freeview boxes - are most lousy ?

On Sat, 11 Jul 2009 16:30:22 +0100, Java Jive wrote:

You don't want to know, see my reply to Rod. She's either very much
mistaken or living in different laws of physics to the rest of us.

I've been Googling for details of energy-saving and "eco" kettles to see
if there is anything that fits the description that Kay gave.

The nearest is the Philips HD4686 Energy Saver:
http://www.p4c.philips.com/files/h/h...92_pss_eng.pdf

It has a temperature control - 40, 60, 80 or 100°C. It also has a "keep
warm" button to maintain the temperature.

http://stuff.tv/review/Philips-HD4686-Energy-Saver/

That review says "there's a 'keep warm' button that maintains your
chosen temperature, while you juggle cups and teabags".

I would be amazed if the "keep warm" button was intended to maintain the
temperature of the water all day long. That just wouldn't make sense.

I assume the kettle is called an "energy saver" because of the ability
to chose the temperature to which you want the water heated, rather than
bringing it to boiling point every time.

Other approaches to energy saving are at:
http://www.uk-energy-saving.com/eco-...ng-kettle.html
and
http://www.uk-energy-saving.com/ener...rgy-sense.html

Those both offer accurate measurement of the amount of water to be
heated. This avoids energy being wasted in heating water that does not
need to be heated.

On Sat, 11 Jul 2009 16:15:45 +0100, Peter Duncanson
wrote:

Can you tell us what make and model it is please?

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On Sat, 11 Jul 2009 17:23:58 +0100, Peter Duncanson
wrote:

The nearest is the Philips HD4686 Energy Saver:
http://www.p4c.philips.com/files/h/h...92_pss_eng.pdf

Useful for someone doing a lot of cooking with sauces, etc, perhaps,
but could hardly be seriously described as energy saving in any other
situation.

Other approaches to energy saving are at:
http://www.uk-energy-saving.com/eco-...ng-kettle.html

That's the one that was the subject of my original diatribe, the
dangerous one that only lasted two years, and, simply because of that,
could hardly be described as eco-friendly at all. *Any* eco-friendly
device needs to be built to last so that the environmental 'overhead'
of producing it and disposing of it at the end of its useful life is
spread over as many years of use as possible.

http://www.uk-energy-saving.com/ener...rgy-sense.html

Looks ok.

I seriously wonder though whether any concealed element kettle is
truly eco-friendly. We concluded in the original thread of April 2007
that exposed elements were almost certainly more efficient, and they
have the useful advantage of being replaceable, thus extending the
kettle's useful life.

Those both offer accurate measurement of the amount of water to be
heated. This avoids energy being wasted in heating water that does not
need to be heated.

Yes, that's an important point, and is why for most situations a jug
design which can boil as little as a single cup is almost certainly
going to be better than other designs.

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In article ,
Java Jive wrote:


I seriously wonder though whether any concealed element kettle is
truly eco-friendly. We concluded in the original thread of April 2007
that exposed elements were almost certainly more efficient, and they
have the useful advantage of being replaceable, thus extending the
kettle's useful life.

There is no inherant reason why a concealed element can't be replaced.
indeed, it should be an easier job since you shouldn't need to worry about
a water tight seal. It's just that, nowadays, spare parts for 'cheap'
appliances are not available as the cost of getting the job done by someone
who has to be paid would mean it was cheaper to buy a whole new unit.

--
From KT24

Using a RISC OS computer running v5.11

Java Jive wrote:

I seriously wonder though whether any concealed element kettle is
truly eco-friendly. We concluded in the original thread of April 2007
that exposed elements were almost certainly more efficient, and they
have the useful advantage of being replaceable, thus extending the
kettle's useful life.

I beg to differ.

An exposed element kettle has a minimum water depth sufficient to cover
the element.

A concealed element has a minimum depth sufficient to cover the bottom -
which is a trivial amount.

If you are making a cup of tea I think you'll need more than a cup's
worth of water to cover the exposed element. In this case you are
heating water that you don't need.

BTW my concealed-element one appears to be self de-scaling. Bits fall
off every so often, and it never builds up to any extent.

