Electric Shower Question

[grumbas]

Question for the elextrical experts - 9.8kw shower, 40A breaker - by my reckoning it should be ok in normal use (ie not running full temp). Obviously not by the book but 40A is the largest breaker available for the consumer unit I've got!

Naturally I'll need to upgrade the existing 6.5mm cable (I think) to 10mm, but thats easy enough despite being a ~10m run.

Thoughts people?

[ChrisRS]

I ran a 10mm cable and use a 50A breaker on my 9.5kw shower, new breakers only cost a couple of quid from wholesalers, not had no problems so far (Still alive!)

Edited because i didn't read your post correctly! Should be ok with a 40A breaker but your better off waiting until someone comes along who knows what their talking about!

Edited by ChrisRS on Sunday 26th October 21:52

[Mars]

P=VI, or I=P/V, which in your case is 9800/230, which = 42.6A

However your shower is probably rated at 9.8KW for a 240V supply. I'm currently getting 251V at home, but it can dip to around 230V on occasion.

So assuming you only get 9.8KW with a 251V supply you'd need a 39A fuse, but I still reckon your 40A fuse is too small. Switch-on might/probably will cause a minor surge.

[mr_fibuli]

I think the shower will draw the full power whatever temperature you run it at too - they usually control the temperature by adjusting the water flow rate, not the amount of power used. Sure you can't get hold of a 50 amp breaker?

[Ganglandboss]

Mars said:

P=VI, or I=P/V, which in your case is 9800/230, which = 42.6A

However your shower is probably rated at 9.8KW for a 240V supply. I'm currently getting 251V at home, but it can dip to around 230V on occasion.

So assuming you only get 9.8KW with a 251V supply you'd need a 39A fuse, but I still reckon your 40A fuse is too small. Switch-on might/probably will cause a minor surge.

A shower rated 9.8kW is not going to draw 9.8kW at 251V - it will draw more. The only constant in the equation is the impedance of the shower; the current consumption will vary according to the voltage. Many showers show different power ratings in the manual according to the voltage.

For the purpose of calculations such as this you should always use the nominal voltage which is 230V in the UK.

9800/230 = 42.6A ~ A 45A breaker is needed.

---

My advice to the OP is get a qualified spark in - they will know how to do it correctly and also sign off your part P certificate.

Dave - qualified spark.

[tim the pool man]

This might be seen as a stupid question, but WTF is an "electric shower"? I often read it on here, must be something peculiarly English?

What does the electric part do? Heating? or boosting the pressure?

[rabw]

Just put the 40A fuse in and see how it goes? If anything it'll be too small, so worst case scenario is that it blows and you'll need a bigger one...

[Ganglandboss]

tim the pool man said:

This might be seen as a stupid question, but WTF is an "electric shower"? I often read it on here, must be something peculiarly English?

What does the electric part do? Heating? or boosting the pressure?

Heats the water. Pumped showers are usually referred to as 'power showers'. I wouldn't fancy a 9.8kW pump boosting the pressure - it'd be like showering under four fecking Karchers!

[jimmyjimjim]

tim the pool man said:

This might be seen as a stupid question, but WTF is an "electric shower"? I often read it on here, must be something peculiarly English?

What does the electric part do? Heating? or boosting the pressure?

It's essentially a large kettle with water passing through it. It's an instantaneous water heater, if you want to google for it.

Oddly enough, another of your fellow country men asked this question a few days back; seemed to like the idea and was thinking about trying to introduce them to Aus.

[tim the pool man]

Ah, OK, we have instantaneous HWS here but not dedicated to a shower, and usually gas

[GlenMH]

tim the pool man said:

Ah, OK, we have instantaneous HWS here but not dedicated to a shower, and usually gas

A lot of people have those too. Also there is the mains pressure hot water cylinder method which is f...ing expensive!

Electric showers only need a single pipe water supply.

