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Old 28-04-2018, 01:28   #1
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Freezer thermostat - analogue or digital?

I am changing my fridge set up from fridge + freezer with individual holding plates, to a spillover system with both holding plates in the freezer

Thermostats are both analogue
I understand I need a freezer thermostat to replace the fridge one

Is there any benefit to change to digital thermostats and will I see any noticeable gain?

Can one thermostat control both compressors or do they need individual controls?
I suspect not but worth asking........

Is there a dual channel digital thermostat?

I have 3 digital controllers, with one to turn the spillover fan on and off as required, and as a bonous give me digital temperature readout in the fridge.
Another will give me digital readout in the freezer, so that advantage of the digital thermostat is moot

I was told here that these controllers will not replace the thermostat. I still do not understand why these controllers cannot use their set points and integral 20A relay to turn on the BD50 compressors?
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Old 28-04-2018, 05:34   #2
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Re: Freezer thermostat - analogue or digital?

I just installed an Inkbird digital thermostat on my freezer. Its only been about 2 weeks, but so far its been fantastic.

https://www.amazon.com/Inkbird-All-P...nkbird+digital

It gives you the option to attach the sensor whereever you want in the cabinet, or on the plate.

If I was in your situation, I would be tempted to try and control both compressors with one unit. According to the documentation on my compressors, the control circuit is a resistive sensing circuit with 15ma of current on the wire. I would be temped wire the "C" wires together on one relay input, then wire the "T" wires together on the other relay input. However, you might have an issue with each controller "seeing" the other controller and running continiously.

A better solution would be to use the Inkbird to control 2 separate automotive relays. Then those relays could control each compressor. Your total investment would be under $25.

Maybe one of the refrig specialists will join in and call me an idiot. However, until then, that would be my plan if I was in your situation.
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Old 28-04-2018, 05:36   #3
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Re: Freezer thermostat - analogue or digital?

Quote:
Originally Posted by Hoghead View Post
I am changing my fridge set up from fridge + freezer with individual holding plates, to a spillover system with both holding plates in the freezer

Thermostats are both analogue
I understand I need a freezer thermostat to replace the fridge one

Is there any benefit to change to digital thermostats and will I see any noticeable gain?

Can one thermostat control both compressors or do they need individual controls?
I suspect not but worth asking........

Is there a dual channel digital thermostat?

I have 3 digital controllers, with one to turn the spillover fan on and off as required, and as a bonous give me digital temperature readout in the fridge.
Another will give me digital readout in the freezer, so that advantage of the digital thermostat is moot

I was told here that these controllers will not replace the thermostat. I still do not understand why these controllers cannot use their set points and integral 20A relay to turn on the BD50 compressors?
Digital temperature controllers are a far better option than old vague mechanical types. For a start they are very accurate, you can properly set the cut out temperature and the hysteresis (or cut-in) and you have the bonus of a temperature read out.
Whoever told you they can't replace a thermostat is wrong because the ARE a thermostat! They can be used in any application where temperature control is needed and that includes controlling the old Danfoss and now Secop BD50 compressor range. Better still they can be remote located.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 28-04-2018, 09:19   #4
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Re: Freezer thermostat - analogue or digital?

OzePete,
What digital thermostat do you recommend?
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Old 28-04-2018, 10:06   #5
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Re: Freezer thermostat - analogue or digital?

Totally go digital. Programmable hysteresis, they are the best change you can make.

I installed these... $40.00

AKO - Thermostat / Controller (Panel)
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Old 28-04-2018, 15:37   #6
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Re: Freezer thermostat - analogue or digital?

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Originally Posted by Paul L View Post
OzePete,
What digital thermostat do you recommend?
As the previous poster said..
The Elitech STC-8080 12VDC controller suits your job but if you can find an Elitech STC 600 12VDC controller they are better (But near twice the price) as they are water proof and have remote relay. We use the STC 600 Elitech only now and being water proof has made them near 'bullet proof'
The digital controller can be located anywhere and the probe wires extended to suit so if you choose the STC8080 you can locate in a good dry space.
BTW, if you have a 110 or 240VAC Elitech controller you can slide the cover off and remove / bypass the tiny transformer so it will operate from 12VDC.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 28-04-2018, 21:02   #7
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Re: Freezer thermostat - analogue or digital?

I have three of these - 12V and an internal 20A relay

https://www.aliexpress.com/item/W323...311.0.0.Fk9DWF

Cheap enough to throw away if the Elitech or other brands are really any better.

