Frigoboat Freezer Problem

[Marg]

Re: Bizarre FrigoBoat Behaviour !
Hi Guys.
John here. I have the frigoboat K50F with keel cooler. I have been keenly reading your posts about your systems and have learned a lot. My problem is somewhat different, mine started with a ?low charge? and before I know what I now know, I recharged with a 134a substitute that contaminated the system. I have had the system evacuated and recharged but the same problem persists. Playing with the charge I beleive I have the optimum charge as I have spilled small amounts of refridgerant until the frost crept back from the compressor into the insulated tube. The frost never reached the compressor. So it seems everything is operating fine, except I cannot get the box temp down under 20 fahrenheit. My shut off temperture for the freezer is 0 fahrenheit. The whole plate frosts very quickly to that temperature (30) and then creeps one degree every hour or two. At a certain point it will even climb a few degrees. I have left it run for 24+ hours without reaching below maybe 20 degrees. At no time, even when the temperature is climbing, does the frost leave the evaporator. Now the box is almost empty from the initial problem. I can't see that having a great affect. I am presently in Nanaimo Britsh Columbia with a water temp of 55 degrees. Left to my own devises I was planning on evacuating the system, washing it out with nitrogen, possibly replacing the dryer with something larger. Through your conversations I am led to believe you can install a dryer on the liquid line?
Can someone continue my education and save my ass?
Thanks John

[Richard Kollmann]

Marg, The condition you describe is normally caused by poor condenser cooling (Keel cooler), Thermostat problems, Too much refrigerant or Contaminated refrigerant.

On you unit, good condenser cooling is when line leaving keel cooler going to evaporator is cooler than 110 degrees and warmer than 70 degrees F.

Thermostat can be bypass with a jumper wire letting compressor run till minimum temperature of evaporator reaches zero. Not box temperature.

Too much refrigerant on a capillary tube system like yours will be indicated by frost covering 100% of evaporator and some small portion of line after evaporator.

Contaminated refrigerant with air or any other gas will cause refrigerant drift problems inside evaporator. In other words Frost will not be present at beginning of evaporator tubing its phase change will occur later and maybe frost only the last half of evaporator and return line.

What is suction pressure 15 minutes after starting compressor with a warm box?

What is suction pressure when box temperature stops dropping below 20 degrees? And what is evaporator temperature at that time?

[Marg]

Hi Richard, Thanks for your feedback.

Keel Cooler
We have checked the temperature of the fluid exiting the Keel Cooler and its about 78*F. About mid run. Seems OK?

Thermastat problem
The thermastat is not turning off the compressor as the box temperature (0*) has not been reached.

Too much refrigerant
This may be a point. I have charged this system so that all of the evaporater is frosted with the frost just leaving the box but not going past the insulated portion of the return pipe. Is this overcharged?

Contaminated refrigerant
It is very possible. The system was evacuated, after I charged it with a can of Red Tek 12a replacement, but only for a short time, maybe 10 min. The whole plate is frosting quite quickly.

The suction pressure after 15 min of running was 2psi. This box was not warm when started 42.4*. Evaporator temp 2.5* Box temp 38.6*.

After 3 hours the suction side was -5psi. Evaporator temp -12* Box temp 26.6*.

I am running these tests with the box empty and a rag stuffed into the cut out for the pipe to enter. Do you think I sould try filling the box and sealing the hole?

[Richard Kollmann]

I was wrong when I said your system would function well with high pressure liquid at 70 degrees F. Your 78 degree reading with 55 degree seawater destroys volume of refrigerant flow as proven by 2psi after 15 minutes instead of 6 to 8 psi, and a minus pressure of 5 after 3 hours. It is unlikely that a Danfoss BD compressor keel cooler system will reach low freezer temperatures in cold seawater. At 78 degrees 134a liquid pressure is producing less than 80 psi at expansion cap tube and 115 to 125 psi is desirable to keep suction pressure flow up. Abler Barbour offered a solution to this problem 20 some years ago by covering part of air cooled condenser with cardboard. Circulating water cooled refrigeration high pressure can be regulated by reducing water flow.

Reducing the amount of compressible gas space between compressor and keel cooler by adding additional refrigerant may increase both high and low pressures increasing flow. Frigoboat does not provide a high pressure port needed to determine what high pressure actually is. You know that adding refrigerant will cause frost on return line and as long as it stays away from compressor and compressor is warm it should not harm compressor. The only other option I see is to operate this box as a 45 degree refrigerator/cooler. I was told by a service tech in the northwest that he adds refrigerant to this type system coming from South California to improve performance.

