Shower Cable

[SUNRAY]

True. I was talking about as situation in which overload protection is actually required - and, as you say, in some situations some people will argue that the load is such that an 'overload; is 'unlikely', such that the regs only require fault protection.

I can't think of any particularly good reason why that argument cannot be used in relation to a circuit (hence cable) supplying (only) an electric shower, but I have to say that I don;'t recall having seen the argument used in that context.

Kind Regards, John

I feel it has been mooted within this forum, in fact I'll go further and make the statement for exactly the situation you have calculated for based on the 45.7A

 

[JohnW2]

I feel it has been mooted within this forum, in fact I'll go further and make the statement for exactly the situation you have calculated for based on the 45.7A

'The arument' (that overload protection is not required) usually shows its face in the context of ovens or immersions. As I said, I don't recall it having been wheeled out in relation to showers, but can't really see why it could not!

Kind Regards, John

 

[EFLImpudence]

Scousepark is correct, the circuit breaker needs to be below the ccc of the cable and higher than the design current to comply. Even in otherwise perfect conditions applying the 0.95 Cmin correction factor to 6mm cable (47A) brings the ccc to below 45amps. The next available circuit breaker is 40amps, so although ‘6mm will be fine’ it doesn’t comply.

Aren't you applying the Cmin 0.95 in the wrong situation? It doesn't apply to CCC as such.

If it happened then the current would also reduce.

At 216V (actual 0.94) the [10.5kW @ 240V} shower would only draw 39.4A

 

[JohnW2]

Scousepark is correct, the circuit breaker needs to be below the ccc of the cable and higher than the design current to comply.

Indeed - although, per subsequent discussion, not if one decides to invoke 433.3.1 and conclude that overload protection is not requured/

Even in otherwise perfect conditions applying the 0.95 Cmin correction factor to 6mm cable (47A) brings the ccc to below 45amps. The next available circuit breaker is 40amps, so although ‘6mm will be fine’ it doesn’t comply.

Eh? Since when did Cmin have anything to do with CCC or overload protection? It surely only exists to correct 'maximum Zs' figures so as to ensure adequate fault protection with supply voltages down to 218.5V, doesn'r it?

The length of the run is also a factor for complying with volt drop (I make it around 35m max length to meet 5% volt drop on a 10.5kw appliance on a 6mm cable).

The 5% figure is only guidance. Regulations only require that VD should not be so great as to "impair the e'safe functioning" of the load, and I see no way in which a reduced supply voltage to a shower could possibly render it 'unsafe'.

Ignoring volt drop the next length limit will be to meet minimum fault (short circuit) current for the breaker, this could be a factor with a high Zdb/Ze and long run to the shower.

Sure, that might be an issue in some situations. However, I presume you are referring to my response to the suggestion that the OPD rating depends upon the length of the cable run - which it doesn't. The OPD must be rated appropriately in relation to cablke and load, but not anything else..

Kind Regards, John