Author Topic: Frigoboat Air Cooled Unit Will Not Stay On  (Read 6542 times)

mayball

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Frigoboat Air Cooled Unit Will Not Stay On
« on: March 04, 2014, 04:36:12 pm »
This air cooled Frigoboat has an air cooled condenser and a thin plate evaporator. When I first saw it, it was empty of refrigerant. I charged it with R-134a until fully frosted, and replaced a leaking shrader valve core. Later the owner reported that it was not cooling again. This time, the fan would run for one minute drawing one amp. (which I know to be excessive for a BD-35 without a fan relay). Then the compressor would start to run, drawing about 2.7 amps for about 2 seconds, and beginning to pull down the suction before stopping. Then the fan would start and, although it has no LED, it would give a two beep signal on my ohmmeter. This would continue for one minute.

The puzzling part is that, even with the black lead disconnected from the F terminal on the module and, of course the fan not running, it would still give a two beep signal on the ohmmeter between the D and the small plus terminals, and would not allow the compressor to run. Is there now a problem with the module? Or is there a way to "reboot" the module so it would stop giving the two flash diagnostic with the fan disconnected?

Don May
Don

Richard

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #1 on: March 05, 2014, 07:38:58 pm »

Sounds like too much refrigerant to me or refrigerant is contaminated. Was the refrigerant you used pure with no additives?

Best thing to do at this point is disconnect everything connected to module terminals  except power red and black wires then install a jumper wire across terminals C and T  With NO meters connected just power and CT jumped across turn power on. Compressor should run unless you added to much refrigerant or there is a low voltage spike in boats wiring. If compressor does run let it run for a while then connect fan. If it does not run connect a fully charged battery direct to module bypassing all boats electrical connections. Now if compressor does not run remove some refrigerant until it does run.

mayball

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #2 on: March 09, 2014, 02:52:07 pm »
Turned the breaker on with only the power wires installed and with a jumper across the C and T terminals. The compressor did not run. Ran the power wires directly to a battery also with the jumper. The compressor did not run. Removed refrigerant to 60 psig, to 32 psig, and to 15 psig. Each time, the compressor still did not run. When unloaded in this manner, the unit drew an instantaneous 2 amps, 2 seconds at 1 amp, then zero amps for one minute. Then it tried to start in the same manner again. I removed the module and found all three windings had resistances of 2.6 ohms.
Don

Richard

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #3 on: March 10, 2014, 07:32:47 pm »
Time to test that module or try another module you know is good. If you were in the US I could loan you a new module but I will not ship outside the US.

mayball

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #4 on: March 14, 2014, 05:23:06 am »
I have not returned to the boat, but I did attempt to use the module on another compressor. The compressor attempted to start, but immediately stopped. I have a spare used module that works, which I will install on the Frigoboat unit, and let you know how it does.
Don

mayball

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #5 on: March 18, 2014, 07:07:09 pm »
I replaced the control module with a working one, and inserted a relay in the positive side of the fan circuit so the fans were driven by power directly from the breakers when the fan circuit was energized. The compressor started up normally, but when the system had stabilized with about half of the plate frosted, it reverted to the original problem, whereby the compressor tried to start each one minute, but would not start. When it was running normally, the system, including the fans, was drawing 3.3 amps.
Don

Richard

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #6 on: March 20, 2014, 01:55:00 pm »
Problem started with no refrigerant then after you added refrigerant compressor would not run.

When Danfoss BD compressors will not maintain governing speed it will be because of::
 1. Starting or running amperage draw too high
2.  Fan module terminals are drawing too much current
3. Voltage to unit is not pure there are either voltage spikes caused by boats power grid or old wiring connections. It is also possible unit has a bad battery ground.
Each of the above conditions with the exception of a bad ground can be pin pointed by installation of a 10 to 20 milliamp troubleshooting 12 volt LED.

