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My plumber fitted a new (very nice) shower that requires a 40 amp supply onto the existing wiring which is 30 amp, after 10 minutes under the shower it will cut out as the fuse trips (and is v.hot). I like the new shower and don't want a less powerful one. It is on 6 mm cabling and is directly connected through a wlex box that has 30 amp written on it. What I want to know is if I buy a replacement fuse for this box that is rated 40 amp will it work as required.

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Cheers Matt OC

hi matt its sounds as if u have installed a shower with a rating of over 8.5 kw can u check? if it is over 9 kw u will have to replace the 6mm twin earth cable with 10 mm and have a 40 amp fuse please dont be tempted just replacing the fuse of the fire risks darryl

THIS OPERATION REQUIRES CERTIFICATION BY AN ELECTRICIAN QUALIFIED TO DO SO UNDER PART P OF THE BUILDING REGULATIONS.

It wasn't over 8.5 kw but the cable was buried in plaster and maybe in a cavity wall for a long stretch so maybe that is why it was running warm. I just didn't feel comfortable with it so we've now got it running on a more modern 32 amp mcp and it seems fine now the shower does not cut off even after 1/2 an hours full power shower! Thanks for the feedback as unless I had actually felt the wire myself I would have left it as a 45 amp mcp which may have been a little dangerous I guess.
Cheers,
MOC

You can check online for a chart that tells u the size of cable to use for the size of shower and the length of the cable run.All showers i wire these days i run a 10mm cable although i had to buy a shower to run of a 30amp mcb with 6mm cable that was existing.i just used the chart and it works fine and is within the load that is suitable.