BD35 compressor issues and project design

[Kossco]

Hey there, new to this forum but not new to refrigerators, arrived because all my google searches on the danfoss compressors gave me results from this forums discussions.

I am seeing that Richard Kollman seems to be the SME on this BD35 and apparently theres a book he created that teaches a DIYer all they need to know about refrigeration systems? But i cant find a source online anywhere? And his website does not seem to be functioning. Instead of wasting everyones time with endless questions, i thought id try to find a source for that first... Thoughts?

But onto the problem at hand... I am intending on building a cabinet from vacuum insulated panels and stripping the BD35 compressor and associated parts from a 12V fridge i bought out of a semi truck. It was cheaper than buying new and i generally prefer to repurpose things than send them to landfill. I wanted to learn about reefer systems thru this project. Until i have a source for VIPs and the tooling required to evac\charge the coolant, i am just running the fridge as it was made but whatever manufacturer it was.

It operates well, cooling the freezer section to -18*c and fridge down to 1*c on coldest setting (but i leave it around 4*). Ambient temperatures have been between 4*-23*C. But to maintain this, it is running nearly constantly. Im reading that this fridge should run between 40-50amp hours MAX on hot days but have seen 70-80a\h draw in a single 24 hour period. It is drawing between 3-5amps when running. Seals on the door look good. Using infrared thermometer, i am not finding any cold air leaks and excessive frosting is not an issue. Cooling fan operates as expected. Top of the compressor is 40*c max temp during long operation periods. Thermostat works as intended. Power supply is strong, when solar is charging its easily over 13Vs, brand new battery replaced this year. Proper wiring and good clean connections. I cannot get the test LED to light up based off the troubleshooting guide wiring from + to D terminals but i may have the wrong type of bulb (i only had a LED bulb from an automotive dash, it lights up off a 12v source but maybe its not suitable for this? Im not sure why i cant get it to light up)

From the troubleshooting ive read and performed, its pointing me to beleive low refrigerant. This is a sealed system with no valves, just the pinched off tube into the compressor. I cannot visually see any signs of leakage thru the "is there oily\dusty build up near joints" method.

My questions are:
What else should i look for to determine problem?
What other details would you like to help troubleshoot?
Is it worth desoldering the pinched tube and adding a valve to recharge this myself or am i better to pay an HVAC guy to do it (based on tools i would need to purchase to acheive this and potential to do more harm than good)?
Where can i learn all a DIYer needs to know to build\desing their own project (id like to build dual zones and learn about designs for efficiency and how best to place cooling plates etc)

My future project for this would require me re do all the coolant lines anyways so i feel like investing in tooling is worth it.

[GordMay]

Greetings and welcome aboard the CF, Kossco.

Marine Refrigeration books, by Richard Kollmann*
“12 & 24 Volt Refrigeration Manual”
“Do-It-Yourself Boat Refrigeration”

*Richard’s Profile ➥ https://www.cruisersforum.com/forums...lmann-831.html
[His Last visit to CF was June 4, 2022, but he hasn’t posted since April 13, 2022]

Richard’s E-mail: Richard@kollmann-marine.com

[Richard Kollmann]

Originally Posted by Kossco

Hey there, new to this forum but not new to refrigerators, arrived because all my google searches on the danfoss compressors gave me results from this forums discussions.

I am seeing that Richard Kollman seems to be the SME on this BD35 and apparently theres a book he created that teaches a DIYer all they need to know about refrigeration systems? But i cant find a source online anywhere? And his website does not seem to be functioning. Instead of wasting everyones time with endless questions, i thought id try to find a source for that first... Thoughts?

But onto the problem at hand... I am intending on building a cabinet from vacuum insulated panels and stripping the BD35 compressor and associated parts from a 12V fridge i bought out of a semi truck. It was cheaper than buying new and i generally prefer to repurpose things than send them to landfill. I wanted to learn about reefer systems thru this project. Until i have a source for VIPs and the tooling required to evac\charge the coolant, i am just running the fridge as it was made but whatever manufacturer it was.