Andy

On Sat, 11 Jul 2009 22:05:48 +0100, Andy Champ
wrote:

A concealed element has a minimum depth sufficient to cover the bottom -
which is a trivial amount.

I think though, if you read the actual instructions for most, perhaps
all, concealed element kettles, the minimum amount is more than this.

If you are making a cup of tea I think you'll need more than a cup's
worth of water to cover the exposed element. In this case you are
heating water that you don't need.

Shouldn't do, if it's well enough designed, though of course not all
are, or perhaps I should say 'were' seeing they've all but vanished
now.

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In article ,
Kay Robinson wrote:
On Sat, 11 Jul 2009 10:19:28 +0100, Roderick Stewart
sharpened a new quill and
scratched:

In article , Kay Robinson wrote:
The present [kettle] is a cordless energy saver one
I've had for five years, you put water in, set the thermostat, then
leave it on for the day only filling when necessary. The consumption
used to keep the water just at the boil for five cups of tea is equal
to boiling one cupful from cold. It's saved me money on my electric
and time when I want a cuppa (except when it needs refilling).

I think there is some false reasoning here. The energy required to boil
five cups of water from cold is the same however it's done. I don't
understand how you can be saving energy by expending the *additional*
energy needed to keep it hot all day.

Rod.

I take it then that you believe switching an immersion heater on only
when you need hot water is the way to go? Thermastatic controls have
moved on since WWII. It may take 1000w to heat a kettle up from cold,
to keep it hot may only take 1w per hour.

That depends entirely on how well insulated the container is. Water tanks
tend to have considerably more insulation than kettles. And you still
don't understand energy units. You can use any number of watts to heat up
water from cold - the question is how long for. 1kW for 10 minutes or 3kW
for 3 minutes? The unit is kilowatt hours not kilowatt per hour.

Kay

--
From KT24

Using a RISC OS computer running v5.11

"Kay Robinson" wrote in message
...
On Sat, 11 Jul 2009 10:19:28 +0100, Roderick Stewart
sharpened a new quill and
I take it then that you believe switching an immersion heater on only
when you need hot water is the way to go? Thermastatic controls have
moved on since WWII. It may take 1000w to heat a kettle up from cold,
to keep it hot may only take 1w per hour.

Kay

Look Kay, you really are out of your depth here. This isn't the sort of
woolly issue where people like you can spout unsubstantiated drivel, and
wacky theories abound, it's a scientific question which can be settled by
the application of some simple straightforward physical principles. These
guys on here know their stuff. They have been trained to use scientific
method.

An example of your woolly thought and lack of knowledge is the expression
'may only take 1w per hour' which you use above.

Firstly it's 'W', not 'w'.

Secondly '1W per hour' is meaningless. You could say '1W for an hour' --
that's 1 Watt of energy expended for an hour -- but not '1W per hour'
Struggling with the distinction? I thought so.

Thirdly, and most important, you've just made that figure up. It's a totally
spurious statistic. That behaviour might be acceptable amongst you wooly
thinkers, but it certainly ain't science!

This sort of muddled thinking is prevalent amonst certain types of people
and it explains a lot of barmy stuff -- shen fui, astrology, gold plated
speaker leads, etc.

Bill

On Sun, 12 Jul 2009 18:58:49 +0100, Kay Robinson
wrote:

On Sat, 11 Jul 2009 10:19:28 +0100, Roderick Stewart
sharpened a new quill and
scratched:

In article , Kay Robinson wrote:
The present [kettle] is a cordless energy saver one
I've had for five years, you put water in, set the thermostat, then
leave it on for the day only filling when necessary. The consumption
used to keep the water just at the boil for five cups of tea is equal
to boiling one cupful from cold. It's saved me money on my electric
and time when I want a cuppa (except when it needs refilling).

I think there is some false reasoning here. The energy required to boil
five cups of water from cold is the same however it's done. I don't
understand how you can be saving energy by expending the *additional*
energy needed to keep it hot all day.

Rod.