Without this LED each area of probable cause must be tested separately. You reported bypassing of all boat's electrical wiring while using an external battery source, and eliminating electrical loads on Module terminals C and T. Cause of  High current from excessive or contaminated refrigerants high pressure on start up would have been eliminated by lowering static refrigerant pressure to 15 psi. This would mean not enough refrigerant to be condensed creating a pressure differential across cap tube.

The two trouble areas that can not be defined by LED codes are electronic module difficulties and troubled thermostat and its wiring.
You bypassed thermostat and changed module and still there is troubles with compressor not running.

It is difficult to go beyond this point and blaming system’s problem on compressor armature rotation lock up with out seeing a three LED Flashing code when past experience tells us these compressors almost never lock up. Frigoboat’s history of refrigerant capillary tube blockage on keel cooler models performs much the same as this air cooled one. The safest conclusion would be if boats power grid and boat’s wiring is not the cause of compressor not running then replace complete system.
In the past others have replaced either the evaporator assembly or compressor to find they still have the original trouble.

mayball

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #7 on: March 28, 2014, 05:20:35 pm »
Thanks for the advise, Richard. This unit continues to baffle me. I returned to boat after the unit was off for 10 days, and found the following static conditions: 51.7 psig and 12.84 volts, directly connected to an independent 12 volt battery. I installed a clip-on ammeter to the plus power line and jumpered the T and C terminals. The compressor did start up, pulling the suction steadily down to 28psig, while drawing 3.3 amps and the voltage dropped to 12.64-12,55 volts. Then the compressor stopped. My voltmeter between the D and plus terminals indicated three 12 volt pulses, then a pause and again three pulses, etc. for one minute. Then the unit tried to start, drawing instantaneous amperes of 8.5 and 10 on two separate checks.

I cannot see why, after 10 days the unit would start running, or why, after drawing no more than 3.3 amps the diagnostic would decide the unit was overloaded and shut it down. What do you think?
Don

Richard

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #8 on: March 29, 2014, 01:47:18 pm »
Compressor start up and running after several days rest along with an overload signal if that is what you got by using a voltmeter instead of an LED would indicate possible capillary tube blockage. An overload LED signal code is three flashes and repeated again every 4 seconds. You reported static pressure on suction port before start of 51.7 psi. When started compressor  went into a normal pump down phase drawing 3.3 amps while compressor ran at minimum 2000 rpm. While compressor ran in pump down mode suction pressure only dropped to 28 psi then compressor stopped. If this was a true 3 flash code amperage would have exceeded 10 amps plus signaling electronic module to stop compressor. Did you see an increase in amperage just before compressor stopped?

Capillary tube blockage seems to be a problem on Frigoboat keel cooler units after 5 years in service. The actual cause of these blockage problems is still not known. If there was a high pressure service port on your unit it would be easy to confirm that cap tube blockage was the trouble. With only low pressure readings you must rely on pressure and amperages to define cause of overload: Moisture in refrigerant, Solid material blockage of over 90% flow restriction, or a mechanical problem in compressor. If after an hour with compressor turned off pressure does not return to normal static pressure you know there is solid material and not ice in cap tube. Ice blockage melts very quick and a sound can be heard inside box when built up pressure brakes lose.


mayball

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #9 on: March 29, 2014, 02:05:12 pm »
My eyes were averted, watching the suction come down, when the unit kicked out, so I didn't catch the amperes when compressor went down. Next time I will put the meter on "max" to capture that current. My experience with a cap tube blockage, either from a particle or ice, is that the suction pulls quickly into a vacuum, faster than the discharge rises. In any event, I can splice in a discharge pressure tap, using a second disconnect and get more data.
Don

Richard

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #10 on: March 30, 2014, 12:10:26 pm »
If you install the High Pressure gauge port you will be able to confirm quickly if cap tube is plugged. You will also be able to test compressor using gauge set as a replacement for evaporator. 

