| Author |
Freezer temperature
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| About energy and refrigerators/freezers
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The best (meaning A++) refrigerators and freezers use very little
electricity. So, ti goes without saying that you should buy one of
these A++ rated fridges or freezers. Liebher is one of the premium
manufacturers of A++ refrigerators an freezers. Chest freezer is the
best.
A few calculations...
Liebherr GTP 1826 Premium 166 litre chest freezer uses 142.4 kWh/year.
This comes down to 390W per day and 16W per hour. Liebherr KTP 1740
Premium 150 litre table-height refrigerator uses 84 kWh/year, which
comes down to 230W per day and 9.5W per hour. Put together they consume
25.5W per hour. A solar panel cabable of producing the needed of energy
per day is not very large nor expensive. And a soler panel produces the
most energy on sunny hot days when the most cooling energy is needed.
But, here's a couple of guestions...
Different foods need different temperatures for preservation. Fish
probably needs the lowest freezing temperatures.
1. So, is it good to have one small freezer set to -18 degrees celcius
and another set to -30 degrees celcius?
The temperature should be chosen according to the lowest reguirement,
which is fish. Or you can (of course) take care not to preserve fish
more than 2-3 months if the temperature is only -18 degrees celcius.
Freezers should allways be lept full of frosen foods. The energy
consuption figures are based on this assumption. If the freezer is full
at all times, the bigger freezers consume way less (up to 50% less)
electricity per litre than the small ones. That's bechause they have a
lot more frozen mass inside, when full. And what ever you put in them
will be a smaller portion of the total mass inside and will freeze much
quicker and with less energy than in a smaller freezer.
2. So, is a half full 400 litre freezer more or less energy efficient
than two 100 litre freezers that are full. All being (of course) the
chest type A++ freezers.
And, allways make sure that the refrigerators and freezers are placed
in a place in you house that is as well ventilated as possible and as
cool as possible and far away from any heat sources.
Placing a refrigarator or freezer in a very closed and poorly
ventilated place possibly near to a stove can increase the electricity
consuption up to 500%!! That is, it will consume five (5!) times more
energy than it potentially could to do the same job!!
PS. I do not have any affiliation with Liebherr whatsoever, I am just
using their products to make an example.
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| nicksanspam@ece.villanova.edu 2005-11-02, 9:21 am |
| max <maxxrock@luukku.com> wrote:
>Liebherr GTP 1826 Premium 166 litre chest freezer uses 142.4 kWh/year.
>This comes down to 390W per day and 16W per hour. Liebherr KTP 1740
>Premium 150 litre table-height refrigerator uses 84 kWh/year, which
>comes down to 230W per day and 9.5W per hour. Put together they consume
>25.5W per hour...
You might enjoy learning the difference between power and energy.
>Freezers should allways be lept full of frosen foods. The energy
>consuption figures are based on this assumption. If the freezer is full
>at all times, the bigger freezers consume way less (up to 50% less)
>electricity per litre than the small ones...
Would you have any evidence for this article of faith?
Nick
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| Derek Broughton 2005-11-02, 10:21 am |
| max wrote:
> About energy and refrigerators/freezers
> ---------------------------------------
>
> The best (meaning A++) refrigerators and freezers use very little
> electricity. So, ti goes without saying that you should buy one of
> these A++ rated fridges or freezers. Liebher is one of the premium
> manufacturers of A++ refrigerators an freezers. Chest freezer is the
> best.
>
> A few calculations...
>
> Liebherr GTP 1826 Premium 166 litre chest freezer uses 142.4 kWh/year.
That doesn't sound particularly impressive. Mine, of about the same size,
uses ~500Wh/day. I'm betting mine was much cheaper than the Liebherr.
> This comes down to 390W per day and 16W per hour.
Serious mixing of units. You mean 390Wh/day. Averaging 16W.
> Different foods need different temperatures for preservation. Fish
> probably needs the lowest freezing temperatures.
Really?
>
> Freezers should allways be lept full of frosen foods. The energy
> consuption figures are based on this assumption. If the freezer is full
> at all times, the bigger freezers consume way less (up to 50% less)
> electricity per litre than the small ones. That's bechause they have a
> lot more frozen mass inside, when full. And what ever you put in them
> will be a smaller portion of the total mass inside and will freeze much
> quicker and with less energy than in a smaller freezer.
