Norcold BD35F Danfoss running but not cooling properly

[actionpaintball]

DE-0061 Norcold fridge. 2.5 years old (conveniently 6 months out of warranty). This is a closed system with no tapping/filling valves (yet). I have a 101N0500 controller (12v DC and 120 A/C). This fridge acts the same way on both DC and AC power supply:

Cools and seems to operate OK for the first few hours or so. The cooling plate frosts to about 90 to 100 percent. Freezer will get to about 20/25 degrees F and fridge about 40/45 degrees F. Compressor and fan will continue to run but cooling temperatures stabilize and the freezer begins to thaw/defrost and cycle starts over again. The compressor and fan don't ever seem to shut off and the fridge and freezer never bottom out to the point where the thermostat will shut the compressor off.

I have tried bending the capillary tube that not help anything. Door seals are good and the cabinet is tight. I visually checked for R134a leaks and will borrow a good sniffing tool this weekend for good measure. My best guess now is some kind of wax or moisture contamination that is freezing at the capillary tube expansion right before the plate.

I used an inline FLUKE meter and a clamp on amp meter and when running the system only draws 1 amp and then goes down to .5 to .6 amps measured at the 110v white or black wire entering the controller. The fan is drawing .1 amps alone which is in spec. There are no error codes present on the aftermarket installed LED (verified to function when a low battery was installed on the 12 volt side). The amperage seems really low...am I measuring it correctly? (A/C amps). compressor is getting 33 to 34 volts a/c (but this may be a 3 phase feed?). I have seen where most people recharge the system based on compressor amperage draw of 5.0 to 7.0 amps....why is mine below 1.0 amp?

I have the 2500 rpm 677 ohm resistor installed. Removing it made no difference. I want to exhaust all potential problems before I tap into the refrigerant system. I have access to a recovery machine, vacuum machine, nitrogen and virgin R134a to refill if needed.

Freezer is now in my garage an off the boat. All wiring checked out fine on the boat and garage supplied power. Everything is clean and looks nearly new. Some condensation off the back of the fridge where the lines enter/exit the box.

Any suggestions before I add a valve? My main concern is low amp draw.

[beetlejuice30]

Sounds like a low charge, use soap and water to find leaks also look for a collection of dust where there's oil there's a leak. Definitely not a three phase feed, where is your voltage 34 volts? Ac or dc?
How badly did you bend the capillary tube? ( not good to do)
Do not run compressor with a low charge. The high superheat will cause compressor failure.
How hot is the compressor when running?
To add freon you must install a hot tap. Should be able to use a hand torch. On a system with a capillary tude you must charge to subcooling not superheat can be done tho. If the compressor is sweating and cold you have added to much freon compressor will fail.
Hope this helps


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[actionpaintball]

Compressor temp is 95 to 105 degrees F. Controller temp is about the same (IR gun).

I did not bend the capillary that much, just enough as recommended to free up a small obstruction if present.

34 volts a/c measured from controller to compressor.

Internet says that the BD35F converts to a "3-phase input to fixed coils that drive the rotor".

[beetlejuice30]

Temp seems ok
Checking the superheat would be your next step

No worries on the capillary then.

Don't have that much experience with ac/dc power converter or what ever control they have. With a ac unit it requires a capacitor to start the motor, dc not sure.
What are your input voltages to the unit?
I Do have a lot of three phase power experience. The only way I know of creating three phase with balance legs and phase, is a roto-phase and capacitor bank. Plus doesn't have enough wires to be three phase.
I find new things everyday that surprise me so who know with out looking at it.


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[beetlejuice30]

The compressor should have a service stub off of it. Just a pinched line install a valve there.



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[motion30]

I know some of the old Norcold units With the swing compressor use AC voltage through I was under the impression the Danfoss use DC current I could be wrong

[Richard Kollmann]

If unit will generate frost on evaporator then later frost changes to cold condensate even after one hour this could indicate cap tube restriction, although I would rule out restriction unless someone has tampered with refrigerant. Tampering with refrigerant at this point would be a much bigger mistake. Did refrigerator function normally on 12 volts when 110 volt power was removed?

