MCB cuts off

[funkye]

Hi I have a 10.5kW shower (ivory III) and when I turn it on higher power, MCB cuts off.

I have 30 amp MCB at the moment, main circuit is 100 amp.
Can I put there 40 amp?

I'm not sure, but wire to the shower is 6mm. How can I find out exact measure of the wire?

Thanks.

 

[Aragorn84]

Your shower is too powerful for that 6mm cable.

It should be on a 10mm cable, protected by a suitable breaker.

Has it just been fitted?

 

[Carpman]

10.5kw shower will pull 45.7A

So fitting a 40A will still cause tripping of the MCB.

Assuming your cable 'is' 6mm it has a current carrying capacity of 47A.

I'm guessing that you have recently upgraded the shower ??

I would suggest you either down grade the shower or replace the cable and circuit protective device.

10mm cable and 50A circuit brealer would do nicely all protected by an RCD

 

[funkye]

it's been fitted 6 months ago.

So we use it half a year with 30 amp MCB.

and what if I put there 40 amp?

In the manual they say 6mm for 38amp

 

[Steve]

In the manual they say 6mm for 38amp

Why? Your shower pulls 47 amps!

You need a 50 amp MCB and 10mm² cable. End of.

Or a new 7.5kw shower. Sorry.

 

[funkye]

would 8.5kW shower work with 40 amp breaker and 6mm cable,
or is it better to replace cable with 10mm and use higher breaker?

 

[Steve]

The thing is, you cant go uprating the MCB without knowing full well the route of the cable. If it runs through insulation or is bunched with other cables, it may not be capable of carrying 40 amps.

Its cheaper to replace the cable and MCB, but you will need an electrician, or to notify, so this ramps the cost up. But the same applies to replacing the shower itself - it needs notifying. But whoever installed it should not have left it like this.

 

[thompsk]

Put a 40A in there you run the risk of the cable melting ! and a house fire, upgrade the cable and the MCB do a calc here http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

 

[Carpman]

would 8.5kW shower work with 40 amp breaker and 6mm cable,
or is it better to replace cable with 10mm and use higher breaker?

8.5kw pulls 37A

So yeah that will fit nicely with a 6mm cable and 40A circuit breaker.

providing that you 'DO' have a 6mm cable and the circuit is protected by an RCD.


Rgds



Carp

 

[Aragorn84]

Still depends how the 6mm is routed as to wether it can safely carry even 40A...

 

[Steve]

would 8.5kW shower work with 40 amp breaker and 6mm cable,
or is it better to replace cable with 10mm and use higher breaker?

8.5kw pulls 37A

So yeah that will fit nicely with a 6mm cable and 40A circuit breaker.

providing that you 'DO' have a 6mm cable and the circuit is protected by an RCD.

Also provided that the cable is capable of carrying 40A. The rating of the protective device must be equal to or less than the rating of the cable.

 

[funkye]

Thanks guys,

how much should be replacing the cable approx.?

 

[Carpman]

You live in the filthy south, it could range from anything between a bucket of jellied eels or a monkey.


Seriously though just contact a few electricians in your area for a quote.



Rgds



carp

 

[Spark123]

The 10.5kw is usually the 240v rating so it will pull around 44A, still too much for a 30A breaker but an electrician will be able to sort it out properly.