User manuals of some freezers indicate that for the first few hours after switching on the new freezer, one should not put any food into it. For instance, I am looking at a specimen that requires me to wait for 6 hours before starting to fill it.
Note that this is unrelated to letting the freezer stand upright for a while before switching it on.
This rule is alluded to on various non-product-specific websites, as well. Two examples:
- "When you've set it to what you want, give it a few hours before you start filling it up with food – some fridges have a light that'll let you know when it's ready."
- "It is only in the case of new freezers that you must wait a number of hours before storing frozen foods (You should consult your manufacturer’s handbook for more information)."
What is this restriction based upon?
If I put some frozen food (bought in a frozen state) into a new freezer right after switching it on for the first time, what could happen?
- Is it bad for the food?
- Is it bad for the freezer?
- Is it bad for either of these no matter what, or only in specific circumstances?
- Or is it one of those restrictions that are reiterated by many who do not actually remember what the rule was for and under what circumstances it was applicable?
UPDATE: Here are some clarifications, as the scope of this question appears to be unclear.
First, I am not asking for
- what the restriction says
- what might be a valid guideline if I ignore the restriction
- how I might preserve frozen food during the initial period
I am truly looking for the technical rationale behind the restriction as stated.
Best Answer
Most of the "cold" in a freezer isn't stored in the air. It's stored in the contents of the freezer, and in the walls (air has a very low volumetric specific heat). However, the thermostat controlling the compressor works off the air temperature.
If you start filling a freezer before it's had a chance to properly cool the walls down, the food is exposed to an effective temperature that is far higher than the freezer's setpoint: heat gets transferred from the walls to the food, warming it up to unsafe levels. Only once the walls reach thermal equilibrium with the air is it safe to start filling the freezer.