Redring Instantaneous Water Heaters and Showers

16 Jun 2011
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United Kingdom
I'm planning to buy a 12kw redring instantaneous water heater for my bathroom, it will power a basin and shower.

I'm fairly sure the mains water pressure in my area is weak and I want a decent shower.

Should I be aiming for a manual power shower? Such as this:

Or should I purchase pump and shower separately?

Any advice is welcome.
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you can't use a power shower direct from the mains, they're designed for use from a loft tank.

And a 12 kW instant shower heater isn't going to deliver enough heat for a power shower anyway.
Good point. The blurb on them says a max flow of 5 litres per minute. Is that a decent shower, relatively? What shower would you recommend I use?
Good point. The blurb on them says a max flow of 5 litres per minute. Is that a decent shower, relatively? What shower would you recommend I use?

5 litres per minute at what temperature rise?

The flow rate for a 30°C temperature rise may be half that for a rise of 55°C (required in winter when mains temperatures are not far from zero).

2.5 litres per min is pretty feeble.

If you want to be accurate, time your cold tap filling a 5 litre bucket.

If you want to be crude, pee in a beer glass.

If you haven't got adequate incoming mains water then no amount of heat will give a decent shower. You will have to use a stored and pumped system.

Most showers have an indication of their required water supply; something like a 'rain forest' shower is going to be around 20lpm and that has to be *hot* water.

If you have a moderately good cold water supply then a mains gas water heater or combi boiler at about 30kW output will be 3x better than anything electric (and cheaper to run).
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Our loft conversion has a Redring powerstream 9.5KW which runs the basin and the shower.

To get a reasonable shower it is linked to the specifically designed Redring Shower Mixer Kit part no 85793620. It's not the prettiest shower but because it is designed to work with the powerstream you actually get a proper shower not unlike a std non power shower.
With reasonable mains pressure the shower is OK, but the top temperature is (unsurprisingly) determined by the input water temp. So in the summer the heated water is hotter than in the winter.

The 9.5KW unit is not really man enough for the job and whilst the shower is never cold, sometimes (in the winter) it would be nice to be hotter.

Would I recommend - well if it's the only solution then it works and quite well, particularly the high power versions but if there's room for a combi-boiler I'd go that way.
Oh and worth remembering that you will need a dedicated MCB or RCBO with a direct run from the consumer unit to the shower in 16 mm2 cable if you go the powerstream route

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