Electric Shower - basic questions

[prose]

Sorry in advance for the stupid questions!

I am about to replace our electric shower that has gone kaput. I am replacing an 8.5kW one with another 8.5kW unit but want to check that the cable and breaker is the right sort.

Is there an easy way to check that the cabling and breaker is the correct size?

Thanks in advance.

 

[Hann]

I am about to replace our electric shower that has gone kaput. I am replacing an 8.5kW one with another 8.5kW unit but want to check that the cable and breaker is the right sort.

An 8.5kW appliance will draw a current of 8500/230 = 37A, so an MCB of 40A will be required for the radial circuit with a cable size of either 6mmsq or 10mmsq depending on cable installation method and the length of cabling required.

You can check the current breaker and cabling installed at the consumer unit. First determine which circuit and breaker the shower is on. I'd advise you to turn the main switch off and prove that the supply to the consumer unit is indeed dead, before poking around with cables. There is a table somewhere on http://www.tlc-direct.co.uk/Book/Contents.htm that shows the dimensions of different cable sizes.

Other things to take into consideration are that this circuit will need to be protected by a 30mA RCD, so you may need to consider using a 40A 30mA RCBO instead of a MCB if there is no RCD protection already in place. Also supplementary bonding may be required depending on your installation characteristics.

It would be useful to know why the original shower went kaput.

 

[prose]

Thanks for that - very useful.

The shower was very old - I'd say probably about 10 years old and stopped heating the water.

Are all MCBs interchangeable or do I need to find one specific for my consumer unit?

Thanks again.

 

[bongos]

Are all MCBs interchangeable or do I need to find one specific for my consumer unit?

The same make as your consumer unit/other MCB's.

 

[ban-all-sheds]

If you had an 8.5kW shower before, and your new shower is 8.5kW, why do you think you should change the MCB?

And you can't just change an MCB - its rating has to be matched to the current carrying capacity of the cable, which in turn depends on cable size and how it's installed.

 

[trey]

How is replacing a shower covered by part P? Is it notifiable as it's in bathroom, or exempt for some reason?

 

[Hann]

How is replacing a shower covered by part P? Is it notifiable as it's in bathroom, or exempt for some reason?

The key word is 'replacing' - replacing fixed equipment is not notifiable. What's notifiable and not notifiable is covered on p.8 of Approved Document P (see link, and download section of resulting page)

http://www.planningportal.gov.uk/england/professionals/en/4000000001253.html

 

[ban-all-sheds]

How is replacing a shower covered by part P?

It's covered by it because it is work on low-voltage fixed electrical cables and fixed electrical equipment located on the consumer’s side of the electricity supply meter in a dwelling.

Therefore whoever replaces it is legally required to make reasonable provision in the design and installation in order to protect persons operating, maintaining or altering it from fire or injury.

Is it notifiable as it's in bathroom, or exempt for some reason?

Read Schedule 2B.

 

[Softus]

I ... want to check that the cable and breaker is the right sort.

why do you think you should change the MCB?

RTFP.

How is replacing a shower covered by part P?

All domestic work (on the consumer side) is covered by Part P, but it isn't notifiable because it's listed in 2B.