One other problem I see is the delta T temperature between evaporator and box temperatures of 36 degrees. When this Delta T exceeds 20 I usually figure evaporator surface area is too small or box insulation is poor.

[Marg]

This system has run successfully for 2.5 years. We installed it in New Zealand and have sailed from there back to French Polynesia. We have been here in British Columbia through last winter when the water temps would have been much colder and the system has performed well through out. Before this current problem the freezer would draw down in about 50 minutes on level one. I have just installed a new evaporator on a local technician's advise. I will finish this installation and seal the pipe access hole with foam and fill the freezer with our provisions that are in a friend's freezer and see if I can't improve that Delta T number. Maybe play with the charge until I see frost leaving the insulation on the return line.

[Richard Kollmann]

If you were able to get good performance under identical seawater conditions before then technician is probably correct in replacing evaporator assembly do to capillary tube restriction. Frigoboat US is aware of the capillary tube restriction problem do to location of filter dryer. This will be the first time I have heard that tube is only partly blocked if replacement corrects problem. Frigoboat usually advises a procedure of tapping on tube to let material from cooler fall back into larger line until new evaporator and correct installation of filter can be accomplished. Well designed systems all filter liquid refrigerant before it reaches expansion device orifice. Make sure Technician installs a filter in liquid line of new evaporator if you do not want this to happen again.

[Marg]

Hi Richard,
This is the new evaporator plate that I have put into our freezer and the problem still persists. Do you think with a good long vacuum and a nitrogen flush you could get away with not changing the evaporator again with the instalation of a properly placed drier? Leave the old drier in the system? And would a larger drier in the liquid line be preferable?

[Richard Kollmann]

Marg, Is there a chance that compressor speed was changed to a lower Rpm. this with cold seawater could create lower than normal suction pressure? Is your unit equipped with a speed controller? If speed is controlled by a single resistor what is its value or what speed is compressor running at if you know?

After twenty five years troubleshooting these small 12 volt systems Frigoboat’s keel cooler models are the only ones with refrigerant flow problems. It seems that they generally run three to five years before refrigerant flow problems show up. I have seen live aboard boaters buy complete new systems after replacing one two or three evaporator assemblies. Deep vacuuming refrigerant circuit is worth a try but with only a low pressure side service port and a 8 to 9 ft long .029 orifice tube it is unlikely an object restricting it will move the full length of orifice tubing. All Keel cooler Frigoboat models I have seen have filter/dryer installed incorrectly on gas return line at compressor instead of liquid side prior to inlet of capillary tube orifice. If you are correct that unit worked fine in 55 degree seawater and were able to open up restriction I would install correct filter. When installing new filter leave old filter as is. Then even after installing new filter the risk is still there that future blockage material may still be located in old line between new filter and capillary tube. The correct time to instill a filter between condenser keel cooler and cap tube is when new evaporator is connected.

As a solution to this problem those planning to purchase a Frigoboat keel cooler system should purchase along with this system their correct liquid line filter dryer.

[Marg]

Hi Richard,
We have the Smart Speed Control on our system and it has been running at the highest level (6). It starts at three but quickly moves to six.
There is a high pressure service port on our unit, just as the line leaves the compressor before heading down to the keel cooler. Before the quick connect. Would this additional port assist in moving any contaminant in the capillary tube? In my layman mind you could add nitrogen to one side and suction to the other that would have a great pressure on any restriction. Would this be reasonable in this system?
Having such a small oriface tube are driers readily available say RParts?
With all your vast experience is there another brand that you could recomend? Has Isotherm developed a keel cooler? Realizing as I'm sure you do that energy efficiency is critically important as we are nornally on the hook and suppling our own power.

As a different problem with all this testing, we have found that our 'Carel' thermostat is reading significantly higher than another electronic thermostat that was perchased years ago when struggling with our original Glacier Bay System. We are going to reset the unit and see if it will come back to it's senses. This discovery has closed the gap between box temp and plate temp somewhat.
The new probe was inserted at the same height as the Carel and when the new probe read 0*, the Carel read 20*. That would bring the Delta T from 38.6* down to 18.6*. This also with the top of the box slightly ajar to allow the probe wire entry.
John

[Richard Kollmann]

If your SSC speed controller is the one with 6 separate LEDs it is doing what it should going to high speed if compressor runs continuously. this rules out compressor running to slow.

