Freezer Not Holding Temp?

[StarryHorizons]

Hey All,

During some troubleshooting of our Isotherm CR90f freezer, I installed a Carel ir33+ digital thermostat control. The temperature set point is for -13C/8.6F and the compressor cut in temp is set for -10C/14F. Another thermometer which measures temp among all the frozen meats reads about -16.2C/2.8F and -14.1/6.6F at those levels.

We managed to get the first problem fixed, but what is concerning now me is how quickly the freezer temperature raises from that -13C to -10C. It only takes about 15-20 minutes with the freezer about 60% full. Right now, it's night time in Mooloolaba and the outside/room temp is about 18C/64F.

Does that rate sound normal or do I likely have a problem?

The freezer has a crack in the interior plastic, and I drilled a hole to fit the Carel temp sensor. Both of those have been filled up with silicone, though I'm not 100% sure how long the crack was there before I noticed it.

Thanks for the help!

David

[OzePete]

Originally Posted by StarryHorizons

Hey All,

During some troubleshooting of our Isotherm CR90f freezer, I installed a Carel ir33+ digital thermostat control. The temperature set point is for -13C/8.6F and the compressor cut in temp is set for -10C/14F. Another thermometer which measures temp among all the frozen meats reads about -16.2C/2.8F and -14.1/6.6F at those levels.

We managed to get the first problem fixed, but what is concerning now me is how quickly the freezer temperature raises from that -13C to -10C. It only takes about 15-20 minutes with the freezer about 60% full. Right now, it's night time in Mooloolaba and the outside/room temp is about 18C/64F.

Does that rate sound normal or do I likely have a problem?

The freezer has a crack in the interior plastic, and I drilled a hole to fit the Carel temp sensor. Both of those have been filled up with silicone, though I'm not 100% sure how long the crack was there before I noticed it.

Thanks for the help!

David

Hi David,
things to do:
1, smear silicon over the Carel controllers sensor probe to water proof it.
2, place the sensor into a small container of water and locate towards the centre of the freezer area. (A small skinny glass is ideal)
3, Expand the hysteresis (differential) to say 5C That is -14C cut out and -9C cut in.

The above will help a lot but you may also have a saturated insulation problem, but best to set up as above first, allow a couple of days running then see how it runs.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[StarryHorizons]

Originally Posted by OzePete

Hi David,
things to do:
1, smear silicon over the Carel controllers sensor probe to water proof it.
2, place the sensor into a small container of water and locate towards the centre of the freezer area. (A small skinny glass is ideal)
3, Expand the hysteresis (differential) to say 5C That is -14C cut out and -9C cut in.

The above will help a lot but you may also have a saturated insulation problem, but best to set up as above first, allow a couple of days running then see how it runs.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

Thanks for the quick reply. I'll have to work on the sensor tomorrow as I've had about enough freezer for the day!

When I pull it back out is there any way to test and see if the insulation has become saturated?

[OzePete]

Originally Posted by StarryHorizons

Thanks for the quick reply. I'll have to work on the sensor tomorrow as I've had about enough freezer for the day!

When I pull it back out is there any way to test and see if the insulation has become saturated?

If possible run your hand over the cabinets outer walls (specially the base) and see if you can detect any abnormal coldness or sweating. If the cabinet, while operating as a freezer, shows no signs of outer liner coldness then it is most likely ok. From your brief description and assuming this is a cyclic system, the rapid temperature rise is understandable the way it was set up, so will be interesting to see what the suggested alterations achieve. I wouldn't be too concerned about the insulation at this stage.

Cheers OzePete

[Boatguy30]

Those stock units are super inefficient. Very little maybe 2-3" of insulation? It's all thermodynamics. Doesn't matter what's in it. Going to run a tin and in doubt keep true freezer temps in high ambient temps.

[oleman]

Originally Posted by StarryHorizons

Hey All,

During some troubleshooting of our Isotherm CR90f freezer, I installed a Carel ir33+ digital thermostat control. The temperature set point is for -13C/8.6F and the compressor cut in temp is set for -10C/14F. Another thermometer which measures temp among all the frozen meats reads about -16.2C/2.8F and -14.1/6.6F at those levels.

We managed to get the first problem fixed, but what is concerning now me is how quickly the freezer temperature raises from that -13C to -10C. It only takes about 15-20 minutes with the freezer about 60% full. Right now, it's night time in Mooloolaba and the outside/room temp is about 18C/64F.

Does that rate sound normal or do I likely have a problem?

The freezer has a crack in the interior plastic, and I drilled a hole to fit the Carel temp sensor. Both of those have been filled up with silicone, though I'm not 100% sure how long the crack was there before I noticed it.

Thanks for the help!

David

Commercial freezers have to be able to hold 0F.
What gives with +14F freezers in small boats?

[Lepke]

The way I understand those freezers work is when other power is available (shore power or alternator) the unit runs to a colder temp and freezes the holding plate to act as a block of ice so the unit doesn't turn on for an extended time. Later on battery power it doesn't cool as far down to save the battery.
Any freezer or reefer benefits from additional insulation around them if you have room. Also when on shore power, if you add containers of water and allow them to freeze, they help hold the temp and you don't displace as much cold air when opening the door.
Where does the heat from the condenser go? Is there enough airflow.

[a64pilot]

Originally Posted by oleman

Commercial freezers have to be able to hold 0F.
What gives with +14F freezers in small boats?

If it is a conversion from an icebox to a freezer, then the manufacturer of the equipment can’t possibly know how well the box is insulated.
I believe that well insulated ice boxes were rare, sort of like unicorns.

[john61ct]

Originally Posted by oleman

Commercial freezers have to be able to hold 0F.
What gives with +14F freezers in small boats?

Unrealistic to try to get commercial onshore freezing capabilities on most smaller boats with very limited power input while offshore.

And overkill expense when that level of performance isn't usually required.