CU 32->40a fuse upgrade

good idea John.

There is a 40A fitted to that, (and it's next to the switch, and so is the shower one), so unless the tab has been incorrectly cut off, it allows 40A ones in some cases
 
nice-but-dim said:
Thanks - that's a relief …and so I won't fret about upgrading my shower fuse from 32 to 40a.

But I'm getting confused about the different types - and prices up to £30+ - of Wylex B40 40 amp fuses I can buy. I've found this one at £5.40 but it sounds like it won't work in my old-school CU:
https://amzn.to/3jZU5cs
…and then some are C40 which means nothing to me except that I should presumably avoid.

I do have one (old) Wylex B40 40amp fuse installed which has "3000" stamped on it and not much else. So any advice will be much appreciated.
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terryplumb said:
Turn mains power off and open the shower front casing .The cable is visible there. Take some pics and post here. Also look at the showers isolation switch ( ceiling pull cord type or wall switch maybe ) the supply cable is visible there ,again take pics and post here.
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Having just rediscovered the shower wall switch on the back wall of a built-in wardrobe, it is a simple power switch with no socket or fuse caddy. No wires are visible so I will remove the shower unit's front casing later - or possibly tomorrow now as I am being harangued to do other jobs - and take a photo.
(This wall switch has been permanently "On" for 20 years btw - which I assume is now bad practice.)
 
flameport said:
40A MCBs for that fusebox are obsolete. 6/10/16/20/32 are the only values available now, other than dubious used efforts from ebay and other vendors of tat.
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Thank you - I wondered why they were hard to find.

It might be possible to use the 40A 'hob' one for the shower and the 32A for the hob, however that also depends on whether that particular fusebox can support 40A devices at all - many were limited to 30A maximum.
Those that can do 40A devices typically only allowed them to be installed in one specific location.
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The one already on the board was installed by a qualified electrician so I can only assume that it is compatible. My Electrolux hob is rated 7.4kW and we do sometimes use all four rings - and they all have a power boost function so I would only switch this MCB to 32A if there were no risk of tripping the power in mid-cooking.
hob-rating.jpg

If the shower cable is 6mm² is may be possible to use that with a 40A device, although how and where the cable it's installed will need to be established, as will the total length and various other factors.
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I hope to get a photo of the wires coming into the shower by tomorrow.

Although one has been mentioned, there is no RCD in that picture.
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It's definitely there, just out of shot - and it works.

Ultimately that fusebox is several decades past it's replacement date, your existing 8.5kW shower is already overloading that 32A device, and the noticeable difference between an 8.5kW shower and a 9.5kW shower is somewhere between insignificant and none at all.
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I know the fusebox is old but it's working and declared safe every year by my SEE inspector. But your last comment gives me food for thought.
 
nice-but-dim said:
I have a master RCD attached to the consumer unit
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Im still not sure if you have an RCD. And your shower circuit must have one*

*not a requirement back in the day that your ancient fuse board was installed, but it is an aboslute requirement these days.

Also, the shower MIs will require you to have an RCD.

Electricity and water and humans are a dangerous combination,
should a fault occur.
 
Bit of a sidetrack, but talking about showers and RCDs, I have seen showers installed with 10mm² cable running from henley blocks to 45A double-pole RCD direct to shower with no Overcurrent Protection Device! Whoever installed that needs his arse kicked pretty damn hard!
 
Taylortwocities said:
Im still not sure if you have an RCD. And your shower circuit must have one*

*not a requirement back in the day that your ancient fuse board was installed, but it is an aboslute requirement these days.
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I appreciate your concern for my safety but I'm not sure why I would say that I have an RCD fitted if I don't have one - or that my system passes my annual SSE inspection if it didn't. True, I don't know much about electricity - but that makes me extra-cautious, not gung-ho.
 
nice-but-dim said:
I appreciate your concern for my safety but I'm not sure why I would say that I have an RCD fitted if I don't have one - or that my system passes my annual SSE inspection if it didn't. True, I don't know much about electricity - but that makes me extra-cautious, not gung-ho.
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nice-but-dim said:
would need to swap the existing 32a CU fuse for a 40a fuse. Is there a way for an idiot to safely tell what size the wiring is on that circuit as I gather I need 8mm for the bigger fuse and have no idea what's installed?
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nice-but-dim said:
I have a master RCD attached to the consumer unit and I think I also have a fuse in the shower spur socket.
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Not knocking you but we have to be sure what you mean.


What is an annual SSE inspection?
 
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