cable and rcbo size for 8.5kw shower

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using the calcs, please can you confirm the correct cable size and rcbo for a 8.5kw triton electric shower. The cable will run from the consumer unit, 11m to the isolater switch, 2.4m of which is in a wall cavity in conduit the rest running in floor joists, then 5m from the switch to the shower, thanks
 
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Well, the calculation gives 6mm² cable and 40A RCBO.

That assumes the cable runs through NO thermal insulation.
Also, if the cavity to which you refer is the outside wall cavity this is not acceptable.

Edit - Sorry I missed the conduit so unless you can run the cable surface clipped or buried in plaster it would be necessary to use 10mm² cable.
 
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Don't forget, its a black gloss shower. Maybe it has different characteristics to all the other showers in the World.
 
Yes, "Oh dear".

You asked this question before: //www.diynot.com/forums/electrics/what-size-wiring-elecrtic-shower.294455/#2143415

and you were given the answer before: //www.diynot.com/forums/electrics/what-size-wiring-elecrtic-shower.294455/#2143549

Then you asked it again: //www.diynot.com/forums/electrics/what-size-wiring-elecrtic-shower.294455/#2143636

and you were given the answer again: //www.diynot.com/forums/electrics/what-size-wiring-elecrtic-shower.294455/#2143999

Yet here you are, asking the same question for the 3rd time.

Either you are unable to work it out, or unwilling to do so.

Whichever, please just go away and get an electrician.
 
i didnt have the shower before but its arrived today. Is it best to put a 30amp rcbo in with 10mm cable, i could always uprate the rcbo that way
 
Just put 16milli in with a 50A RCBO and then you're future-proof.
 
Can't be less than 50A surely? "The regs are in the van & I can't be bothered..." scenario.


EDIT: These are the figures TLC has supplied:

Required Cable Size 16 mm
Voltage Drop 1.61 Volts.
Percentage Drop 0.70%
Current Load 52.0 Amps
Max Cable Load* 53.6 Amps
 
Tut tut. 16mm², Reference Method 103, Iz=______?
Can't be less than 50A surely? "The regs are in the van & I can't be bothered..." scenario.
I was surprised, too, but it's actually only 42.5A. However, whether or not what the OP has decribed is necessarily Method 103 (the worst of all) is maybe not so certain.

Kind Regards, John.
 

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