Hi Dan,
Do you really need to fit a chart recorder? you will still need to change the chart every so often anyway. surely you will only need to check the temps when there are deer in the chiller. it might be easier to record manually and perhaps fit a digital low temp alarm. i supose it depends on the location of your chiller. We use a wireless system called i spy but it's very complicated and needs a PC to run it. one other thing is that if you are using your chiller temp as a CCP then you will need to have calibration records for whatever equipment you use to log temperatures, this will be easier with a hand held thermometer rather than a chart recorder.
Ezzy