Waeco/ Danfoss Refrigeration Overgas or restriction?

[Ding Duck]

Hi All,
perhaps one of the Boffins out there may be able to shed some light on a Refrigeration problem
The compressor is, I believe a Danfoss BD35 (although can't read any nameplate details). Controller is a Danfoss 101N0320 with AEO.
The compressor Current is about 3.5A when first started in an ambient of around 25c or so (frig compartment is same temp) The current slowly ramps up and after about 45 mins can be as high as 8A. The compressor will shut down, wait about 1 min and try to restart. I have tried running this in constant speed mode by adding a 180ohm resistor to the T'stat circuit, with similar results to above
I will get 3 flashes on the diagnostic terminal when compressor tries to restart, suggesting high Pressure differential or overtorque. This is when I turn the system off for about 15 mins.
The Evaporator will get cool, but can't say to what temp this is as someone mounted it behind the lining in the frig compartment. It is essentially sandwiched between 2 layers of insulation, the skin and the foam.
I did notice the digital temp controller would indicate the temp coming down, usually showing a decrease of around 5-6 degrees C, then would start rising. I assumed the controller was faulty, but have verified it is Ok by using a fixed resistor and placing the PTC in cold and warm water. (it is not quite calibrated correctly, but is consistent)
The PTC is mounted about 150mm from where the Evap lines exit the frig compartment. The sensor was not mechanically fixed to the Evap lines rather tucked under the thermal insulation around these pipes.

The Evap lines are completely surround by thermal insulation, back to about 75mm of the Compressor
My plan was to
(a) remove the thermal insulation back to about 200mm of the Evaporator and see if that improves the situation. May improve the superheat?
(b) Condensor looks ok, but will give a good clean anyway
I have an external cooling fan installed as Compressor is mounted under the sink, next to the frig.
If anyone else has had similar experience, what was their outcome? I'm guessing either overgas or a restriction if Plan (a) doesn't fix it

[GordMay]

Greetings and welcome aboard the CF, Ding Duck.

[Typhoon]

Hi Ding Duck . Sounds like you have a little bit of trouble . I take you don't know any history on this system , also is this an air or water cooled system ? Because you don't have access to the plate to visually inspect it for frost it makes diagnosing a problem even more difficult . Can you hear any noise from the plate at all when it is running ? Also take a look at the system and see if anyone has installed a high side or liquid line service port. This could be a sign of someone attempting to service the system .

Regards John

[Ding Duck]

Hi John
thanks for the reply. The condensor is Air cooled and no visible signs of build up of dirt etc. There is also a reasonable amount of air flow from the Condensor Fan, so guessing this part is correct. I will give the condensor a clean, just to be 100% sure. By touch, the Temp of the pipe is 'hot' coming from the Compressor and 'not quite as hot' leaving the Condensor.

There are no service valves installed on the Liquid Line

Good point, I haven't checked to see if there is gurgling on the Evap end. We will some distance from the boat, so will check this over the next day or so.
The Evap does get down to temp as we can form frost in the fridge compartment. The Evap is a "L' shape and temp appears uniform. Being installed behind the skin can be misleading.
Cheers
Ding

[Typhoon]

Hi Ding Duck.

Are you still having the three flash shut down. ? Or has it sorted itself out ?

If it occurs again from a warm start I suspect moistures in the system. On a warm start the refrigerant will flow as normal at first until ice collects around the cap-tube low pressure side and then restricts the flow , you can observe this by watching the amps slowly increase and the sound from the evaporator plate will diminish . This may have occurred if there had been refrigerant added to the system improperly . The only cure is to evacuate the system down to below 500 microns. This may take a while as the oil in the system will absorb some of this moisture and it takes a long time at low pressures to boil it out , warming the system with a hair dryer can speed up the process. I some times leave the vacuum pump on over night. You should also replace your filter drier.

Moisture in your system will combine with the refrigerant and create acids that will damage the system from the inside out . It attacks the inside of an aluminum evaporator plate and the windings inside the compressor and every thing else it is in contact with. Having pure refrigerant only inside the system is a key factor in its longevity.

