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Ding Duck · 01-03-2017, 22:13

Richard, Evap piping as discussed

Richard Kollmann · 02-03-2017, 06:57

The picture and charts tell the story. Compressor start up normal but amperage not stable during first 10 minutes of pump down and continued to rise for the next 8 minutes. At 18 minutes evaporator temperature changed and amperage went to zero.

Assuming this unit was never tampered with and it did operate without problems at some point with excessive resistance pressure drop sub cooling of high pressure line.

I do not have a test stand with a BD35 compressor but I do not believe 8 amps will cause module to stop compressor as your chart shows at 18 minutes. I believe graph is confirming my earlier item number 3 test this step is important in bypassing all boats electrical wiring to refrigeration unit. Copy of Item 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 electrical current from other boat electrical circuits a trouble code of three flashes will occur. I recommend eliminating this possibility by temporarily connecting Danfoss 12 volt power module plus and minus direct to a 15 amp fused fully charged battery. Failure of poor boat’s grounding system may very well be your only problem.

I always provide a sequence of non destructive tests first before destructive work like tampering with refrigerant flow.

Typhoon · 02-03-2017, 07:25

Hey Greg , Richard may be right , check your voltage at the machine when you are drawing those 8 amps . Wouldn't that be good .

Regards John

Richard Kollmann · 02-03-2017, 09:23

John, Voltage at machine is not going to be readable in pulsating voltage alternating equally in three phase coils. Simple non destructive troubleshooting Item 3 as I suggested has proven to work in three cases on Danfoss BD variable speed compressors in the last year.

Solution to problem as defined resolved by new wiring between Danfoss control module and house battery bank.

Typhoon · 02-03-2017, 09:52

Quote:

Originally Posted by Richard Kollmann

John, Voltage at machine is not going to be readable in pulsating voltage alternating equally in three phase coils. Simple non destructive troubleshooting Item 3 as I suggested has proven to work in three cases on Danfoss BD variable speed compressors in the last year.

Solution to problem as defined resolved by new wiring between Danfoss control module and house battery bank.

Hi Richard ,

This is what Danfoss says , pretty much the same thing.

"
Power supply (Fig. 1)
The electronic unit must always be connected
directly to the battery poles (2). Connect the plus
to
+
and the minus to
-
, otherwise the electronic
unit will not work. The electronic unit is protected
against reverse battery connection.
For protection of the installation, a fuse (3) must
be mounted in the
+
cable as close to the battery
as possible. 15A fuse for 12V and 7.5A fuse for
24V circuits are recommended.
If a main switch (4) is used, it should be rated to
a current of min. 20A.
The wire dimensions in
Fig. 2
must be ob-
served.
Avoid extra junctions in the power supply system
to prevent voltage drop from affecting the battery protection setting. "

I recommend with my installations no more then a 3% voltage drop across the wire to the compressor . And of course a dedicated wire with its own fuse or breaker to the battery or panel with nothing else connected to it .

http://files.danfoss.com/TechnicalIn...cei100b602.pdf

Regards John.

Ding Duck · 02-03-2017, 23:34

I ran the Compressor today as you indicated off a Battery only. No other power source connected to the controller. Pretty much got the same results as before, with a Trip at 19mins and Current of 9.1A. Min Battery Volts was 12.4V
The inlet temp to the Condensor was close to +50c, while temp at bottom turn of Condensor was probably just below ambient of 30c?
Where I am a little confused is the temp reading from the Sensor? The system worked 'fine' previously, maybe high Amps when temp got down, but sensor used to reduce. Would read down around 5-6c or so. Could even form a thin layer of ice on the skin inside the fridge. (Remember the Evap is mounted behind the skin of the fridge, sandwiched between skin and insulation. Don't ask me why)
The only thing that has altered is the temp sensor now reads high, goes down slightly, then back up.
As the Captube is wrapped all the way along the suction line, it could have previously never read anything but Liquid Line temp. If we were low of Gas, then Comp would run at low Amps? Is this correct?
If there is a restriction, would we expect the opposite? High Temp, High Amps?
We have proved the temp controller and sensor, by using fixed resistor, putting in cold water and hot water. Readings as would be expected give or take a degree or 2.
When trying for a restart, you have to wait approx 1 hour before compressor will get away. In between time, it will attempt start and definately not get to speed (Bogs down) so the 3 flash error could possibly also be interrupted as a 4 flash. Guess the unit determine where on the curve it decides if it is 3 or 4 flashes.
I'm at a loss but keep going back to the temp controller readings and what could have changed?

Thanks and Cheers
Ding

Richard Kollmann · 03-03-2017, 06:47

With steady increasing amperage and evaporator temperature also creeping higher for 18 minutes it points to one of three possibilities:
1. Contaminated refrigerant with air or a high pressure refrigerant like a blended refrigerant. It is not unusual during the start up pump down cycle on cap tube systems for pressure to drop into a vacuum allowing air to inter through a servicing port seal.
2. Too much Refrigerant for a warm climate.
3. A restriction in refrigerant flow combined with too much refrigerant.

If all suggested tests given earlier were completed correctly I would suggest removing a very small amount of refrigerant after system was turned off for 30 minutes. If this small removal of refrigerant does not extend compressor running time repeat process until compressor will stop on command of thermostat. Do not forget to wait 30 minutes in between each test run to insure compressor is not in a vacuum.