It operates well, cooling the freezer section to -18*c and fridge down to 1*c on coldest setting (but i leave it around 4*). Ambient temperatures have been between 4*-23*C. But to maintain this, it is running nearly constantly. Im reading that this fridge should run between 40-50amp hours MAX on hot days but have seen 70-80a\h draw in a single 24 hour period. It is drawing between 3-5amps when running. Seals on the door look good. Using infrared thermometer, i am not finding any cold air leaks and excessive frosting is not an issue. Cooling fan operates as expected. Top of the compressor is 40*c max temp during long operation periods. Thermostat works as intended. Power supply is strong, when solar is charging its easily over 13Vs, brand new battery replaced this year. Proper wiring and good clean connections. I cannot get the test LED to light up based off the troubleshooting guide wiring from + to D terminals but i may have the wrong type of bulb (i only had a LED bulb from an automotive dash, it lights up off a 12v source but maybe its not suitable for this? Im not sure why i cant get it to light up)

From the troubleshooting ive read and performed, its pointing me to beleive low refrigerant. This is a sealed system with no valves, just the pinched off tube into the compressor. I cannot visually see any signs of leakage thru the "is there oily\dusty build up near joints" method.

My questions are:
What else should i look for to determine problem?
What other details would you like to help troubleshoot?
Is it worth desoldering the pinched tube and adding a valve to recharge this myself or am i better to pay an HVAC guy to do it (based on tools i would need to purchase to acheive this and potential to do more harm than good)?
Where can i learn all a DIYer needs to know to build\desing their own project (id like to build dual zones and learn about designs for efficiency and how best to place cooling plates etc)

My future project for this would require me re do all the coolant lines anyways so i feel like investing in tooling is worth it.

You must first understand the principle of the refrigeration unit you have
1. the troubleshooting LED will only flash a code signal when there is an electrical problem preventing compressor from running.
2. The evaporator temperatures in box will indicate how well the unit is running and if refrigerant volume is correct..
3. the thermostat turns compressor off and on, if kept running box temperature will keep dropping.
4. the amperage draw tells how much work is being done at that point in time. When your BD 35 compressor is first started it will reach 5 amps of current draw in 10 minutes. If after 10 minutes compressor is performing at less than 5 amps compressor speed is set too low or refrigerant volume is less than correct or speed is set too low. Compressor speed setting can be determined by milli amps of current flow in thermostat wire loop, See Danfoss compressor data sheet
5. How cold will box inside get if thermostat is bypassed for 24 hours?

[Kossco]

Thanks for the reply Richard!

Where can I get a copy of your books?

I have confirmed the LED light does work but i get no flashing so i assume no epectrical issues. I have since had the system recharged after having a service valve added, pressure tested, vacuumed and r134a added by frost back method.

It no longer runs on. My battery life is working as expected. But i do notice the compressor only runs for maybe 60 seconds at a time now (when the fridge is at set temperature), which seems too short. What do i need to do to test\troubleshoot the thermostat? Pre recharge, the compressor was running for very long periods and getting hot with no frost back on the exit line. The freezer would obtain -18*c and fridge 1*c if set to coldest setting. After recharge, compressor runs short periods with frost back occuring within a minute. Freezer does not get to minus temperatures but will maintain a -4*c if a frozen item is in it. Fridge maintains set temperature as desired (set between 3-4*c. The compressor will run longer if i have to cool it (ie leaving fridge off overnight and then turning to kax setting in the morning, it will cycle for the time required to get the fridge temps back in line.

I will leave the fridge on for 24 hours today and report temperatures.

[Kossco]

Overnight ambient temperatures, 17*c, freezer -11*, fridge -4*, drawing 2.6amps. morning ambient has risen to 27* and will likely increase by afternoon, fridge is maintaining same temperatures and amperage. Will report final #s after the full 24 hours but the compressor has run without interruptions so im assuming thermostat issues?