Wow there’s really is a lot of misunderstanding and ignorance here when it comes to fridges and their loads.
As a general rule, most (but not all) frozen loads can be run with the fridge set to Auto (stop/start), the unit will start when the internal air temp (NOT the product temp) drops to a certain point. Set the fridge to -22 and it will generally cut in when the temp rises to -18 thereby maintaining at least -18 for the duration of the journey for the purposes of providing a satisfactory thermograph print out.
The main exception to this is ice cream, most factories will insist in the fridge being set to -22 > -25 and run on constant.
Packaged fresh meat and dairy generally needs to be run on constant run to maintain air flow through the box, but some can be run on stop start during the cooler months as long as the trigger temp for restarting isn’t set too far away from the actual set temp.
Fruit, which can be run anywhere from +5 > +14 is not particularly temp sensitive but is very prone to ‘burning’ with the initial cold blast of the fridge starting if the top front layers aren’t properly protected, so constant is preferred to stop this damage.
I never pulled pharmaceuticals so can’t comment, except to say I believe in many cases the maintance of an accurate constant temp is very critical and switching off the fridge would quickly destroy the load.
Fresh hanging meat is a nightmare and best left to the experts as it’s invariably loaded while still warm and unless much care is taken to get the temp down slowly (something the fridge was never designed to do) then it’s very easy to completely ice the fridge unit up and stop it doing anything useful except make a lot of noise.
If running on constant then a Thermo King will rev to get the temp down then once there it will tick over but still go to max revs approx once an hour and when it finishes defrosting.
A Carrier will do exactly the same except it usually has the facility to turn it to ‘silent’ running. This doesn’t actually mean silent but does mean it will not rev regardless of what the fridge is doing, so no max revs when it’s defrosted.
Unfortunately the silent facility is only available if the company haven’t switched off the facility in the master control menu. Many companies now don’t trust drivers and limit the options they can use on the units.
Many fridges have remote monitoring theses days, the option to switch off is often not up to the driver. Switch his fridge off with the wrong load on and he’s in trouble, the companies in trouble, and if it goes unnoticed it might mean food goes into the supply chain that is no longer fit for human consumption.
A fridge driver can often make life easier for those around when parked up.
Any load will happily run on constant, and the constant thrum of a fridge running on constant helps to block out other noises, but revving and stop start will obviously disturb sleep. After 25 years pulling fridges it took me a good 6 months to sleep properly again without the soothing hum of the fridge when I gave the job up 2 years ago.
I was often threatened with my fridge being switched off. I always took a pic of the guy at my door demanding such and also one of the unit he got back into. Whether or not this would have been deemed acceptable evidence to plod if someone had switched it off I never found out as no one did.
One local to me company have all their fridges set to constant and no silent options to protect the goods of their major customer after experiencing problems at RDC’s because drivers had run the fridges on silent, and on Auto during the summer and the units weren’t capable of maintaining the temp.