Fridge Thermostat

[pvb]

i should have edited the post and changed the values as I added the second paragraph in an edit.
All I can say is that I had a chap working for me who built all the camper and Nicholson fridges that all had eutectic plates and he used the temperatures that I do and Iceberg Norcool who built all Nautor Swan fridges amongst many others such as the one I serviced for many years on Velsheda use -5 for fridge and -25 for freezer plate temps.

I think my concern is that yours was the second instance in this rather short thread of the OP being given completely incorrect advice by supposed experts. If it wasn't for we simple souls who actually read installation instructions, the OP wouldn't be getting the right advice.

 

[owen-cox]

Thank you. I was told by a fridge engineer that the accumulator should be cooled to minus 14 degrees! I might need to experiment with settings. As far as I can tell there is no way of actually attaching the probe to the accumulator and ensuring it remains in contact.

If I remeber correctly CLD ised to supply a metal clip that clipped the thermostat bulb to the edge of the plate. They did fall off sometimes could it have dropped to the bottom of the fridge? Please note the temperature you need is -5 for eutectic as pointed out by pvb

 

[owen-cox]

I think my concern is that yours was the second instance in this rather short thread of the OP being given completely incorrect advice by supposed experts. If it wasn't for we simple souls who actually read installation instructions, the OP wouldn't be getting the right advice.

Point taken. Unfortunately i was pottering about doing jobs on my own boat at the same time as looking at the forum.

 

[GHA]

Nowhere near cold enough! Accumulator holding plates usually run at -8 to -12 degrees.

This is a danfoss bd35, skinny plate so presumably an evaporator plate? Arduino doing the job of thermometer set to off at 3.5 and on at 5 deg c ambient. Graph of ambient and the plate :

 

[Norman_E]

If I remeber correctly CLD ised to supply a metal clip that clipped the thermostat bulb to the edge of the plate. They did fall off sometimes could it have dropped to the bottom of the fridge? Please note the temperature you need is -5 for eutectic as pointed out by pvb

I suspect that if it did have clip it was lost before I even bought the boat. I have some JB Weld on board so will try that to attach the existing thermostat bulb.

 

[owen-cox]

This is a danfoss bd35, skinny plate so presumably an evaporator plate? Arduino doing the job of thermometer set to off at 3.5 and on at 5 deg c ambient. Graph of ambient and the plate :

That will be an aluminium roll bonded evaporator plate as is the norm. The temperatures are also as you say ambient so the plate temperature is going to be higher than a plate mounted one. Sometimes it is better to control plate temperature so that you can set an off set point of say -2 and then switch on point of above 0 degrees so that the plate has a chance to defrost between cycles. If you set yours too low you will find the plate freezes up and gets a lot of ice build up especially if there isnt a good seal on the door of the fridge. This allows moist air in and condenses and builds up on the plate. Unfortunately with eutectic hold over plates this is inevitable and a defrost is required from time to time. Some digital thermostats can have a defrost cucle built in so that for example yiu can set every 24 hours a cycle where it switches off until the temperature reaches 5 degrees and then restarts. Some larger systems have heaters to heat the cooling section quickly without warming up any food. You could if you found this to be an issue with an arduino system program this in I expect.
I have seen a couple of systems where the timer stuck( and as is typical of a boat) on the defrost cycle and it took a -20 freezer to +50 degrees for a whole night. £20,000 worth of meat had to be cooked very quickly!