The trick in installing service port is preventing flux and solder from blocking tube at joint.

mayball

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #11 on: April 07, 2014, 07:06:59 pm »
Good News! Today I returned to the boat and found the suction pressure at 35.4 psig, the lowest I had dropped the pressure in trying to start it last time. As before with a lengthy down time, the unit started up fine, drawing 3.12 amperes @ 12.30 volts, with a 10 psig suction (after stabilizing with some added refrigerant). 0.3 amps of the above current was fan current. I had not installed a discharge tap.

I then began adding refrigerant, agonizingly slowly, over 2.5 hours, until at 21.8 psig and 3.6 total amps, I began measuring the superheat at the evaporator outlet (not compensating for suction pressure drop) at 13 degrees F. At this point, the evaporator was not fully frosted. So I added a little more until the suction pressure was 20.3 psig, total amps 4.4, and superheat 6.3 degrees F, which is lower than the 9 degrees I was shooting for, but did fully frost the evaporator.

I have asked the owner to check the unit through a few cycles of the thermostat, since it did not cycle when I was there. I still wonder whether it will start OK when fully charged.
Don

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #12 on: April 08, 2014, 02:58:58 pm »
Your reported information is difficult to understand after 2.5 hours you were able to get suction pressure (low Pressure) to drop to 20.3 psig  (6 Psi relative to Atmospheric pressure that is used in the US). You must be confused between Psig and psi. What confuses me is before adding refrigerant low pressure was 21.8 psig or psi of 14.1 psi and by adding refrigerant you were able to lower suction pressure. Adding refrigerant to a capillary tube flow control device refrigerator will increase suction pressure.

I still can not understand why you started with a unit that lost refrigerant do to a service valve leak and all the troubles you had in between. When using a low pressure gauge that reads in Psi of 120 and down to Vacuum to 30 inches proper pressures on this small system will after 30 minutes with 134a refrigerant read 4 psi to 11 psi. Lower the evaporator temperature the lower the pressure. It is possible on low temperature freezers to have pressure lower than 4 Psi. It is also possible to have a low pressure above 11 psi but only on systems with Thermo Expansion Valves. Boats with cap tube expansion devices away from manufacturer’s service centers are best serviced by measuring superheat using frost line on evaporator.




mayball

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Re: Frigoboat Air Cooled Unit Will Not Stay On
« Reply #13 on: April 09, 2014, 11:30:47 pm »
Sorry for the confusion in my unit of pressure. Psig is the common unit for pounds per square inch gauge, which is the pressure relative to atmospheric pressure. I use this unit to distinguish it from psia, which is pounds per square inch absolute. Psig equals psia minus atmospheric pressure. Psi is an ambiguous unit because one does not know whether it is relative or absolute.

The trouble I was having, up until this last post, was that as I added refrigerant to the undercharged system, the frost would advance through the channels of the evaporator until it was about half frosted. At this point, the compressor would stop and exhibit 3 pulsed on the LED circuit. This time, I charged it very slowly, over a period of 2.5 hours, so as to not overload the compressor. Other things I had done to remedy the problem were to put the fans on a relay and to replace the electronic module with another (used) one. These steps were covered in previous posts.

The reason I was using the actual superheat at the outlet, rather than the frost line, to determine the full charge, is because I thought the unit is fully charged when the last of the liquid has flashed to a gas, and the gas has heated by 9 degrees (superheat) when the gas reaches the evaporator outlet. This is a moving target because the liquid in the evaporator channels tends to surge. The frost line is at the point where the refrigerant reaches the freeze point of water (32 degrees F at sea level). This would mean that the frost line indicates where the refrigerant liquid or gas reaches 32 degrees F, not necessarily where the last of refrigerant liquid flashes to a gas.  According to the PT chart for R-134a, that refrigerant boils at 32 degrees F at a pressure of 27.8 psig.

In any event, I am happy to report that this unit is now functioning properly and cycling on the thermostat.
Don