Unsatisfactory EICR is an absolute shower?

I know this is not what you want to hear, but irrespective of any regulations or load, I would always install a 10mm cable.
I have just installed a replacement electric shower and I would never buy anything below 10.8KW. The shower that I installed only cost £240 which is nothing really when you want to keep your tenants happy. (Avoid "air boost" models which are a gimmick and the source of future unreliability.)
You are pretty near the limit on a 6mm cable but there is no arguing with your personal fault free experience, except perhaps by process followers & club members.
Any future commenters should note that this is about your installation and no one else's.

I had similar situation only difference is the electrician discussed with me before finalising the Eicr and replaced the 40a to a 32a and issued a Satisfactory Eicr. What I do find is a lot of electrician do milk it in multiple other ways too many to list in here. It is almost a blank cheque when they enter a property. Also the level of inconsistencies if you get 3 different electricians in the same property they will all come up with different things.

I'm finding EICR problematic in terms of getting consistent and reliable guidance and implementation. Fortunately I have a degree in electrical engineering and I can at least have a sensible conversation with any contractors. It must be difficult for any landlords who can't question what they're being told.

There is also the "response curve" to consider - "A" is the fastest-acting, and "D" is the most sluggish, therefore more appropriate for inductive loads, starting currents, etc.
This 8.5KW would represent an "overload" of almost 11% for a 32A breaker.
I believe (though I stand to be corrected!) that this should be OK for long enough to take a decent shower, especially with a "C" or "D" curve
It seems that we should expect the MCB not to trip for several hours with an overload of less than 13%, according to my reading of
https://img.c3controls.com/image/upload/resources/c3controls-Understanding-Trip-Curves.pdf
So, IF I'm right, this should solve the problem (provided the shower is not replaced with a more powerful one) - but some of you may have differing views?

When I needed to replace a shower in a rented property, the electrician did a through check of the electrics before he agreed to install and produced a minor works certificate to show compliance. Which I then showed to the person doing the eicr to show that all works were compliant at the time of install

If your electrician gave you a 5 year certificate and installed the shower before certifying and it ends in 2022 why didn't you get him to do the EICR if it needed to be done? Only asking as it would be for him to rectify any of his work if didn't conform wouldn't it?

Reply to the comment left by Judith Wordsworth at 14/04/2021 - 11:27
Which could still be done?

In my opinion, it is perfectly OK to wire up an 8.5Kw electric shower heater and fuse it with a 40Amp breaker, though on the border line, yes we all have to draw a line somewhere, it has worked flawlessly for 4 years , this cable is not overly underrated but just on the border line. even with a continuous long use it is never going to reach 70degrees in temperature and these cables can withstand a greater amount of temperature than rated , this is taken in at maximum length of the cable being 9m.

Reply to the comment left by Mike at 14/04/2021 - 11:39
I'm with Mike on this one.
Just for info I been a registered sparks for many years and would have quite happily given a satisfactory on a 6mm, 40amp and 8.5kw set up.

I would always have used 6mm on a 40amp b curve breaker (resistive load usage)- any talk of c and d curve breakers on this thread for an electric shower is nonsense should be ignored as such.

For regs purposes your main consideration is the installation method for the cable. Under reference method C as we call it (e.g under floorboards, buried in the plaster etc) , a a 6mm cable will carry 47amps. This current carrying capacity (ccc) will be derated if the cable is run through insulation or in conduit/ mini trunk etc.

The protective device also needs to be smaller than the ccc of the cable. When I went to school 40amps was less than 47amps. And bear in mind your load also needs to be smaller than the protective device- 36amps give or take in your case. So unless you have an reference method issue I ask where is the problem?- You dont have a problem.

Normally I would give more slack on circuit design (e.g your 54amp ccc ring circuit is proteced by a 32amp b curve breaker).

But lets apply commonsense- its a shower. Its used for 5- 15 minutes at a time maybe 2 or 3 times a day. Its not under constant loading. Using commonsense even a 9.5kw shower only runs at 40amps - 9500/240= 39.6amps.

Electricians have been arguing about this on the sparks forums for years and will continue to do so (6mm v 10mm) by the way so I expect someone to contradict me.

But I will continue to install at 6mm ref method C as i have done for 30 years problem free and will continue to pass installations i find that way.

And out of interest if there was an overloading issue on this set up it would show up on the insulation resistance test of the 6mm.

I've got properties on rent from the early 90s I've done this way and the IR is still smashing out my meter at >999megohms so that demonstrates there no issue there either.

As say sparks disagree all the time but thats my take.

Reply to the comment left by Judith Wordsworth at 14/04/2021 - 11:27
One of the reasons I didn't go back to him was that on the Domestic Electrical Installation Certificate the validity was shown as "5 years or change of tenant". There is no legal requirement to have a new EICR at every change of tenant, but if it is stated on the EICR then there may be?