Flow rate from electric shower

[Chalked]

Can anyone tell me what flow rate to expect from a 9.5kw shower? Got to attend a rental house where the customer is complaining about lack of flow. It could be a blockage in the shower, or head. But would like to measure the rate, in case I need to explain that they will only pass so much.

cheers.

 

[Scott_D]

On a new one they claim max of around 10lpm for Mira and triton
I don't know at what temperature though

 

[chris watkins]

It is dependant on the incoming water temperature & the desired outlet temperature.
This time of year with with cold at less than 10degC you would not get anywhere near the 10L/m .
You could work it out if you need to, let me know probably have a formula some where.

 

[Chalked]

Thanks Chris.
Let's say the water is 13 degrees and they want a 43 degree shower. So a 30 degree rise.

 

[joni os]

For a 9.5Kw shower:- Rise in temperature of water. multiplied by. flow in litres/min equals 133
ie, 133/T = flow in litres/min.
For 10Kw use 140 and pro rata for other values.
eg, 35 rise in temp:- 140/35 = 4 litre/min

 

[Shower Engineer]

I get this problem all the time, especially in winter, people’s expectations are sometimes a little too high.
To accurately calculate the flow rate you need to know the cold water temp, about 9 degrees at the moment, the temperature required, say 40 degrees and the voltage, say 231. I put that into a spreadsheet and voila!



If you want a copy of the spreadshhet just PM me an email address and I will send it to you.

 

[Johannes]

I always check for any restrictive ball iso's on the cold water supply to the shower. If so replace with full bore iso's. Remove shower head and measure flow into a jug with head first. Then with head. Had a couple where changing the head made all the difference.

See if you can get a pressure gauge onto the cw supply near the shower.

I have an Aqualisa Quartz 11kw in my family bathroom. To be fair it doesn't feel any different to the old triton t80z 8.5kw it replaced. I thought that going up to an 11kw shower when I refurbed the room would enable a stronger flow for same temperature. Not so. Sometimes it's just the way that the showers are made (internal restrictions etc).

BTW can't recommend Quartz as it's on it's second engine in 4 years. Common fault :-(

 

[chris watkins]

Very nice Shower Engineer, I like that beats my lame attempt below.

Kg/s = (Watts )/(4.187 (shc) × 1000 × ∆t)

 

[Shower Engineer]

Very nice Shower Engineer, I like that beats my lame attempt below.

Kg/s = (Watts )/(4.187 (shc) × 1000 × ∆t)

The spreadsheet (which isn't my work) uses the formula :-
Flow Rate l/m = ((60*(((Operating Voltage/(240/(Nominal kW rating/240)*Operating Voltage))/4.18*(outlet temperature-inlet temperature)))))

I find an easier way to prove that the shower is working correctly is to use a clamp meter. You can then see how many Amps the shower is using. Measure the voltage, say 235. Find the rating of the shower, say 9.5Kw (9500w). Simply divide 9500/235 so you can see how many Amps your clamp meter should be showing, in this case 40.42A. Much easier than checking flow rates, provided you have a clamp meter :smiley2:

 

[zzzjim]

..... Volts x ....Amps your clamp meter should be showing, in this case 40.42A. Much easier than checking flow rates, provided you have a clamp meter :smiley2:

I love this as there is no arguing with the laws of physics !
( + peace of mind volts finding their way there )

 

[joni os]

Very nice Shower Engineer, I like that beats my lame attempt below.

Kg/s = (Watts )/(4.187 (shc) × 1000 × ∆t)

Much simpler in BTUs Chris. With a few approximations so a calculator not needed.
10.5 X 14= 147 Divide by rise in temp (This time 31) 147/31= 4.7 litres/min