new consumer unit and shower cable question

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hi all,
moved home last year and ...

the old consumer box i had looked a bit past it so i thought i would change it while i was putting in an extra shower.

got a consumer unit with 10 nsb's(mcb's)
4x6amps + 1x16amp
4x32amps + 1x40amp (on the rcd side)rcd 80A 30ma

main switch 100A

shower i got mira sport 9kw
bought some 10m fte


before (old consumer) a gainsborough se 9.5kw shower had a 6mm fta from consumer with a 30amp fuse
was that right? :eek:

the old consumer unit didn't have trip itself, but whoever had put a 240v 50hz 80A load 100ma trip switch in.

so from the meter the tails went to trip switch then to old box.

i have fitted new 9kw shower (in ensuite) with 10mm cable and pull switch to 40A nsb on the rcd side

the old shower (9.5kw)(in bathroom) still has 6mm cable and ive connected to to 32A nsb on rcd side (wondered whether i should get another 40A nsb?)

have what i've done be ok?

hopefully you can understand what ive written.
thnx in advance. :D
 
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What sort of supply earth do you have?

I have a really nasty feeling you have removed a main RCD from a TT setup
 
RF Lighting said:
What sort of supply earth do you have?

I have a really nasty feeling you have removed a main RCD from a TT setup

don't think i removed any main rcd
whats a TT
just going to take a piccy of consumer set up
 
FFS. People decide they are competent to rip apart the heart of their electrical installation without even knowing basics like supply types. Or indeed, I suspect, inspection & testing.

Jeez......How do you sleep at night?
 
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have just emailed admin with piccy
have read in another post how to upload (thnx to spark 123)
thanx

 
3 earth types that are commonly used, in short

TNS- where you are supplied with a earth return path down the supplyers cable- usually via the armour of the supply cable. you can identify this normally because the earth will be 'sweated' onto the supply cable.

TNCS- combined earth/neutral, the neutral and earth use the same core in the supply cable and are split in your installation.

TT- no earth return path supplied so you have to obtain an earth via an earth spike usually, somewhere on your property. TT systems therefore have higher resistances back to the supply transformer earth and thus require rcd protection on al circuits normally via a 100ma rcd and a 30ma rcd for circuits that require it.....


so what the guys are trying to say is if you have a TT supply and youve removed the 100ma rcd then you have dropped a clanger!

you really need to find out what supply type you have before worrying about anything else. maybe a better photo would give us a clue.

did you do any tests on your work? insulation resistance? continuity? efli?
rcd trip times?

maybe you will be better off getting a qualified/competent spark to come in and do a PIR.
 
he hasn't removed the RCD! the tails do go through it still! though it looks a little old. press the test button, see if it knocks your 'lectric off.

AND he appears not to have a TT system! (earth lead from service head) though its hard to tell from the photo.

2 showers in the same single-phase installation is a questionnable thing to have done without testing the integrity of the installation first, or ensuring only one shower can be used at any one time.

Do you know how to work out amps, when given a voltage and wattage?

If you did, you'd know that your 9.5kw shower draws 41 amps. not 30. Both your showers need to be on 40 amp MCBs (its ok to overload them slightly, as its an intermittent load), AND need to be RCD protected. 40+40 = 80, so then you're fully loading BOTH the RCDs, without even thinking about any other loads (ring mains, kitchen etc). As the RCDs cannot trip on overload, theres a possibility their contacts could weld shut and then not trip on any earth fault / ELECTROCUTION that occurs. Ever.

The truth is, you shouldn't have bought a split load CU. You need a properly designed electrical installation, suited for your home's specific load requirements. There's a chance that a good spark will salvage certain parts of this, but a lot of it will need re-hashing. You dont need 2 RCDs for a start. A split load package set is NOT a one-size-fits-all solution. Every installation is different.

Oh, and you've broken the law by not notifying the building control and getting them to come and test this work.
 
Oh, and you've broken the law by not notifying the building control and getting them to come and test this work.

I'll second that

You are seriously overloading the supply.

I hate to say this but if you get an electrician to sort the mess it'll cost you a lot more than the money you thought you'd save doing such a job yourself.

Also your insurers would not pay out if the worst happened.

Would you tackle a gas boiler renewal hopefully NOT I rest my case
 
Crafty wrote

he hasn't removed the RCD! the tails do go through it still! though it looks a little old. press the test button, see if it knocks your 'lectric off.

well i did say IF.......didnt think the origonal description or indeed the photo' were very clear to be honest so was requesting confirmation. ;)

ill agree though that this post is proof if ever its needed that unqualified people shouldnt be doing work even on their own installation if it is beyond them.

no offence intended to you mr elwood but you should be on the phone to a sparky very soon.
 
Quick question for Crafty....
Do the showers HAVE to be protected by an RCD
I always thought that according to BS7671 electric showers dont have to have protection from an RCD and that it is only shower manufacturers that recommend RCD protection to cover their backsides.
 
Well ok, the showers aren't required to be on an RCD UNLESS the manufacturer says so, but I would always put them on an RCD because of the water and electric and naked bodies scenario.
 
Wylex do not recommend that their units are loaded with more than one circuit 40A or higher.

Please seek the advice of an electrician, possibly a PIR.
 
securespark said:
Wylex do not recommend that their units are loaded with more than one circuit 40A or higher.

Picked up a pre-assembled 17w wylex split load in B&Q a good few weeks ago for a quick look and it came with 40A and 45A breakers in it, one was in the rcd side, one wasn't
 
I stand to be corrected, but seem to remember this, and not just from Wylex, from other, too.

I'll ring Ian Kenworthy (technical guy) at Wylex tomorrow (0161 998 5454)
 

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