Surely you can see that is common sense.

The simple fact is that by complying with calculations made at a lower voltage means that any unit installed on a system with a higher voltage will automatically be safe because the overall load of the unit will be lower...

WOW. We've already established you don't know your physics, don't embarrass yourself more by not understanding Ohm's Law. For a resistive load, such as a shower, if you increase the voltage, the current increases, and the load increases by a square law.