OT: Super Freeze button

According to the manual of my side-by-side fridge-freezer, the "super freeze" button freezes things quicker. Great.

Can anyone tell me what it actually does, and how? I mean, I naively thought if I have my freezer at -19degC, and I put in some fresh meat to freeze, doesn't it normally try to freeze it as quickly as possible - that is to say, to maintain the temperature at -19 given the relatively warmer food I've put in?

I'm sure I'm missing something - what's the point of this?

Reply to
TD
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I think it actually tries to get the temperature lower than the usual set-point. I'm sure I've seen ours at -25°C when the FF button has accidentally been pressed and left for a while.

SteveW

Reply to
SteveW

I repeat, what's the point of this? :D

Reply to
TD

Putting in any significant amount of fresh food is going to raise the temperature well above the recommended maximum of 18 deg c for many hours. The idea is you run the compressor continuously by pressing the FF switch some hours *before* putting the new stuff in, the temperature will still rise, but from a lower starting point Once you have put the food in and closed the door you might as well turn off the FF, as if it goes above 18 (or your normal set point) it will run anyway.

Of course turning FF on wont make it get colder quicker, it will just get colder.

Its surprising how many people think turning up a heating thermostat will make a room heat up faster.

Reply to
Graham.

Well not quite, the freezer takes some time to adjust to food being added.

The lower than the set-point is a side effect. Usually the fast freeze setting over-rides the thermostat and runs the compressor continuously. Obviously this will lead to the freezer getting colder than it normally does.

Err as it says in the manual, to freeze things faster.

Reply to
Steve Firth

I'm ignoring modulation and other proportional control in arguing this.

Reply to
Graham.

Including my otherwise intelligent wife. I've installed a new thermostat that she doesn't know how to set.

Bill

Reply to
Bill Wright

Oh do tell!

My usually bright eldest has had this explained to him many times yet I still found it turned right up and the room like a sauna when he was not there.

Problem solved when I discovered the locking pins in the thermostat. When he complained it would not turn anymore, I just told him he had broken it with the constant turning.

Reply to
Ericp

Also the temp in the freezer gets down to cutoff point before the core temp of the food is anyway near so the FF button overrides the thermostat to allow the food core temp to stabilize.

Reply to
F Murtz

It shorts out the thermostat so the thing runs continuously.

Reply to
harry

It might. Some mechanical thermostats have a heater inside them to give better control. Also depends on the thermostat location.

Reply to
harry

To give the owner frostbite?? Brian

Reply to
Brian Gaff

OK, I don't mind parading my ignorance. If a room is cold but not yet colder than the temperature set on the thermostat, then turning up the thermostat surely *will* make the room heat up faster than it would if you did nothing.

Or am I missing something obvious?

Reply to
Bert Coules

AOL!

And anyway, if the radiators are not warm, the CH is not on!

Perhaps *elementary control systems* should be taught at secondary school?

Reply to
Tim Lamb

Ah, perhaps I am. The room will heat up *sooner*, not *faster*. Is that the point?

Bert

Reply to
Bert Coules

the word "faster". The radiators will heat up the room at exactly the same rate as long as the thermostat is calling for heat. In your example the room wasn't heating up at all before. Turning up the thermostat should make the final temperature higher - but the time taken to get to the temperature you want won't change.

Reply to
charles

Not really:-)

The purpose of the thermostat is to maintain the temperature of the room/house/fridge/cooker etc. at the preset level.

The rate at which the temperature changes is not dependent on the difference between the actual temperature and the preset level but on other conditions such as radiator sizing, boiler output temperature, window open etc.

Reply to
Tim Lamb

Thanks to Charles and Tim. Your posts were evidently written pretty much simultaneously with my own follow-up, made once I did in fact realise the difference between "faster" and "sooner"...

Bert

Reply to
Bert Coules

Yup. I think the point being made is that some people think that if the room is 15 degrees, then turning the thermostat up to 35 degrees will make the room warm up quicker than if they turned it up to 20 degrees. In reality, the room will reach 20 degrees in exactly the same amount of time whether you turn the stat to 20, 25, 35 or 100 degrees. In the same way that you can't make a ceiling light brighter by flicking the switch harder.

Of course, if you "override" the stat by turning it up to the point where it calls the boiler for heat, then indeed the room will warm up sooner than if you hadn't touched it.

Reply to
Mentalguy2k8

No good. It still happened in an office full of professional control engineers.

Chris

Reply to
Chris J Dixon

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