Author Topic: Archive 18  (Read 3749 times)

Richard

  • Administrator
  • Sr. Member
  • *****
  • Posts: 329
    • View Profile
Archive 18
« on: May 03, 2012, 09:32:59 am »
Refrigerator Performance  Archive 18
I am having a problem identifying the real problem why the ice melts at all in the freezer. The refrigerator should be 33 to 40 degrees F and common boat icebox converted freezer should have temperatures from +10 to +22 degrees F. The divider separating the two areas should provide enough insulation to keep a 20 degree separation. To achieve this temperature separation the divider needs to be at least one inch thick insulation, and any airflow between the boxes must be limited to provide this temperature differential. I will need a good deal of information about you refrigeration system and boxes before I can give advice. Performance report for small 12 volt ice box conversion unit Project Index Date____________ Refrigerator performance is not the same on all boats do to how they are installed, used, and the type of components selected. This questionnaire may seem long but it is structured to provide the information needed to identify type of refrigeration equipment, detect any refrigeration problems and advice corrective action if needed. You should not need any assistance to complete this form and the only tools needed are two one dollar thermometers and a tape measure. Each answer is important but if it can't be answered, leave it blank. I will need your E mail address if I need additional information. Information about Boat and Equipment 1. Boat make, length and age. 2. Alternator size and does it have a smart voltage regulator? If there is sources of alternative energy wind or solar describe them. Is your boat equipped with a amp or amp-hr meter like a Link? 3. House battery bank amp-hrs. 4. Describe refrigerated box or boxes including size, also the approximate amount of insulation around box. 5. If there are two refrigerated boxes side by side what is the thickness of the divider between them? 6. Manufacturer of refrigeration unit and model. Is it air or water cooled? 7. What is the compressor model number? Danfoss BD2.5, BD3, BD35, BD50 or other. If the paper model number is missing there will be a stamped number on compressor dome. 8. If air cooled describe location of compressor and what prevents the same cooling air from passing through condensing unit again. Pictures would help. 9. What type evaporator is in the box, and its size in inches length with and depth? If the box has a spillover system I assume the evaporator is in the freezing side, Yes? Describe how the spill over works? If it is a fan how big is it and what turns it off and on? 10. If your system has a BD35 or BD50 compressor do you know what speed the compressor is set to run at? If you have an Adler Barbour with a BD50 compressor the number is on a paper decal on the outside of thermostat cover will answer two questions for us, the speed of compressor and whether it is a freezer or refrigerator thermostat. 11. Do you know how many amps your unit draws? How do you know that? System Performance: 12. Temperature range owner would like to see in each box? Refrigerator 40? to 50? or 33? to 43? F. Freezer 14?to 22? or 0? to +10? F. 13. On air cooled units have you vacuumed the dust from the intake of condenser coil since new? 14. Is there frost or condensation any where outside the box after running several days in hot weather? Or does the box's exterior or lid feel cool in hot weather? 15. Does condensation form inside the lid? Does excessive frost build up on evaporator? Are there any holes in the box that are not closed up? Have you checked the lid seal by closing it on a thin ribbon? This test must be done all the way around lid? It ribbon pulls out without resistance lid seal is not effective. 16. Describe the performance of your refrigeration system as you see it, with as much detail as you can. And advise if anything was done to refrigeration system since new. 17. What number do you set on thermostat dial as a norm and do you know the box temperature at that setting? Are you satisfied with that setting? Onboard Performance Tests: During the following tests average ambient cabin temperature and approx seawater temperature will be required as these temperatures can be used to then project worst case planned cruising grounds performance. 17. Average Ambient air Temp during tests.________ 18. Approx. seawater Temp.________ 20. Because each boat is located in a different cruising area I need to know where it is now and future planed cruising area. 21. Setup system for a long test run of at least 12 to 24 hours with thermostat set to maximum cold. 22. After the compressor has run for more than 30 minutes check for frost on evaporator and return line outside the box. A thin layer of frost should be present over 100% of the evaporator unless it is a holding plate with solution in it. The copper return line outside the box may have frost on it, if so how far from the refrigerated box does it extend, please measure length. Report findings 23. After the compressor has run for a long time it should cycle off and on at this point place an inexpensive thermometer in front of the condenser to read the air temp interring condenser, and a second thermometer in the cabin area just outside the compartment where condensing unit is located. This test is for air cooled units and not water cooled units. With both thermometers in place for 20 minutes and compressor running report Temperatures. 24. Time one complete compressor cycle time either from one start up to the next start up or from the time it stops to the next time it stops. List cycle Time______ 25. After completing test in items 23 an 24 place thermometers in refrigerated box and freezing section if there is one. Use a small object like a cardboard box to hold the thermometers off the bottom and in the center of boxes and measure height from bottom of boxes to thermometers.___________ 26. The system is still on and thermostat is still full cold. Near the end of this 12 to 24 hour test check the frosted areas again and report where there is or is not frost.__________ Also record thermometer readings is boxes.___________ Report Findings to, richard@kollmann-marine.com

