shower wiring 9.5kw

[nardoblue]

Hi just removed the old shower 8kw on 6mm three core wiring and was going to fit a 9.5kw shower ,10mm three core cable and 45amp fuse. Couldn't get the cable out of the wall so can I fit the new shower, the thing that is confusing me is the charts for the power rating of the cable,my cable is just under the surface and only 2m from the fuse box, or should I go back and get a lower rated shower unit, if so will 8.5kw be alright on the old spec wiring? Thanks Nardoblue

 

[breezer]

as the cable needs to be replaced why not rip out old one? or put new one surface mouted in trunking?

 

[AdamW]

Nardo, are you asking if you can install the new shower on the existing wiring, instead of ripping it out and upgrading it?

When you say "3-core cable", are you talking about this type of cable:

or this type of cable:

I suspect you are talking about the first type, which is "Twin and earth". When people talk about 3-core they usually mean the second type.

Unfortunately, for a 9.5kW shower you are limited to 10mm twin and earth, 6mm doesn't meet the voltage drop limits. 6mm only meets the regs for an 8.5kW shower if it is in conduit.

If it was me, I would rip out the old cable, install 10mm in a conduit and have the 9.5kW shower. A bit of disruption to your decor (although as breezer says you can surface mount the cable in trunking), but worth it for the extra oomph in the shower.

 

[dingbat]

Unfortunately, for a 9.5kW shower you are limited to 10mm twin and earth, 6mm doesn't meet the voltage drop limits.

Sorry to butt in Adam, but that's not right. At full power a 9.5kW shower will draw 41.3 amps on 230V, which, at 7.3mV/A/m means you will get a voltage drop of around 0.3 Volts per metre. You could run up 30 metres and still meet the 4% limit.

6mm only meets the regs for an 8.5kW shower if it is in conduit.

8.5kW draws 37A and 6 sq mm twin-and-earth cable is rated at 47A if clipped direct, which is the reference method used for embedding in non-insulating building materials, such as plaster and tile. (And 35A if embedded in an insulating wall)

If it was me, I would rip out the old cable, install 10mm in a conduit and have the 9.5kW shower.

Me too, but for a short run 6sqmm will actually do (just). What is probably more important in this case is that the existing cable is tested for insulation resistance and teminations checked/made properly.

 

[AdamW]

I was using the TLC volt drop calculator

I did consider saying "6mm should be OK for a 2m run", but I don't think it is worth the risk, just in case someone reads this later and thinks "well my run is only 10m, I'll use 6mm too!"

a 9.5kW shower will draw 41.3 amps on 230V

Ah, but don't they rate showers at 240V? In which case it is 39.6A.

Glad for your explanation on clipped direct, I always assumed it meant fastened to the wall with cable clips, and buried in plaster counted as "embedded in a thermal wall". Worth knowing for future projects.

 

[dingbat]

I was using the TLC volt drop calculator

Don't believe everything you read on a website!

a 9.5kW shower will draw 41.3 amps on 230V

Ah, but don't they rate showers at 240V? In which case it is 39.6A.

They often rate them at both 230V and 240V. In the absence of this information I used the entirely theoretical UK standard supply voltage

 

[dw3101]

Whats up, dont like the advice received on scoobynet?

David