Shower switch wiring

[Alfie25]

Are LAP products any good? e.g.

http://www.screwfix.com/p/lap-50a-dp-ceiling-pull-cord-switch-white/7251g

 

[EFLImpudence]

Average.

 

[DrJimFranklin]

45A or 50A switch will be satisfactory.

9.5kW is just under 40A.

Hate to **** on your parade but your incorrect, I assume you erroneously calculated using 240V, but you should, as per BS7671 (In fact as per the 15th and 16th Editions of the IEE Regs - Before it became BS7671) the correct voltage for design calculations is 230V and for a 9.5kW load that is 41.3A, as such all cable calcs etc should be based on this.

Everyone here is giving out advice, yet no-one has asked the obvious questions...what size is the supply cable and how far is it from the Consumer unit...very important when installing items of equipment, especially with significant loads..The Switch and the MCB are irrelevant to a cable burning out. An incorrectly installed cable will cause arcing and heat generation at a terminal when loose, if the switch has a fault then the switch would display obvious signs of heat stress, usually a golden browning of the plastic or pitting of the cover on the switch plates. However the switch and the MCB are tits on a fish if the cable is incorrect.

 

[ban-all-sheds]

Hate to **** on your parade but your incorrect,

He almost certainly is not, at least not in the way that you think he is.

I assume you erroneously calculated using 240V

How do you know that he was wrong to at least start with using 240V? Are you unaware of how common it is for shower manufacturers to use a headline figure for their product's performance at 240V?

but you should, as per BS7671 (In fact as per the 15th and 16th Editions of the IEE Regs - Before it became BS7671)

Actually it became BS 7671 very early in the life of the 16th.

the correct voltage for design calculations is 230V and for a 9.5kW load that is 41.3A, as such all cable calcs etc should be based on this.

Only if 9.5kW is the load of the appliance at 230V. It almost certainly is not. The most likely figure for the load at the official U0 is about 38A.

Everyone here is giving out advice, yet no-one has asked the obvious questions...what size is the supply cable and how far is it from the Consumer unit...very important when installing items of equipment, especially with significant loads..The Switch and the MCB are irrelevant to a cable burning out.

So is the length of the cable.

 

[winston1]

What is more his actual supply will almost certainly be nearer 240v than 230v.

BS7671 is nonesence it tell you to calculate using a voltage that rarely exists in practice.

 

[ban-all-sheds]

the correct voltage for design calculations is 230V.

I nearly added a warning in my reply to alert you to the possibility of yet more tedious b****cks from Winston, who, basically, is simply too thick to understand what the word "nominal" means.

We have all had to put up with his ignorant drivel for years - sadly he won't stop because he is also too thick to realise that he is wrong.

 

[Taylortwocities]

...

 

[Taylortwocities]

Don't start that again…please…..

All of this speculation is pointless. The CPD on the circuit is 40amp.
The OP needs a switch that is rated at 45A or more. They all are.

 

[winston1]

the correct voltage for design calculations is 230V.

I nearly added a warning in my reply to alert you to the possibility of yet more tedious b****cks from Winston, who, basically, is simply too thick to understand what the word "nominal" means.

We have all had to put up with his ignorant drivel for years - sadly he won't stop because he is also too thick to realise that he is wrong.

Actually more intelligent than you.

If an item is rated at x kW at 240v then these are the figures you use to calculate current. IF you than use it on a 230 v supply it is a simple matter to work out the current taken at 230 v.

Problem is no one in the UK has a 230 v supply, as you will notice if you actually measure it.

 

[ban-all-sheds]

Actually more intelligent than you.

No - that's more TAS delusion on your part.

 

[DrJimFranklin]

If an item is rated at x kW at 240v then these are the figures you use to calculate current. IF you than use it on a 230 v supply it is a simple matter to work out the current taken at 230 v.

Problem is no one in the UK has a 230 v supply, as you will notice if you actually measure it.

The problem is you clearly do not understand what you are talking about in this context. The supply voltage for the UK has a NOMINAL rating of 230V..that means all design calculation should be undertaken using this voltage. It of irrelevant what you measure with your B&Q kill you quick ****y Chinese made multimeter Winston. If I take a random measure of the properties where I live I can hazard a guess most will come in at 238.6V as an AVERAGE that will fluctuate over the course of a day.

