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
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
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
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.
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.
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.
(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
Danfoss 101Z0500 Controller Wired and Installed
Refrigerator Directed Connected to Fully-Charged Fused 125Ah 12V Battery
Danfoss 101Z0500 Block Diagram
- Mounted and Detached