Wiring in a whirlpool bath

[John Orrett]

Hi all; my missus wants a new bathroom suite, and we are (sorry - she is) looking at a whirlpool spa type thingy bath. I'm just wondering about the electricity needed for the pump. The nearest electricity is next door in my daughter's bedroom through a normal plug socket. The spec says that it must be protected by a fuse switch (30 mA) by a 31A or 16A fuse. Furthermore, this circuit must contain a dual-pole circuit breaker with a contact aperture of at least 3-mm. The potential equiliser (at least mm squared) is to be connected to the motor plate. At this last bit, all I saw was white noise :-). Our local friendly plumber will hook up the power to the pump but won't fix the wiring. Question is - is it OK to feed this out of a normal plug socket or does it need something meatier? I'll be getting a local spark in to do the job needless to say! Thanks John

[Dan delaMare-Lyon]

John, - Saninova bath by Maax?

In which case my installer has used our shower circuitry (as we no longer have an electric shower. Downrated the MCB to 16A from 32A (it was powering a 9.x kw electric shower) - a dual pole isolating switch with a 5A fuse is in line with the pump on the bath (as the total draw on the motor to the whirlpool is ~200W so 5A is *plenty* and allows for any inrush). It being the shower circuit it already had a ceiling mounted 45A pull switch that breaks the circuit - which is nice as we have a toddler who seems to like to press buttons.

The bath does have a "no water" protection against this - but the total isolation is nice :)

The whole CU is protected by an RCD of sufficient sensitivity to cope with the needs of the whirlpool kit anyway.

Have to say - he was quite suprised how cryptic the information was about it - but when he actually sat and worked it through - it all made sense :) We were lucky that we could re-use the shower wiring though. We'll be putting a pump on the HW side in the cupboard with the water tank tho as our hot flow is a little bit piss poor - so the bath takes a good while to fill :)

Cheers Dan.

[G&M]

Okay - no problem for me then. But surely the shower must have some form of HD kill switch so putting everything else off it shouldn't be a problem ?

[Owain]

"John Orrett" wrote | Thanks for that Dan. We still have our shower (we actually want to | upgrade to a power shower) as I like a shower wheras my missus | likes a bath.

A *power shower* is okay, as that only requires a small amount of electricity for the pump.

But a 10kW instantaneous shower fully loads a 40A circuit.

Owain

[Smudger]

OK, the point is this.

Modern Instantaneous showers have a power rating of 9-10kW.

So, the current demand is 10000/240 = 41.6Amp.

The biggest MCB you will get for a domestic installation is 45Amp.

In order to specify the cable, you have to take into account the rating of the MCB (45A); the demand current (41.6A) which, when combined with the length of the cable gives you the voltage drop; the installation method, which may mean that you have to derate the cable; and you must have a disconnection time of