New electric shower - old fuse box

LeeUK

LeeUK

LeeUK

Soldato
Joined
1 Mar 2008
Posts
6,350
Location
Deep North
My electric shower needs replacing but my fuse box is old with rewireable fuses. Current shower has it's own 30amp fuse within this fuse box.

I hear it is now illegal to wire up new showers this way and they must have an RCB or whatever.

I've had a quote from one electrician who says he will just install new shower and just leave it on the old wire/fuse. Is this dodgy?
 
You don't have to have a new fuse box when you get a new shower..

The options are either a shower needs RCD protection or supplementary bonding in the bathroom which roughly means extra earth/boding cables between pipework and circuits in the bathroom so they are all at the same potential.

If supp bonding is present then you dont need a new cu but its still a good idea, if supp bonding isnt present already the a new cu is a better safer option than putting the bonding in.

Plus 30A = 6mm cable i would guess, need to make sure new shower isnt too powerful or get the shower cable rewired to 10mm.

So all depends if you have supp bonding already and if you want to be safer and have an RCD or not as you are soaking in water with electric right next to you etc
 
Not sure if it has any bonding or not. If it does then I can't see it anyway. The cable for the shower comes out of the house from the fuse box along the external wall and back into the bathroom and goes through a pull-cord isolator switch from the ceiling. I suppose it would be pretty easy to have that cable upgraded. I was thinking of just a separate RCD fuse switch located next to old fuse box just for the shower.
 
HardwareGeek said:
You don't have to have a new fuse box when you get a new shower..

The options are either a shower needs RCD protection or supplementary bonding in the bathroom which roughly means extra earth/boding cables between pipework and circuits in the bathroom so they are all at the same potential.

If supp bonding is present then you dont need a new cu but its still a good idea, if supp bonding isnt present already the a new cu is a better safer option than putting the bonding in.

Plus 30A = 6mm cable i would guess, need to make sure new shower isnt too powerful or get the shower cable rewired to 10mm.

So all depends if you have supp bonding already and if you want to be safer and have an RCD or not as you are soaking in water with electric right next to you etc
Click to expand...


Hmmmm... not sure I agree with this!!
Amendments in the 17th Edition & IEE wiring regulations (BS7671) strongly suggest to me that RCD's are now mandatory in bathrooms!

It also shouldn't be an either or, when dealing with electrics a belt & braces approach should always be taken especially in high risk areas such as bathrooms (water, low resistance, conductive extraneous components ..etc) and external sockets due to earth equipotential zones!!

IMHO a sparky that installs a new Electric shower that isn't both RCD protected and earth bonded correctly is a poor electrical engineer!!

As for the OP, the best way is to spur off from the supply and install a RCD protected shower unit CCU in parallel to your old re-wireable fuse box. Making sure you use 10mm cable for the electric shower and that you also move the old lighting radial for the bathroom so that it too is RCD protected by the new shower CCU.

Something like this:
http://www.toolstation.com/shop/Ele...er+Easy9+Shower+Unit+1+Way/d190/sd2901/p62342
Then just buy an extra 6A MCB for the lighting circuit. You MUST however replace the 6mm cable as 50Amps is way too high to protect copper with such a low CSA.

/16TH Ed qualified

Regulation 701.411.3.3
In specific locations such as those containing a bath or shower there is a requirement now to provide RCD protection on all circuits, including the lighting and shower circuits.
Click to expand...
 
Last edited:
C.R.A.Z.Y said:
Hmmmm... not sure I agree with this!!
Amendments in the 17th Edition & IEE wiring regulations (BS7671) strongly suggest to me that RCD's are now mandatory in bathrooms!

It also shouldn't be an either or, when dealing with electrics a belt & braces approach should always be taken especially in high risk areas such as bathrooms (water, low resistance, conductive extraneous components ..etc) and external sockets due to earth equipotential zones!!

IMHO a sparky that installs a new Electric shower that isn't both RCD protected and earth bonded correctly is a poor electrical engineer!!