Yes, high pressure port can assist in dislodging something stuck in inlet of capillary tube. First you need to establish a performance base line of high and low side pressures across cap tube. After purging air out of servicing gauge set with refrigerant, connect both gauge hoses to service ports. Now with a warm box start compressor in 10 minutes record suction pressure, if below 6 psi add refrigerant to obtain 6 to 8 psi. This must be done in a time window under 20 minutes total running time. If you are unable to make adjustment in time window between 10 and 20 minutes turn off unit and let evaporator warm up and try again. When refrigerant volume is set as described run system 15 minutes more and record both suction and high pressure and frost length towards compressor. This process means we have set refrigerant to match ambient air and seawater conditions so do not add or remove refrigerant any more. With thermostat set full cold record box temperature and high and low pressure along with frost line each hour for 4 hours or till suction pressure drops below 3 positive psi. Of course stop compressor if frost line reaches compressor.

After the above test, if performance is not satisfactory Yes, I would try to open capillary tube with Pressure and vacuum. Remove refrigerant pressure from suction low pressure side of system this will prevent loss very little oil.

With little or no refrigerant in system Connect vacuum pump to high pressure service port and refrigerant bottle to low pressure service port. I would not use nitrogen as pressure above 100 psi can destroy Roll Bond aluminum evaporators.

I prefer standard thermometers and thermostats for boat refrigerators.

[Marg]

Hi Richard,
We did the test adding refrigerant between 10 and 20 minutes to keep the suction side between 6-8 psi. After running for 30 minutes the suction was 3.25 psi, at 2 hours it was 0 psi and afer 3 hours it was -1 psi. Between 3 and 4 hours I added more refrigerant to try to keep the low side positive. At this point fearing my gauges leaking I removed them. We continued running and when the numbers slowed to almost a stop we cycled the compressor off, left it for 10 minutes and restarted, several times which helped the numbers reduce. After 7 hours it reached its shut off of 0. We let it cycle many times through the evening. The hold over is dismal (minutes) because of the empty box. But each compressor cycle that ran from 4* to 0* lasted 20-30 minutes. Is this extremely low, low side pressure due to a blocked capillary tube? Could it be from a blocked dryer?
I have attached a photo of inlet and outlet at the evaporator and am wondering if this is a drier.
Thanks John

[Richard Kollmann]

I do not see how I can help you if you do not follow my instructions. You were instructed not to add refrigerant after it was correctly adjusted in time window of 20 to 30 minutes. You did not report high pressures or frost coverage. In order to pinpoint actual problem I need a base line performance to begin with.

A blocked dryer when there is still refrigerant flow should be indicated by frost covering filter. I have been informed by Frigoboat’s top man in US that the item in picture adjacent to evaporator is not a filter. Filter dryer is attached to compressor.

You say “The hold over is dismal (minutes) because of the empty box.” This means to me that insulation may now be wet or if VIP it has lost its vacuum or thermostat’s differential is set too low. If there is X degrees of heat infiltration, and there always is, into a box this will not change energy consumed box full or empty, all that changes is compressor runs longer when box is full. It is true a full box has less cold air to be replaced with warm air when front door refrigerator doors are open. If during this test door remained closed and evaporator temp reached thermostat setting stopping compressor dismal performance can not be blamed on refrigeration unit.

You indicated this system reached low freezer temperatures before in very cold seawater and now performs poorly. The only changes between then and now are wrong refrigerant was added and evaporator assembly was replaced with new one in picture. Contaminated refrigerant was deep vacuumed out and replaced with pure 134a. Frigoboat has several different evaporators, Is the replacement exactly the same as the one removed? Did incorrect refrigerant have oil in same container?


Have you discussed this problem with Rob at Frigoboat US? He is the only one that knows all of the problems and solutions with this system.

[propellanttech]

I believe the problem is the possibility of mixed oil contamination. All 134a refrigerants contain oil. If trying to switch back, there is no way to remove the oil without breaking the system apart or flushing. I'm not sure of all the detriments, but do know, 12a doesn't like the oil from 134a.

12a to 134a = good
134a to 12a = bad

Just the information I know........may or may not be the problem.

James L

[Marg]

Hi Richard,

In our test run, after the first 10 minutes, the high side was 105, the low side was 6 and the plate was starting to frost. After 30 minutes, the high side was 109, the low side 3.25 and half the plate was covered with frost. At 40 minutes the high side was 105, the low side was 2.6 and the plate was covered with frost.

We have not discussed this problem with Rob at Frigoboat. Would you happen to have his email address?

We really appreciate all the time you have spent explaining and helping us trouble shoot this Richard,

[Marg]

Thanks for that James. We got the feeling that adding 12a was a bad thing.