Shower circuit design.

Sparkingchip: 
 

Why would an electrician install a 10 mm twin and earth circuit protected by a B32 MCB for a 8.5 kW shower?

Twenty years ago I was taught to do circuit design one stage at a time completing the complete process. So I was taught that the very first thing to do is to assess the load and calculate the design current, then select an appropriate circuit protective device that matches or is greater than the load and go on from there completing all the stages of the design process in sequence.

When I did the 18th Edition course we did not do that, we did “bite sized“ chunks of the calculation, we were coached to pass the exam by just doing the bit of the calculation that was likely to come up as a question.

The teaching process is just simply inadequate, as we can see from this discussion people are coming up with circuit designs without following the full process and are failing to design a circuit for a water heater that complies with the Wiring Regulations or is really fit for purpose.

Does it matter  if electricians are just going to use an app on their phone to do the calculation? 

Yes it does,  because apps and software will only give the correct answers if you know what information to input, you still need an appreciation of the process. You  obviously would not get this design using an App or software as they would select a 40 amp device.

With the shower circuits you get to a point where you are just using a standard circuit and installing by rote, ensuring that you avoid running the cables in insulation, after you have done a few shower circuits you just keep repeating the design, unfortunately though if people have got the design wrong they may well keep repeating the mistake.

The train system needs a shake up starting at the top with City and Guilds and the other bodies that award qualifications to electricians working on down through the colleges and training centres to ensure that electricians are taught the complete requirements of the various aspects of the trade and not just bite sized chunks to get them through the exam.

Sparkingchip: 
 

Why would an electrician install a 10 mm twin and earth circuit protected by a B32 MCB for a 8.5 kW shower?

Twenty years ago I was taught to do circuit design one stage at a time completing the complete process. So I was taught that the very first thing to do is to assess the load and calculate the design current, then select an appropriate circuit protective device that matches or is greater than the load and go on from there completing all the stages of the design process in sequence.

When I did the 18th Edition course we did not do that, we did “bite sized“ chunks of the calculation, we were coached to pass the exam by just doing the bit of the calculation that was likely to come up as a question.

The teaching process is just simply inadequate, as we can see from this discussion people are coming up with circuit designs without following the full process and are failing to design a circuit for a water heater that complies with the Wiring Regulations or is really fit for purpose.

Does it matter  if electricians are just going to use an app on their phone to do the calculation? 

Yes it does,  because apps and software will only give the correct answers if you know what information to input, you still need an appreciation of the process. You  obviously would not get this design using an App or software as they would select a 40 amp device.

With the shower circuits you get to a point where you are just using a standard circuit and installing by rote, ensuring that you avoid running the cables in insulation, after you have done a few shower circuits you just keep repeating the design, unfortunately though if people have got the design wrong they may well keep repeating the mistake.

The train system needs a shake up starting at the top with City and Guilds and the other bodies that award qualifications to electricians working on down through the colleges and training centres to ensure that electricians are taught the complete requirements of the various aspects of the trade and not just bite sized chunks to get them through the exam.