cabling an electric shower

[Goldberg]

10.5Kw shower needs at least 46Amps.

No. It will draw a maximum of 43.75A at 240VAC.

DIY and apply to LABC

Actually, it's a notification, not an application. And it's quite important to do this the other way around, i.e. to notify first.

Additional info:
You'll need 10mm2 T&E

Did you look into a crystal ball to see his intended cable route and installation method?

Anything less than clipped direct (method C) will require a larger cable (table 4D5 for reference).

Why?

 

[GaryMo]

I took 45.7A as quoted as the current rating, the OPD being 50A and referred to table 4D5.

Obviously it would now need confirming if the 10.5kW rating is at 230v or 240v before advising on a 45A (if available) or 50A OPD.

 

[PrenticeBoyofDerry]

Goldberg
The OP has not been back since posting, so they seem to be little interested in the replies given.
But just to confirm
It was mean't that he can DIY but needs to apply, fill in application form to building contorls to notify them of the work to be done, worked the current off 230v.

 

[Goldberg]

Obviously it would now need confirming if the 10.5kW rating is at 230v or 240v before advising on a 45A (if available) or 50A OPD.

Have you ever seen a shower that's rated at 10.5kW at 230V?

Anything less than clipped direct (method C) will require a larger cable (table 4D5 for reference).

Why?

The OP has not been back since posting, so they seem to be little interested in the replies given.

Other people read the topic and would get the wrong advice from your post.

It was mean't that he can DIY but needs to apply, fill in application form to building contorls to notify them of the work to be done

But that isn't what you wrote.

worked the current off 230v.

Why?

 

[GaryMo]

I don't make a habit of looking at shower ratings so I couldn't say for certain.

Like I said, I reffered to table 4D5 - take a look.

 

[PrenticeBoyofDerry]

The OP has not been back since posting, so they seem to be little interested in the replies given.

Other people read the topic and would get the wrong advice from your post.

Don't think I've give wrong advise

It was mean't that he can DIY but needs to apply, fill in application form to building contorls to notify them of the work to be done

But that isn't what you wrote.

You've interpreted it wrongly

worked the current off 230v.

Why?

Because 4.1 of the electricians guide to the building regulations states that standard circuits that have been designed for dwellings are assumed typical 230v in the UK.
What do you work to?

 

[ban-all-sheds]

If you assume a supply voltage of 230 then you have to use the ratings of the appliances at 230V, not 240V

 

[Goldberg]

deleted

 

[Goldberg]

I don't make a habit of looking at shower ratings so I couldn't say for certain.

So how do you know it's not rated at 253V?

Like I said, I reffered to table 4D5 - take a look.

I don't need to look - did you misread the table and take the figure for 6mm² cable?

It was mean't that he can DIY but needs to apply, fill in application form to building contorls to notify them of the work to be done

But that isn't what you wrote.

You've interpreted it wrongly

I haven't interpreted it at all. You wrote two different things, so clearly one of them is wrong.

worked the current off 230v.

Why?

Because 4.1 of the electricians guide to the building regulations states that standard circuits that have been designed for dwellings are assumed typical 230v in the UK.

If you install a shower that's rated as 10.5kW at 240V, and the supply voltage is in fact 230V, then the current drawn will be lower, i.e. < 42A, not more, i.e. not > 46A.

What do you work to?

If you're asking how I calculate the current drawn by a shower that's rated at 240V, then I use 240V.

If you're ignoring the manufacturer's rated voltage, then why aren't you using 216.2V instead of 230V?

Could it be the case that you're not actually thinking about what you're doing, and are just plugging in a figure of 230 (for a single phase supply) whenever you see the word "voltage"?

 

[GaryMo]

253v? Don't be ridiculous.

As I said, I referred to table 4D5 on the assumption that a 50A OPD was to be selected.
The only reference method for 10mm2 t&e which would support 50A or above is C.

I took 45.7A as quoted as the current rating, the OPD being 50A and referred to table 4D5.

Why is this so hard to understand?

 

[Goldberg]

253v? Don't be ridiculous.

Or do you find these ridiculous?

As I said, I referred to table 4D5 on the assumption that a 50A OPD was to be selected.
The only reference method for 10mm2 t&e which would support 50A or above is C.

Why is this so hard to understand?

I don't know - let me know when you've understood it.

 

[GaryMo]

I've yet to see rating plates state 253v on domestic appliances state 253v.

What are you getting at with 4D5?
Does yours state differing figures than mine?
Are you telling me that 4D5 has 10mm t&e rated above 50A for more than just installation method C?

 

[PrenticeBoyofDerry]

Why are some so petty and negative?

 

[matt1e]

If you assume a supply voltage of 230 then you have to use the ratings of the appliances at 230V, not 240V

????????????
think I know what you are getting at BAS
do you mean "If you assume a supply voltage of 230 then you have to adjust the ratings of the appliances for 230V, not 240V

rerate them I should have said
then I agree

matt

 

[Goldberg]

If you assume a supply voltage of 230 then you have to use the ratings of the appliances at 230V, not 240V

think I know what you are getting at BAS
do you mean "If you assume a supply voltage of 230 then you have to adjust the ratings of the appliances for 230V, not 240V

rerate them I should have said
then I agree

Without wishing to speak for him, I believe that he doesn't mean that at all.

The only time it's acceptable to use 230V in a calculation for an electric shower element is when working out the resistance, if you know that the rating by the manufacturer is the power dissipated at 230V.

Showers, amongst other appliances, are specified by the manufacturer to have <some power rating> at <some supply voltage>. For example, 10.5kW at 240VAC.

Usually, they also state the rated power at 230VAC, e.g. 10.1kW. If they don't, then you can simply work it out. This isn't an "adjustment" of the rating, or a re-rating, or a de-rating, or anything else - it's just an understanding of what the resistance is of the element that the manufacturer has manufactured, and the current that it will draw.

For this reason, it isn't competent to design an electric shower circuit to work at 230V, because it be overloaded when the real-life supply voltage of 240V is applied.