Shower 40amp fused

[pdgwent]

Hi,
Could anyone assist me with the following ratings.

My shower is 8 - 9.5kw, with 10mmsq cable, approximately 9-10mtrs in length from CU. Have pull cord switch etc, but noticed in the Wylex CU box
we have 40 Amp HRC Fuse Carrier/Base.

Is this sufficient.?

Cheers!

Peter.D

 

[Albert]

The 10mmsq, in the worst scenario can carry 43A (the best scenario up to 70A). The max consumption of your unit is about 41A, if you take in consideration diversity it will be under 30A. So the cable is ok for the load, the fuse has to be of a value smaller than the cable capacity, if it is 40A it seems ok to me. The volt drop is about 1.8V which is well in the 4% limitation. One more thing is missing and it is the Zs (earth fault loop impedance value), this value is important as it will verify that the fuse will trip in case of fault. from experience; I do not think that there is a problem in this type of arrangement at this size but you might have a bad earth connection or another factor that will increase the Zs value and than your fuse might not trip when it should.

 

[pdgwent]

Thank you Albert for an informative reply.

Best wishes,

Peter.D

 

[ricicle]

if you take in consideration diversity

Why would you use diversity on a shower circuit.On it's max. setting it will be drawing full current for the whole duration it is on.

If you are in any doubt about the Zs of any circuit then an RCD can be used to ensure disconnection times are met.Most manufacturers (and sparkies) recommend the use of 30 mA RCD's for electric showers and IMO are essential.

 

[GaryMo]

if you take in consideration diversity

Why would you use diversity on a shower circuit.On it's max. setting it will be drawing full current for the whole duration it is on.

You wouldn't. A shower is classed as an instantaneous water heater and as such is exempt from diversity so its 100% of its FLC.

 

[Lectrician]

Diversity? On or Off?

LMAO

 

[Albert]

It is possible that I looked on the wrong column in the OSG , sorry, yet I checked it for full load so I think you should let me off the hook .

IF this is a new circuit in the bathroom (special location), the work has to be notified and even more important be tested and certified. I do not agree that the RCD is there to cover for a possible fault that results of not testing it properly... I agree that RCD (RCBO) is a good idea, do not forget that the RCD itself has to be tested (x1/2, x1, x5, I delta n all in 0deg and 180deg).