wingless' Danfoss BD50F / 101N0500 Refrigerator Problems

[wingless]

Background
My 2000 380 Searay Sundancer was built with a Nocold DE-461 refrigerator. That refrigerator was always a problem and was replaced in August 2009 with a new Isotherm CR187 stainless refrigerator.

The original refrigerator depended upon a long, convoluted air path through hidden boat cavities for proper cooling. Frequently, owners of these boats would fail to understand those requirements and put stuff into those cavities, blocking the cooling flow.

This new Isotherm has an excellent design. The refrigerator has a pair of fans to draw fresh room air across the rear-panel condensor coils, then expel that air back into the room, all from hidden front-panel vents that are only visible when the doors are opened. This design permits the refrigerator to be installed into a fully-sealed box.

Most Searay owners fail to understand the boat construction and partially disassemble the old and the new refrigerator to get it through the salon entrance. In my case I instead removed / replaced the appropriate boat parts so the fully intact refrigerator would fit through the opening without any issues. I also resolved the fit problem that prevented others from fully inserting the replacement refrigerator into the salon cabinet.


Cooling Problem
The Isotherm CR187 refrigerator has a Danfoss BD50F variable speed R-134a compressor and a 101N0500 12V / 24V controller.

The refrigerator has been in almost continuous operation since installation.

There have been infrequent instances where the refrigerator stopped cooling, permitting the interior to warm, then resumed normal operation without any user intervention. Those instances were not possible to explain from external events. The unit was supplied normal +12VDC nominal battery voltage and 120VAC nominal line voltage.

Recently the refrigerator has fully stopped cooling. The two cabinet fans run continuously, with a periodic momentary audible tone change when the compressor makes a VERY short duration attept to run. A hand on the compressor at that time feels the movement from a very short internal motion bump. It feels like the internal parts are moving freely, from the inertia of movement.

The R-134a refrigeration circuit has not been altered in any way, from when the unit was manufactured, then delivered new to me for this first installation.


Diagnostics
The controller has a diagnostic 10mA LED connection Faston tab. I used a red superbright T1-3/4 LED and a series resistor to limit the ~13VDC current to well under the 10mA specification, made that into a long wiring harness and permanently mounted that LED behind one of the vents. This permits quick / easy initial investigation of any current and future problems by simply opening the freezer door to visually observe the flash codes.

In my case I am getting the 3-flash Motor Start Error code.

There are potential problems that have been analyzed to determine if they contribute to the problem.


Fan Connection
The Danfoss fan specification lists the maximum load as 0.5A (Average) and 1.0A (Peak), with the controller permitting a higher current during the first two seconds.

The controller will stop both the fans and the compressor when excessive fan current is detected. In my case the fans are running continuously, but this was checked regardless.

The fans were disconnected from the controller, but the 3-flash error code remained unchanged.


Thermostat Failure
It is possible that the thermostat might fail to provide a low-resistance connection that would signal the compressor to run. The test for this would be to remove the thermostat from the circuit and to short those terminals on the controller.

In my case, the system was built with the optional series resistor on that thermostat loop to increase the compressor RPM speed. Mine has a 1.48K Ohm series resistor to operate the compressor at 3,500 RPM, instead of the 2,000 RPM selected without the resistor.

The thermostat terminals were shorted together, no effect. The thermostat terminals were shorted using that 1.48K Ohm resistor, also no effect.

As an aside, the multimeter resistance leads were nulled out and the multimeter was used to measure the continuity from the thermostat. The thermostat is providing a very low 0.28 Ohms of resistance to the controller.


Boat Wiring Defeciency
It is possible that the boat wiring would fail to provide sufficient voltage and current to satisfy the requirements of the refrigerator.

For my testing I temporarilly relocated one of my six fully-charged Lifeline GPL-31XT Group 31 12V 125Ah batteries to directly behind the refrigerator.

The refrigerator was wired to receive 12.9VDC power, through a 20A fuse, directly from the battery, with zero boat wiring connected, also no effect on the problem.


Potential Problem Resolution
Given that the R-134a refrigeration circuit is unaltered and that the hand-on-compressor-bump feels like unobstructed internal movement inertia, my guess is that the controller has failed.