As for the OP, the best way is to spur off from the supply and install a RCD protected shower unit CCU in parallel to your old re-wireable fuse box. Making sure you use 10mm cable for the electric shower and that you also move the old lighting radial for the bathroom so that it too is RCD protected by the new shower CCU.

Something like this:
http://www.toolstation.com/shop/Ele...er+Easy9+Shower+Unit+1+Way/d190/sd2901/p62342
Then just buy an extra 6A MCB for the lighting circuit. You MUST however replace the 6mm cable as 50Amps is way too high to protect copper with such a low CSA.

/16TH Ed qualified
Click to expand...

Depends on what you are doing, a new shower circuit if you rewired to 10mm would need to be up to current regs but if just replacing an old shower on the old circuit you are not required to bring it upto current regs with an RCD if its got supp bonding afaik.

Also supp bonding is not longer required in current regs afaik and has been superseded by RCD protection but guess you could still do both.
 
You don't need a new consumer unit, you can fit single RCD's for a shower and it'll be within regs.

Personally I'd just scrap the electric shower an fit a mixer though, electric showers are crap.
 
I hung mine off the old wire fuse box.

It's slightly under rated but nothing gets warm
pitchfork said:
Personally I'd just scrap the electric shower an fit a mixer though, electric showers are crap.
Click to expand...

One boiler fault and you are stuck with cold showers, I'd rather pay slightly more for a shower and know it's likely to work.
If I build a second bathroom I'd swap the units over though and have a mixer.
 
I'll get a few more proper electricians in and see what they say. The first one was a bit dodgy off MyBuilder.com.

I don't really want to shell out for a whole house rewire with new consumer unit but I am willing to have a separate shower CU fitted.

Also with electric showers, like what bitslice says, if boiler goes on blink I still have hot water for a shower.
 
One shower fault and you are stuck with cold showers also.. a mixer shower if possible will give you a better shower, depends on your boiler set up though.

In this situation I'd be looking to price up a 10mm cable (8kw is pretty much your max on 6mm) and a small 2 way cu in which I'd fit 2 RCBO's one for the shower and one for the lighting. But as seems to be the case I'd first try to persuade you to upgrade your current board.

And can we stop signing off with /16th Ed ?

It's not even current and I've worked with folk who have 15th,16th or 17th ed and I'd not trust them to wire a plug!
 
Last edited:
If you are replacing an existing electric shower you do not need to comply with the 17th edition anyway. That's for new circuits/installations.

EDIT

In readiness for the inevitable backlash from some:

"Information published by ELECSA ‘The 17th Edition, your
questions answered’"
Q - If I replace an existing electric shower, do I now have to provide RCD
protection for it?
A - No, unless RCD protection is required by the manufacturer’s installation
instructions, or a new circuit is required (to provide for increased load,
for example).
 
Last edited:
bitslice said:
One boiler fault and you are stuck with cold showers, I'd rather pay slightly more for a shower and know it's likely to work.
If I build a second bathroom I'd swap the units over though and have a mixer.
Click to expand...
Yeah, and if the shower or any of the connecting gear goes you have no shower at all.

If the boiler goes just run a bath and bung in a kettle of water until you get it sorted, boilers go wrong less than showers.

Not to mention crap water pressure, if it doesn't blast the skin off your skellington it aint a proper shower in my eyes.
 
C.R.A.Z.Y said:
Hmmmm... not sure I agree with this!!
Amendments in the 17th Edition & IEE wiring regulations (BS7671) strongly suggest to me that RCD's are now mandatory in bathrooms!

It also shouldn't be an either or, when dealing with electrics a belt & braces approach should always be taken especially in high risk areas such as bathrooms (water, low resistance, conductive extraneous components ..etc) and external sockets due to earth equipotential zones!!

IMHO a sparky that installs a new Electric shower that isn't both RCD protected and earth bonded correctly is a poor electrical engineer!!

