Digital Thermostat in Fridge

[lawrence_craig]

Originally Posted by OzeLouie

Yes it will if set up correctly.. Best to locate the sensor sealed in a small amount of liquid so that it best represents product temperature. This will also reduce daily start ups improving efficiency.

For a start put the SET value (cut off) at say +1C and the HYS at say 4C This will cause the unit to cut off at SET +1C and rise by HYS 4C to cut in again at +5C. Adjust warmer or colder later if needed.

Note: SET is an actual temperature setting cut-out while HYS (or differential) is the number of degree the temp rises above the SET value before starting up again.

I really like the idea of immersing the temperature probe in a small amount of liquid. Makes a lot of sense.

[raingolfer]

I want to replace the mechanical control in our frig. Frigoboat unit
I’m confused as to what to do with the existing wire connections from the mechanical switch. They are labeled “thermostat” C and T

Can someone help with a diagram?

[Coolerking]

Remove the wires from C and T and put them into the switch terminals on the digital thermostat, supply 12/24dc to power terminals on digital thermostat, connect sensor to sensor terminals on digital thermostat.
You will need the correct temp sensor, either a ptc or not, it should say on the label on the digital thermostat.

[OzeLouie]

As above, connect from c and t then to the controller as instructed. This controller pictured would see that connection to terminals marked 'Cooling' but that may vary depending on the controller brand.
The probe connections are usually clearly marked as are the power supply terminals.
Highly recommend the Elitech controllers as they are world leaders, reliable and come with the correct probe and detailed instructions. Elitech is marketed under many brand names but the STC1000 is a good basic controller.

[Coolerking]

It's an NTC probe, I didn't see the pic for some reason.
If that's the actual t-stat you have then it is super simple if you have the probe.
We use the Elliwell line of digital controllers, but they are far more complicated than the one OzeLouie posted, which in my mind is better frankly for your application, we use many of the features on ours to control evaporator defrost/drain heater cycles, alarm states and other crap. Many are tied directly into the ships main PLC panels and can be accessed at any station.
I like the simple ones.

[OzeLouie]

Originally Posted by Coolerking

It's an NTC probe, I didn't see the pic for some reason.
If that's the actual t-stat you have then it is super simple if you have the probe.
We use the Elliwell line of digital controllers, but they are far more complicated than the one OzeLouie posted, which in my mind is better frankly for your application, we use many of the features on ours to control evaporator defrost/drain heater cycles, alarm states and other crap. Many are tied directly into the ships main PLC panels and can be accessed at any station.
I like the simple ones.

Yes CK, Elitech make some brilliant controllers and a wide range. They are heavily into temp controls and data loggers for Covid vaccine storage these days. We us a water proof Elitech controller and like you say it has many functions including the ability, via a remote relay, to control condenser temperature and provide condenser temp readout by simply pressing down button.

Important in maintaining condenser temp to within engineered parameters preventing over and under condensing.. as you would know a major problem with marine systems subject to widely varying environments.

[sailjumanji]

We installed the Dometic Intelligent Temperature Control (ITC) in our Dometric Elegance 130 liter refrigerator. It replace the standard thermostat, and fits in a pre-molded location on the back wall of the fridge. The standard thermostat is underneath the freezer section cold plate, and performs poorly when encased in ice. The ITC thermostat operates within a 4 deg F range. It works very well. As such, we also installed one on our freezer (no pic). Other than having to drill a hole for the thermostat wire and attach the thermostat, the rest was simple plug into the controller. Wife especially likes the ability to look at the internal temp readout without having to open the fridge or freezer, which also reduces cycling.

(Sorry, got no idea why some of the pics are sideways. At least they are not upside down!)

[AndyEss]

I use an Inkbird digital thermostat and it works fine. Right now, I have it set for 4 deg F hysterisis (36-40 deg F).
I also combined an inexpensive powermeter (about $20 from Amazon) to monitor my fridge energy use.
I recommend everyone toss their old tube thermostats and convert to inexpensive and reliable digital ones. As others have noted, they also give you direct temperature readouts:

[Gypsy23]

Originally Posted by OzeLouie

Yes it will if set up correctly.. Best to locate the sensor sealed in a small amount of liquid so that it best represents product temperature. This will also reduce daily start ups improving efficiency.

I am using one of these thermostats and it works well. You mention imersing the sensor in a liquid. My sensor is in a small plastic box 20x35mm which is not suitable for water but could manage some type of gell. Can you suggest anything for the purpose? Vaseline??


Tks

[OzeLouie]

Originally Posted by Gypsy23

I am using one of these thermostats and it works well. You mention imersing the sensor in a liquid. My sensor is in a small plastic box 20x35mm which is not suitable for water but could manage some type of gell. Can you suggest anything for the purpose? Vaseline??


Tks

Hi Gypsy. The idea is to slow the controllers reaction so that the system function is smoother and avoid short cycling. For example if something warm happens to be placed near the sensor probe. I suggested water in a sealed file but think anything that slows the transfer to or removal of heat from the probe would be ok. Vaseline could be interesting, please let us know how it goes for you.

[raingolfer]

Digital controller is installed. Temp set for 40F. Compressor was running quite a bit more trying to get to that temp. It’s 85F here. I need to put the sensor in liquid.

Curious result. On about day 2, all the frost on the evaporator plate melted? Still seems to be cooling. Did compressor shutoff for a period and it warmed up enough to melt ice?

[skipgundlach]

Originally Posted by raingolfer

Digital controller is installed. Temp set for 40F. Compressor was running quite a bit more trying to get to that temp. It’s 85F here. I need to put the sensor in liquid.

Curious result. On about day 2, all the frost on the evaporator plate melted? Still seems to be cooling. Did compressor shutoff for a period and it warmed up enough to melt ice?

40F and ice don't compute from this end...

There might be several reasons that the frost disappeared - particularly if it was merely surface frost (no buildup of note), but without taking heat out (compressor running, and a presumed healthy system), frost won't persist at 40F...

[Coolerking]

40 degree temp setting will require a 25 degree evaporator.

[Gypsy23]

Tks OzeLouie, I'll try a couple of gells sometime in the future. Heading into winter now so not on board so often.

[Coolerking]

We use a small length of copper tube with an ID big enough to fit the probe and some mineral oil.
Cap it off, place it on the wall in the correct position, slide the probe in and top it off with the oil.
It will keep the unit from cycling, and give the temp a chance to recover.