Two schools of thought on 9.5KW showers

[cedrich]

Hi

Plumber just installed 9.5 KW Gainsborough shower and the existing 30amp fuse blew in CU. (It is a 25 year old Memera 3 CU with a 30 amp cartridge fuse for the existing smaller rated electric shower)

I know that technically 9500/240 = 41.3amps there or therabouts. I also know that the board wont take anything greater than 30 amp so I need to upgrade CU completely or get one of those shower extension gizmos fitted with an integral RCD etc....

However, the plumber fella insists that these requirements were mainly introduced to satisfy EURO civil servants and that his electric cooker (oven and burners and kettle etc) run well on 30amp. He advised me to try another new 30amp fuse and it seems to work so far. (He thought the other might have come to the end of its natural anyway)

Is there a kernel of truth in what he sayeth? I have 10mm cable which is something and don't want to make the changes now if they can be avoided. Short of blowing the fuse periodically, will it be safe based on the cable size and his logic?

Many thanks

Cedrich

 

[Belle427]

plumbers+electrics=disaster

 

[securespark]

The reason he "reckons" the oven runs well on a 30A device is that diversity has been used. This makes allowance for the fact that not everything on the cooker will be on full whack at the same time.

This cannot be done for showers.

You should make sure EVERY aspect of the circuit is capable of taking the increased load. This includes, EB supply fuse, main tails, meter, consumer unit, fuse or breaker, cable and switches.

You also need an RCD, as it is almost certain a requirement of the shower manufacturer.

 

[sm1thson]

water and electricity dont mix so:
i) make sure shower are wired correctly RCD's, bonding etc
ii) dont mix plumbers for electricians.

 

[RF Lighting]

Paperwork?

 

[cedrich]

Just wondered whether it was likely to cause fatal accident or fire if used.

Cedrich

 

[securespark]

If you like a gamble, you could always wait and find out...

 

[DESL]

However, the plumber fella insists that these requirements were mainly introduced to satisfy EURO civil servants and that his electric cooker (oven and burners and kettle etc) run well on 30amp. He advised me to try another new 30amp fuse and it seems to work so far. (He thought the other might have come to the end of its natural anyway)

I'm afraid that's all bovine excrement.

I have never know a fuse come to the end of it's working life. If they did they would have a best before date stamped on them.
They are obviously designed to work once!! Overload or short circuit.

I suggest you get the plumber fella to put it right so the installation complies with wiring and building regulations.

But I have the feeling you paid cash and didn't get a traceable invoice, an electrical installation certificate & building regulations cert.

 

[plugwash]

Just wondered whether it was likely to cause fatal accident or fire if used.

pretty damn unlikely, electrical accessories are made of self extinguising plastics and you aren't overloading by very much or for very long.

one thing to remember about fuses is that each time you overload a fuse even if you don't blow it you will weaken it, the result is after a number of uses it is likely to blow.

still you could do with it getting it sorted sooner rather than later both because of the lack of RCD protection (which while not a reg is considered by most to be a very desirable extra safety measure on shower circuits), the annoyance of periodic fuse replacements and the fact that you will most likely be considerablly shortening the remaining usable lifetime of your CU.

 

[cedrich]

I know your advice makes sense.

Am speaking to a spark this week to resolve.

Thanks for your advice.

Cedrich

 

[securespark]

I have never know a fuse come to the end of it's working life.

They can get gradually weaker due to constant overload.

 

[bernardgreen]

They can get gradually weaker due to constant overload.

And in a damp area or a corrosive atmosphere the wire can corrode away changing the rating to a lower amperage.

Not to mention the wire stretched when the screw is tightened dragging the wire round with it.

 

[dingbat]

It is a ... 30 amp cartridge fuse

 

[bernardgreen]

It is a ... 30 amp cartridge fuse

They do survive far longer longer than bare wire but even they are not totally immune to the environment. But yes the effect is negligable.

 

[kevnurse]

I would bite the bullet and get a second CU fitted with an RCD. You can then move your downstairs socket circuit and cooker into the new CU.