Shower 32amp breaker

There is nothing to stop anyone sticking any old shower onto an original shower circuit. Happens all the time with plumber/builder/DIY electrical replacement [delete as applicable]. There always seems to be a default position on this new forum to blame an electrician. If you are an electrician with more than a few years experience, it being your primary occupation, you fully understand what happens in reality rather than in the cossetted world of BS7671 perusal.

With an arrangement as the OP, the B32 may become trigger happy over time. So it progressively will not tolerate 33-35 amps for shortish   durations. That is when an electrician gets the call. Personally, I see this happen more obviously when we get to 9kW plus. Even then, it is usually at least 6 to 12 months after the bigger shower is fitted. All that happens is one day they find the MCB will go off after 3 or 4 minutes of use.

In ye olden days 6mm and 7 kW was the norm. I would suggest that an electrician wiring a new shower circuit in the last 20/25 years would have defaulted to 10mm, even if the original fitted shower was 7kW or so.

At home I have 8kW on a 10mm on a B32. No problems, no issue for many years.

Showers last 5 to 10 years. They will be replaced often in a lifetime of the final circuit. So someone gets the call fix/replace a shower.  More often than not the client wants bigger bang for bucks, so will want the most powerful fitted. The circuit is not given any consideration, unless an electrician is involved. Of course, then the client may not like the answer, so goes back to the builder/ Plumber/ DIYr for the big bang for bucks.

If you feel the 8.5kW on the B32 is of concern, check all the connections for overheating. Check the MCB and the conductor for signs of heat damage. If there are no signs and it is reasonable that this has been in service for at least a few months, there is no problem to worry about.

Of course, things can go the other way. Someone may decide to change MCB for a 40 amp, but did they then consider what the installation method for this shower cable really is? Insulation is progressively now everywhere, especially with the extra layer thrown over the top on a grant. It is very rare that the shower cable is not going to be covered by something in an attic; with new builds in the last 20 years this insulation will also be in floor voids. So you could, in an effort you feel is required "to comply" with one bit of BS7671, fall foul of a more onerous consideration of BS7671.

All things considered, excepting the unknown installation method and unknown length of circuit, I would be quite comfortable with the existing situation. You would also accept that there is a very small chance, in the next one or two years, that you may need to replace the MCB.

There is nothing to stop anyone sticking any old shower onto an original shower circuit. Happens all the time with plumber/builder/DIY electrical replacement [delete as applicable]. There always seems to be a default position on this new forum to blame an electrician. If you are an electrician with more than a few years experience, it being your primary occupation, you fully understand what happens in reality rather than in the cossetted world of BS7671 perusal.

With an arrangement as the OP, the B32 may become trigger happy over time. So it progressively will not tolerate 33-35 amps for shortish   durations. That is when an electrician gets the call. Personally, I see this happen more obviously when we get to 9kW plus. Even then, it is usually at least 6 to 12 months after the bigger shower is fitted. All that happens is one day they find the MCB will go off after 3 or 4 minutes of use.

In ye olden days 6mm and 7 kW was the norm. I would suggest that an electrician wiring a new shower circuit in the last 20/25 years would have defaulted to 10mm, even if the original fitted shower was 7kW or so.

At home I have 8kW on a 10mm on a B32. No problems, no issue for many years.

Showers last 5 to 10 years. They will be replaced often in a lifetime of the final circuit. So someone gets the call fix/replace a shower.  More often than not the client wants bigger bang for bucks, so will want the most powerful fitted. The circuit is not given any consideration, unless an electrician is involved. Of course, then the client may not like the answer, so goes back to the builder/ Plumber/ DIYr for the big bang for bucks.

If you feel the 8.5kW on the B32 is of concern, check all the connections for overheating. Check the MCB and the conductor for signs of heat damage. If there are no signs and it is reasonable that this has been in service for at least a few months, there is no problem to worry about.

Of course, things can go the other way. Someone may decide to change MCB for a 40 amp, but did they then consider what the installation method for this shower cable really is? Insulation is progressively now everywhere, especially with the extra layer thrown over the top on a grant. It is very rare that the shower cable is not going to be covered by something in an attic; with new builds in the last 20 years this insulation will also be in floor voids. So you could, in an effort you feel is required "to comply" with one bit of BS7671, fall foul of a more onerous consideration of BS7671.

All things considered, excepting the unknown installation method and unknown length of circuit, I would be quite comfortable with the existing situation. You would also accept that there is a very small chance, in the next one or two years, that you may need to replace the MCB.