My guess is that the controller has internal failure(s) preventing normal operation.

The attached Danfoss block diagram shows that the controller has several stages, prior to providing power to the compressor. The 12VDC / 24VDC and the 85-265VAC both go through a SMPS resonant coverter to create 27VDC. This then goes through a boost coverter to create 27-45VDC. That voltage then powers the inverter that drives the motor.

My guess is that one of these internal controller stages has failed on my refrigerator.


Assistance Requested
(1) How is the controller detached from the compressor and refrigerator? The removal steps are not immediately obvious and I don't want to damage the parts.

(2) How can I get the removed controller analyzed? This reply from Richard Kollmann indicates there is a Danfoss test stand. My location is near Fort Lauderdale, so I can bring (or ship) my controller for diagnosis.

(3) Is internal controller documentation available? My decades of electronics design experience, including power electronics and motor controllers, leads me to lean towards breaking open the "Do Not Open" box and attempt repair. That effort is improved when documentation like schematics are available.

(4) The Danfoss documentation shows my 101Z0500 controller as being used with the BD250GH Twin compressor. The sticker on the compressor reads BD50F. Any thoughts on that difference?

(5) Anything else? Please let me know if additional information would be useful to diagnose the problem.



Original Norcold DE-0061 Refrigerator


Isotherm CR187 Refrigerator w/ Currently-Failed Danfoss BD50F Compressor and 101Z055 Controller


Diagnostic LED Mounted on Top Shroud / Behind Hidden Top Vents






Cooling Side Vents / Top Vents / Forced Air Fans / Condensor Coils (Top Shroud Not Installed)




Danfoss 101Z0500 Controller Wired and Installed


Refrigerator Directed Connected to Fully-Charged Fused 125Ah 12V Battery


Danfoss 101Z0500 Block Diagram


Internet Controller Images - Mounted and Detached

[wingless]

Originally Posted by wingless

Assistance Requested
(1) How is the controller detached from the compressor and refrigerator? The removal steps are not immediately obvious and I don't want to damage the parts.


Danfoss 101Z0500 Controller Wired and Installed

Here are additional Internet images.

It looks like the mounting screw that retains the controller to the compressor is concealed by a label on my unit.

Correct?

[wingless]

Yes, the single screw is removed.

That detaches the box-shaped cavity from the box-frame-shaped compressor side.

There are three round horizontal pins poking out the side of the compressor.

The controller has connector receptacle sockets on the end of a pigtail harness that just slide off the compressor pins.

[wingless]

The Danfoss 101N0500 controller was disassembled and inspected for damage / repair.

The entire circuit board and components were conformal coated in silicone for long-term harsh environment protection.

That silicone conformal coating was removed by me.

There are a handful of components that may be inspected / tested / measured / replaced without the circuit board schematic.

There is one deteriorated capacitor that is visibly swollen that should be replaced.

However, it is unlikely that the circuit board may be repaired without the schematic or assembly drawing. Both documents were requested from Danfoss and from Secop. Both companies will not provide that documentation, so I am not going to be able to repair this failed module.

The 10-year old 101N0500 controller that was used in my refrigerator has been superseded by a new part number the 101N0510 controller.

That new part number controller has been ordered to replace my failed part.



Conformal Coated Component Side


Conformal Coated Solder Side


Cleaned Annotated Component Side


Cleaned Annotated Solder Side


Danfoss Controller Block Diagram

[DeBe]

At the very least i would try replacing the 3 larger capacitors marked in red. It will probably then work. Its a fair chance the voltage for the actual compressor drive is collapsing at start due to dried out capacitors. The only fault its loging is that the compressor has not reached an apropriate speed.

[wingless]

Thanks very much for the information!

All three tall capacitors are marked as 470µF / 63V, even though on my board they are all different colors and sizes.

The one capacitor that is swollen on my board measures as zero capacitance, marked as 27V adjacent to the coil on your image.

The other two capacitors measure fine, when removed from the board.

All three will be replaced and the board checked for operation.

Other parts will also be checked.

[Richard Kollmann]

On the N0500 Danfoss module if compressor will not run on either AC or DC power the cause is most likely inside the module. If unit runs on AC and not on DC trouble is with low voltage or dirty boat wiring voltage that can not be detected with a volt meter.

