What do Additional Bi-Metal Sensors Do

[kubcat]

Hi all.

I have a Whirlpool top freezer frost-free basic fridge, which is nearly identical to the gladiator garage works garage fridge (google gladiator garage works fridge to see it) with an operating range of 0-100 F.

After comparing the parts list of the 2 fridges, the only real differences I found are for the thermostat, and 2 bi-metal sensors in addition to the defrost bi-metal sensor (one each in the fridge and the freezer).

Can someone please explain how these additional sensors work together with the new thermostat to extend the lower operating temperature from ~55F to 0F?

Thanks,
Kubcat

[monkey spanners]

So you have a fridge freezer that you keep in a garage that in the winter is not keeping the frozen food frozen because the garage is cooler than the fridge stat setting and you are trying to make it work somehow?

Do you keep any food in the fridge compartment?

I have heard of people modifying the interior light switch so that is always on to provide a false load in the fridge compartment. No idea if it actually works though...

[Brian_UK]

I'm afraid that your 'search' request doesn't provide us with any information regarding the technical details of this unit.

It appears to have electric heater as well so perhaps they are something to do with that.

Perhaps contacting the manufacturer might be the best option.

[kubcat]

The only heater in either fridge is the standard defrost heater used in a frost-free top freezer design. It is my understanding that this heater is controlled by a combination of the bi-metal temperature sensor in the freezer, and the duty cycle of the compressor (heater runs 30 minutes for every 8 hours of compressor time, unless the temperature is over 45F in the freezer already or something like that) I believe that is how a current standard frost-free combination fridge/freezer works.

If the only differences between the two fridges are the thermostat and the additional bi-metal sensors. My suspicion is that in my fridge, the thermostat turns on the compressor only when the fridge calls for it (which is seldom in the winter, if at all), but the 0-100F version uses additional bi-metal sensor in the freezer to switch on the compressor when the freezer needs it, even if the fridge doesn't. I am not sure of the role the 3rd sensor in the fridge unit plays. Does anyone know?

[fridge doctor]

OK, here's what you got. Yours is the basic model, and is not intended to be located anywhere other than a kitchen (or room otherwise warmed as part of the house). You have only one thermostat control, and the sensor for this is located in the 'fridge' section. Under normal circumstances this works fine and controls both fridge and freezer sections.

If the appliance finds itself operating in an unheated space during winter (particularly a cold winter), it will cease to function effectively. The reason is that the single thermostat control to which I referred has a factory pre-set function built in, which, after reaching temperature, will not allow the compressor to restart until the thermostat sensor reads 40 degreesF. The reason for this is simply to ensure that the auto defrosting of the fridge section works. In other words if the thermostat was allowed to restart the compressor before 40 degrees was reached, there would still be frost/ice on the evaporator, and it would build up steadily from there on, reducing the efficiency of the fridge to almost nil in a matter of days. So the function of the thermostat is to prevent this from occurring. Obviously under conditions where the ambient temperature of the room in which the fridge is kept are not rising to 40 degrees, the evap remains too cold for the compressor to start - resulting unfortunately in a gradual defrosting of the freezer compartment.

The other model you refer to has a bimetallic strip (fixed temperature device) located on the outside of the cabinet. And when the ambient falls to 40 degrees or less, the bimetallic strip comes into play and makes a circuit to a small heater located in the fridge evap area, which in turn ensures that the fridge is 'artificially warmed' sufficiently to bring the compressor back on and thus maintain regular cycling and thereby save the frozen food in the freezer section.

In short, on a practical level there is nothing you can do. Your refrigerator will not work successfully in an ambient at or approaching the freezing point of water.

I hope you have understood, and found this short article informative. Normally this site is reserved for technical help between professionals who earn a living from the knowledge they have gained. Yours is not a 'repair' that could be dealt with by any technician which is why I have chosen to answer it, but please bear in mind for the future that refrigeration systems are not to be fooled with, and the old adage 'a little knowledge can be a dangerous thing' might have been written with refrigerators in mind.

Happy New Year.
Trevor