I take it then that you believe switching an immersion heater on only
when you need hot water is the way to go? Thermastatic controls have
moved on since WWII. It may take 1000w to heat a kettle up from cold,
to keep it hot may only take 1w per hour.

What matters is not the development of thermostatic controls but the
prevention of the loss of heat from the water.

The immersion heater in my hot water cylinder is on for a couple of
hours before I get up in the morning. It is not on again until the
evening. During the morning and afternoon the water is kept hot by the
substantial insulation on the cylinder. There is no need for top-ups
from the immersion heater unless I use a lot of hot water during the
day.

In article , Kay Robinson wrote:
I think there is some false reasoning here. The energy required to boil
five cups of water from cold is the same however it's done. I don't
understand how you can be saving energy by expending the *additional*
energy needed to keep it hot all day.

Rod.

I take it then that you believe switching an immersion heater on only
when you need hot water is the way to go?

Yes. That's what a combi boiler does. It doesn't waste energy keeping a
tank of water hot when nobody's using it.

Thermastatic controls have
moved on since WWII. It may take 1000w to heat a kettle up from cold,
to keep it hot may only take 1w per hour.

That's right. It takes 1000W for a few minutes to boil a kettle.

But to boil a kettle and then keep it hot all day takes 1000W for a few
minutes *plus* whatever it takes to make up for thermal losses throughout
the day. Even if the extra is only a small amount, it's still more than
just boiling the kettle.

Rod.
--
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On Mon, 13 Jul 2009 12:06:02 +0100, brightside S9
wrote:

pedant mode
There is much confusion about energy and power and the Watt. There has
been an ongoing discussion in The Times about the inability of their
writers to understand the difference, (The Times and science again).

The unit of ENERGY is the Joule. (SI symbol J).
The unit of POWER is the Watt. (SI symbol W).

One unit of power is one unit of energy divided by one unit of time
(the second, SI symbol s). Hence power W = J/s, or the *rate of use*
of energy.

The *amount of energy* used (as recorded by your leccy meter for
example) is Kilowatt hours. This is the units of watts multiplied by
the units of time, or (J/t)*t i.e. Joules.

It's perhaps a more convenient unit for electricity bills than Joules,
but it's probably used mainly for historical reasons. I'm not sure
what other countries do.

1 Kilowatt Hour = 3,600,000 Joules

An example:-

You have a 3kW immersion heater. This means that it is *power* rated
at 3kW. This is the rate at which the heater *uses* energy, i.e J/s.
If you have an old fashioned leccy meter this is indicated by the
'speed' of rotation (angular velocity) of the disk, or on a newer
leccy meter, the *rate* at which the led flashes.

The faster the disk turns, the more power is being *supplied*. The
amount of energy *used* is recorded on the leccy meter as kWh. This
is the number of revolutions of the disk or flashes of the led to add
one kWh to the meter reading. Look at your leccy meter, it will tell
you how many revolutions or flashes it takes to record 1kWh of energy
used.

Leave your 3kW immersion heater on for one hour and the *energy* used
(3000W/3600s)*3600s = 3000J or expressed on your leccy bill as 3kWh.
So 1kWh = 1000J = one thousand SI units of energy.

A slip there ...

The correct calculation = 3*1000*60*60 = 10,800,000 Joules, or, more
conveniently, 10.8MJ!

So kettles, like immersion heaters, use energy to heat the water.
Energy is Joules and is not time dependant. i.e it matters not how
fast the kettle comes to the boil, nor how much water there is in it,
(assuming no heat loss by radiation from the kettle) the same amount
of energy is used to bring the volume of water in the kettle to the
boil, whether it takes one minute or one hour or whatever time
interval is chosen.

It should now be obvious that to keep a kettle of water at a given
temperature, given that it is impossible to stop heat loss by
radiation from the kettle, it will take energy to achieve the
maintenance of the required water temperature.

Exactly, but I suspect you're wasting your time :-)

/pedant mode

Shed salesmen and domestic appliance manufacturers either don't know
the facts, or try to confuse you with power and energy. They will say
anything to flog the stuff.

So Kay, you've been conned by whoever flogged you the kettle.

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