Refrigerator problem?

[Ian_Edwards]

This is a graph of the refrigerator on the boat, for an overnight period, when the door wasn't opened.
You can see that it is working, but I think that the temperature range is to big. It's swinging between +2.64C and +8.95C.
I think that the ideal range should be between about +2C and plus +5C.
I can adjust the thermostat down a bit to get to +2C, but I don't think that will bring the +8C down very much.
The refrigerator is 17 years old.
It looks like the compressor is working Ok, but the thermostat is on its way out.
I can probably replace the thermostat.
I noticed that the milk was going "off" much quicker than I expected.
Any comments or am I over thinking this again?

 

[yotter]

It might be worth trying a new thermostat, if its a Danfoss compressor its just spade connectors to the controller. If it needed to re gassed I suspect the cycles would be more often.

 

[Boater Sam]

Possibly working too hard and the heat off the compressor is warming it up due to it being short of gas after this length of time.

 

[yotter]

Just to add, it looks like a very long run time for the compressor, mine runs about 10% on 90% off if the lid is kept shut. Perhaps it does need gassed?

 

[Dogone]

The gap between on temp switch and off temp switch is the switch hysteresis. You need a much smaller value. 2 deg C or less. Replace the thermostat with a better spec unit or adjust it if you can or go to an electronic one where you get a display and flexible settings. Carel is a good brand, which I have fitted in my boat.

 

[yotter]

A cheaper option, I use one of these as a digital indication of engine temperature, but it does have a switched output which I have never used but could perhaps be used to control a fridge temperature. Perhaps a bit of a faff to fir though. Hopefully the link will wort otherwise google STC100 temperature.

https://www.amazon.co.uk/XLX-Microc...ccbb8c3c503c3f6c9afcecdc51e2d4c9&gad_source=1

 

[Dogone]

A cheaper option, I use one of these as a digital indication of engine temperature, but it does have a switched output which I have never used but could perhaps be used to control a fridge temperature. Perhaps a bit of a faff to fir though. Hopefully the link will wort otherwise google STC100 temperature.

https://www.amazon.co.uk/XLX-Microc...ccbb8c3c503c3f6c9afcecdc51e2d4c9&gad_source=1

Brand: XINGYHENG ‘nuf said.

 

[yotter]

Brand: XINGYHENG ‘nuf said.

Fair comment. I have just checked, many suppliers for STC 1000,but not sure who mine was from, I have 2 and very good quality for a few years use now.

 

[Alex_Blackwood]

View attachment 180075
This is a graph of the refrigerator on the boat, for an overnight period, when the door wasn't opened.
You can see that it is working, but I think that the temperature range is to big. It's swinging between +2.64C and +8.95C.
I think that the ideal range should be between about +2C and plus +5C.
I can adjust the thermostat down a bit to get to +2C, but I don't think that will bring the +8C down very much.
The refrigerator is 17 years old.
It looks like the compressor is working Ok, but the thermostat is on its way out.
I can probably replace the thermostat.
I noticed that the milk was going "off" much quicker than I expected.
Any comments or am I over thinking this again?

Aside from what others have said. eg. Thermostat differential etc. The compressor is obviously bringing the temp. down but the rise in temp seems unduly rapid. Maybe that needs investigating.

 

[vas]

Fair comment. I have just checked, many suppliers for STC 1000,but not sure who mine was from, I have 2 and very good quality for a few years use now.

+1, have two on my two fridges, work nicely and keep a range that I can configure as I wish

V.

 

[Ian_Edwards]

Thanks for all the replies.
Although it seems obvious now, I hadn't thought of the system needing re-gassing.
With two problems, it seems like new fridge is the real answer.
I tried re-gassing the freezer, but that did work long term, after the second attempt, which didn't last very long, I bought a new freezer.

 

[chris-s]

We had something that looked very similar with a new fridge setup, turns out it was the victron battery protector I had fitted inline with it that was malfunctioning/misreading the supply voltage. Removed it and all good.

 

[yotter]

We had something that looked very similar with a new fridge setup, turns out it was the victron battery protector I had fitted inline with it that was malfunctioning/misreading the supply voltage. Removed it and all good.

View attachment 180096

Trying to avoid thread drift but that is very intuitive data from your Victron setup, can I ask (trying not to be nosey) what Victron product(s) provided this
Angus

 

[Ian_Edwards]

Just a thought, the fridge has a dual power supply back box. It runs of AC mains or 12v DC, and switches to AC whenever AC is available.
For this test the fridge was running on AC shore power.
I can't see why that should make any difference, but someone else may see a link.

 

[chris-s]

Trying to avoid thread drift but that is very intuitive data from your Victron setup, can I ask (trying not to be nosey) what Victron product(s) provided this
Angus

Ah, the screenshot was from the app that links with a thermometer we keep in the fridge, not a victron product, sorry for the confusion.
We had a victron battery protector inline with the fridge to prevent it draining the batteries, but found that when it should have been passing power thru it wasn’t even after checking the settings on it. What the graph appeared to show was the fridge getting cut off, it’s temperature rising until the victron decided the voltage was high enough to turn it back on, and then the temperature would begin to drop.

 

[Beneteau381]

Possibly working too hard and the heat off the compressor is warming it up due to it being short of gas after this length of time.

Why would "length of time" mean less gas? Time has nothing to do with it. They are sealed unlike pulley driven ones. The only place they can leak is from the quick connects O rings and if they go the system empties. Classic mistake, fridge not working, needs gas! Not necessarily! At 17 years the little compressor piston(s) could be getting worn and its not as efficient. Fridges in an ideal world should run at 4degC This keeps food from spoiling quickly, the actuality of it is they run at 6degC ish! Because of the usually inefficient insulation, people dont like the noise of the compressor and turn them up a bit!