When purchasing systems with preparatory secrets in them it pays to carry a spare. Refrigeration units are not always designed for tropical climates so process heat disposal sometimes needs additional fan assistance. Electronic control modules last much longer when condenser heat is controlled and when boats refrigerator wiring is top quality all the way to battery.

[bensolomon]

Great job on the diagnostic process!! Very thorough.

[wingless]

Originally Posted by DeBe

At the very least i would try replacing the 3 larger capacitors marked in red. It will probably then work. Its a fair chance the voltage for the actual compressor drive is collapsing at start due to dried out capacitors. The only fault its loging is that the compressor has not reached an apropriate speed.

Thanks for the image.

The parts identified in the image have been tested against the manufacturer's data sheet. (Note, the part identified in the image as IRLR02AN is really IRLR024N.)

So far I have determined that only the one tall capacitor is bad, the one that is visually swollen.

Both 8TQ080S diodes are bad. The BZW50-33B diode is bad. The IRF2804S and the IRLR024N FETs are bad.

The large full wave rectifier and the glass fuse are both good.

[wingless]

Originally Posted by wingless

The IRF2804S and the IRLR024N FETs are bad.

Update, the FET tests performed were for loose parts and are not applicable for parts attached to the circuit board.

The appropriate tests were performed and these FET parts test fine.

[wingless]

Originally Posted by wingless

The Danfoss 101N0500 controller was disassembled and inspected for damage / repair.

The 10-year old 101N0500 controller that was used in my refrigerator has been superseded by a new part number the 101N0510 controller.

That new part number controller has been ordered to replace my failed part.



Conformal Coated Component Side


Conformal Coated Solder Side

The replacement 101N0510 controller has arrived, been installed and normal refrigerator operation has been restored.

The trick to installation is to hook the back edge, then rotate on an arc so the front ends up in the correct position, prior to installing the retention screw.

[redsky49]

Were there multiple component failures, aside from the capacitor, and was this a cascading failure due to ????


Any insights?

[wingless]

Originally Posted by wingless

Thanks for the image.

The parts identified in the image have been tested against the manufacturer's data sheet. (Note, the part identified in the image as IRLR02AN is really IRLR024N.)

So far I have determined that only the one tall capacitor is bad, the one that is visually swollen.

Both 8TQ080S diodes are bad. The BZW50-33B diode is bad. The IRF2804S and the IRLR024N FETs are bad.

The large full wave rectifier and the glass fuse are both good.

Originally Posted by wingless

Update, the FET tests performed were for loose parts and are not applicable for parts attached to the circuit board.

The appropriate tests were performed and these FET parts test fine.

Originally Posted by redsky49

Were there multiple component failures, aside from the capacitor, and was this a cascading failure due to ????


Any insights?

Yes, multiple part failures. Some were measured w/ the parts still soldered to the circuit board. The capacitors were measured after removing from the PCB.

The controller is not going to be repaired by me at this time.

[wingless]

Originally Posted by redsky49

... was this a cascading failure due to ????

After normal operation was restored, I touched the components to gauge operation.

Even though the compressor was running properly the exterior surface of that pump was hot.

That hot compressor is adjacent to the control electronic module.

Heat is detrimental for electronic life.

I'm considering the addition of a small fan, pointed at the compressor, to decrease it's temperature. If added, it would need to account for the 500mA maximum controller fan current limitation, with the two existing fans remaining operational.

My guess is the controller failed from reaching the end of life for some components, with temperature being one factor hurting that life.

[Richard Kollmann]

Originally Posted by wingless

After normal operation was restored, I touched the components to gauge operation.

Even though the compressor was running properly the exterior surface of that pump was hot.

That hot compressor is adjacent to the control electronic module.

Heat is detrimental for electronic life.

I'm considering the addition of a small fan, pointed at the compressor, to decrease it's temperature. If added, it would need to account for the 500mA maximum controller fan current limitation, with the two existing fans remaining operational.

My guess is the controller failed from reaching the end of life for some components, with temperature being one factor hurting that life.

RV refrigerators installed in boats operating in warm climates generally need additional condenser and process heat disposal. The first sign of future trouble is high amp draw and can not keep hand on compressor do to heat.