Using a 8.5KW shower on a 6mm circuit.

[Goody]

Hi,

This is the scenario;

The kitchen is now converted into a bedroom and there is a bathroom adjacent to that bedroom. The client asked me to re-route the 6mm cable and install a electric shower in the bathroom.

This is what I proposed to do:

1. 8.5KW shower (8500/230=37 amps)
   
2. 6mm T&E cable (current carrying capacity 46 amps, reference method C - Table 6E1 On-site Guide)
   
3. 40A MCB

10mm would be ideal but 6mm is what I am given to play with.

Please, guys, let me know if I am being over ambitious!

Cheers!

 

[mattmoo1974]

Nothing wrong with that mate, Just IR the cable to make sure its a healthy piece of 6mm

 

[electromonkey]

I second that. I dare say a 32A breaker would be sufficient.

 

[Dan23584]

I second that. I dare say a 32A breaker would be sufficient.

I agree, how often is that shower going to be run at full whack for long periods of time.

 

[PB1]

In practice also the supply may be closer to 240v, so actual current drawn would be closer to 35 amps than 37.

 

[mattmoo1974]

I agree, how often is that shower going to be run at full whack for long periods of time.

Never have kids!!

 

[sparky1502]

i would as a matter of course put in a 32a mcb

 

[Knobhead]

In practice also the supply may be closer to 240v, so actual current drawn would be closer to 35 amps than 37.

How did you work that out? Given it's a resistive load.

 

[micknew]

8500 divided by 240=35.41, simple?

 

[Knobhead]

Now work out the resistance of the load and work from there.

 

[micknew]

Unless ohms law has changed you will get the same result.

 

[PB1]

Ok, so r=v/i, r=240/35.4, r=6.7 ohms

 

[Amp David]

I second that. I dare say a 32A breaker would be sufficient.

Yeah, how many time has this been done with no problems at all, and showers been in for 10 years!

 

[Knobhead]

In the OP it states 230V. Using 230V it works out at 6.22 Ώ. Use that with 240V and you will get 38.5A.
Nobody has changed ohm’s law. Same resistance with a higher voltage gives higher current. Simple?

 

[micknew]

You are right of course, missed the point that the stated KW is calculated at the 'new EU voltage' of 230V.
I stand corrected.

 

[telectrix]

well, i would always use 6mm , method C, up to 9kW.

 

[telectrix]

buried in a masonry wall or uninsulated stud wall is still method C.

 

[fuzzydunlop]

Not to cast aspersions on goodys clients but I'm guessing (know) to comply with fire/building regs (esp being given permission to turn a kitchen into a bedroom) a degree of insulation would be required

 

[Dan23584]

Goody, do you post a question on here for every job you do?

If your customers were ever to see your posts you'd never work again

Is the point of this forum not to seek advice?

 

[PB1]

In the OP it states 230V. Using 230V it works out at 6.22 Ώ. Use that with 240V and you will get 38.5A.
Nobody has changed ohm’s law. Same resistance with a higher voltage gives higher current. Simple?

Ah yes of course simple, except for when I'm being an idiot. Thanks Tony.