45amp cartridge fuse for 8.5kw shower on 6mm cable - is it ok?

[jonnyplatt]

I've noticed that my daughter's 8.5kw shower is connected using 6mm wiring to a switched single fuse box which contains a BIG 45amp fuse (cartridge?) labelled ME45A, Lawson BS1361, BS88, 415AC80. This goes to an RCD.

Isn't 45amp a bit big for 6mm cable (the cable runs 2m inside an insulated wall and then 2m under thick loft insulation)?

I think the shower was fitted 15years or more ago by the previous owners.

 

[m4tty]

Yeah 45a is too big for 6mm if it's run through insulation so your right it's wrong.

Tbh I'd change it to a 32a fuse unless your daughter spends 1hr plus in the shower it'll be fine. Others may disagree as the shower is pulling around 36a at 240v which a 32a fuse will hold for at least an hour without checking graphs in the regs book.

See what others think. Are you a sparky, training or diy'er?

Cheers

 

[kme]

40A is available; though to be honest, for the scenario you describe, that would be too much - but better than 45A

The next size down is 32A - As M4tty says,your shower uses a little more than that, so it isn`t ideal.........

I`d look at getting the cable out from under the insulation for a start- and perhaps give it some "breathing space" where its in the wall.... Drop the cartridge to a 40A, and you`ll be within spec. - as long as the cable IS 6mm; not imperial!!!

Notwithstanding the above, alterations to a shower circuit need to be tested & verified - I would personally notify building control if I changed the OCPD - but you DO need a test cert for it.

KME

 

[jonnyplatt]

Thanks for that. I obviously need to give some attention to it then. I have a rule that (in general) if it ain't broke don't fix it. So I'd be reluctant to sart messing about with the cable as there haven't been any problems in the 10 years she's lived there. I certainly don't want to mess about with the shower circuit. I could however try giving the cable a bit more air space around it.

A lower rated fuse seems to be the best answer but I've had a quick look and there seems to be alot of BS 1361 and cartridge fuses so not sure which one to pick. I've tried one of these from B&Q but it's far too small: (Wylex 35A Cartridge Fuses - Wylex 35A Cartridge Fuses, BQCFL35).

Anyone any idea where I can get a 32 or 35 amp or even a 40amp (shower instructions state 35amp) fuse that matches her ME45A, Lawson BS1361, BS88, 415AC80. Will they stock them at the electrical factors?

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Update: It looks as if this 'House Service' fuse is probably the fuse Edwardes Bros Website.

Unfortunately it looks as if it only comes in 30amp, 40amp and 45amp so I guess it will have to be 40amp?

Expensive and hard to find aren't they!

 

[paul b b]

hi jonny,

if it aint broke dont fix it quote in this situation is wrong sorry, this could result in the cable melting and burning the house down in worse case. not scare mongering, just things you see day to day on site makes you wonder.

im guessing there is no rcd on the circuit? so how about a little shower unit with rcd and breaker in one? would be a better job and give better protection on the shower circuit.

also as others have said, give the cable some space, insulation can half the current a cable can carry!

make sure you isolate and test for dead before doing any work!