Regards John

[CGirvan]

Originally Posted by ColdEh Marine

I some times leave the vacuum pump on over night.
Regards John

John, quick question, would vacuuming the system down then closing the valves and leaving it under vacuum over night do the same thing?
I'm on a mooring and will have to run the vacuum pump with the generator so obviously wont want to run it all night.
My other thought was to do a triple evacuation as someone else suggested but haven't come up with an economical source for nitrogen that I could use on the boat, any ideas?

[Typhoon]

Originally Posted by CGirvan

John, quick question, would vacuuming the system down then closing the valves and leaving it under vacuum over night do the same thing?
I'm on a mooring and will have to run the vacuum pump with the generator so obviously wont want to run it all night.
My other thought was to do a triple evacuation as someone else suggested but haven't come up with an economical source for nitrogen that I could use on the boat, any ideas?

Good question. I understand your dilemma. The problem is a quick vacuum down to 500 microns won't hold very long as the moisture boils off , it tends to climb and then no more boiling occurs. The pump running and continue to run will keep that that vacuum down to the point where the boiling occurs and continue to boil away. I have done it both ways triple evac and long runs of the pump. Depends on the problem that a system has or if its a new build I'm doing.

Warming the system to 100 degrees will help .

You may want to take a slip for a night or two just to plug in and run your pump.

Nitrogen can be hard to get in some places , you almost have to have an account with a compressed gas supplier to get any .

If you send me your system I will evac it for you and send it back at no charge , just pay the shipping . Its a little service I offer , the hard part is getting the system out .

Regards John.

[Ding Duck]

Thanks John, it is a distinct possibility. There has been nothing done to the system in the 2+ years we've had the boat, but would be in line with your description. I haven't had the chance to go back down and have a look, probably tomorrow.
If this was the case, Would I expect to see if Temp increase on the High side of the Compressor. I was thinking if in normal operation, the High side Temp would increase to a certain value and then remain approx at that value? If a restriction occurs, pressure would increase and so should temp? This would be using an external thermometer rather than guage pressures.
Anyway, thanks again for your assistance and let you know what I can find out.
Cheers Ding

[Typhoon]

Hi Ding .

I'm a little confused , you have not touched your system in over two years and it was working fine up until recently ? If moisture is your problem , how did it get in ? Over charging should be ruled out unless you have added refrigerant recently.

Regards

[Ding Duck]

Sorry, the system had been working although the amps would increase over time. As the system can form a thin layer of ice on the skin inside the fridge, I put the High amps down to increased Compressor load due to temp. It's only since I discovered the funny readings on the Temp Controller I started to take notice. The system was probably tripping on Press Differential? From what I have been able to determine, these systems are also very critical when it comes to the amount of charge in the system.
Sorry for the confusion

[Typhoon]

Originally Posted by Ding Duck

Sorry, the system had been working although the amps would increase over time. As the system can form a thin layer of ice on the skin inside the fridge, I put the High amps down to increased Compressor load due to temp. It's only since I discovered the funny readings on the Temp Controller I started to take notice. The system was probably tripping on Press Differential? From what I have been able to determine, these systems are also very critical when it comes to the amount of charge in the system.
Sorry for the confusion

I was reading over your previous posts and see that the plate is behind the liner . At first you had the classic symptoms of moisture in your system , but as you say you have not tampered with the refrigerant then I suspect it may be something else .

So, once the evaporator is down to temperature and the insulation around the plate is the same temperature as the plate , it is seeing a very light heat load but the thermostat is telling the compressor to keep going and is FLOODING the evaporator with liquid refrigerant which traveling down the suction tubing and getting back to the compressor .This is a very bad thing and could damage your compressor if you let it continue This sounds about right since you are now starving the condenser . Hence your strange condenser temperatures.

There would be two cures for this , remove the plate from the liner and mount it in the open air of the fridge with a 1/2 gap between it and the liner . This way you would have a much more consistent heat load on the evaporator relative to the box temperature and all the flashing of the refrigerant would occur inside the the evaporator and not travel to the compressor . The other thing you could do for the time being is make sure you are controlling the compressor with the evaporator temperature not the box temperature .

