#### Elite_electronics

Be advised first you need to ascertain how much current you are drawing from the consumer unit worst possible case

After this then and only then can you decide on the maximum power of your shower unit should the consumer unit have sufficient power spare

You need to take the power measurement of all isolators and add them together to work this out I.E (i1+i2+i3....) this will give you maximum power used at full peak in the consumer box in amps

Next take the maximum power rating of the consumer box normal household is 60Amp on rare occasions this may rise to 80amp

Subtract your previous calculation from this measurement

You now have available power left

From this work your way from a 2kw shower unit upwards work out the current

(Power In kilowatts*1000)/240 = amps

in this case the answer would be 8.3 amps

If this doesent exceed the maximum power rating of the box your ok to use that unit DO NOT EXCEED THE MAXIMUM RATING OF THE CONSUMER BOX

This will also determine the size of cable required and also the maximum rating of your mcd unit

If you dont follow these instructions you will land up with a bl**dy fire on your hands with serious consequences possible life loss and a complete rewire of the house with The electrics Bourd on your case yes thousands of pounds worth of damages

You have been warned

Ahh, why are you telling us all this mr elite? Is it a question?

I need to find myself a 1kW shower

With respect Elite, your post is ridiculous and demonstrates you have little knowledge of the subject at hand.

My consumer unit has a main Isolator rated at 100A, this is actually pretty standard. Consumer units with 63A and 80A Isolators are available, but it is usual to put in 100A where the supply will allow it.

Further, if I add up all the potential total load of my entire installation...

Garage/workshop 50A 300mA RCBO
Ring 1 32A 30mA RCBO
Ring 2 32A 30mA RCBO
Ring 3 32A
Ring 4 32A
Boiler 16A
Alarm 6A
Fire Panel 6A
Lights 1 6A
Lights 2 6A
Security Lights 3A

Therefore there is the POTENTIAL to draw 221A across the main switch of my consumer unit.

However this will never happen, firstly a little thing called DIVERSITY, not all circuits are consuming load or even full load at any one time. In fact the chances of any of the circuits running at anything like their full potential is laughable.

But secondly, and most importantly, the BS1361 Fuse installed in my service cut out is only rated at 100A, so taking the fusing factor into account, I cannot draw anymore than 115A via my main fuse in the worst possible scenario.

In fact on most days I would say I use a total of about 6kW of electrical energy....hardly fire starting are we.

I think that in future, before you go handing out your advice, you should do a little homework and actually understand what you are taling about before you go giving people bad advice.

Incidently, you should do all electrical calculations with 230Vac not 240Vac as you suggest

il78 said:
I need to find myself a 1kW shower

Now that should be interesting!!

Hi FWL,

Communications ??
I wonder :-

"Be advised first you need to ascertain how much current you are drawing from the consumer unit worst possible case "

Does this mean to convey the consumers own (naturally diversified) worse pos. case, as oppose to a globally worse case using the max fuse ratings.

Just a point, no criticism.

P.

110% behind FWL, on this one.......for once

il78 said:
110% behind FWL, on this one.......for once

109% Behind "FWL" On All One's........The 1% Is Allowing For My "Diversity"

FWL

However this will never happen, firstly a little thing called DIVERSITY, not all circuits are consuming load or even full load at any one time. In fact the chances of any of the circuits running at anything like their full potential is laughable.

IS THIS WHY YOU KNOCKED MY SUGGESTION OF APPLYING DIVERSITY TO A COOKER CIRCUIT IN A PREVIOUS POST????

Hmmmm..........

Secure, you misunderstand I think. Applying Diversity to a whole Installation or even ring mains is logical and sensible for the total potential load is unlikely to be pulled at once.

However it is not wise to apply it to a cooker circuit as a general rule.

I agree and accept that many people will no likely pull the maximum permissable load through their cooker, the chances they will have it all on full power at the same time is very unlikely, HOWEVER it is very likely, and common, for up to 90% of the maximum potential load of a cooker to be drawn on a regular basis, for this reason diversity should be left out of the equation.

I use easily 90% of the full potential of my cooker..it's gas not electric, but the same principle applies. If it were electric then I could still be drawing up to 40A through it at any one time, so installing the circuit I would simply assume the full potential load for the circuit.

I repeat

In fact the chances of any of the circuits running at anything like their full potential is laughable.

EXCEPT COOKER CIRCUITS, you should have said....which can easily draw 90% of f.l., you said.

Secure, perhaps you would like to re read my post, where do you see cooker mentioned???

There is not one as there is no cooker circuit wired into my cottage, so my statement is TRUE and accurate for the post I was actually discussing.

Just a thought: the point of diversity is so that you don't have to run cables the size of your arm round a ring mains as you will never see 13A from every socket at once. I would guess that a ring main never sees more than 15% of what it would see if you did draw 13A from all sockets at once. Wiring for 100% capacity would be impractical. Thus diversity makes sense here.

If you take the cooker circuit (and its brother, the shower circuit) into account: you might never draw more than 90% of full load. However, wiring the circuit to accomodate 100% load is not going to be a problem. It is quite likely that you won't have to go up a cable size. If you did need to upgrade, it would only be one size bigger!

Showers are either on or off like kettles.

Accepted cooker loading guidelines are all very well, but they do assume that you never start both ovens and the entire hob all at once.

ban-all-sheds said:
Showers are either on or off like kettles.

Accepted cooker loading guidelines are all very well, but they do assume that you never start both ovens and the entire hob all at once.

The problem with assumptions is that often they are proven wrong.

When the compnay was first started, one of our prime earners was offering an emergency 24 hour call out service. I cannot tell you the amount of times we would be called to Multi-occupancy houses, shared accomodation or simply LARGE family homes (the family not the house necessarilly) and the cooker circuit would keep tripping when they cooked, or the cables was over loaded and a smell of burning was noticed by people.

As I have said before, diversity has it's place, and ring mains are certainly one of them, as is the entire installation, but you must use common sense when dealing with circuits connected to equipment which has a reasonable chance of being used at full power at some point in it's life expectancy.

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