On Thu, 06 Jul 2006 20:01:25 +0100 someone who may be Owain
wrote this:-

So, if you want more hot water than your available source of energy can
provide instantaneously, you have to heat the water in advance over a
period of time and then store it. This is why a 3kW immersion heater on
a cylinder can give a better shower than a combi boiler of 10x the power
- although obviously only until the stored water runs out,

Part of the skill of designing a stored hot water system is to
ensure, for some level of confidence, that the stored water does not
run out. This is something of a black art, especially in places like
hotels and hospitals. In a large house it may often make sense to
have more than one cylinder, rather than one large one.

An extreme example of the value of stored hot water systems are
showers for use in case of nuclear contamination. One wants a great
deal of hot water suddenly and a plant to create that amount of hot
water instantly would be very large and very expensive. It is far
better to store the hot water ready for the off, accepting the
standing losses.

then it's a
wait of maybe several hours for the store to heat up again.

Though that does depend on the heating strategy. For daytime use the
immersion heater should get the top part of a cylinder up to
temperature in 30-45 minutes. If it doesn't then more cylinders or
more heaters may be desirable.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54