One for the fridge spillover system controlling a computer fan at 0.3A
Easy enough

Another was planned for the 2 compressor + 2 holding plate system in the freezer.
The third is either a spare, or to control the second compressor in the event that using a single controller is a bad idea
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Old 28-04-2018, 21:19   #8
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Re: Freezer thermostat - analogue or digital?

Lots of them with a 2 relay output x 12 VDC:

https://www.aliexpress.com/wholesale...o+relay+output

Can one not simply connect each individual relay to its own BD50 compressor?

I will have a circulation fan in the freezer compartment so hopefully both holding plates will be at similar temperatures

They all seem to have cool on one relay and heat on the other. Not sure if the set points could be entered so that one could use both in "cool" mode
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Old 28-04-2018, 21:28   #9
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Re: Freezer thermostat - analogue or digital?

Quote:
Originally Posted by Hoghead View Post
Lots of them with a 2 relay output x 12 VDC:

https://www.aliexpress.com/wholesale...o+relay+output

Can one not simply connect each individual relay to its own BD50 compressor?

I will have a circulation fan in the freezer compartment so hopefully both holding plates will be at similar temperatures

They all seem to have cool on one relay and heat on the other. Not sure if the set points could be entered so that one could use both in "cool" mode
Hi HH,
Regardless of brand I think you will find that Elitech manufacture all of those. We use their STC600 because it is waterproof and supplied with twin remote relays.
They usually have SPDT switching so you should be able to control two systems with one device but why bother when they are so cheap! Also with two devices you get to have two temp monitors at all times.

Cheers OzePete
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Old 29-04-2018, 04:11   #10
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Re: Freezer thermostat - analogue or digital?

Quote:
Originally Posted by Hoghead View Post
Lots of them with a 2 relay output x 12 VDC:

https://www.aliexpress.com/wholesale...o+relay+output

Can one not simply connect each individual relay to its own BD50 compressor?

I will have a circulation fan in the freezer compartment so hopefully both holding plates will be at similar temperatures

They all seem to have cool on one relay and heat on the other. Not sure if the set points could be entered so that one could use both in "cool" mode
Those are the exact same unit I linked to on Amazon (branded Inkbird).

First.. Although they say 2 relay, one relay is for heating and one is for cooling. I have found no way to make both relays operate as cooling relays (without physical modification). However it would be trivial to cut a trace on the board and run a jumper wire to make both cooling relays.

Second.. You need to look closely at the descriptions. Some of these devices have a "delay" setting and some don't. You NEED the "delay" setting. It prevents the unit from trying to cycle the compressor on too quickly before the pressure has equalized.

I took mine apart before installation. Although its not "waterproof", the board was conformally coated. Pretty hard to beat at $15 shipped directly from Amazon's warehouse, with Amazon's warranty.
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Old 29-04-2018, 10:02   #11
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Re: Freezer thermostat - analogue or digital?

Chiming in with another question. I have an old 110V 3/4 hp motor dual plate, dual cabinet system with analog thermostats.. One side gets and maintains its chill and then the entire system shuts down where both sides should run independently. Not sure why this is happening but I suspect a faulty thermostat. I will test this and assuming that is the case could I replace both thermostats with one of these?

Origin Elitech ECS-180neo 110V Digital Temperature Controller Centigrade Thermostat w Sensor
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Old 29-04-2018, 21:51   #12
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Re: Freezer thermostat - analogue or digital?

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Originally Posted by travellerw View Post

Second.. You need to look closely at the descriptions. Some of these devices have a "delay" setting and some don't. You NEED the "delay" setting. It prevents the unit from trying to cycle the compressor on too quickly before the pressure has equalized.
Mine are single relay units so one for each compressor. Or I could splurge and buy a cheap dual relay unit and cut and jump the trace as you suggest

Delay is programmable from 0-10 min.
What is an appropriate delay?
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Old 29-04-2018, 22:39   #13
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Re: Freezer thermostat - analogue or digital?

Quote:
Originally Posted by Hoghead View Post
Delay is programmable from 0-10 min.
What is an appropriate delay?
Typical is 3 min.
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Old 29-04-2018, 22:40   #14
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Re: Freezer thermostat - analogue or digital?

Quote:
Originally Posted by Hoghead View Post
Mine are single relay units so one for each compressor. Or I could splurge and buy a cheap dual relay unit and cut and jump the trace as you suggest

Delay is programmable from 0-10 min.
What is an appropriate delay?
3 minutes should see your system balance out for a zero load start

Sorry Rich, didn't notice your prior post...
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Old 30-04-2018, 07:19   #15
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Re: Freezer thermostat - analogue or digital?

That's called a Double Blind Answer Confirmation from two Eutectic Holding Plate guys....ha ha ha....

Cheers Pete
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