Freezer door left open alarm

On rare occasions I have left our (upright) freezer door not fully closed. I doubt that it got significantly less cold inside, and the compressor probably worked hard, but when I came to open it the following day, it was a mass of icicles and frozen condensate, requiring a total defrost to clear it.

It happens that Chris Hogg formulated :

As was mine, which is why I decided a solution was called for..

In which case a simple temperature sensor might not register the problem if the temperature doesn't rise far enough. Perhaps a microswitch on the door, connected to a time-delay system, allowing you a few minutes access to the freezer before the alarm goes off?

Chris Hogg was thinking very hard :

As said, it works fine, responding quickly to the door being opened. It generally shows minus 17.5 to 18.5C, alarm set to trigger at higher than minus 13.5C. Left open for a full minute, the alarm sounds, but easy to ignore if you wish to, because it only sounds once per minute.

Do you mean minus 13.5C?

Bill

Bill Wright expressed precisely :

Sorry, yes minus 13.5C

why not just use the door to control a switch like they do for the fridge light, never did understand why a few pence on such a device was not on all freezers. Cue Tommy Steel, i Puts the Lightie On on deca. Brian

Brian Gaff formulated the question :

It already has a built in 'temperature too high' warning light, but when lit it is not obvious unless you look at it with the door open and when you are in the utility room. I wanted an audible means of knowing when in the kitchen, that the door was left open or the temperature in the freezer went to high. So this serves to warn if the door has been left open, power has been lost, or the freezer has suffered some other failure.

Mine didn't, just quite a bit of black mould on the inside of the door, easy enough to get rid of.