New bathroom plan - 3rd party head on electric shower?

[underclassy]

Hi all,
A mate of mine recently asked if i'd upgrade his family bathroom. At present he has a mixer tap off his bath (tank fed) but he'd like a separate shower enclosure and a satisfying hot shower with decent pressure. I'm in favour of a shower enclosure with a 10kw electric shower. I notice as the market shifts towards digital remote electric showers, there are very good deals on the more traditional wall box electrics - specifically the Aqualisa Quartz which looks just the job.Have a nasty feeling he's willing to spend 300 quid extra not to have a box on the wall but my real question is: Can I change the head supplied with the shower for, say a 8" 'rain' style head? What might be the issues here? I understand I need a 45 or 50A circuit installed on the consumer unit, a 10mm2 cable and isolator pull switch fitted in zone 3 which is all straightforward enough.
Alternatively, are the digitals worth the enormous expense and do they all run off a mains spur, presumably up in the loft?
I thank you!

 

[Dan Robinson]

8" head??? Not a chance mate.

Electric showers have a fraction of the required flow rate.

A satisfying shower will never be had from any shower head off and electric shower IMO.

 

[underclassy]

Ah, so there are no decent electric showers out there. How about mains fed? Does this mean my only option is to upgrade the cylinder and fit an inline pump to both feeds?

 

[stem]

The problem with an electric shower is that the hot water they produce decreases in the winter when the incoming water is colder. If you check the specification of the shower you are considering you will probably find that a 10kW shower can produce between 5 litres (winter) to 8 litres of water (summer) per minute at about 40 degrees C.

A rain style head normally requires 10 litres per minute.

Alternatives are a power shower, where a pump is used to boost the existing stored hot water system, or a combi boiler which can produce mains pressure hot water, but other simultaneous demands on the water supply elsewhere in the house will reduce its capacity.

 

[underclassy]

Yes I thought as much - can't get more pressure without a pump but that'll run the hw tank dry in no time with a rain head - no desire to upgrade tank so back to Electric with the head provided. Any current favourites? Sounds like I should get highest wattage available, though down in the soft south and his loft is hardley insulated so cold water prob not that cold. They're no eco-warriors!

 

[Charnwood]

Electric showers have a fraction of the required flow rate.

Blimey, a troll parrot!

 

[underclassy]

Ok, I get the message.
(Retreats to balcony with service revolver. A single shot is heard.)
CURTAIN

 

[stem]

That'll run the hw tank dry in no time with a rain head

Is a 14 minute shower long enough?

A hot water cylinder normally contains 120-140 litres. The bottom where the cold water enters will be cool, so lets be conservative and say you have 100 litres of hot water available.

For a rain head using 10 litres / minute. Then based on 7 litres / minute coming from the hot water supply and 3 litres / minute from the cold. (Obviously, the hotter the stored water, then less hot and more cold will be used) 100 litres supplied at 7 litres per minute will last 14 minutes.

This completely ignores any additional heat which will be put back into the cylinder if the boiler is on at the time. Also if more than one person is showering, then additional reheating can occur between showers.

By all means go down the electric route but it's a case of "horses for courses". Stick with a suitable shower head. Don't use a rain head with it. (Imagine the performance from a 7 Series BMW fitted with the engine from a Ford KA. They just don't go together)

Apart from the disappointing performance, you may also like to consider how you will connect a rain head, which tend to use concealed / fixed plumbing to an electric shower that has a flexible connection. Also most electric shower manufacturers stipulate that you must use the shower head supplied by them otherwise their warranty is invalidated.

 

[underclassy]

Thanks for that Stem, despite the seas boiling, this unlikely candidate likes a 20 minute shower - longer if possible. I'm also aware of the potential hazards of fitting concealed pipework but just needed some backup re suitable options - I knew I wouldn't end up putting a monsoon head on an electric shower but it's nice to have the rational solution applied.
Anyone any experience of Galaxy Aqua electric showers? (Am being bombarded by suggestions every time one of the clients walks past a plumber's merchant.)