Glen

[Bruggy]

Not all MCB's are the same you will need one with a type B characteristic. Also your double pole isolating switch will need to be rated accordingly.

ETA. I thought in the UK you had to be a qualified/registered electrician to carry out any domestic installation nowadays?

Edited by Bruggy on Monday 27th October 06:06

[deviant]

Bruggy said:

double pole

[Lord Pikey]

grumbas said:

Grumbas said stuff

any you lecture me about lecci stuff! the cheek of it.

just put a 40 in and see if the sucker blows

Lord Pikey

Edited by Lord Pikey on Monday 27th October 06:46

Edited by Lord Pikey on Monday 27th October 06:46

[sparkypete]

You will need to install a RCD or RCBO to the circuit if your consumer unit does not have one fitted to the main incomer. As previous posts you should get the works looked at by your local sparky.

Pete

[ALawson]

sparkypete said:

You will need to install a RCD or RCBO to the circuit if your consumer unit does not have one fitted to the main incomer. As previous posts you should get the works looked at by your local sparky.

Pete

Our sparky is doing just that 45A RCBO, 10mm cable for a 9.5 kW shower. With a double pole pull strig switch thing.

[Road2Ruin]

grumbas said:

Question for the elextrical experts - 9.8kw shower, 40A breaker - by my reckoning it should be ok in normal use (ie not running full temp). Obviously not by the book but 40A is the largest breaker available for the consumer unit I've got!

Naturally I'll need to upgrade the existing 6.5mm cable (I think) to 10mm, but thats easy enough despite being a ~10m run.

Thoughts people?

For gods sake man get an electrician in you obviously dont know what to do and quite frankly do you want to risk the cost of something major going wrong. For example its not always a case of just runing larger cable it also depends on the siting of the cable to prevent overheating and thus a fire. 6.5mm may have been fine but 10mm may not be.

[ALawson]

http://www.tlc-direct.co.uk/Technical/Charts/Volta...

[grumbas]

Lord Pikey said:

grumbas said:

Grumbas said stuff

any you lecture me about lecci stuff! the cheek of it.

just put a 40 in and see if the sucker blows

Lord Pikey

Thats rich after being stuck in your loft at 10pm one night in darkness trying to figure out what on earth you'd done to the lighting circuit that kept throwing the RCD! And your supposed to be an electrician

Just spoke to a mate (who would check everything, and do the part P bit for me), and has suggested this solution: http://www.screwfix.com/prods/42858/Electrical/Con...

So looks like an easy job and I can buy that fancy shower I've been watching on ebay, put pipe/cable in the right place and carry on with the tiling.

Thanks for the input all.

[Pigeon]

tim the pool man said:

This might be seen as a stupid question, but WTF is an "electric shower"? I often read it on here, must be something peculiarly English?

What does the electric part do? Heating? or boosting the pressure?

It's a fking dangerous piece of st installed when people can't be arsed to run a proper hot water supply to the shower. It is supplied with cold water and has a heater of around 10kW which warms it up as it comes out. 10kW is marginal so you get a somewhat dribbly shower if you want it hot, or you can have a decent flow and shiver. If someone turns a tap on elsewhere the flow drops so the temperature rises and you get scalded.

The heater unit is about half the size of a tin of beans and if anything blocked up it would explode soon as look at you, not to mention that if the insulation fails you're standing in the water. The units are fking badly made in China and make no pretence at sealing the box with all the electrics in it which is mounted on the wall inside the shower cubicle.

They should always be fitted to a circuit protected by an RCD but incredibly the regs don't require this I don't think, and half the time people can't be arsed even to make sure the earthing is top notch or even remotely adequate.

It's not like it's even that much easier to install one supply pipe and a special heavy duty circuit than it is to install two supply pipes and have a proper shower - especially now some bunch of horrid little nazis give you grief over working on your own electrical wiring in your own home. So it's pointless as well as dangerous and ste.