As for the OP, the best way is to spur off from the supply and install a RCD protected shower unit CCU in parallel to your old re-wireable fuse box. Making sure you use 10mm cable for the electric shower and that you also move the old lighting radial for the bathroom so that it too is RCD protected by the new shower CCU.

Something like this:
http://www.toolstation.com/shop/Ele...er+Easy9+Shower+Unit+1+Way/d190/sd2901/p62342
Then just buy an extra 6A MCB for the lighting circuit. You MUST however replace the 6mm cable as 50Amps is way too high to protect copper with such a low CSA.

/16TH Ed qualified
Click to expand...

All lovely and applicable to new installations as countless people have pointed out, it seems sparkies are getting as bad as central heating installers. Nice to see you've decided to call yourself Electrical Engineers as well to match the Gas/Central Heating Engineers spawned by the Corgi con.
 
Current old shower is 7kw and I'm thinking of a 9+kw replacement. Don't even think I have seen 7kw ones anywhere these days.
 
It's likely you have a 6mm cable feeding your shower at the moment. (Need to check) if you are going for a 9kw shower you will be needing to upgrade that to 10mm cable, in which case you really should be fitting a RCD, see my previous post.
 
We've just switched ours over to an RCD when we did our bathroom (by choice, bath needs electric, shower is off combi boiler). One thing about fuse boxes that I now appreciate is their ability to ignore small problems.
Our hall lights trip everything in bad weather now but a lamp in the lounge stays on.
 
What you need to tell your sparky is (to save changing the main CU for your house)

Add a sub 17th edition CU (1 way board will do), with a 40a rcbo, 10mm cable to the shower switch, 10mm cable from the shower switch to the shower.

Job is a good one, and upto 17th ed ammdt 1.

Have you thought of having your main CU upgraded to 17th ed ammdt 1 at all?
 
I've got an rcd on my shower from a secondary consumer unit so nothing really had to change.

I would get a pro in as well everyone's knows water(impure water) and electrics don't mix well. Shouldn't be expensive by any means if you're keeping the same wire.
 
What hasn't been said (I don't think) Is that those wylex standard boards (which the OP likely has) are generally rated at a maximum of 30A per way (yes you can buy 45A breakers and 1361 carriers for the wylex standard ranges, but those are designed for fuse boards which have a separate way designed to take them - they actually have a tab on the back to try and prevent use in unsuitable boards)

So you are generally limited to 7kw shower.

So pointless adding a sub DB. Its either board change, or henley blocks and a separate shower board (not installed as a sub board)
 
Traffic_Warden said:
What you need to tell your sparky is (to save changing the main CU for your house)

Add a sub 17th edition CU (1 way board will do), with a 40a rcbo, 10mm cable to the shower switch, 10mm cable from the shower switch to the shower.

Job is a good one, and upto 17th ed ammdt 1.

Have you thought of having your main CU upgraded to 17th ed ammdt 1 at all?
Click to expand...

I have thought about having the old Wylex rewireable fuse box replaced for a new CU but not sure how easy that would be, or if I would need a whole house rewire to do it properly. Old box only has 4 fuses, 1x5A for lights, 2x15A for sockets and immersion heater, and 1x30A for shower. There is another single Wylex box with just one 30A fuse for the hob/oven.

Adam_151 said:
What hasn't been said (I don't think) Is that those wylex standard boards (which the OP likely has) are generally rated at a maximum of 30A per way (yes you can buy 45A breakers and 1361 carriers for the wylex standard ranges, but those are designed for fuse boards which have a separate way designed to take them - they actually have a tab on the back to try and prevent use in unsuitable boards)

So you are generally limited to 7kw shower.

So pointless adding a sub DB. Its either board change, or henley blocks and a separate shower board (not installed as a sub board)
Click to expand...

If I added a single RCD CU just for shower then it won't be coming from the old Wylex board, but directly from the meter so can be over 30A surely?
 
You must log in or register to reply here.
Back
Top Bottom