Ding Duck · 08-03-2017, 03:55

Richard, John, had a little better result today and maybe closer to finding a solution.
Before started the Comp, I 'blipped' a bit of gas out of the system from the charging port on top of the Compressor.
The ambient temp was about 4 degrees C lower than the last test. Compressor was running Variable speed mode. Inlet Temp to Evap (Liquid Line) went from
Ambient 26.5 down to 21.1 Celcius. Amps ranged from 4.4 to 4.9A. This took 9 mins

Temp rose from 21.1 to 26.5 Amps rose to 7.0A This was from Time +10 to +28 mins

As I notice the Amps start to rise, I gave the Condensor a squirt with a spray bottle of water. This corresponded with a reduction in Current. Dis this 3 times.

Cycled the system off using T'stat and tried for a restart at +49mins. No restart, 3 flashes. Did this until T+53mins when got a restart.

From T+53 to T+64 :Liquid Line tempo dropped from 28.9 to 26.2 C. Amps was 4.4 to 4.9A

From T+65 to T+142 Temp rose to 28.8 Amps at 6.35A
Had a couple of squirts of water in between these readings

Compressor cycled off on T'stat at T+145.
At T+180 'blipped' some more gas from compressor and tried for restart. Amps on restart was 9.0, but dropped to 7.0 continuously. The Liquid/ Suction lines at exit of Evap were cold enough just to form condensation. When Comp shut down although I couldn't get in to hear, you could feel liquid moving in the tubes.

As previously mentioned the Evap is sandwiched between the insulation and the fridge liner so I can't actually get to it. Dd managed to get he temp probe somewhere close and had reading of 14.4 on Evap. Inside fridge temp was approx 7 celcius. This was Air temp approx 3/8" from fridge liner. There was a small layer of ice forming on the skin where the Evap would be.

From here, definite improvement from where we were, albeit slightly lower ambient temp. I'll try for an additional fan across the condensor to see if that improves reduces Amps on Compressor.
'Blip' a bit more gas from system see if that makes any improvement.
Any other suggestions?

Preperation H (Hammer) is going back in the box for the moment!
Cheers

Typhoon · 08-03-2017, 05:55

The thing that has me so confused about your system is that you say it was functional and you have not tampered with it. So what has changed? Now if you remove a bit of refrigerant it seems to cool and you start to hear gurgling in the lines. So my question is how did that excess refrigerant get in there ? You checked the access valve cap and that was tight and there was a rubber o ring at the bottom. That would be the only place that air could get in the system ? If that is causing your over charge senerio . Air in the system brings moisture . Not good . The only other thing I can think of would be a partial or intermintant captube blockage . I still think you should get that plate into the air , out of the wall. Improve and stabilize the heat load on the evaporator . Also if you had a none aeo controller , that would help diagnosing the system , just a few thoughts . Good you got some thing out of it .

Regards John

Richard Kollmann · 08-03-2017, 06:41

Ding, If you were to indicate that in the past the refrigeration system did provide adequate enough cooling to satisfy thermostat setting then friction of too many turns of cap tube around return line can be ruled out as a problem.

Your tests seem to show that refrigerant is not condensable enough causing a continues increase in amperage so the next step would be to remove all refrigerant and dehydrate system with a refrigerant vacuum pump.

Ding Duck · 08-03-2017, 10:22

Hi John, the thing that alerted me was the Temp Controller issue. Previously, the Temp indicated would decrease down to around 10-12 C. Fridge was cooling, but in hindsight was drawing High Amps. Something happened and Temp indicated would go down then back up as indicated in the readings shown here previously. Hence thought I had a dodgy controller and went through the checks and proved it wasn't the controller.
The only changes made have been to reposition the sensor closer to the Evap Inlet/ Exit on the case and to remove the thermal insulation which had been run all the way back to the Compressor.
This is why I suspected there may be a blockage / restriction

It would be good to move the Evap into the fridge, but would require just about a complete tear down of the Galley. It's 'glassed in on both sides, but probably seemed like a good idea at the time for whoever installed it. New L shaped Evap and plumbing is easier
Cheers

Ding Duck · 08-03-2017, 10:39

Sorry Richard, I don't quite understand. If the Gas is not compressable enough?
Assuming it is 100% R134A not a mixed gas, are you suggesting I'm not getting enough back on the suction line?
The inlet to the Condensor is pretty hot, around 105F (measured) with quite a good temp drop across the Condensor. This is by feel only.
If I'm not getting the correct amount of compression (pressure), would this be indicated by a lower temperature on the Condensor?
Could you elaborate further please
Cheers

Richard Kollmann · 08-03-2017, 12:03

I am saying if system as installed worked well in its present mechanical condition why is there a major change in high refrigerant pressure now?

A Danfoss BD 35 compressor will peek at a high amperage around 7 to 10 amps on start and drop to 4 or less than 6 amps during the pump down 10 minute phase. Any amperage above 6 amps is an indication of a problem. In order to trigger a LED code of three flashes control module is experiencing amperage above 8 to 10 amps which is what is currently happening after running 18 minutes.

Because your chart shows amperage does not stabilize at 10 minutes but continues to rise there is either:
Contained refrigerant most likely a non condensate gas like air or nitrogen mixed in with refrigerant. Each of these gases will not be liquidized at the correct operating pressure of this 134a refrigerant unit.

Moisture in refrigerant will not cause high amperage when the capillary tube system is correctly charged with refrigerant.

Your attempt to lower refrigerant volume and solve the problem leads you to the super dehydration process required on 134a systems with POE oils.

Ding Duck · 08-03-2017, 12:47

Thanks Richard, by Super Dehydration process, I take it you mean
Heat to approx 100F
Vac system out (4 Hrs min)
Moisture content less than 500 microns
Recharge with 300g of R134A

Cheers