Author Topic: Archive 30  (Read 3529 times)

Richard

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Archive 30
« on: May 02, 2012, 05:26:59 pm »


 Archive 30

Configuration of refrigerator for cooling flow

I posted to my web site pictures of both the cabinet the unit is installed in: http://netsecuritypro.com/refercab.jpg and the back of the unit where compressor and condenser are located: http://netsecuritypro.com/referback.jpg the fan is mounted on condenser to left and pulls air in as noted by direction arrow. With these pictures can you provide any insight in how to improve air flow.

Books
My books and much more information on boat refrgeration is available on my web site at www.kollmann-marine.com. Don't forget to watch the slide show on what works and what does not.

Do it Yourself Boat Refrigeration
I looked on amazon for the book Do it Yourself Boat Refrigeration. Seems like none are available. Can you suggest a source where I can purchase it. Jack

Location & Direction of aux fan
Last fall I added an additional vent and muffin fan to help cool the enclosure my 8 cu ft. marine fridge is in. I have the fridge out and am trying to decide if I need to change where fan is, direction etc. Compressor and condenser are located at lower rear of unit in a cutout across the back and fan on condenser sucks air from left to right looking at unit from front. Air goes thru condenser then over compressor and then electronic unit for compressor. As luck would have it all vents are on right side of enclosure toward rear; two near bottom ( lowest one has my added fan ) and one up high. With unit installed there is about 4 inches of air space on sides and back. I think some type of cross ventilation across lower back of unit would be best but that is not possible on my boat. My question concerns the aux fan. Right now it blows in on the lower vent and I am wondering if that fights the airflow going in other direction from consenser fan. Should I reverse it to pull air from lower vent? Our should I be pulling air with fan on upper vent. Not really sure what is best?

Engine Vs Electrical driven refrigeration
I am presently leaning toward a three battery bank of 100 amp AGM group 27 batteries with a three stage temperature sensing regulator on my existing 80 amp high output alternator Vs. the engine driven system due to the reasonably small size of my refrigerator box of 3.0-3.5 cu ft. So please put my order through on your 12/24 refrigeration book. If I decide that I want to pursue the engine driven system then it was still $41.00 well spent for the information. Thank you again for your help. Andy

Box Fabrication
My books are more for refrigeration systems to be used as ice box conversions into a refrigerator/freezer. There is very little information in either book that will help with production fabrication of insulated enclosures. I have no experience with rigid poly foaming processes and the molds needed to create insulated cabinets. I would think the best source for information on this subject will only be available from the poly foaming industry. Controlling the density of polyurethane foam insulation and creating a moisture barrier around it is important.


Hello Buzz, I just installed the same outfit in my boat and had the same question. See the previous thread "Thermostat Tube". Anyway, Richard indicated that the clear plastic sleeve should be part of the 2.5 inches clamped to the evaporator. Ray

Power Plate Performance.
After reading last Aprils thread on this subject todays question is the same, is poor performance of refrigerator/freezer caused by refrigeration unit or excessive heat load of size of box? You first reported that the Adler Barbour ran six hours before cycling off with a current draw of 8 amps and plate temperature only dropped to 14 Degrees. It was difficult at that time to blame the size of box or insulation or even the equipment hardware for this problem as there was excessive amp draw, excessive run time that indicated refrigerant contamination, poor condenser cooling or too much refrigerant. Your action at that time was to turn off water pump, remove some refrigerant, and improve airflow through condenser. You borrowed a vacuum pump and planed on evacuating refrigerant from system. Currently based on todays post the freezer cycles between 24 and 28 degrees with thermostat set on index number 4, what happens if thermostat is set to full cold number 7? You reported that you do have a freezer thermostat ( C1502JR1500 ) which should have a temperature range of something like +18 to -26 degrees F. Normally the skin temperature of an evaporator plate must be at least 20 degrees colder than box temperature. A correctly installed thermostat probe only senses plate skin temperature and the knob setting numbers have no correlation to temperature. If the plate temperature is not reaching low temperatures you may never have a functional freezer. On your system if evaporator plate is not reaching a low temperatures it will be caused by thermostat setting or refrigerant problem since condenser cooling is good. When refrigerant process and thermostat control is eliminated as a cause of poor performance insulation and equipment selection is all that is left. If the insulation does not contain moisture and there is three inches or more of urethane then it should achieve freezer box temperatures of +15 degree in the tropics. As I mentioned last year I have received complaints about Adler Barbours power plate's lack of capacity in warm climates. Here are my thoughts about your boats refrigeration system: A 3 cu ft freezer and 4 cu ft refrigerator with 3 plus inches of good insulation cruising in tropical waters could consume 75 to 100 amp-hrs per day. This projected power consumption is based on 15 degree freezer and 33 to 40 degree refrigerator. A well designed air cooled condensing unit with a BD50 compressor, which you have, can produce approximately 12,000 Btu of cooling at +14 degrees F. evaporator temperature, this is twice the capacity needed for your boxes. The problem seems to be with the evaporators ability to match compressors maximum output. WAECO/Adler Barbours catalog does not list the power plate VD160 for a combination box of 7 cu ft it is listed for a 4 cu ft freezer. The ending number on thermostat housing of 1500 indicates the size resistor for setting compressor speed. A 1500 ohm resistor will allow compressor to run at maximum speed of 3500 rpm.. If you were to buy a VD152 evaporator or their custom formed evaporator for small freezers they would also be sold with the 1500 rpm resistor on thermostat. These two evaporators have twice the surface area heat absorbing capacity of your power plate. Conclusion You must accept the fact that to have a freezer/refrigerator with 12 volt refrigeration in these boxes the daily power consumption will be high and you should plan the onboard DC power grid to support daily total boats usage of 150 amp-hrs. You should establish a current base line of system performance by recording the following; ambient air temp, compressor cycle time and compressor off time, plate temperature near thermostat sense tube at start up and stop time, current draw ten minutes after start and again before compressor stops running. This will provide a base point that can identify problems and later have something to compare to if changes are made. It is obvious the compressor is inefficient and overpowering the evaporator (power plate). If air were forced over plate by a small fan, efficiency of plate can be improved but do not expect box temp to improve more than 6 degrees colder. What will reduce daily amp-hrs is to reduce capacity of compressor by changing speed control resistor at thermostat. At 2500 rpm the BD50 amperage will be reduced when plate is cold to 4 amps. I do not believe that more insulation will result in a marked improvement in lowering box temperature but lowering plate temperature could improve performance. Suction pressure is a good indication of what is occurring inside the power plate. With pure 134a refrigerant there will be a reduction in suction pressure with each reduction in plate temperature as long as compressor runs. Six psi gauge pressure with 134a should indicate zero degrees inside power plates tubing and around +10 degrees plate surface temperature.[color=darkred:fce1119375][/color:fce1119375][color=darkred:fce1119375][/color:fce1119375][color=darkred:fce1119375][/color:fce1119375]

