Norcold BD35F Danfoss running but not cooling properly

[Lady-Lou]

Richard is right not to invert system as you have a mechanical system not an absorption system. An absorption system uses a heat source to create refrigeration not a compressor. Inverting it could cause damage.

[Richard Kollmann]

``Disconnect wires from terminals C and T and place a jumper across C and T. By bypassing thermostat and its wiring compressor will run all the time at slowest speed indicating thermostat is the only problem if box and evaporator remains cold.

I have given you three ways to rule out moisture blockage. Moisture in refrigerant is very unlikely on a totally sealed unit with no service ports and has operated for extended time

[Sardean]

I hope you find the problem . Cant wait to hear some good news. Like the other refrigeration techs said Do NOT turn unit over it will stuff it. If you have a blockage you should see a temprature change on pipe work where blockage is as the gas sqeezes through blockage it should expand causing a clod spot. Watch for floodback when you bypass thermostat. ( suction pipe on compressor will get frost , if compressor starts to ice up remove thermostat bypass). If you get floodback while doing this test for 12hrs it means gas charge is good, no blockage and temp is very low in freezer.


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[Sardean]

Oops dyslexic typo cold not clod


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[sv.antea]

I have a similar problem and in fact ran a thread few weeks ago trying to get help diagnosing it. My Danfos35 Frigoboat aircooled system would on start up frost over the whole evaporator, but then the hiss would slowly go quiet, the frost would melt. On advice of a friend, I have warmed up the area on the evaporator where the capillary ends in the plate, and sure enough, the singing returned and the plate frosted over again, for half hour. Tried it several times, first with a hairdryer, later just rubbing the evaporator expansion spot vigorously with finger to warm it up. Worked every time. So the consensus was blockage by ice from moisture in the freon. I was little incredulous. First: nothing was ever done to the system since installed 5 years ago, so how did the moisture get in? Second I suspected electronic problem, since the currrent dropped of when the cooling stopped. Wrong thinking. I have since learned that when blockage stops the freon flow, the current actually decreases. In my case from 3.5A when running normally, to less than an amp. And closer inspection showed oil spreading from a joint on one of those patent couplings, suction side. So bad O-ring. In fact, the joint was loose.
I have replaced the O rings, 3 per coupler, but haven't evacuated or recharged the unit yet, as I am in process of adding insulation to the ice box.
I hope it will all work when I am done. It worked flawlessly for 5 years.

[Richard Kollmann]

On small blocked capillary tube systems where refrigerant volume is correct within 15to 25 grams, yes the amperage drops because all of the refrigerant becomes condensed liquid between condenser and cap tube, Low pressure also drops.

O ring line connectors Frigoboat uses seem to be prone to leaks. When the leak is on the suction side of connector moist air can be drawn in when low pressure drops into a vacuum. Small amounts of moisture case sludge and acids that break down materials that can cause intermittent flow inside small capillary tubes long orifices. The difference between cap tube freezing and sludge blockage is timing of each type flow cycle restriction. Ice formation is going to produce a steady evaporator temperature in the mid thirties while sludge is less predictable.

I have seen boaters spend one to four thousand dollars trying to solve cap tube related troubles and finally replacing complete system. I do not work on boat refrigeration anymore. If a unit is confirmed to have cap tube blockage do not think increasing high pressure will fix the problem. Dehydration can solve the moisture problem but it will require very deep super vacuuming. The Danfoss compressors today use Ester POE oil that refuses to release moisture mixable in it oil. I recommend warming all components of system to 100 degrees F and keep warm while vacuuming for 4 hours. And do not starting 4 hours till the deepest gauge vacuum is reached. Very few technicians have a micron meter but true dehydration of ester oil is achieved between 300 and 100 micron. I find when a refrigeration servicing gauge set reads a vacuum of 31 inches there is still over 5000 microns of pressure in your system.

[seasick]

I apologize for my earlier post suggesting that you invert this unit for 24-hours. Do not.

I made a bad assumption that Norcold's DE models we're the same as their many Amonia based units which use AC/DC and propane. The DE models are not.. The amonia based systems can often be brought back by "burping" inverting them.

