Calibrating Thermostat with Adler Barbour Compressor Cycles

[windseeker33647]

I have a Adler Barbour 2.5 Cold Machine using R12 with a medium size evaporator box in an empty 6 cubic foot ice box. The amperage starts at 6 and decreases to 5 prior to the compressor stopping. With the thermostat in the maximum position, the compressor cycles off when the temp in the evaporator box is 10 degrees. The compressor starts again after about 7 minutes when the box temp is 20 degrees. If the thermostat connections are jumped, the box temp goes to 0 degrees in about 9 minutes.
It appears that the thermostat is malfunctioning and prematurely shutting off the compressor. The thermostat sensor tube is installed on the side of the evaporator with the appropriate 5” loop under the retaining bracket. Other than buying a new thermostat to see if that is the problem, are there other approaches to sync the thermostat with the compressor capability?

[Stu Jackson]

Not sure what you're after here. Seems to me if you left the T jumpered for longer it would get even colder. So?

[windseeker33647]

The compressor has the capability of cooling to 0 degrees when the thermostat is bypassed. My objective is for the compressor to automatically reach the same low temp by using the thermostat. Currently the thermostat, when set at the maximum position, turns off the compressor at a temperature of 10 degrees.

[Richard Kollmann]

Originally Posted by windseeker33647

The compressor has the capability of cooling to 0 degrees when the thermostat is bypassed. My objective is for the compressor to automatically reach the same low temp by using the thermostat. Currently the thermostat, when set at the maximum position, turns off the compressor at a temperature of 10 degrees.

Sounds like thermostat is installed correctly as long as sense tube is not touching a cold spot other than at the 5 inch end.

I would again test the system with thermostat disconnected from control module and jumper on module thermostat terminals. Now if you let it run without it stopping evaporator temp will drop to minus 16 degrees below zero as long as there is no air movement in side box, an compressor never sysles off. If compressor did stop during this test I would suspect an electrical problem. If compressor ran but cooling stopped I would suspect a refrigerant flow problem.
If all else fails replace thermostat and and its wiring.

[jibstay]

I replaced my thermostat with this programmable digital unit:

Inkbird Dual Stage DV 12V Digital

https://www.amazon.com/dp/B019I3YCFS/ref=cm_sw_r_cp_api_glt_i_WBCSXZWK1Z5G1TDP8DFQ?_enc oding=UTF8&psc=1

[Richard Kollmann]

Originally Posted by jibstay

I replaced my thermostat with this programmable digital unit:

Inkbird Dual Stage DV 12V Digital

https://www.amazon.com/dp/B019I3YCFS...ing=UTF8&psc=1

Would you not want to find out if thermostat was the problem first. A digital thermostat might create a more complicated problem.

[stormalong]

Originally Posted by Richard Kollmann

Would you not want to find out if thermostat was the problem first. A digital thermostat might create a more complicated problem.

The OP said that by jumpering out the thermostat it would get to zero in nine minutes. A digital one is a good solution. IIRC those thermostats came in two versions with appropriate ranges for refer or freezer. Looks to me like he has the wrong thermostat.

[Richard Kollmann]

Originally Posted by stormalong

The OP said that by jumpering out the thermostat it would get to zero in nine minutes. A digital one is a good solution. IIRC those thermostats came in two versions with appropriate ranges for refer or freezer. Looks to me like he has the wrong thermostat.

There is a 30% chance you are correct but from information provided there is a 70% chance you are wrong. I always like to confirm by non destructive testing the actual cause saving time and money.

[stormalong]

Originally Posted by Richard Kollmann

There is a 30% chance you are correct but from information provided there is a 70% chance you are wrong. I always like to confirm by non destructive testing the actual cause saving time and money.

Can you elaborate on this?

[Tsuru]

Here is my experience, take it for what it's worth. Early last season I struggled with temperature control in our AB cold machine. The unit was 19 years old at the time. I read up on the tutorials on how to diagnose the problem and felt that I had a reasonable understanding of a way foreword.
Before any of that I spent $30 + on a new AB thermostat, and invested the 15 minutes installation. Repaired the problem.
A digital thermostat may have been more accurate, pinpointing the problem before investing a few dollars was probably the reasonable course of action.
I probably just got lucky, but in my world analog control, is just fine and spending under $50 to replace a part that's probably at end of life was a risk I was willing to take.

[Richard Kollmann]

Originally Posted by stormalong

Can you elaborate on this?

I will give you only the short answer as it is a waste of time to explain why the billions of small refrigerator with induction cooled evaporators and cap tube refrigerant control are more efficient, when compressor is controlled by evaporator temperature cycling times. This fixed speed Adler Barbour displays a amperage and evaporator temperature reduction pattern as long compressor is running. If my simple test was done and resulted in minus 10 to minus 16 degrees F the thermostat is a problem as refrigerant flow and electrical problems were eliminated by my test. The correct setting efficiency of any thermostat is to prevent it from over powering evaporator.

[windseeker33647]

Thanks Richard and others for the inputs. I will follow Richard’s recommendations and provide feedback after next weekend. Appreciate your assistance.

[stormalong]

Originally Posted by Richard Kollmann

I will give you only the short answer as it is a waste of time to explain why the billions of small refrigerator with induction cooled evaporators and cap tube refrigerant control are more efficient, when compressor is controlled by evaporator temperature cycling times. This fixed speed Adler Barbour displays a amperage and evaporator temperature reduction pattern as long compressor is running. If my simple test was done and resulted in minus 10 to minus 16 degrees F the thermostat is a problem as refrigerant flow and electrical problems were eliminated by my test. The correct setting efficiency of any thermostat is to prevent it from over powering evaporator.

Who said anything about not controlling the refer by measuring evaporator plate temperature?

I have two A/B cold machines, BD50 compressors, newer than the OPs. Both are controlled by digital thermostats with sensors directly attached to the evaporator plates in the location where A/B provided holes to attach the the thermostat probes. They work fine.

The OP also said his present thermostat is attached to the evaporator.

[Richard Kollmann]

Originally Posted by stormalong

Who said anything about not controlling the refer by measuring evaporator plate temperature?

I have two A/B cold machines, BD50 compressors, newer than the OPs. Both are controlled by digital thermostats with sensors directly attached to the evaporator plates in the location where A/B provided holes to attach the the thermostat probes. They work fine.

The OP also said his present thermostat is attached to the evaporator.

If you are controlling evaporator temperature and not box temperature you are OK. Windseeker's problem has nothing to do with where thermostat monitors temperature. I only answered your question that had nothing to do with the thread OP.

[windseeker33647]

I jumped the thermostat contacts and let the compressor run for two hours. The compressor never shutdown and the amp draw varied from -4.5 to -4.8. The steady state low temp was -5 degrees. I changed out the thermostat with another used thermostat and selected the maximum setting. The steady state temp reached a minimum of +8 degrees before the thermostat shutdown the compressor. The compressor restarted after 3 minutes when the temperature had increased to +10 degrees. The thermostat maintained the +8/+10 cycle for the duration of the one hour test. So changing the thermostat achieved a low of +8 degrees versus the prior low of +10 with the original thermostat and cycled to maintain a range of +8/+10 degrees versus the previous range of +10/+18. Based on Richard’s analysis/test, additional freon is probably needed to achieve the desired low of -10/-16 degrees.