Electric Shower Wiring

[erethryn]

Hi,

I'm currently installing a 9.5kw shower, I have 10mm T&E cable, and was planning on running it to an old Wylex consumer unit (which uses blade fuses), I have a 45A Plug-in MCB to replace a 30A fuse which was used for an electric cooker. My main fuse is a 60A, will this be enough to cope with a 9.5kw shower, or am I going to have to harass my electricity supplier for an upgrade?

Is it possible to use just the MCB, or do I have to use an RCD too? Depending on responses, I may return the MCB, and get one of these shower units:

this

and from what I've just read...a Henley block too! What type of cabling would I need to link from the block to the new cu, as the 2 cables from the isolator both look like standard T&E (ie. grey)!

Also, I'm fitting it in a tiled bathroom, and was wanting to run the cable up the wall through trunking, I have 25x16mm PVC trunking, this will only be used between the shower and the loft, approximately 70cm, can I do this, or am I at risk of setting fire to my bathroom?

Sorry there's so many questions, but I want to make sure I have all the necessary information before I start messing around with mains electricity.

 

[AdamW]

Funny you should mention a 45A MCB in a 60A Wylex, a thread just last week brought this topic up

here

Note Securespark's first comment: 60A Wylex cannot be used with a MCB greater than 32A.

I have seen a 60A Wylex used with a 45A MCB, and it looked so dangerous that you really wouldn't want to use your new shower! For the sake of what a new CU costs, perhaps you should consider upgrading to a 100A, or having a separate CU for the shower? It isn't the easiest solution, but if you do what you say you will stand back, look at it, and think "Why did I spend a weekend doing THAT?!" I cannot stress just how cack it looked!

 

[securespark]

Sorry. Your 60A supply is not enough. You need at least a 100 or 125A supply. And check the meter: this is often not up to the job, either.

These upgrades will be carried out by the REC - Regional Elec. Co.

If your old Wylex CU has a main switch of less than 100A, this will need changing too. The sub ton ones are not designed to accept any device over 32A.

I would strongly recommend an RCD (or RCBO if you upgrade the CU).

If you use a sep. board you will need 16mm2 tails, but if you are going to this trouble, I would bite the bullet and change the whole kaboosh for one neat unit.

Trunking or conduit should have a spacing factor of 45%, ie not more than 45% of the internal area should be occupied by cable, so the size of trunking needs to be approx twice as big (internally) as the cable(s) you intend to run in it.

 

[plugwash]

i thought all tails on a 100A fuse domestic even if feeding a small boar should be 25mm

i hate to say this but the recs are not usually interested in upgradeing thier side until you blow it (at which point they treat it as an emergency job)

replace the CU with a modern split board and wire it to the meter with 25mm tails

if you blow the service fuse that is when you call the rec

 

[erethryn]

Okay, I've now finished sobbing quietly... Things never go smoothly! and from what's been said, I'm not going to get this shower running as soon as planned.

So the overall recommendation is go for something like:

this

(just as an example)

Remove the Wylex CU, and rewire the circuits into the new board, with the shower and sockets on the RCD side? What is the recommended RCD amperage? I've noticed 63, 80 and 100A mentioned.

Then just sit back and wait until the main fuse blows, then contact my REC...

As for 'tails', I understand these are the wires from the isolator to the CU, but what type of wire is it, single core, double core? Forgive me for sounding dense, but I'm learning...

 

[plugwash]

imo the rating of an isolator or rcd should be at minimum either the sum of the breakers leading from it or the fuse before it (which may be upgraded to 100A later)

so i would stringly advise getting a 100A isolator and a 100A rcd

also buy a brand like mk or wylex or hager that have been making cus for a long time to make it easy to get parts in future

 

[Big_Spark]

imo the rating of an isolator or rcd should be at minimum either the sum of the breakers leading from it or the fuse before it (which may be upgraded to 100A later)

so i would stringly advise getting a 100A isolator and a 100A rcd

also buy a brand like mk or wylex or hager that have been making cus for a long time to make it easy to get parts in future

Plug...with respect, your taking the Guy off track and talking rubbish quite frankly.

