On Fri, 17 Sep 2004 14:09:08 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Fri, 17 Sep 2004 13:35:31 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .


You can work out how long the water will last from the store - about
90 litres when mixed with cold accounting for a 6 minute shower at
15lpm. After that, it drops to 11lpm

Oh my God more mentalist. The store stores water at least at 60C, we
shower
approx at 38-40C as the water is being drawn off the boiler is
simultaneously re-heating. You have been told this so pay attention.

I did, and I also produced the complete calculation demonstrating how
poor the performance really is.

It was wrong.

Er no.

The equation of

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

is the correct one to apply when liquids of different temperatures are
mixed.

I know that division and multiplication are a bit more difficult than
adding and taking away, but you'll get to that in next year's class.



how much did your
boiler and store cost?

Boiler and cylinder together were about £1800.

My God! a house gas supply can give 212 cu foot per hour. You can buy
two
combi's that consume close to that figure giving about 25 litre/min. And
no
cylinders and a backup if one drops out. Lateral thinking me boy.

It is bad practice to use deprecated units. It is even worse to mix
them.

Your suggestion would produce 22lpm of warm water

Stop making things up.

The arithmetic is quite clear.



at 40 degrees and
require the entire supply to do it, leaving nothing for other
appliances.

It would still need roof storage in my case and seemingly in a lot of
other people's cases as well and still not protect against a failure
in either the electricly nor the gas supply.

In short no redundancy apart from appliance failure.

I have complete backup for all services and appliances and can get
superior performance so there is no point in worsening that.

A;All that expensive kit and space it takes up.

I don't have a space problem for it, and more to the point is does the
required job.



I can run two showers or a shower and a bath very quickly and not have
to worry about them going cold or taking an eon to fill and run.

Two combi's consuming 20 cu foot/hr will pour the water in me boy, pour
it
in.

Trickle, more like.

You really don't know.

You need to read through the sums. Don't worry about the
multiplying and dividing - it's similar to the adding and taking away
- you just do it more times.


So two Alpha CB 50s would be well within a domestic gas supply

Right on the edge and requiring upgrade to run anything else.

and give you
showers in abundance and
NEVER run out of water,

unless any single one of the services fails.

And Krakatoa could erupt too.

In the last year, I have had failures of all three services at
different times.

It is quite common so depending on something needing all three is a
risk.





..andy

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