[sv.antea]

As ever, grateful for Richard Kollman's reply. Yes, I was curious why the current drop. Meanwhile, I have bought a Robinair 15150 two stage vac pump, adaptor, hose with a valve and the freon fill kit from auto store. Apparently I am short one "micron vacuum gauge" and can't justify adding it on the altar of the ice cube god. So I propose to hook up the pump and leave it on overnight, with a incandescent bulb in the icebox keeping the temp at 100F, not knowing the progress of the pump-out, and carefully add freon the next morning and see if it works. And see if it lasts.
Any danger I will go too far and start boiling of the oil? Should I flush the system with freon before starting the pump? If so how? It has some air in it now since I replaced the O-rings.

[Sardean]

Its not possible to vac it down to far. Take notice of the noise it makes as it pulls a vac. You can tell if there is a leak or if it is still pulling stuff out of system by no more gas/ air bubling through the vac pump. Before you hook it up block the intake and notice the noise this is as low a vac as it will get and is what you want to acheive.when you get used to the vac pump noises you dont need a guage to tell ifvits pulled a vacuum.

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[sv.antea]

Thanks Sardean, that's the kind of news and advice I like to get. No more things to buy. I like that.

[Richard Kollmann]

I am sure that the Robinair pump is advertised to draw a vacuum to or below 100 microns. My point is and was before is calling attention to the fact that removing moisture from 134a refrigerant and POE oil is very very difficult to dehydrate requiring new methods.

I would not leave a light bulb in box unattended as evaporator or box liner can be damaged not to mention starting a fire in boat.

Go ahead with the dehydration process only if you have confirmed there is truly ice blockage and not an electrical or thermostat problem.

Two days ago was our big trash day when I put out two systems with refrigerant flow problems for trash pickup. One of these units I paid $40 to ship to me. The other came out of a local boat. After 24 hours of super dehydration I decided it was sludge and tried to flush thick oil out of compressors with no success. For information on dehydration, using gauges and servicing refrigerant see Section Refrigerant Charge on my web site. Warning,There are many areas in the world where it is not legal to work with any refrigerant without proper certification. This requirement may also include your unit even with only 2 ounces of refrigerant.

[actionpaintball]

I am still doing some testing. Even though my system is using a 110/12v dual controller, I lined up a simple 3 pin 12 volt only controller to test the system for a possible controller malfunction. Hopefully have it in a week; I did turn the setting from 5 down to 3 after cleaning connections and securing/cleaning the ground and the freezer was at 28 degrees and fridge was 42 degrees after 24 hours plugged in on 110V AC. I will be checking on seeing if it still goes through the complete defrosting cycle in the next day or two.

[actionpaintball]

48 hours: Freezer is holding at 18 to 28 and fridge at 42/45

[a64pilot]

Originally Posted by SV THIRD DAY

So here I am working on painting my boost stripe in the boat yard yesterday when I get the same type of call I get almost weekly, it goes like this:

Client: Hey Rich, I need to buy a new compressor/condensing unit, mine died.
Me: Can I ask you why you think your unit is dead?
Client: ya, it won't start up and my dock neighbor knows about refrigeration came over and said it was dead.
Me: Do you mind if I ask you a few questions and give you a few tests?
Client: Well, ok. But my buddy is an expert and already did all the known tests.
Me: I'm sure he is, but just humor me. So can you first run a temp DC power line right from your battery plus and minus terminals to the black box controller on the compressor?
Client: man, that's a pain in the ass and I checked voltage with my volt meter at the unit and it says 12.3v and my volt panel on the ships display says 12.9v, so I don't have a voltage issue.
Me: I understand it may look that way, but trust me, I go through this all the time and I don't want you to buy a new compressor/condensing unit if you don't really need one.
Client: well ok, I will do it, but I'm telling you, my boat has the most beautiful wiring you have ever seen. It just can't be my million dollar boat's wiring.
Me: well do the test and call me back even if it's a Sat or Sunday I will be here.
Client 45mins later: Well I'll be damned...when I wired the unit straight to the battery it fired right up, I can't believe it. So then I started looking around and found that the power panels ship ground was loose and when I fixed that, now my unit works. Thanks a lot for saving me $1495 on a new unit!
Me: You are welcome amigo....now back to painting.

That's the norm....
The problem is (as Richard points out) there is no in the field test to see if your controller has failed/burned out and died. You have to arrive at that determination by the process of elimination or by swapping out a known good controller.

Good to find out it was poor electrical connection, those fixes are the ones I like, no real money spent, just time.

[actionpaintball]

I am not 100% sure its fully "fixed". I will run it at the 3 setting for another day and move it up to 4 and 5 and see if its till performs the same. I can live with a 28 degree freezer and 42 degree fridge. I also need to load it with some water/ice and see if it can keep everything stable.