Hysteresis

[Graham_Wright]

I recently installed a remote thermometer on the fridge.
I was shocked to find the temperature swung between -2°C and 9°C.
The fridge is by Frigoboat.
I have another thermostat that has three twiddle screws but every time I fiddle, I seem to break it.
Any ideas please?

 

[yotter]

Is the sensor close to the cold plate, it will vary in temperature depending on the compressor cycles, but +9 seems a bit warm.

 

[andsarkit]

That does seem quite a wide variation. I checked my home fridges with a termerature monitoring recorder and found a variation of about 6 degrees on one while the inverter one was much better at about 2 degrees variation.
You could probably find an electronic temperature controller from China that would allow you to set both on and off temperatures which would probably also use more electricity and wear out the compressor with constant starting. The real answer is an inverter controlled variable speed compressor but I doubt these are available for boat fridges.

 

[OCuea]

How good is the thermometer?
I bought 2 that turned out to be useless and the 3rd different make shows a constant 5 deg C in my house fridge- I know it should be 3 but can’t get it to be constant there….. so constant 5 it has to be.

 

[Concerto]

I bought a cheap (£5 from Aldi or Lidl) battery thermostat that shows indoor and outdoor temperature. The outdoor sensor is on a fine cable about 2m long and I have found placing it at the bottom of the fridge/cool box about halfway from the cooling plate seems to keep the reading fairly stable. I do find the outside temperature does alter the internal reading so I have to adjust the fridge thermostat to keep it between 3 and 5C. The main thing is it works. The only upgrade I have thought about is adding a computer fan to circulate the air within the fridge for a more even temperature.

PS I did use a digital point thermometer to check the thermometer reading and found it very close, so I have confidence in the reading from the fridge.

 

[OCuea]

Adding a fan good idea. Some fridge manufacturers do it. Shame they don’t all do it. Not rocket science or expensive is it? Weird weird world.

 

[Graham_Wright]

I will check the thermometer. I have a scientific calibrated one ( that, in 1981?, recorded a temperature of -28°C in the garage - lower than the official record!).
The sensor is at the bottom of the fridge compartment.