10KW to 9.8KW Shower

[pinzy]

Hi there,

10 years ago we had a 10KW shower installed using 10mm cable with a switched 40A MCB (Wylex). The installation was signed off by elec. board. I'm in the process of replacing with 9.8KW Mira Azora.

1) Now, am I ok leaving the 40A fuse with a new 9.8KW shower? (The ratings on new one are stated as 9KW - 230V/9.8KW- 240v.) At 240V this works out 40.8A?

2) The existing 40A wylex switched fuse has an orange base. I cannot find one that is 45A (green base) so does that mean 50A with new base?

Please let me know if you need more ino.
Thanks.[/img]

 

[electronicsuk]

Leave the fuse as it is. Although your supply voltage probably is 240v, our nominal supply voltage is 230v. If you didn't have any problems with your old, larger shower than you're highly unlikely to have any with a smaller replacement unit.

However, if the shower is fed via a rewirable fuse then I would question whether or not there is any RCD protection in place for the shower? The manufacturer's instructions probably stipulate that one be installed.

 

[PrinceofDarkness]

The main consideration, Pinzy, is that the current rating of the circuit cable should exceed the rating of the MCB.

As you're replacing the existing load with a slightly lower load, and as the the existing load has survived the last 10 years, you don't really need to change the existing MCB (even though it will still be loaded to the hilt).

It seems that you have 'plug-in' MCBs, in which case you won't find a 50A MCB anyway.

Do you have RCD protection for that circuit - or any circuit for that matter? And have you had the installation 'inspected' in recent years?



Lucia.

 

[pinzy]

I have the main Consumer Unit with RCD protection and the the shower MCB is separate as there weren't any spare blocks. Yes it is a plug-in type of fuse.

 

[ban-all-sheds]

View media item 22421
How is that supplied?

Any chance of a photo of the inside of the main CU showing where the cable is connected?

 

[Steve]

The installation was signed off by elec. board.

Really?

 

[PrinceofDarkness]

I very much doubt that the tails to that shower unit are connected to the main CU, because the O/P has stated that there wasn't a spare way. So, it's likely that those tails go to a Henley Block.

'tis a pity that there might not be an RCD for the shower, but for replacement of the actual shower unit, the O/P has no obligation or need to fiddle with the existing protection.


There is the small matter, though, of the main switch rating for that 1-way Wylex unit, if connected directly to the mains.


Lucia

 

[Steve]

I have a feeling, and so does ban, i think, that those tails go direct to the RCD in the CU.

 

[PrinceofDarkness]

Are you on about doubling up a pair of tails into the output of a standard RCD, Steve?


This installation is bad enough as it is, without resorting to that practice.



Lucia.

 

[ban-all-sheds]

I have a feeling, and so does ban, i think, that those tails go direct to the RCD in the CU.

They might, they might not.

They might go to the supply side, or the load side.

They might be safely connected into terminals which can take more than 1 cable, or a bus-bar prong and a cable, or they might not.

 

[PrinceofDarkness]

I should think so too!


The thing to bear in mind is that this installation is ten years old and has been certified by the local EB - according to a previous edition of the 'Regs'. The O/P intends to connect a lesser load to that existing circuit.


So, what's so wrong with that?



Lucia.

 

[pinzy]

Ban, Steve, PoD,

Thanks for all your responses. I hope this helps

View media item 22428
I have the certificate the elec board signed off when the shower was being installed but haven't had any further checks.

 

[pinzy]

one more to the left...

View media item 22429

 

[wingcoax]

What a spiders web! And the EB signed it off?

 

[PrinceofDarkness]

I don't see a spider's web as far as it concerns the shower installation of 10 years ago. The tails (as I thought they might) go to a mains- splitter DP Henley Block. So, the untidy spider's web wiring to the main CU has nothing to do with that independent supply to the shower.

It's a pity that the shower doesn't have RCD protection, but then, it was installed during a period when installers weren't RCD mad.

The main question here is the issue of the MCB size......



Lucia.