Actually in addition to the C&G electrical installation and design qualification certificates I have a certificate issued by Triton the shower manufacturer to say I have been trained to install showers.
I attended a free two day training course at Triton and I was the only electrician who attended that particular session, the others were plumbers and guys leaving the armed forces doing repatriation training.
We did the electric showers on the second day, as we started the trainer looked around the room at his twenty students and said “Actually there’s only one person in the room who can install electric showers” it seems I’m still in the minority over fifteen years later.
Learning by rote and “monkey see, monkey do” are all very well until you encounter a situation which you have not seen before and isn't in the textbooks. I have no doubt that this forum provides the answer to some of these questions, but it doesn't help when you are on site and need the solution right away. That's when being able to work it out is required.
And it might be better in another thread, but ‘what does an electrician need to know ? ' is actually a very interesting question, and not a simple one to answer.
There is an odd mix of learn by doing, such as how to dress cables neatly into awkward shapes, terminating SWA or MICC, and the physics/academic that relates to current ratings, temprature, diversity and so on.
Then there is a mix of roles - some sparks will spend their entier life maintaining designs by others, and arguably need to be very good at fault finding, but no great new designs needed. Others will be the reverse and spend most of the time designing for new, and of them there will be many copying the OSG, but a few going out onto a limb with the unusual locations, extreme environments or weird loads, and then there is a cross-over with the alarms and antennas sort of folk, and the audio visual and theatrical. All electrics, but with very different skills and varying degrees of custom/practice vs on the fly redesign.
I agree (though I missed it in the original Q too) that anyone claiming the competence to install an 8.5kw shower should be up to division of watts by 230 to get a current, and selecting the rest of the parts to match or exceed that. It quite possibly will not trip on a 32A breaker but that is not a design process that withstands proper scrutiny.
I agree (though I missed it in the original Q too) that anyone claiming the competence to install an 8.5kw shower should be up to division of watts by 230 to get a current, and selecting the rest of the parts to match or exceed that. It quite possibly will not trip on a 32A breaker but that is not a design process that withstands proper scrutiny.
Mike.
Quite, 8500 divided by 230 is hardly a difficult sum particularly for people who have a mobile phone at hand to use as a calculator.
On the way out of the house today a threw the question at my wife ” If you have a shower which uses around 37 amps do you need a 32 amp circuit breaker or a 40 amp circuit breaker?” and without any training in electrical installation at all she got the answer right and said 40 amps.
With all due regard to my wife and well done her for getting the right answer, it’s not a difficult question.
I carried out an electrical inspection and test today and will issue an E.I.C.R. Just out of interest, and because I could not see a rating label on an unfamiliar electric shower protected by a 45 Amp M.C.B., I carried out a load test with a clamp meter with the shower set at maximum. The meter read 37 Amps. Why a 45 Amp M.C.B. in this instance? The whole installation is protected by a 50 Amp M.C.B.
I agree (though I missed it in the original Q too) that anyone claiming the competence to install an 8.5kw shower should be up to division of watts by 230 to get a current
Or 240 … see earlier posts. For example, this 8.5 kW shower is only 8.5 kW at 240 V, 7.8 kW at 230 V (although still if you have a look at page 2 of the manufacturer's instructions, a B40 is recommended by the manufacturer).
Which is the same answer as you get from the Wiring Regulations.
Sparkingchip, I think you have missed the point that Regulation 411.3.3 only applies where protection against overload is required. It's arguably not required for a shower (although see my earlier post, I would prefer it).
However, I'd agree it makes not a blind bit of difference if the shower manufacturer is recommending a B40, and also if you take into account frequent overload and loading factors for the CU and adjacent mcb's …I would never select In < Ib.
Surely the breaker is protecting the cable, not the load. By that logic it should have a 37A breaker then to protect the shower? If the cable is big enough to take 45A then it could have a 5w LED lamp on the end and still be ok
Surely the breaker is protecting the cable, not the load.
The breaker has to protect the cable against fault current ("adiabatic" or “let through” in the case of mcb's and RCBOs) - Section 434.
Depending on the nature of the load, the breaker may have to protect the cable (and load) against overload current (Reg 433.1.1). Protection against overload current may be omitted if the load is fixed - Regulation 433.3.1(ii) - provided protection against fault current is provided according to Section 434.
Further, OCPDs may be expected to protect a load as well as a cable (both are, according to BS 7671, classed as electrical equipment, and if the load is a fixed item of electrical equipment, it's part of the installation in terms of its selection and erection at least) … although I understand there is a misconception in the industry about this.