The BD35 cooling fan always runs on 12 volts even when AC converter inside 500 module changed compressor module voltage to 24 volts. Because troubleshooting LED does not respond in any way I would first run a new temporary ground wire direct from 12 volt battery to Danfoss module ground and power unit without AC using a 12 volt battery. If you did confirm before that after running one hour with cold condensation only that compressor runs continuous and stays warm it may indicate the control module has lost one pulsing phase. Next step is to try another Danfoss three pin 12 volt module to rule out module as cause of trouble. If at any time evaporator develops frost, avoid shooting yourself in the foot be messing with the two ounces of refrigerant in that system.

If frosting of evaporator never occurs then and only then would you want to question refrigerant volume on this very small variable speed BD35 compressor
but only after trying another module first.

[actionpaintball]

Even though this is a closed refrigerant system and has not been opened, I believe I have a capillary restriction and.or moisture.

If the compressor has audible loss of flow, if I heat the capillary tube just as it gets larger and expands into the plate (see pic), you can hear the flow increase and cooling resumes for about 15 minutes until it seems to freeze up again.

The amp draw of .5/.6 seems to be common for 110v AC. Using an inline DC amp meter on battery power I am getting 5 to 6.5 amps which appears to be in spec. A quick wattage conversion for A/C would be .6 x 110 = 66 watts which correspond to 12 X amps=66 watts or about 5.5 amps. Some people have suggestion to charge the system based on DC amps to about 5 to 7 amps at 12/13 volts DC.

I have two capped/crimped service ports that are 6mm in diameter that should be good for low and high pressure taps (see pic). I am still reluctant to tap into the closed refrigerant system, but I am pretty sure I have a moisture or wax or ? restriction that temporarily solves itself with a little bit of heat where the cap tube expands into the cooling plate (evaporator).

This is my 1st dual voltage fridge, but I have rebuild some classic coke machines, tons of auto AC units, household fridges, heat pumps ect...

[newhaul]

Follow Richards advice and check with a known good control module before fooling with the freon.

[SV THIRD DAY]

Originally Posted by actionpaintball

Some people have suggestion to charge the system based on DC amps to about 5 to 7 amps at 12/13 volts DC.

Those people are smoking crack....ignore them before they screw things up!
First run the separate 12v power supply straight from the pos/neg battery terminals to the unit.
Next see if you can get ahold of a known good controller to swap out and see if that's the problem.

Low hanging fruit first before playing Dr with the solder torch and screwing with the charge.

[Sardean]

Check the condenser is getting plenty of air and is clean

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[a64pilot]

Originally Posted by Sardean

Check the condenser is getting plenty of air and is clean

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Of course do what Richard and Rich suggest with power and module, but this is very good advice, could cause the problem and is easy to check and or rectify.

The other day we were on day two trying to get an aircraft AC system to perform and I walked up and just happened to see the piece of cardboard that ships with the condenser to protect the fins, was still there. Guess what the problem was

[Richard Kollmann]

I can understand your reluctance to follow my time consuming troubleshooting program but it can pinpoint where the trouble is. You can call a trained HVACR technician and end up replacing complete unit after spending hundreds of dollars. Frigoboat keel cooler models are the only units with Danfoss BD compressor systems that seem to have cap tube restrictions caused by compressor oil thickening.

This variable speed duel voltage models are more difficult to troubleshoot:
• I have found that loss of one phase in module will slow compressor speed.
• A poor ground has changed compressor speed without causing LED to flash.
• All of Danfoss electrical control modules are high risk of failure from heat and voltage spikes.
• Heating high pressure does increase volume and pressure of refrigerant but in this little system it can be a misleading test. Moisture causing flow blockage is detectable buy cold condensate on evaporator instead of frost, as well as flocculation of amperage, and refrigerant hissing sound in evaporator starts and stops as moisture freezes and melts in cap tube. This freeze and thawing acts like a thermostat producing cold condensate on evaporator.
• Before making the decision to take destructive action by tampering with refrigerant or even connecting a gauge to this unit it is best to rule out the above non destructive tests. If system is low on refrigerant there is a leak to find and fix. If it turns out to be cap tube restriction by overheated refrigerant or mechanical material it is usually best to replace complete unit.

[actionpaintball]

I appreciate the advice and will follow it. Everything I suggested is just speculation. I am just trying to understand the electrical reasoning in my head before I throw time/$ at it because I do not have a second controller handy to swap. I might try and send mine out to be tested. Is there any way to test that the controller is supplying 3 good compressor signals? I have a multimeters and an oscilloscope.

[actionpaintball]

While I line up getting my controller tested and/or swapped, is there any way to test the compressor rpm as well as the three separate signals?