I've been trying to get hold of a -80 freezer, so this sounds like it would be just the ticket. Mind if I buy it off you?
Setting freezer temperature.
- Thread starter ericmark
- Start date
I've been trying to get hold of a -80 freezer, so this sounds like it would be just the ticket. Mind if I buy it off you?
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Just get some containers which will survive those temperatures, move to Antarctica, and put them outside the back door.
As I recently wrote to eric, the temperature obviously will not 'keep going down and down', indefinitely, even if it's running continuously. The temperature of the freezer cavity can never get below the temperature of the coolant, and it would make no sense for manufacturers to waste money creating a domestic freezer which did/could achieve a coolant temperature appreciably below -20 ° - hence my experiences with leaving the 'rapid freeze' switch on for several days.Kind Regards, John
Absolute(ly) not.
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That would certainly sound far more sensible, given the considerable variation in freezers.
Mind you, I suppose what really matters is the surface area of the cavity (and its insulation), rather than its volume. Once the temperature in the cavity has been reduced to the desired level, how much ongoing power (if any!) will be needed to keep the cavity at that temperature will depend only on the heat transfer through the walls/lid/doors of the freezer - which will be crucially dependent upon their surface area and how well insulated they were. If insulation were 'perfect', it would require no power at all to maintain the cavity temperature!
As volume increases, surface area increases much less rapidly (in proportion to square, rather than cube, of linear dimensions for simple shapes) - so one would expect larger freezers to be more efficient.
Kind Regards, John
That's disappointing to hear, not only because I won't get my -80C freezer but also because it occurred to me that if he left it going for a few days and got it down to -273.15C, he'd be in line for a Nobel gong. That would certainly pay for a new freezer.
Indeed - as you will have seen, BAS has already made that point (well, I assume it's the point he was making!), albeit in a somewhat BAS-like 'cryptic' fashion
Kind Regards, John
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It is the standard annual energy (SAE) which is the magic figure that took me ages to find out where it comes from. This PDF does give the formula which needs multiplying factors it would seem all based on a fridge at 5°C and with for example a freezer at -18°C you multiply the volume by 2.15 if frost free then times by an extra 1.2 and then also correction if not designed to run a 25°C and so on.
So SEC = volume corrected x M + N + 50
So if one looks at a 32 litre freezer like mine then using 146 kWh/annum it would be 36% but if frost free it would be 35% and if a chest 40% because of the correction values and the assigned M and N values. All would drop into A+.
With a fridge/freezer the M and N values change. But it would seem the A+, A++, and A+++ rating are not really important it's better to just look at the kWh/annum.
It would seem however these energy labels have reduced the range. Today you never get a freezer bigger than the fridge. Samsung have been crafty here they make a matching fridge and freezer which stand next to each other making it look as if it an American Style fridge freezer but it is too different units. As a result the SEC is better as they are using different M and N values for each unit.
I have a 230vac/12vdc fridge but today you can't buy the with 230vac option built in as only if the 230 - 12 volt dropper is separate are they exempt from the requirement to be A+ or better.
Where the energy source is primary other than electric they are also exempt so does not cover caravan types.
So SEC = volume corrected x M + N + 50
So if one looks at a 32 litre freezer like mine then using 146 kWh/annum it would be 36% but if frost free it would be 35% and if a chest 40% because of the correction values and the assigned M and N values. All would drop into A+.
With a fridge/freezer the M and N values change. But it would seem the A+, A++, and A+++ rating are not really important it's better to just look at the kWh/annum.
It would seem however these energy labels have reduced the range. Today you never get a freezer bigger than the fridge. Samsung have been crafty here they make a matching fridge and freezer which stand next to each other making it look as if it an American Style fridge freezer but it is too different units. As a result the SEC is better as they are using different M and N values for each unit.
I have a 230vac/12vdc fridge but today you can't buy the with 230vac option built in as only if the 230 - 12 volt dropper is separate are they exempt from the requirement to be A+ or better.
Where the energy source is primary other than electric they are also exempt so does not cover caravan types.
Well, it's obviously the kWh/annum which matters to one's pocket, but one clearly has to take the size of the fridge or freezer into account when making comparisons - one obviously would not expect a massive one to cost the same to run than a tiny one!
Kind Regards, John
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Well I went to the trouble to work out the standard annual energy consumption so I could in turn work out the A+ , A++ and A+++ limits for a given fridge, freezer, or fridge/freezer and tagged it onto an existing page used to compare fridge and freezer.
Here is the page it is at the bottom of the page plus link to where I got the info.
The small 32 litre freezer my mother has needs to be better than 177 kWh/annum to get A+ but to get A++ it would need to be better than 133 kWh/annum which is really a huge jump. Manufacturer says it's 146 kWh/annum.
My Samsung is ratted 277 and it would seem 279 is limit to be A++ so just scrapes in. But rate it as a freezer instead of fridge/freezer and it's only A+ all due to the way the standard annual energy consumption is calculated.
To my mind the rating is so complicated as to be near useless. Why should a built in unit be allowed to be less efficient than a stand alone? Or a frost free be less efficient than non frost free. Or upright be allowed to be less efficient than a chest freezer.
Here is the page it is at the bottom of the page plus link to where I got the info.
The small 32 litre freezer my mother has needs to be better than 177 kWh/annum to get A+ but to get A++ it would need to be better than 133 kWh/annum which is really a huge jump. Manufacturer says it's 146 kWh/annum.
My Samsung is ratted 277 and it would seem 279 is limit to be A++ so just scrapes in. But rate it as a freezer instead of fridge/freezer and it's only A+ all due to the way the standard annual energy consumption is calculated.
To my mind the rating is so complicated as to be near useless. Why should a built in unit be allowed to be less efficient than a stand alone? Or a frost free be less efficient than non frost free. Or upright be allowed to be less efficient than a chest freezer.
I think that sums it up well. Maybe I'm cynical, but I suspect that these ratings were not designed for anything more useful than playing lip service to 'the cause'.
Kind Regards, John
A cynic is just an experienced optimist.
Not just Samsung - plenty of makers do larder fridges and larder freezers which match.
Even the Real Thing is like that:
http://www.subzero-wolf.co.uk/product_details.aspx?pID=2&sw=0
http://www.subzero-wolf.co.uk/product_details.aspx?pID=96&sw=0
Maybe it's simply that people want more space in the fridge than the freezer?
Maybe, or maybe it becomes a problem to stop the fridge getting too cold if too high a proportion of the 'box' is at -18° ?
Kind Regards, John
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