Electric shower poor flow when turned up

[Jonsaid]

Hi,
My electric shower is rubbish! When it's on cold the flow is ok, as soon as you turn up the temperature the flow rate reduces meaning the best I can have is a warmish shower with really poor flow.
The landlord's maintenance guy has been out and said it's because it's only an 8.5kw but I'm sure I've seen 8.5's with perfectly decent flow?
The bathroom is on the first floor and there is a boiler downstairs, a hot water cylinder on the landing and a cold water storage tank in the loft. The flow at the kitchen sink is fine but the taps upstairs (bath/basin) aren't great but ok.
Any advice on how to be able to get a decent shower would be much appreciated!

Thanks in advance.
Jon.

 

[baboopeter]

hi,the water heat is controlled by the flow,the more you turn it up the slower the flow of water. You must take into account the water feed isvery cold due to the weather,it will improve as the weather gets warmer, If you change to a bigger heater you may have to change the cable. b.p.

 

[Jonsaid]

Thanks bp.
I thought the pressure for the shower would be fine seeing as its mains fed and it's good at the kitchen sink, so is it just a case of the shower has to slow the water down in order to heat it? So if I put in a bigger shower like a 10.5 with a new cable that should sort it? Is there any other reason it could be so bad? It's just that even though it's only 8.5 I'm sure it shouldn't be this bad!
Could I put a pump on the mains feed, if the heater had a stronger flow of water would it perform better? (not quite sure of the logic behind this!)
J.

 

[baboopeter]

Hi Jon,
There are restrictors inthe shower unit that only allow through enough water that the heating element can cope with. your mains pressure should be enough. I changed my old unit for a new Gainsburough 10.5 and the difference was huge, even with the freezing weather we just had,2/3rd full was hot enough. But i also had to change the cable to i think 10ml. bp

 

[Jonsaid]

Thanks bp, sounds good to me! Will change the unit and get a spark to wire it up.
Jon.

 

[flameport]

a hot water cylinder on the landing and a cold water storage tank in the loft.

Dump the electric shower and have a plumber fit a booster pump and a mixer shower, which will use the stored hot water that you already have.

 

[ban-all-sheds]

Hi,
My electric shower is rubbish! When it's on cold the flow is ok, as soon as you turn up the temperature the flow rate reduces meaning the best I can have is a warmish shower with really poor flow.
The landlord's maintenance guy has been out and said it's because it's only an 8.5kw but I'm sure I've seen 8.5's with perfectly decent flow?

The important thing to remember with electric showers is that ye cannae change the laws of physics.

The specific heat of water is 4.19J/gK.

An 8.5kW shower will be able to put 510,000 joules per minute into the water.

I've just measured the temperature of the cold water coming into my house at 6.9°C.

If we assume a desired shower temperature of 40°C, that means the water temperature needs to be raised by 33.1°.

The amount of water which can be raised by 33.1° by 510,000J is:

510000 ÷ 4.19 ÷ 33.1 = 3677.3g

So your 8.5kW shower, assuming it's working at 100% efficiency, will deliver a flow rate of about 3.7l/m.

To put that into some kind of perspective

1) 15l/m is the rate at which most people think "Ooh yes - that's a nice powerful shower".

2) In the US showers are limited to 9.5 litres per minute.

 

[gman76]

Are you sure that it is plumbed to the rising main?

My GF's rented house has the shower plumbed to the header tank - the flow is terrible & the "low flow" indicator comes on as the temp. is increased.

Cowboys.