Now if I go into the buildings I manage and take a measure...Low and behold, the majority will be at 230V as it is stabilised by UPS systems and other line attenuation equipment...so, as the Regs clearly stat 230V, I suggest that you stop arguing over something where you will lose every time as it will save everyone the hassle and stop ****y posts

 

[DrJimFranklin]

Hate to **** on your parade but your incorrect,

He almost certainly is not, at least not in the way that you think he is.

Picky as usual, however he is still wrong and your later comments in this posts and the following one about Winston demonstrate that.

I assume you erroneously calculated using 240V

How do you know that he was wrong to at least start with using 240V? Are you unaware of how common it is for shower manufacturers to use a headline figure for their product's performance at 240V?.

I KNOW he is wrong because the Regulation state he is WRONG. It is not my opinion, it is a Fact as per BS 7671 Appendix 2 section 14. The UK supply 230 V +10% - 6% and this is what ALL design calculation are based on for single phase services.

but you should, as per BS7671 (In fact as per the 15th and 16th Editions of the IEE Regs - Before it became BS7671)

Actually it became BS 7671 very early in the life of the 16th..

Actually I know that, but read my comment, the fact is the 230V Nominal was stated from the 15th edition (Yellow cover) in around 1983 and as the 16th edition was published prior to it becoming BS7671 my comment is factually correct no matter how you interpret it.

the correct voltage for design calculations is 230V and for a 9.5kW load that is 41.3A, as such all cable calcs etc should be based on this.

Only if 9.5kW is the load of the appliance at 230V. It almost certainly is not. The most likely figure for the load at the official U0 is about 38A..

Totally irrelevant. The unit is rated at 9.5kW and the supply voltage has a NOMINAL rating of 230V, thus to comply all calculation must be based on these figures and not one you pick out of your head to try to win an argument with yourself...

Everyone here is giving out advice, yet no-one has asked the obvious questions...what size is the supply cable and how far is it from the Consumer unit...very important when installing items of equipment, especially with significant loads..The Switch and the MCB are irrelevant to a cable burning out.

So is the length of the cable.

See the section in Bold...are you the only person in the UK who does not understand that is enquiring about cable length? or is it that you simply have to have the last work all the time to make yourself look big Kevin? really no need for this nonsense is there?

 

[bernardgreen]

Totally irrelevant. The unit is rated at 9.5kW and the supply voltage has a NOMINAL rating of 230V, thus to comply all calculation must be based on these figures and not one you pick out of your head to try to win an argument with yourself...

The Cara 9.5 kW shower is rated at 9.5 kW when the supply is 240 volts. And derates to 8.7 kW when the supply is at the nominal 230 volts.

Calculation gives an element resistance of 6.063 Ω at 240 volt and 6.08 Ω at 230 volts. ( the difference could be due to rounded up rating values or different temperatures in the element )

The current at 230 volts will be 37.9 amps
The current at 240 volts will be 39.6 amps
The current at 253 volts will be 41.7 amps ( the maximum supply voltage 230+10% )

If one uses 230 volt and 9.5 kW the calculated current is 41.3 amps ( W=V*I )

So calculations using 9.5 kW and 230 volts result in a current value that is incorrect. Fortunately this in-correct value is close enough to the maximum current ( non fault at 253 volts ) to be safe in connection with the selection of over current protection devices.

 

[EFLImpudence]

I suggest that you stop arguing over something where you will lose every time as it will save everyone the hassle and stop ****y posts

Good advice. You may care to follow it.

 

[winston1]

If an item is rated at x kW at 240v then these are the figures you use to calculate current. IF you than use it on a 230 v supply it is a simple matter to work out the current taken at 230 v.

Problem is no one in the UK has a 230 v supply, as you will notice if you actually measure it.

The problem is you clearly do not understand what you are talking about in this context. The supply voltage for the UK has a NOMINAL rating of 230V..that means all design calculation should be undertaken using this voltage. It of irrelevant what you measure with your B&Q kill you quick ****y Chinese made multimeter Winston. If I take a random measure of the properties where I live I can hazard a guess most will come in at 238.6V as an AVERAGE that will fluctuate over the course of a day.

Now if I go into the buildings I manage and take a measure...Low and behold, the majority will be at 230V as it is stabilised by UPS systems and other line attenuation equipment...so, as the Regs clearly stat 230V, I suggest that you stop arguing over something where you will lose every time as it will save everyone the hassle and stop ****y posts

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.