No. Yes, they're more efficient when full - you're not chilling air. And
bigger freezers are more efficient, because they have better volume to
surface area ratios, and probably more efficient compressors - but your
reasons are all wrong. No matter how much frozen mass you have inside a
freezer, if you add 1kg of 20C ground beef, it'll take _exactly_ the same
energy to freeze it.
--
derek
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| nicksanspam@ece.villanova.edu 2005-11-02, 6:21 pm |
| Derek Broughton <news@pointerstop.ca> wrote:
>No. Yes, they're more efficient when full - you're not chilling air.
No.
>No matter how much frozen mass you have inside a freezer, if you add 1kg
>of 20C ground beef, it'll take _exactly_ the same energy to freeze it.
But it will freeze faster if the freezer contains more frozen mass.
Nick
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| Solar Flare 2005-11-02, 7:21 pm |
| Has to do with chilling ***MORE*** air everytime you open the door. Less food
means more air to quickly drain out and give up it's cold, being replaced by
warm humid air.
<nicksanspam@ece.villanova.edu> wrote in message
news:dkb49a$b3m@acadia.ece.villanova.edu...
> Derek Broughton <news@pointerstop.ca> wrote:
>
>
> No.
>
>
> But it will freeze faster if the freezer contains more frozen mass.
>
> Nick
>
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| nicksanspam@ece.villanova.edu 2005-11-03, 4:21 am |
| Solar Flare <s.flare@hotmail.com> wrote:
>... Less food means more air to quickly drain out and give up it's cold,
>being replaced by warm humid air.
And more food means more cold surface to condense moisture
from more airflow when the door is open.
You are incorrect. We've done the numbers already.
Nick
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| Derek Broughton 2005-11-03, 10:21 am |
| nicksanspam@ece.villanova.edu wrote:
> Derek Broughton <news@pointerstop.ca> wrote:
>
>
> No.
Yes. It's not at all like you to _not_ give the numbers you say you've
already run.
>
> But it will freeze faster if the freezer contains more frozen mass.
But that's not relevant. It isn't saving energy if it freezes faster.
--
derek
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| 4partee 2005-11-03, 12:21 pm |
| On Wed, 02 Nov 2005 14:32:58 -0500, nicksanspam wrote:
> But it will freeze faster if the freezer contains more frozen mass.
Yes, the mass already in the freezer will act as a sink for the heat in
the added mass. Given enough already frozen mass, freezing
would occur unaided; like when you make homemade ice-cream.
Energy will be needed to restore the total mass to the desired
temperature.
--
John & Sue
'04 GMC Safari
'99 Starcraft Starflyer (Shuttlecraft)
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| nicksanspam@ece.villanova.edu 2005-11-03, 6:21 pm |
| Derek Broughton <news@pointerstop.ca> wrote:
>
>Yes. It's not at all like you to _not_ give the numbers you say you've
>already run.
It is, after the first time. We've been through this over and over.
Where are your numbers?
>
>But that's not relevant.
It is, since that was the OP's claim.
Nick
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| Solar Flare 2005-11-03, 7:21 pm |
|
More food means less air flow. Why would moisture condense when the air around
the food pockets is below freezing?
Done the figures? Liar
<nicksanspam@ece.villanova.edu> wrote in message
news:dkcfav$bf4@acadia.ece.villanova.edu...
> Solar Flare <s.flare@hotmail.com> wrote:
>
>
> And more food means more cold surface to condense moisture
> from more airflow when the door is open.
>
> You are incorrect. We've done the numbers already.
>
> Nick
>
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| Derek Broughton 2005-11-03, 9:21 pm |
| nicksanspam@ece.villanova.edu wrote:
> Derek Broughton <news@pointerstop.ca> wrote:
>
>
> It is, since that was the OP's claim.
It would be if it was his only claim. He claimed it took less energy.
"And what ever you put in them ... will freeze much quicker and with less
energy than in a smaller freezer." I never argued that it wouldn't be
quicker, I did say it wouldn't take less energy. You chose to argue the
irrelevant part - the part I hadn't disagreed with.
--
derek
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|
|
>
> No. Yes, they're more efficient when full - you're not chilling air. And
> bigger freezers are more efficient, because they have better volume to
> surface area ratios, and probably more efficient compressors - but your
> reasons are all wrong. No matter how much frozen mass you have inside a
> freezer, if you add 1kg of 20C ground beef, it'll take _exactly_ the same
> energy to freeze it.
