Looking to install a 10.8kw unit - therefore 10mm electrical cable and suitable breaker. Question is, do I need to worry about where this cable goes? The ideal route is going to be under some floorboards, into an attic and under some loft insulation.
Being a competent diy'er but not a sparky as such, is this advisable? Is the cable likely to get hot for example?
Any suggestions much appreciated
Yes, so simply move the insulation out of it's way!
The ideal route is going to be under some floorboards,
Thanks for the quick response. Are there any other safety issues I should be aware of?
On top of the insulation would be greatly preferred.
What length is the cable run? Will it be fed from a RCD protected supply? What protective device do you plan on using (fuse / MCB etc)? What earthing system does your house have?
Given the above you can work out the prospective fault current at the shower and hence the disconnection times, and you can also check the earth fault loop impedance. You will also need to check the maximum voltage drop is not exceeded.
You need an isolation switch - preferably in the same room but not somewhere that can be reached from in the shower.
You suplimentary equipotential bonding will need to be up to scratch unless you plan to implement 17th edition style 30mA RCD protection for all circuits in the shower room.
Wow - thanks John.
up to 15 metres (10mm cable)
Not well up on this - was going to get a sparky to plumb it into my fuse box - the highest rated breaker in the box is 45A so I'm guessing he will fit a separate 60A breaker/isolation switch or whatever is necessary
I have no idea. I thought all houses were earthed the same
Okay, now I'm lost.
I was going to fit a pull switch isolation switch in the bathroom which cannot be reached from the shower but through which it's mains supply will obviously pass.
Meaning?
Thankyou for the advice - although you've lost me a little on some of this
Best get that sparky to do the whole job then, or at least plan it and (him/her) being willing, allow you to do some of the 'donkey work'.
On Mon, 17 Mar 2008 03:32:05 -0700 (PDT) someone who may be snipped-for-privacy@googlemail.com wrote this:-
10.8kW at 230V comes to a little under 47A, according to Mr Gates' calculator and my fingers, so a 50A MCB sounds likely.There is also the question of whether the consumer unit/supply can take this. What does the 45A MCB feed? What rating is the "electricity board" fuse?
Then it is a good idea for you to get someone else to design and fit the installation. They may allow you to do some of the donkey work however, such as drawing through cables.
Remember that instant electric showers involve the water people stand in passing over a bare uninsulated heating element. The water is in direct contact with the electricity. That means the shower must be installed properly, or it is likely to be dangerous to use.
It is a good idea for you to get someone else to design and fit the installation. That is the best advice you will receive here.
Un-insulated - No - it is mineral insulated. The water is not in contact with the electricity.
Many, many years ago was there not a Tomorrow's World item on an electric water heater in which it was implied (or maybe even stated) that the electricity *did* go directly through the water? I have a feeling that they laboured the "electricity and water don't mix" in the lead into the item.
That would be an electrode heater which are widely used for bulk water heating in industry etc but not AFAIK used domestically.
Owain
Such electrode heaters do exist, but they aren't used in domestic electric showers.
On Mon, 17 Mar 2008 12:07:34 GMT someone who may be "John" wrote this:-
"Water heaters having immersed and uninsulated heating elements" is the phrase used to describe such heaters in the 16th edition. No idea about the 17th as I have yet to need to study it.
There are even water heaters where the electricity passes through the water. These are called electrode water heaters and boilers.
"Water heaters having immersed and uninsulated heating elements" and electrode boilers are the same thing. Normal electric showers are classed as "instantaneous water heaters".
No - check the rating plate and/or instructions for the shower and you'll almost certainly find that the 10.8 kW rating applies at 240 V. For design purposes at 230 V the current will be close to 43 A and the output around 9.9 kW - so a 45 A fuse or breaker will be fine.
Certainly not - see
As already mentioned by others, this is not the case. The elements are insulated. RCD protection is now de rigueur and would be incompatible with an uninsulated element.
And a Part P application (building notice) is required of course...
Nope. They're just glorified electric kettles.
It's not rocket science though, is it? If you don't know, why not just say so instead of being so fecking patronising? This is a DIY group unless you had forgotten. The *rules* may be a little complex (and I admit to not knowing them myself) but I'm sure anyone with a bit more eloquence and patience than you could explain them simply enough.
To the OP, this site may help.
Sorry that's completely wrong. An electrode boiler passes current directly through the medium to be heated. See, for example,
OTOH an immersed and uninsulated heating element is just that - ever seen an Australian electric kettle?
No, I haven't. Would you care to explain further? And, surely, an electrode heater fits the description perfectly?
On Mon, 17 Mar 2008 14:25:25 +0000 someone who may be Andy Wade wrote this:-
Indeed, which is why just before the section entitled, "Water heaters having immersed and uninsulated heating elements", there is one entitled, "Heaters for liquids or other substances, having immersed heating elements", and just before that section there is one entitled, "Electrode water heaters and boilers".
On Mon, 17 Mar 2008 14:19:42 -0000 someone who may be "Tim Downie" wrote this:-
Incorrect. Such heaters merit a special section of the Wiring Regulations, at least they did in the 16th Edition. There are a number of requirements to install them safely. I have no intention of regurgitating them.
I do know, so your point is moot.
Ah.
I have explained why such heaters can be dangerous. Such heaters can be safely installed by DIYers, but those who do not understand earthing are best advised to practice their electrical skills on other projects first. What is likely to be the highest rated appliance in the house and one which involves standing naked, perhaps in a metal bath, in a stream of water which has passed over an uninsulated heating element, is not a good project to practice on.
Excellent, a personal attack. Do keep it up.
No, you haven't. You've explained the dangers of a different type of heater.
Except that there isn't an uninsulated element.
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