"Andy Hall" wrote in message
...
On Thu, 16 Sep 2004 18:22:13 +0100, Pete C
wrote:

On Thu, 16 Sep 2004 13:40:41 +0100, Andy Hall
wrote:

On Thu, 16 Sep 2004 13:11:58 +0100, "IMM" wrote:



The Alpha CB50 has a high flowrate and is wall mounted.


The manufacturers quote 18lpm and since the maximum power rating is
only 28kW, once the small 50 litre store is exhausted, it will drop to
the typical 11lpm. Not very exciting at all.

Hi,

That 18lpm is at 60°C though and the store is 60l, which is enough to
fill a bath in 6 mins. What would you consider a reasonable flow rate
for a shower?

cheers,
Pete.

To be a bit more accurate:

The formula for resultant temperature of mixing water is

Vc[Tf - Tc] = Vh[Th - Tf]

Where upper case V=volume T=temperature
and lower case h=hot, c=cold and f=final

The store holds 57 litres according to the manufacturer

If the mains water temperature is 5 degrees:

Vc[40 - 5] = 57[60 - 40]

Solving for Vc gives 32 litres and a total of 89litres which is not
enough even for an IMM bath of 100litres. For a reasonable bath of
150 litres It is only jut over half way there and at 11lpm will take a
further 5 minutes or more to fill.

At 10 degrees cold temperature, you could add 38 litres but still you
would be at less than an IMM bath and still at nearly 5 mins to fill
to produce a reasonable bath.

You have clearly never seen a CB50 in action they fill 100 litres baths no
problem, summer and winter.