Yes it is a good idea to expose some of that suction tube , as much as you can. Attach the sensor for the thermostat to the bare suction tube as close as you can get to the evaporator plate. It may take a little fiddling with the temperature setting if you are using a digital thermostat . What you want to do is set it at the point where there is no frosting on the suction tubing close to the compressor . This will turn the compressor on and off according to the temperature at that point on the suction line until the box is down to the right temperature. You may need two thermostats to achieve this. You don't want the compressor to run so long that you are getting the flooding situation.

You really want to consider getting that plate into the open air , this will help make the entire system more efficient and stable .

Have you recently moved the temperature sensor ?

I hope this helps a little .

Regards John.

[Ding Duck]

Hio John, some more interesting details.
I removed the thermal insulation from both the Comp end and the Evap end. What I found was the Liquid Line (approx 1/8" Dia) is spiralled around the Suction line all the way from Compressor to Evap. Should I be calling the Liquid Line the Capillary, so we are talking same language?
This line would become hot as the pressure increases, but would be cooled by the Suction line?
Is this where Superheat and Sub cooling come into the equation?

I first ran the system in AEO mode and used the Temp sensor to measure the Inlet Temp to the Condensor.
This is what I got
Time (mins) Amps Temp degrees C
0 4.8 30.5 (ambient)
+5 5.6 40
+10 6.6 43
+15 8.2 44
+20 9.2 48
Compressor tripped at T+24mins. Had to wait in excess of 1 hour before I could get a restart. Trip was always 3 flashes

Anyway, I installed the PTC up next to the exit of the Evap ( about 2") and wrapped some thermal insulation over it to negate external temp effects. Pretty much got the same results as before. Temp would decrease when first started the Comp, then rise accordingly. The Compressor was run in constant speed mode approx 2000 rpm. I have got a long list of numbers for Temp v Comp Amps and probably send these seperately rather than chocking up space here. The suction line at the compressor is definately not cold, slightly warm, probably due to the compressor high amps / heat.

I'm still none the wiser, but am leaning towards some type of restriction?
Over to you Blue Leader
Cheers

[Typhoon]

Originally Posted by Ding Duck

Hio John, some more interesting details.
I removed the thermal insulation from both the Comp end and the Evap end. What I found was the Liquid Line (approx 1/8" Dia) is spiralled around the Suction line all the way from Compressor to Evap. Should I be calling the Liquid Line the Capillary, so we are talking same language?
This line would become hot as the pressure increases, but would be cooled by the Suction line?
Is this where Superheat and Sub cooling come into the equation?

I first ran the system in AEO mode and used the Temp sensor to measure the Inlet Temp to the Condensor.
This is what I got
Time (mins) Amps Temp degrees C
0 4.8 30.5 (ambient)
+5 5.6 40
+10 6.6 43
+15 8.2 44
+20 9.2 48
Compressor tripped at T+24mins. Had to wait in excess of 1 hour before I could get a restart. Trip was always 3 flashes

Anyway, I installed the PTC up next to the exit of the Evap ( about 2") and wrapped some thermal insulation over it to negate external temp effects. Pretty much got the same results as before. Temp would decrease when first started the Comp, then rise accordingly. The Compressor was run in constant speed mode approx 2000 rpm. I have got a long list of numbers for Temp v Comp Amps and probably send these seperately rather than chocking up space here. The suction line at the compressor is definately not cold, slightly warm, probably due to the compressor high amps / heat.

I'm still none the wiser, but am leaning towards some type of restriction?
Over to you Blue Leader
Cheers

Hey Ding , I agree from your data.

Sent you a message through my Email.

Regards John.

[Richard Kollmann]

Ding Duck, Shuts down high amperage after running 20 minutes Your LED trouble code of three flashes would normally indicate an amperage overload. Not knowing manufacture of system makes it difficult to provide a direct troubleshooting approach WAECO may or may not be the manufacture leading people to provide a shotgun approach as a solution in order to be of help.

