Shower Cable Rating - Slightly Different!

[Mirez]

Hi Guys, I've got an 8.5Kw shower which I need to replace - all good shouldn't be a problem (ha-ha)... I looked at the breaker and its 40amp, checked the cable exiting the box and its 10mm. Great, a 9.5Kw shower will be nice upgrade.

Now the problem is I've just come to fit the thing and removing the old shower reveals a 6mm cable, further investigation reveals that it changed from a 10mm to a 6mm at the isolator pull cord.

So, firstly I'm fairly happy that I can't fit a 9.5Kw using this setup as 6mm isn't sufficient - correct?

Secondly, to my mind I need to replace this (2ish meter) section of 6mm as this current set-up isn't acceptable anyway (as the cable down the line is a lower rating then the MCB) - again correct?

Cheers!

 

[wingcoax]

Replace the cable and make sure all connections are tight. You are lucky, in that i have found cables the" other way round" even to the extent of 2.5mm changing to 6.00mm.

 

[Risteard]

Secondly, to my mind I need to replace this (2ish meter) section of 6mm as this current set-up isn't acceptable anyway (as the cable down the line is a lower rating then the MCB) - again correct?

Not necessarily, as long as it provides adequate fault protection (which could be proven by calculation). Overload protection won't be required for the shower as it is a fixed load and therefore cannot overload.

 

[PrenticeBoyofDerry]

I personally feel although it's a borderline case as far as device and load ratings, that I would replace the 6mm cable for 10mm. The reason being that you have found/noticed this, maybe if you leave it as is, sometime in the not so distant future someone may decide to upgrade shower to 10.5kW say, look at the 10mm think that's great and not notice the 6mm (or chose to ignore it once purchased new shower)!

 

[Mirez]

Thanks guys, I think that's exactly what I will do - I can keep my 9.5Kw shower then lol. Cheers!

 

[EFLImpudence]

So, firstly I'm fairly happy that I can't fit a 9.5Kw using this setup as 6mm isn't sufficient - correct?

If the manufacturer states 9.5kW @ 240V AND the 6mm² cable is not in thermal insulation then all is perfectly acceptable.

Perhaps the 10mm² was installed because of insulation but no need to replace the 6mm²

Secondly, to my mind I need to replace this (2ish meter) section of 6mm as this current set-up isn't acceptable anyway (as the cable down the line is a lower rating then the MCB) - again correct?

No, not correct. It's fine (with the above insulation proviso).

I personally feel although it's a borderline

No such thing as borderline. It either complies or it doesn't.

if you leave it as is, sometime in the not so distant future someone may decide to upgrade shower to 10.5kW say, look at the 10mm think that's great and not notice the 6mm (or chose to ignore it once purchased new shower)!

That'll be their fault. Mirez noticed it.

No need to allow for idiots in the future.

 

[westie101]

Though not really required as some say, I would suggest that it comes under the heading of good practice and would strongly agree with the OP that it is the right thing to do.

 

[EFLImpudence]

Nope, no need.

It could have been designed like that, properly.

 

[PrenticeBoyofDerry]

No such thing as borderline. It either complies or it doesn't.

Fair enough

That'll be their fault. Mirez noticed it.

No need to allow for idiots in the future.

As stated, my personal opinion on the best/most sensible solution.
No need to also ignore potential idiotic behaviour in the future or make provisions for upgrades.

 

[mfarrow]

If we future proof for every person's what-ifs then copper prices would be double what they are at the moment.

 

[ebee]

Copper prices are not what they are at the moment anyway- they are double.

Did we mention Part P here?

 

[PrenticeBoyofDerry]

If we future proof for every person's what-ifs then copper prices would be double what they are at the moment.

They can then consider the copper within the walls and ceilings as an investment!