Litres per minute - confused by options...

[MattB83]

I'm trying to sort out a few tasks in my mother-in-law's house in a hurry...

Going to pick up an electric shower tomorrow - will be installed by a plumber but I'm trying to work out which one to get. Current one looks to be 9.5kw but looking at this power rating at Screwfix there's still lots of variation re: litres per minute. Current model seems to be 3.9l/min but they go higher - assuming that this would be limited by however much water is coming upstairs (combi is downstairs but pressure isn't great to any of the taps on either floor). But if I bought a 9.5kw with e.g. 8l/min, would this cause any problems?

 

[cross thread]

The flow rate lowers with litres delivered,so it may deliver 9 litres per minute but only be a 20 deg shower ,at 6 litres it may be 30 degrees.

 

[oldbutnotdead]

Why do you want an electric heated shower when there's a gas boiler on the premises? The combi will guaranteed deliver at least twice the flow rate of hot water than an 8kw electric shower at a third of the cost per minute showering

 

[Johntheo5]

A 9.5kw shower will deliver 4.12LPM at 40C from mains temp of 7C (here, just now), and 5.45LPM in the summer from mains at 15C. It will deliver ~ 8Lpm at full fllow but the temp will only be either cold at 7C or 24C at full power.

 

[MattB83]

The flow rate lowers with litres delivered,so it may deliver 9 litres per minute but only be a 20 deg shower ,at 6 litres it may be 30 degrees.

Thank you - the only mention of temp in any of the specs I've seen in the max water temp - which doesn't seem to vary much, but I haven't seen any breakdown for different flow rates.

Why do you want an electric heated shower when there's a gas boiler on the premises? The combi will guaranteed deliver at least twice the flow rate of hot water than an 8kw electric shower at a third of the cost per minute showering

Cheers - you mean actually make the most of a very expensive Combi, you'll be suggesting they try turning on their radiators next! Sorry on a seriously note my initial thought too but my MIL is concerned as the combi has been really problematic and currently they have barely any hot water (only a couple years old and under warranty but they've been told there's nothing wrong with it by the Worcester engineer and to get a plumber out - subsequent plumber told them nothing wrong with plumbing so we're at a loss at the moment but basically while heating is great, hot water lasts about 10 secs then runs cold throughout house).

Secondly we're sorting this out while my father in law is in hospital with problems related to his Alzheimer's - the idea is to get a very similar looking/operated shower. I could be wrong but when I had a combi powered installed recently (which I love) we ended up with several holes in the tiles to patch up which I know would cause upset as he did the whole bathroom himself - over a long time as we didn't realise but he was having memory problems throughout. Ultimately, just doing what I'm told!

 

[MattB83]

A 9.5kw shower will deliver 4.12LPM at 40C from mains temp of 7C (here, just now), and 5.45LPM in the summer from mains at 15C. It will deliver ~ 8Lpm at full fllow but the temp will only be either cold at 7C or 24C at full power.

Thank you. So I'm still not sure if selecting a 8lpm offers any advantage/disadvantage over a 3.9lpm? Sorry if I'm being slow!

 

[Johntheo5]

You just select the (thermal) power output whether a 8, 9 or 9.5kw or higher, the higher the power output the greater the flow at any given showering temperature, they will all give a max flowrate of 8/9 LPM, you simply adjust the flowrate with the temperature control knob to give you the desired showering temperature. You can also select 1/2 power if you are happy with 2.0LPM just now!

 

[MattB83]

You just select the (thermal) power output whether a 8, 9 or 9.5kw or higher, the higher the power output the greater the flow at any given showering temperature, they will all give a max flowrate of 8/9 LPM, you simply adjust the flowrate with the temperature control knob to give you the desired showering temperature. You can also select 1/2 power if you are happy with 2.0LPM just now!

Great thanks very much that's really helpful.

 

[MattB83]

Thank you all for your helpful comments.

 

[terryplumb]

If you are retro fitting a replacement shower ,you need to give consideration to the positions that the cable and supply pipes are in,particularly if they come through the wall and there is no access behind to change their position. All showers are not the same in terms of the connection points for cable and pipe.
What amperage MCB or fuse protects the shower circuit ?

 

[Johntheo5]

The Triton T80Z fast Fit will accomodate most if not all water and cable positions, I replaced by 15 year old Mira Sport last week with this shower, no problems whatsoever.

 

[Harry Bloomfield]

Any shower rated 9.5Kw, will generally have the same best flow/temperature output as any other 9.5Kw shower. What sometimes does vary is the controls and how good a job they make of controlling that temperature. Some are only able to run at fixed power input to heat the water, relying on the user to vary the flow to set the output temperature. The better, more expensive showers - you can set the temperature you want, and the control system varies the power input, and in some cases the flow, to match what you set on the temperature dial.

Obviously, the higher the power input, the better the shower too, but the cable and MCB rating sets the limit on that, unless it is to be rewired to suit a higher power.