I have a refrigeration unit powered by a Danfoss compressor unit.
The compressor has the ability to operate at variable speeds via a variance of resistance in the thermostat circuit eg. at 1523 ohms .... 3500 rpm whereas at 0 ohms ...... 2000 rpm.
After market add-on's by third party manufactures have allowed consumers to manually change the resister settings to match optimized running conditions or have produced a timing circuit as shown below to 'automate' the change of speed dependent of running time.

The question I ask is what circuits would be appropriate for this operation based on variable times and speed change (resistance dependent) ?

Any thoughts would be appreciated.

Cheers... Bjorn

 

The question I ask is what circuits would be appropriate for this operation

What operation? Manually changing the settings? Duplicate the activities described on your chart? Respond to the koala vs kangaroo population?

 

Heres the circuit ive drawn out of a Waeco fridge that uses a Danfoss BD35F compressor. U1 is an 8bitprocessor that controls Q1 & Q2 to give varying compressor speeds at diferent temperatures. Hope this is some help..

 

#12 .....a circuit suitable to duplicating chart activity. Thanks for a swift response.

debe.....thanks for circuits. The compressor is the Danfoss BD50F ...controller 101N0210.

 

Daryl or anybody who could assist......do have any thoughts as to the make up of the Merlin Smart Speed Controller.....link below.
http://www.veco-na.com/images/Merlin_Smart_Speed_Controller_-_Instructions_-_7.26.11.pdf
Apart the power input, the only interface is between terminals C and T on the controller where the change in current varies the speed of compressor.

Bjorn

 

My thaughts on this are that the beter way is speed controlled by the temperature as in the Waeco system. Where if the temperature rises too high the processor then gives a higher compressor speed. then reduces it when the temperature is nearer where it should be. That being said im not into processor design. My approach in portable 12V DC refrigeration is simple is best. I do have 2 Waeco fridges, but I also converted a Evakool fiberglass esky which has far beter insulation than the Waecos. I just used a $15 electronic thermostat from Ebay. My compressor speed has a switch for economy 2000rpm & power 3000rpm. It spends most of its time on the economy seting, The power setting is only used if ive loaded the fridge up & want it cooled quickly, then it lives on economy. This is my converted Esky.

 

Thanks Daryl.....I reckon the chiller box will be getting a serious workout in those SA temperatures..

As far your comment re a circuit which was temperature/ speed related would be ideal...I totally agree. However I am still curious on how Merlin actuates the speed change using a formula based on run time duration etc. The search goes on.
All the best for 2016......Cheers, Bjorn

 

It would be interesting to know how they arrive at that formula & I assume its done with a microprocessor. I checked out the link you posted but they don't show the other side of the circuit board. All the best to you in 2016 as well. Yes its been a bit warm here. Daryl.

 

The thermostat circuit eg. at 1523 ohms .... 3500 rpm whereas at 0 ohms ...... 2000 rpm.
Which type of motor is it?
how directly the speed is changing.?

The micro used datasheet it of samsung

 

Its a Danfoss 12v/24v variable speed compressor for portable refrigerators. The motor is 3 phase & is driven by a variable frequency.in the controller.

 

I have seen in mechanical lab any time doesn't know how te gas circulation work..

 

Sugest you Google Refrigeration Cycle for further information on the basics.

 

In our region has been several problem by the controller SECOP 101N0212. How could I test it the unit's problem? The LED flash No. is not valid. Somebody knows the circuit? Without the controller could not start the compressor's BD35F. How is possible start the compressor without the control unit?

 

The Compressor canot be run without the controller, as it generates a 3phase voltage from 12/24V DC. Why is the LED flash flash code number not valid? What is your problems with these controlers?

 

The compressor don't start to working just for 10 seconds. The LED twice flash mean: "the fan loads he electonic unit with more than 1 A peak.." But if no any connection to the fan - the flash No. is the same. It is inpossible....The fan current consumption is just 250 mA on 12 V DC....

 

What make & model fridge? I presume you removed the fan connection from F on the controller? If theres no conection on F & there is still a fault code then I suspect the controller is faulty. I have had a faulty fan draw too mutch current on a Waeco fridge.

 

Thank you Debe. The fridge is VITRIFIGO 42 L - Italian. It's on a yacht as fridge. First of all the evaperator was faulty. It's changed for a new one. The cooling circuit is ready - the gas filling is R134a- 50 g. We would able to find the controller faulty but no any drawing for the panel. The inverter technic generally using in the air condition units now. This is key point to controling the RPM of the compressors.

 

My thaughts on this are that the beter way is speed controlled by the temperature as in the Waeco system. Where if the temperature rises too high the processor then gives a higher compressor speed. then reduces it when the temperature is nearer where it should be. That being said im not into processor design. My approach in portable 12V DC refrigeration is simple is best. I do have 2 Waeco fridges, but I also converted a Evakool fiberglass esky which has far beter insulation than the Waecos. I just used a $15 electronic thermostat from Ebay. My compressor speed has a switch for economy 2000rpm & power 3000rpm. It spends most of its time on the economy seting, The power setting is only used if ive loaded the fridge up & want it cooled quickly, then it lives on economy. This is my converted Esky.View attachment 97515 View attachment 97516 View attachment 97517 View attachment 97518

Hi
Thank you for your support. I am new to this forum and have very limited knowledge. I am on a yacht at the moment, my fridge thermostat is not working and the fridge constantly freezes everything. A year ago I bought a thermostat control but have not been successful connecting it. Can you please give me some very simple layman directions on how to connect these? Attached are some photos of what I have... The top two wires obviously supply power to the unit and the red and blue power a small cooling fan next to the compressor. The other wires appear to go to the WAECO freezer box. Inside the freezer box, a grey wire and a green/yellow wire feed a small fan. The other wires are enclosed and there is a sensor there as well. Can you suggest how I should connect the new thermostat control?

 

Hello sailor
If you refer to a previous post (Debe,30 Dec2015) Debe's schematic shows the connections between the Danfoss controller and your digital temperature controller.
The wires marked "C" & "T" on the Danfoss Controller should track back to your old thermostat. You'll need to bypass the old thermostat by disconnecting C & T wires from the thermostat and connect them to Terminal 1 & 2 on the Digital T/controller which is only a switch governed by your new temp.controller.
The temperature sensor (NTC) should be positioned in the refrigeration compartment. The two wires of this sensor are connected to NTC terminals 5 & 6
Terminals 3 & 4 power the digital temperature controller.

 

RV Repairer is right but remove the grey bridging wire in the picture of the thermostat. Ive recently done that to a refrigeration unit on my daughters yacht that had a faulty mechanical thermostat.