Waeco/ Danfoss Refrigeration Overgas or restriction?

[Typhoon]

Yes , the problem is , he can't see the plate . Going to be tough to know when the charge is just right .

Regards John

[Richard Kollmann]

Originally Posted by ColdEh Marine

Yes , the problem is , he can't see the plate . Going to be tough to know when the charge is just right .

Regards John

The plate frost cover method is normally used only to observe changes in refrigerant volume. Accurate refrigerant charge on a cap tube system is by refrigerant weight or pressures and amperage.

[Ding Duck]

Hi John, Richard, this is embarrassing. I installed the second fan in the compartment where the compressor is located by using a relay for both this and Condensor Fan.
While I was at it, I installed a 390 ohm resistor in the Thermostat circuit to run in fixed speed mode. Just happen to have this left over from testing the Temp Controller. This should give a set speed a touch under 2500 RPM.
Fired the system up and Line current was 5.1 Amps. Current reduced to about 4.4A after a couple of minutes. After about 10 mins current crept up to 4.95 A.
Embarrassing part is it stayed at 4.95 A for the next 1.5 hours.
Temp in fridge was coming down accordingly. Have mounted the Temp probe onto somewhere near the back of the Evap plate. It's possibly a little off the plate due to the foam, but close enough for this stage.
As the Air cooled condensor is mounted under the galley sink, there is not a lot of free air in there, so the extra fan is ducted to extract heat from above compressor. Existing outlet of the fan is on the RHS of the cabinet & Air inlet vent is in the centre, with the compressor mounted on the LHS. The Comp wouldn't sit in the airflow if I didn't duct the extraction fan. If I closed the door, Amp would slowly rise to about 5.4 A. Opening the door would see a decrease back to 4.98 after a few minutes.
I would say the current is pretty much on spec for a BD35 running at 2500 RPM ( deduct say 3 watts for Temp Controller, relay and Fan)
After 2 hours of continuous running, the Condensation inside the fridge compartment had formed a thin ice layer, with air temp just off the skin at 3.3 Celcius. The start temp inside the fridge was about 20 Celcius and about 6 litres of water bottles.

Looking at this, I think for some reason it is pretty close to spec's?

As to identification of compressor, this is about he best I can see.
Cheers

[Typhoon]

Hey Greg .

I would love to know your liquid line temperature when the system was not running and what it is now . Captubes are sensitive to liquid line temperature and slows the flow when temperatures rise . That , in combination with all that resistance because of the winding around of the captube around the suction line may have been your problem all along . Glad to hear you got it running . The more you can get cool air around your condenser the better your system will perform .

Regards John

[Ding Duck]

Thanks John, lets hope it keeps going.
As you said, maybe the slightly lower temps have contributed, but we'll keep our fingers crossed.
I'll be back don there in a few days, so we'll see if this was just pure chance.
Been a learning curve to say the least. Anyway, now I've got fault indication, rather than guesswork
Thanks again
Cheers

[OzePete]

Your problem is simple. Your fan is corrupting the Danfoss / Secop motor driver. (Black box). The motor driver is a converter of DC power to 3 phases of AC to cause the compressor motor rotation. 12 VDC fans are somewhat similarly driven in as much as they too have a type of micro processor. A faulty fan can send signal to the Danfoss motor driver causing the driver to incorrectly provide the 3 phase supply to the motor causing a variety of issues including that described by the OP.
We has seen many instances of this so much so that we don't drive our systems fan(s) from the motor driver. We have the motor drivers fan circuit power a relay and the relay supply the fan(s) so as there is no chance of the fan corrupting the motor driver.
The motor driver is an expensive device and should also be protected with a voltage clamp to protect against transient voltages. (Spike arrester)

[Ding Duck]

OzePete, thanks for the heads up. It's a distinct possibility. Prior to the last test, the only fan that was connected was the Condensor fan as per standard configuration, so I guess this maybe introducing some noise back to the Black box. Since adding the second fan, I've wired both of fans through a relay and this is when the system seemed to return to 'normal'? I haven't had the chance to run the system since, so keep fingers crossed for next time.
In regard to the spike arrestor, are you suggesting to connect this to the small + and 'F' terminals. The small +ve is a regulated 12 Vdc so guess we want to keep that side as clean as possible.
Thanks for your assistance

[OzePete]

I am confident that fan corruption is your problem and using the relay will eliminate that.
Regards the voltage clamp question:
We keep records of issues that effect our Ozefridge products and over the years like other makers, we have been bugged with motor driver failure and they are very expensive. The rate of failures of the Danfoss motor driver were unacceptable and hard to understand as the driver is a solid state device and very well conformal coated to protect itself..
So the question was why, and how to prevent it.
We found two external causes and have now eliminated them in our production:
One was corruption from faulty fan(s) which was an easy fix. We now drive the fan(s) via a relay as previously described.
The other was transient voltages. (voltage spikes) Ironically we eventually identified this when motor drivers were failing at a rapid rate on our systems in road trains in outback Australia. We found that spikes were caused by simple things like de-powering a solenoid or winch motor.
The remedy was simple, fit a voltage clamp across the DC power input. (Voltage clamps are often called Zorbs) We fit a 37V clamp to all Ozefridge systems.
These two methods of protecting your compressor motor driver, regardless of brand, can be cheaply and easily added to any existing DC mini compressor to protect the motor driver and hopefully save the cost and inconvenience of failure..
Cheers, Ozepete
www.ozefridge.com.au

[Ding Duck]

Thanks for the advice. Interesting to know about the failures and the remedial action.
Wonder if this was before or after they moved to China?
I think I've got some old Zener Diodes left over from some '12V Panel' which should do the job.
Thanks again for your assistance
Cheers

[OzePete]

Originally Posted by Ding Duck

Thanks for the advice. Interesting to know about the failures and the remedial action.
Wonder if this was before or after they moved to China?
I think I've got some old Zener Diodes left over from some '12V Panel' which should do the job.
Thanks again for your assistance
Cheers

A: This was also occurring long before Danfoss stopped making compressors and sold out to Secop 5 to 6 years ago .
Cheers,
Ozepete