Electric Shower Advice Please...

[skomaz]

OK guys looking for some advice from a tame sparky.

Our electric shower, a Triton Ivory 8.5kw has given up the ghost twice recently but has been easily fixed (failing spade connections leading to a dodgy connection to internal microswitches). I've repaired it relatively easily (replaced the spade connections and put new microswitches in) but I'm starting to lose confidence in it and am wondering what will go next.

So I'm looking at new ones and was thinking of a like-for-like 8.5kw replcement but the wifey would like something more powerful if possible (something to do with washing hair). Hence I've checked out what is currently in place and have found the following:

The domestic supply is 100A to a Memera 21 100A consumer unit. The shower is then fed via an independent supply from a 32A MCB in the consumer unit via 10mm square cable and a 45A ceiling pull cord switch. Cable runs are generally short (the consumer unit is in the coal hole about 1m from the shower itself) but the cable run obviously goes up into the loft and back down, a total of maybe 8m, through a box out against an internal solid wall, the roof void and a cable chase out in a solid outer wall.

I'm slightly concerned that the current MCB is rated at 32A whilst the shower could be pulling up to 37A but it's never tripped out as far as I can recall in 9 years.

However, I'm pretty certain that on the basis of the above I could go to a maximum of 10kw without re-wiring (although would probably go for a 9.5kw unit) but that I would need to change the MCB to a 45A one and ideally would also need to add a 30mA RCD in the circuit as well.

Does this sound right (and yes I know about Part P regarding installations within bathrooms).

Finally - anyone got any good recommendations for temperature stablised replacements that are likely to match the electric and water entry points of the Triton Ivory I already have (I'm thinking maybe Triton T80si).

Thanks in advance

[rwbaldwin]

The limit for 8m of 10mm T&E on top of plasterboard is 10kW. You would need a 40A MCB on a RCD way (assuming you have a split load fusebox).

[Octygone]

As above ...and make sure the earth bonding in the bathroom is correct or ALL circuits in the bathroom (and I mean ALL) protected by 30ma rcd or rcbo

[skomaz]

Many thanks guys - that generally backs up what I thought.

The earth bonding looks good (I know from when I sorted the bathroom when we first moved in that the feed to the shower also feeds the toilet cistern and that there is an earth bond to them, along with another under the bath and I think one near the sink but I'll check).

It's not a split load set up (no RCD to be seen in the consumer unit) so could one be fitted in-line in the circuit rather than changing the whole consumer unit?

Edited 25 September, 2009 by skomaz

[Octygone]

Bond wire should link all metalwork and an earth point on each and every circuit in the bathroom...so cold pipe..hot pipe ..shower circuit...lighting circuit...radiator pipe if central heating etc. etc.

Depending on what make your distribution board is you can get a RCBO to fit....or a new one way distribution board with a 45 amp mcb and rcd.....or an RCBO to fit but this is a bit more involved.....and then of course get it all tested by a qualified tester to stay within the law

[No Waiting]

on the basis of the above I could go to a maximum of 10kw without re-wiring

Shame, as I can really recommend the Mira Sport 10.8Kw...

[skomaz]

Thanks again guys - all good advice as usual and much appreciated. I think breakers for the Memera 21 board are getting difficult to find now so I reckn I might be into a new single way board...

However, I think I may have found the reason for the recent failures... I usually clean the bathroom but SWMBO has taken it on herself to do it the last few months and has apparently beenusing the shower itself to rinse the top of the electric shower (so to speak). Now I know the top of the box has a seal on it but it's only going to be IPX4 rated and I reckon it would need to be X5 or X6 to withstand direct sprays...

I have seen the Mira as I think they do a 9.8kw version.

[skomaz]

Guys - need some more info - The shower has continued to work but is getting dodgy again so I've bitten the bullet and bought a new one at 9.5kw.

I have also found a source for the Mem MCB's that I would need but - there is no way that I can get an RCD to fit (no spare space and they never made them or RCBO's to fit the board.

Hence - could I:

1) fit a two way RCD/MCB mini consumer unit in-line downstream of the existing consumer unit with a 30ma RCD and a higher rated MBC to provide the RCD cover?

2) get a 1 way enclosure with an RCD only and fit that in line downstream of the existing CU

3) Or would I be better taking the supply from the existing consumer unit to a new mini consumer unit with appropriate RCD/MCB such that the supply to the shower doesn't go through the existing board/MCB at all. If this is the case could I do this with 10mm^2 cable for this or would it need to be new meter tails from the meter?

I'm favouring (2) at the moment as it's easiest!

Sorry for all the dumb questions but every time I ask someone I get a different answer...

Edited 14 January, 2010 by skomaz

[VWD]

Thanks again guys - all good advice as usual and much appreciated. I think breakers for the Memera 21 board are getting difficult to find now so I reckn I might be into a new single way board...

Strangely enough -remembered mine is Memera -just checked and it's a 21 ,with two ELCB fitted -one on lights ,the other on the higher current stuff - as is my daughter's house.It's a 100A unit ,but on a recent meter change they down rated the supply fuse to 80

I got CIRCUIT breakers at a little shower shop locally -might be worth a search round the little guys -especially shower shops .But suspect that going from the rewire date on mine that ELCBs won't be available any more -my little shop certainly didn't have any .

[skomaz]

Strangely enough -remembered mine is Memera -just checked and it's a 21 ,with two ELCB fitted -one on lights ,the other on the higher current stuff - as is my daughter's house.It's a 100A unit ,but on a recent meter change they down rated the supply fuse to 80

I got CIRCUIT breakers at a little shower shop locally -might be worth a search round the little guys -especially shower shops .But suspect that going from the rewire date on mine that ELCBs won't be available any more -my little shop certainly didn't have any .

Yep had a phone round all the local wholesalers and none in stock but a search of the internet has come up trumps wth both 40A and 45A QEB MCB's. Hence I now just need and RCD.

I've also just read my post above again and reckon I must have been having a blonde moment - 1 and 3 seem overkill now I've got the MCB's so it looks like 2 is the way to go and only about £20.

Edited 15 January, 2010 by skomaz

[Anolannon]

What about 9.5kw electric shower ,has anybody tried it?