How much of an upgrade do I need?

[StuartX]

Hi all

Our existing electric shower has recently died, after its heating being a little erratic for a while. Likely the elements have packed up. Don't know how old it is (we've lived in the flat for two years now, building is from the 60s, though I suspect shower was fitted sometime later). Anyway, looking to pretty much replace it with something similar. Current model is a Neptune Solo 8.5kW. Thinking of getting a Triton T80xr 8.5kW.

However, having done some reading up (including the installation manual of the Triton), it looks like the electrics need upgrading. For starters, I can't see an RCD. Then, the shower's fuse is 32A and it seems 40A is recommended for 8.5kW. I don't know the wire's thickness - but the flat's pretty small so the length can't be that long. From the positioning, it's likely run through the loft.

Here's a photo (not great quality - sorry) of the fuse box. It looks a bit retro to me! The MCBs are 4x 32A, 1x 16A, 1x 6A (all B). What I'm wondering is:
* Is it a big task to add an RCD to this (given there are no slots)? I guess it can go externally if needs be?
* Can the 32A be simply swapped with a 40A? There's only the two of us, we have gas heating/cooker, and are unlikely to be putting any other high loads through when having showers.
* Despite the recommendations - can a 32A be OK for a 8.5kW given the above? We don't have particularly long showers (that's what baths are for!). If there's any doubt, or it's case of legal requirements, no problem... we'll do the sensible thing. But given the current one seems to have been OK, I have to ask.

I shall definitely be getting an electrician in to fit the shower and do any upgrade work that's required, but I'm asked this so I can get an idea of the scale of the work first - and make sure they do the right thing!. If it's too big, then downgrading to a 7.5kW is an option. I'd ideally like to buy the unit and get it fitted/plumbed before getting the electrician in, to avoid having to pay for two visits - which means making a decision before hand.


Many thanks in advance!

 

[Spark123]

The biggest size for a 32A protective device is 7.5kw.
You should not upsize the MCB without first knowing what size the cable is an that it is adequate for the altered conditions. If the cable isn't big enough then either you are stuck with a small shower or you need to uprate the cable. You may find the CU will not accept a larger MCB base, or if it does only in one position. You need to know what size supply you have and if it is adequate for the new shower. RCD protection is recommended for showers and may be required by the manufacturer.
The electrician will also check that your main bonding i.e. from the metal block next to your CU to the water, gas etc is adequate. Also if he is working to the 16th edition the supplementary bonding in the bathroom is OK.
Depending on the scope the work may be notifiable to your LABC under part p of the building regs hence if you are looking for a spark it is advisable that they are a member of a competent person such as NAPIT, NICEIC, ECA, ELECSA etc, - search here: http://www.competentperson.co.uk/search.asp

 

[Cremeegg]

I'd advise against downgrading any electric shower. Why have shower ratings increased over the years - to provide a better volume of hot water. A 7.5kW shower will feel pretty cold in the winter when water temperature is the lowest. Go for a 10.5kW shower and upgrade the electrics to go with it - they are pretty retro!