On 14 Jan 2006 08:03:11 -0800, wrote:


Andy Hall wrote:

Contrast this with our former arrangement of a fan oven and gas hob,
it could work out that when cooking a complex meal that 10-12kW or
more is released from this lot. Then the windows have to be opened
wide to maintain a sensible temperature. That's what I call a waste.

My last gas bill shows 336KWh for the quarter which is about 3.3KW per
day.
Your estimate equals 16.8 KW per day. Thats what I call waste.

No, because the heat is virtually all used within the house and may be
subtracted from the consumption of the other heating systems.


But anyway the whole point of an Aga is to conserve heat from a solid
fuel source which cannot be modulated easily, and was a great
improvement on the open fire range.

Who said anything about solid fuel?

A gas Aga is thus utterly pointless
in that the gas in a small cheap conventional cooker (or CH boiler)
can be modulated easily and instantly to match demand.


That depends on whether one thinks laterally or not.

How is a conventional cooker modulated? It's turned on and off.

I have a very good quality heating boiler with an exceptional
modulation range of 3kW to 30kW. Most modern boilers only go down to
around 7kW and have to be cycled on and off.

The boiler can, of course, modulate up and down relatively quickly to
match heating demand. However, it typically does not because the
temperature in the house, since it is quite well insulated, does not
change that quickly. During a large proportion of the year, it runs
at about the 3kW level, seldom cycling off at all. At times, the
radiators run at temperatures as low as 40 degrees or so.

THe 700W or so output of the Aga is simply added to the heat from the
CH, so that in effect it is an additional heat source for space
heating. As a consequence, the CH boiler is running at a lower output
than it otherwise would.

In terms of the efficiency of use for space heating, I doubt whether
there is much of a difference in terms of what goes out of the flue
for either heat source.

Therefore, in effect, the heat produced by the Aga forms part of the
space heating, and cooking is free.


You don't need a
£3000 or more cast iron heat sink to save heat - you just turn it on
or off.


Of course, but it is not true to say that this approach to cooking and
providing some of the space heating isn't efficient. It is.




--

..andy