> --
I think this "Freezers should allways be lept full of frosen foods" idea
comes from a misinterpretation of something like "it is more efficient to
have a small freezer full than a larger freezer 25% full". If you are
talking about the same volume of frozen goods. Sure the big freezer is more
efficient per litre than the small one but the total usage would be more.
stu
as always i could be wrong 
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Ok. Power is current (Ampers) x voltage (Volts) = power (Watts). Energy
is usually kJ (kilo joule).
And yes, the smaller surface area is (perhaps the only) reason why a
200 litre freezer is (up to 50%) more efficient per litre than 2 x 100
litre freezers.
And yes, it takes the same amount of energy to freeze a litre no matter
whether you shove it in a big or a small freezer. It just freezes
faster in a big one. So, my mistake.
Just as well as a litre of water takes the same amount of energy to
boil whether yo toss it in a big kettle full of hot water or not.
And yes, the amount of cold air that is replaced with warm air when you
open the freezer is a factor, of course, as it has to be cooled again.
The less frequently you open the freezer the better. No need for a
physics doctorate here.
So. a) It is advisable to try to keep the freezer full. b) It is better
to have one big freezer (full) than the same amount of frozen food in
two smaller ones.
That's all folks
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| max wrote:
> And yes, it takes the same amount of energy to freeze a litre no matter
> whether you shove it in a big or a small freezer. It just freezes
> faster in a big one
..
..
> That's all folks
I wonder
You have to move the same amount of heat energy but in one case
you start near ambient and go down to freezing (from ambient to
ambient, at least partially) in the other you're pumping most of it
up from freezing to ambient.
What's that do to the COP?
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| nicksanspam@ece.villanova.edu 2005-11-04, 7:21 pm |
| max <maxxrock@luukku.com> wrote:
>So. a) It is advisable to try to keep the freezer full.
No.
Nick
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| Solar Flare 2005-11-04, 7:21 pm |
| yes
<nicksanspam@ece.villanova.edu> wrote in message
news:dkgo85$d25@acadia.ece.villanova.edu...
> max <maxxrock@luukku.com> wrote:
>
>
> No.
>
> Nick
>
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| nicksanspam@ece.villanova.edu 2005-11-04, 9:21 pm |
| Solar Flare <s.flare@hotmail.com> wrote:
>yes
No.
Nick
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| Solar Flare 2005-11-05, 9:21 am |
| Yes
<nicksanspam@ece.villanova.edu> wrote in message
news:dkgu32$d52@acadia.ece.villanova.edu...
> Solar Flare <s.flare@hotmail.com> wrote:
>
>
> No.
>
> Nick
>
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| daestrom 2005-11-05, 10:21 am |
| Maybe?
:-)
"Solar Flare" <s.flare@hotmail.com> wrote in message
news:kZadnbBf0I-8MPHenZ2dnUVZ_tWdnZ2d@golden.net...
> Yes
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:dkgu32$d52@acadia.ece.villanova.edu...
>
>
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| nicksanspam@ece.villanova.edu 2005-11-05, 12:21 pm |
| daestrom <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
>Maybe?
Maybe, if you pack food like bricks, with no airspaces. We've had this
discussion before, with numbers, and you are too good to argue with :-)
Nick
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| Solar Flare 2005-11-05, 12:21 pm |
| LOL
Maybe but is there any way of citing references to it?
Usually people just give up arguing with closed minded posters. This doesn't
mean the truth is out.
<nicksanspam@ece.villanova.edu> wrote in message
news:dkij1m$enu@acadia.ece.villanova.edu...
> daestrom <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
>
>
> Maybe, if you pack food like bricks, with no airspaces. We've had this
> discussion before, with numbers, and you are too good to argue with :-)
>
> Nick
>
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| nicksanspam@ece.villanova.edu 2005-11-05, 6:21 pm |
| Solar Flare <s.flare@hotmail.com> wrote:
>Maybe but is there any way of citing references to it?
[color=darkred]
You might Google, or think of a fridge or freezer as a heat exchanger warming
cold surfaces with latent and sensible heat from flowing room air. The more
cold surface, the more air flows. Each time you open it, the room air that air
remains in the fridge needs to be cooled again, but the cold surfaces collect
condensation from flowing room air when the door is open. More food means less
air to cool after the door is closed, but more airflow and condensation when
it is open.
Nick
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