kilowatt ratings and electric showers

That depends on whether you want flow or pressure - the two are quite different.

It's completely linear.

The manufacturers really hide this one because performances for electric showers are so poor.

A 10kW one will deliver about 4 litres/min of water at 40 degree showering temperature when the cold main is at 5 degrees as it is in the winter quite often. You can work out the figure for others by scaling accordingly.

So the water has to be delivered through the heater quite slowly and these units always have a small shower head usually with an option to have fine needle jets so that at least some pressure can be felt.

Personally, I don't like that and think they're pretty bad so would never consider one.

If you are looking for decent flow and pressure, then in the price range that you are considering, you would be far better off with a shower pump and using the existing HW system. It will be better and cheaper to run as well.

Only if you are out of other options. Have you considered a shower pump? Remember also that the purchase price of the shower is only a small part of the total cost of installing the thing. Often you will spend several times the price laying on the electric supply for it.

With electric showers, they are pretty much 100% efficent. Energy in = energy out, and most of that comes out as heat in the water.

Yes that's right.

You can do a quick sum to give you an idear of the performance:

The energy required to heat a litre (or 1kg) of water will be approx

So if you mains water at this time of year is 6 degrees and you want a shower at 40 degrees, you require (40 - 6) x 4200 = 134400 joules per litre of water.

Given that 1 watt = 1 Joule / second, a 12.5Kw shower will give you

So finally divide one by the other : 750000 / 134400 = 5.6 litres / min

Obviously things get better in the summer with warmer ground water, but winter performance of these can be pretty non spectacular as you can see.

You regulate the amount of water going through the shower - as even a 12 kW model hasn't a hope in hell of heating all the flow from the main. You'd need something like three times that to do this.

As Andy sez their p**s poor. Get yourself something like a MIRA excel or event, and for not a lot more money ,alright perhaps a bit more plumbing, and really enjoy:))

Andy Hall was thinking very hard :

Ours is a 7.5Kw installed 20 years ago and I find it adequate even in winter. Of course the flow could be better, but as you say it is a compromise between flow/temperature. In summer it is often too hot.

Agreed, but a separate electric shower is a good standby against a complete heating system failure.

I use an immersion for that, and has the benefit that it supplies all the other hot water taps too.

Dave Plowman (News) submitted this idea :

I have one too, but never needed to use it in 20 years :-)

And the hide of a rhino to stand in front of the water jet

I have a 8kw "cheapy" connected to the MAINS water supply, Pressure and temp in winter is ok, although my son gives out about it. A 10 - 12kw shower will certinly give you good performance, the built in selector switch and water regulator will allow you adjust the flow and temp to suit your needs in winter and summer conditions. IMO every home should have at least one electric shower. --- Pat

;-)

The first time I actually needed mine because the system was drained down to replace all the TRVs it took the MCB when switched on. It did work when installed - honest.

I'm yet to be impressed with a shower fed from a high output combi. But I want a large flow shower rather than high pressure jets.

I doubt you've tried a decent shower. Your son obviously has. ;-)

In message , snipped-for-privacy@eircom.net writes

Your definition of 'good performance' is obviously different to mine.

No it won't, there is never enough flow :-)

I've got better things to spend the money on.

We changed a Gainsboough 9.5kW for a Mira 415 straight off the hot and cold ( we have a combi boiler) and it is far superior.

Sreve

Hmm .. just had a mira excel fitted to a CD50 combi and I am very impressed with the performance, we run the shower head 'inbetween positions' in order to get all the nozzles working otherwise the pressure is uncomfortable. I can't see how you could get better performance than this as flow is governed by the shower head and pressure is around the 2-3 bar mark

Regards Jeff

He he, Best "shower" I've ever had was on a beach in Jamaica. Water was a bit cool but with the air temp around 90F that wasn't a problem. Flow rate must have been in the range of 60l/min, actually a bit on the high side as it pummled you into the sand.... It was part of a small river flowing over a cliff down to the sea.

I much prefer a low pressure/high flow rate shower than a handful of needle jets that take 5 mins to rinse the soap off.

I know the make isn't the most popular but didn't Triton make one that was a flush panel with all the gubbins hidden ina suitable compartment behind for acces.?

Stuart

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