The sum of the FULL POTENTIAL LOAD of all MCB's/RCBO's in any Distribution board will always, usually, be more than the current rating of the Main Isolator..THIS IS NORMAL AND PERFECTLY SAFE.

He does not need to install a split load board, so advising him to get a 100A RCD is daft..even if he did get a split load, the RCD need not exceed 80A @ 100mA

Seimens have been making Electrical eqipment longer than all the other..it is simply a shame that the stuff they seell in their own name is such rubbish..like Wylex!!

I would go for MK, Hager, Crabtree or Merlin-Gerin.

 

[erethryn]

Funny you should mention a 45A MCB in a 60A Wylex, a thread just last week brought this topic up

here

Note Securespark's first comment: 60A Wylex cannot be used with a MCB greater than 32A.

I have seen a 60A Wylex used with a 45A MCB, and it looked so dangerous that you really wouldn't want to use your new shower! For the sake of what a new CU costs, perhaps you should consider upgrading to a 100A, or having a separate CU for the shower? It isn't the easiest solution, but if you do what you say you will stand back, look at it, and think "Why did I spend a weekend doing THAT?!" I cannot stress just how cack it looked!

Sorry to question, but having checked the fuse I'm going to remove, the fitting is identical to the MCB I have, so it will fit straight into the current Wylex cu, is it possible that I have a newer cu that will accept over 32A, or am I missing something obvious? Even if I can get away with it, I am seriously considering upgrading my cu anyway...

Opinions on:

wylex
Contactum
and
MK
although that's way out of my price range

Apparently 45A MCBs are not an option, so for the 9.5kw shower, will I be okay with a 50A MCB, or is that too high rated?

Thanks

 

[plugwash]

you can just about fit a 45A fuse or 40A/50A mcb to a wylex 63A board however the thing won't sit straight because of a tab there to prevent you going it and you are runnign great risk of overloading the isolator

 

[securespark]

Ere

What is the size of the main switch of your Wylex? It should say on the front? If it is less than 100A, you cannot unfortunately fit a 45A circuit.

 

[erethryn]

There's no mention of the rating of the Wylex, the only reference I can find is the rating of the main service fuse (60A), although I've decided to upgrade my cu anyway, at least then I'll have the added safety of the RCD.

Fortunately my electricity supplier is happy to upgrade my main fuse, but I have to provide a certificate from the shower installer to prove it is safe...oh well, there goes my hope of electrocuting myself in the shower.

 

[Big_Spark]

If you upgrade your consumer unit do not use Contactum, they are absolute rubbish.

Of the last two on your list, and I am loathe to say anything good in their favour, Wylex is the better option if you cannot find the funds for MK or Hager.

I am not a fan of Wylex, anyone here will tell you that, but they are Gods compared to Contactum!

 

[securespark]

If your Wylex board is brown and/or less than 6 way, then it def has 60A switch.

If it is ivory and 6 way or bigger it will most likely have 100A switch.

Ring Wylex Technical if in doubt. 0161 998 5454, and speak to Ian Kenworthy. He is actually based at the factory where they are made, and knows EVERYTHING there is possible to know about Wylex boards. And he carries it round in his head! Trouble is, he only works certain days. But it's worth waiting to speak to him, because the other Tech lads are based in Brum, (other offshoots of Electrium empire) and don't know as much as Ian.

 

[erethryn]

Thanks for all the info.

My current board is 4 way and black, so I guess it's a 60A.

I've decided to go with the 12 way split load Wylex board, given the fact that this project is already way over budget.

I'm planning on doing the work myself, and then getting an electrician to check it over for safety, and hopefully give me the certificate my REC needs before they'll upgrade the main fuse. Is this a viable option, are most electricians allowed/willing to do that?

 

[ban-all-sheds]

MK
although that's way out of my price range

Yo - isn't it strange how quality costs?