My first freezer/fridge was a Frigoboat (details in excruciating detail elsewhere in CF).
It had 2F hysteresis in both freezer
, measuring content, not plate, temperatures.
It worked a very nice treat, until it didn't.
Both boxes have NO/NC magnetic contacts which control the circulation fans (one each box) and lights, which come on when the door is open, turning off the fan/s - the compressor is not interrupted if it's running when the freezer
is opened; that's been a very nice feature at minimal cost.
I now have a Sea Frost evaporator (3, in series) plate system with, as seems the industry norm, the probe for the on/off at the bottom of the last plate, with a 6.5F hysteresis (per mfr instruction) - but also has a box thermometer showing what is happening in the box.
Our temperature in the freezer varies VERY widely as a result. I'm not sure that's of issue (I mean, every other manufacturer than FBoat seems to get the on/off probe on a plate, so it must be appropriate).
Our reefer box, supplied by a spillover fan controlled by another digital thermostat, with the FBoat 2F hysteresis, maintains its temperature very closely other than when we warm load it, in which case it comes down until it cycles and then is fine again.
Why wouldn't I want my freezer controlled as it was before (box temp 2F hysteresis)? Seems to me that a more even (mine can vary by 20F!) box temperature would be desirable...