Intermittent problem on fan continuing to run
The problem of the fan continuing to run without the compressor starting has been solved. The grid is cleaned about once a month and rarely shows dirt but vacuumed anyway. After cleaning terminals, verifying the wire size is correct and measuring less then 1.5% drop in voltage from batteries to control unit inlet the problem still existed. We were in the marina so I replaced the two 8D batteries with six group 27 Trojan deep cycle SCS200's for a total of 690 amps in two banks of 345 amps each. The problem has disappeared. It is amazing that the voltage never drops below 12.8 v with fresh batteries. I always thought 12.3 - 12.4 v overnight was normal. Of course, the old batteries were five years old and severely abused when first installed so I assume the effective capacity was gone. Thanks again for steering in the right direction.

New module-tripping breaker
I sent my module to miller marine to test and it was bad. The new unit works fine except the breaker at the panel keeps tripping. Its ok during the day it seems then trips in the middle of the night. Any ideas? Thanks, Rob

Trips Breaker
The BD2.5 and BD 3 Modules have there own 15 amp fuse under a gray plastic cover, if this fuse blows the problem is with the refrigeration system. If the circuit breaker that powers the system trips the problem is a breaker or a boat wiring problem. There is an older model module that has a screw in fuse on front of unit. If your unit is a BD35 or BD50 The modules has no fuse.


Thanks again. I think my batteries are the problem. They are due to be replaced.


Old or low batteries will prevent module form starting compressor but will not trip breaker or blow proper size fuse.

expanding holding plate
Happy new year Mr. Kollmann We still have guests down so I have not yet tried the fine tuning with the increased compressor speed and we are about to re-build the fridge box with much needed new insulation. I now have a new quandry... Recently I was looking after a friends boat which has a 502 engine driven system, as well as a r12 AC system plumbed through the same holding plate. The engine driven system was not working. ( the clutch was not engageing) I found that the thermostat was staying open so when I bi-passed the thermostat the clutch would operate but when I tried to run the system there was no coolant in the system. The system was beyond me so I called in a refer tech (here in Caragena Co.) and he proceeded to charge the system. In the process , after a pop, I noticed that the holding plate had expanded and pushed itself off its mounts. At this time I was assured by the tech. that all was OK and the plate was starting to get cold. Well the expansion valve was lightly frosted and the plate was cool but I felt not cold enough. The tech. continued to run the system and the holding plate continued to expand where now I would estemate it is approx. twice its original width. I shut the system down and noticed that the low side gauge , that the tech. had put on the compressor , went immedatley to max reading . Have you ever heard of this happening before? Do you think the gas is leaking in the freon lines inside the plate and this is causing the expansion? Any sugestions other than to leave Columbia? Sorry to be so long winded but thankyou for your thoughts. Brian

Keeping the Forum Refrigeration Only
Mr. Kollman, Your forum is a favorite of mine and has taught me alot. I am confused about how all these drug and porn dealers get on the forum! Do they actually register and log on in the hope that we would want anything to do with thier products? I am not offended but some may be. Years from now it will be solved but for now we must put up with these people I guess.

Holding Plate Failures
Yes, this type of failure occurs in poorly assembled holding plates or when experimental eutectic solutions are used. There is a picture of this type of failure in my DIY book where the plate blows up to a football shape. There is no repair for the plate and it is very difficult to clean the eutectic solution that is now pumped all through the system. I have read that manufactures who use the experimental solutions in their plates set a limit of two years on their warranty.