A confirmed code of three LED flashes probably would lead a mechanic if unit conforms to recommended Danfoss BD compressor installation specifications.

1. A Danfoss BD compressor code needs to be confirmed to be the first code displayed as an earlier code can be covered up by a restart high differential three flash high amperage code.
2. Increasing amperage in thermostat or its wiring. Compressor speed can exceed maximum rpm if electrical resistance in this circuit exceeds 1500 ohms or amperage is increased to more than 5 milliamps. Simple way to eliminate this as a problem is to disconnect thermostat wires from terminals C an T on module and then connect a jumper wire between module terminals C and T.
3. Danfoss BD compressors sold after 1996 are all variable speed with armature inside excited by three equally sized coils. If for some reason the pulse frequency of these coils is interrupted by dirty current from other boat electrical circuit a trouble code of three flashes will occur. I recommend eliminating this possibility by temporarily connecting Danfoss 12 volt power module direct to a 15 amp fused fully charged battery. Failure of poor boat’s grounding system may very well be your trouble.
4. Poor Insulation in no way has anything to do with cause of LED flash codes or high amperage on a properly designed refrigeration unit.
5. Because of problems with capillary tube refrigerant flow control on Frigoboat keel cooler systems there is a tendency to jump to a conclusion that cap tube blockage is a common problem. There is no factual history to support this false miss directed theory. Cap tube blockage on these Danfoss BD compressor’s other than keel cooler units could cause a three flash LED code. On a conventional system there would need to be too much refrigerant in this system. Blockage of cap tube generally causes amperage to drop rather than increasing enough to activate trouble LED.
6. Sub cooling high pressure line by wrapping it around low pressure line gas return line to compressor is a common practice. If cap tube is wrapped tightly more than 13 times close together over return low pressure line it will cause higher than normal amperage. Because there is no history of anyone tampering with refrigerant or making a change in anyway I would rule out sub cooling refrigerant as a cause of trouble LED code three flashes.
7. On water cooled systems when water is drawn in to refrigerant by leaks in condensers three flash LED codes are common resulting complete system damage.

If the seven nondestructive test items above can be ruled out that leaves a possibility of contamination of refrigerant maybe air mixed in with refrigerant. I would recommend reducing volume of refrigerant until amperage drops below 6 amps.

[Ding Duck]

Hi Richard, Thanks for the reply. In response to your questions as follows
Q1. The systems runs for the time indicated and shuts down. This is not done by the Thermostat as it is still calling for Cooling. Compressor attempts to restart, ie Condensor fan runs then comp draws about 8 Amps or so and shuts down. 3 flashes are indicated. Control unit is 101N320 Danfoss module so should be with AEO from what I have ascertained.
Q2. Have run System by Bridging the Thermostat terminals with short length of Cable. Have also run system with a 180 Ohm (potentiometer) connected so unit should run in Constant speed mode. Same results
Q3. The unit is wired directly to a battery, but Solar charging is also connected to this. Have run the unit without Solar, ie Open Solar +ve C/B. Same type of result
Q4. The system has been previously completely insulated from Compressor to Evap. Condensor is Air Cooled and doesn't seem to have any restrictions in regard to air flow etc.
Q5. Could you elaborate on why Amps may drop on Blockage with Captube? I would have thought that while flow would decrease, the Pressure would increase and create higher load on Comp.
Q6. I think you may have answered the dilema. The Captube is wrapped around the suction line all the way from the Condensor to the Evap. Definately more then 13 times. The length of pipe is about 4' or so. I will attached a couple of photo's and as can see the tightness of the wrap of the Captube. Is the High Amps caused because of too much Superheat on the suction Line and harder for the compressor to pull the vapour?
Q7. Condensor is Air cooled so N/a

Richard, I have also included a chart of the Temp and Amps draw. The Evap Outlet temp would actually be the Captube inlet temp to the Evap.
I cycled the system off using the T'Stat at T+17mins as wasn't getting any better. Generally I would need to wait 1 hour plus before I could get a restart
Not sure if this of any benefit?

Thanks for your input and await any response
Cheers Ding