Replacement of original Dolphin shower which also feeds pump

Dartlec · May 30, 2021

Run into this today at a house my nephew is moving into....

[ElectriciansForums.net] Replacement of original Dolphin shower which also feeds pump

Original Dolphin 860 Shower (8600W) installed on 6mm Twin and Earth - maybe 15m length from the CU, which is an old MK board installed in 1986, but RCD protected - on a 45A MCB.

So far so 'normal'....

However, there is 2.5 T&E fed from the positive side of the valve, which feeds a pump in a cupboard above (via a FCU).

They'd purchased a 9.5kW (@240) replacement, which I wasn't comfortable installing on 6mm cable given that the route is unclear - though mostly between floors I think , but the last part of it is in trunking down the wall to the fitting itself...

The pump is slightly throwing me too - it's clearly an old pump that works when turned on, so was fed from effectively a 'switched live' in the shower - fused with a glass fuse in the shower (FCU before pump above).

Is is possible/compliant to do this in any modern shower? Obviously many of them have electronic internals now anyway, so not always clear where a suitable feed could be taken.

Since there is a toilet next door with sink, which has hot water fed from a boiler, I suggested that they get a plumber to put a normal shower in instead....

Otherwise, It would seem that the way to do it properly now would involve changing the pump to one that has a trigger sensor?

On 6mm of 15-20m, I reckon they'd need 7.5kW (@240) - and that I should probably reduce the MCB to 30A (Old MK 3871 Type 2 board). Having said that, there is no obvious overload of the existing cable, which has been in since 1986 by the looks of it....

Does that sound right, or am I missing an obvious answer that is commonly done? Anyone replaced one of these in a similar situation?

brianmoooore · May 31, 2021

There are electric showers that heat water and have a built in pump. Mira Elite is one I've fitted, but there are probably many others available.

timhoward · May 31, 2021

It may be that the pump predates other changes to the plumbing, eg if boiler is now a combi it might be mains cold water now and the pump might not be needed.

If it still needs a pump, as well as an electric shower with a built in pump, the other option is a simple power shower with just the pump (e.g Mira Go), taking the hot and cold feed from the room next door as suggested. Only 3 amps too then!

Dartlec · May 31, 2021

timhoward said:
It may be that the pump predates other changes to the plumbing, eg if boiler is now a combi it might be mains cold water now and the pump might not be needed.

If it still needs a pump, as well as an electric shower with a built in pump, the other option is a simple power shower with just the pump (e.g Mira Go), taking the hot and cold feed from the room next door as suggested. Only 3 amps too then!

From what I could see It's an older boiler, heating a tank (with back up immersion). Though the other shower in the property is fed normally with no pump that I could see, and as far as I know works fine....

Didn't check whether the water was mains or not now - or whether mains is available in the adjacent toilet... Will have to look into options with pumps, in case a plumber decides a normal shower isn't suitable....

UNG · May 31, 2021

Dartlec said:
From what I could see It's an older boiler, heating a tank (with back up immersion). Though the other shower in the property is fed normally with no pump that I could see, and as far as I know works fine...
Didn't check whether the water was mains or not now - or whether mains is available in the adjacent toilet... Will have to look into options with pumps, in case a plumber decides a normal shower isn't suitable....

It could be that the property has had low mains water pressure problems in the past which may have since been resolved. If you have 2 showers would the mains water pressure be sufficient to run both at the same time without any issues