Swapping electric shower for power shower

Yes, that can be done. A 3A fused spur should be fitted between the pull cord and the shower.

Where is the hot feed coming from? Can you get straight to the cylinder?

There is no life threatening danger in retaining the 40A existing supply to the 45A switch. From a practical perspective 10mm cable is too large for the terminals on most fused connection units. It is therefore often more practical to use smaller cable from the isolator to the fused connection unit and replace the RCBO. But if you were to use a suitably sized fused connection unit, as used in industry, there is no reason why you couldn’t retain the existing supply as is. The protection provided to the shower is unchanged - It has 3A overcurrent protection provided by the fuse in the spur and also 30mA leakage detection provided by the existing RCBO.

The power shower may well use 3 times more water, but it’s not necessarily the case that it will cost 3 times as much to run, as the cylinder can be heated using lower cost means such as; off peak electricity, an oil / gas boiler, or heat pump - These are 1/3 to 1/2 the cost of standard rate electricity.

Did you consider a pumped shower, that'll be way better feeling than a power shower. The pump will also pressuarise all your water, so more power in the taps etc.

Correct - and the shower is all that needs to be protected. Everything else is rated for 40A.

If someone replaces a 3A with a 13A, the shower will have incorrect overcurrent protection. What will happen? It depends on what goes wrong within the shower and what the loop impedance of the circuit is. In an extreme case, wiring within the shower could melt / catch fire, and by extension the plastic housing. No different than any other applicance which has an incorrect fuse fitted in its plug top.

An electrical contractor will assess what is installed currently and see what is the most efficient solution - this may well involve changing the RCBO - but there are alternative solutions which meet current wiring regulations.

How about a T80 mains feed if you can swap the cold feed T90 to mains.

The constraint with the any electric shower is the rate at which the water can be heated within the unit. In practical terms the flow needs to be restricted to allow it reach the required temperature.

The pump in the current shower can develop 1.5bar, so you won’t really notice any improvement in pressure over the tank fed.

With a power shower, the water is heated elsewhere, so it’s only a question as to how quickly it can be pumped to the shower head.

1. No - accepts a cold feed only.
2. Yes - New 40A electrical circuit required.
   
   The performance would also be very poor vs the aqualisa - approx 30% of the flow!
   
   Is the cylinder being heated all the time?
   Would you have space for a larger cylinder?

There will be some variation in pipe entry requirements, also the Aquastream is 24V, all the others are 230V - so there may need to be a new cable run from from wherever the transformer is currently located to the shower.

If it were me, it’d stick with the Aquastream. They are actually a very good shower. How old is it? It may just need a new motor/pump assembly which is a simple swop. It would be worth replacing the dual speed loom at the same time.

Does it look like this?

If the whole thing is past its best, I would just replace it on a like for like basis.

Thanks Lenar, it's an older Aquastream - I think maybe the MK2. It works okay it's just quite loud when running - would that be the pump?

any rough idea what i should expect to pay someone to swap out the pump and the dual speed loom?