Danfoss AEO
Richard, Thanks again for your help. The comment that Danfoss efficiency goes up at lower speeds explains why speed control is important. I have "Do it yourself boat refrigeration" but not the 12/24 volt book. The Danfoss AEO module is around $175 at www.rparts.com I am trying to decide whether to leave the compressor at 3500 RPM, install a selector switch with several resistors (so I can manually vary the speed depending on temperature in the boat), or install the AEO module. When we are using the boat, interior temps rarely exeed 85 degrees F, but when it is closed up at the dock, it can hit 100 degrees. I could simply switch the compressor to high speed when leaving the boat (on shore power) and select a lower speed when on the boat. The AEO module would of course be automatic. Mark

Sea Frost - Holding Plate or Cold Plate?
Mr. Kollman, I am considdering purchase of a Sea Frost "BD" unit with the "Bin" style evaperator. Sea Frost calls thier evaperators "Cold Plates" but they look just like a thin "Holding Plate". Are they a Holding Plate or some type of hybrid? They look like a Holding Plate in shape and size, also they have an expantion valve but looks like a cappilary tube leading to it! I have confidence in Sea Frost's reputation, so I'm quite sure it's a workable idea but just what is it? Thanks, Bill

Heat Removal
joesailor. I prefer the 12 volt four inch 80 CFM muffin fans available from many suppliers; WW Granger or www.mouser.com phone 800 346-6873 has the ball bearing replacement fan for $13 but I think they have a $30 minimum. Stock number 433-BP1202512L cat. 619 Page 1164 As to airflow heat rises naturaly so fan should be in that direction.

Manual speed Control
Contact Nova cool then have a small manual speed panel that slips on compressor module or make your own. See picture slides of this on my web site slide show.

dc or ac/dc
Apologies if this is covered already somewhere on the site, I did several searches but no luck. I'm considering buying a NovaKool 2.4 cubic ft. refrigerator. Boat Electric suggests that I use dc only even tho it will be used at the dock a lot of the time (altho I do not live aboard) plus multi-week and weekend cruising (PNW area). I have a 700amp house bank and a 3 stage Xantrex charger. As the compressor is a dc motor, this makes sense. But is it putting undo strain on my battery system? Would there be an advantage to using AC when at the dock? Thanks

Sea Frost Cold Plates
Sea Frost is an excellent company with great after sales support. The difference between Cold Plates and Holding plates is the holding plate has a liquid eutectic solution inside that freezes the cold plate does not have liquid inside. In the past when comparing the efficiency of the three types of evaporators, Thin aluminum plate, Cold plates and Eutectic holding plates the thin aluminum plate proved to be the most efficient because of its ability to transfer heat. The problem with thin aluminum evaporators is they have a much shorter service life do to corrosion from the inside out and outside in and they are also easily damaged. Of the three metals used for refrigerator evaporators Copper, Aluminum and Stainless Steel, Copper has the better heat conductivity. Holding Plates are for storing energy and do not make efficient evaporators do to heat conductivity of partially frozen solution and conductivity of stainless steel. I manufactured Cold Plates at one time mechanically bonding copper evaporator coil to a stainless steel cover plate limiting the heat transfer to only the areas where there was contact. Today I understand that Sea Frost and others are using highly efficient heat sink gels to conduct heat from refrigerant copper tubing to stainless plate. I have not tested Sea Frost Bin or Cold plate evaporators but I see no reason not to recommend them. They have used the Pressure Regulated expansion device instead of capillary tubes for at least twenty years on their small 110 volt units. These fixed pressure expansion devices provide a fixed evaporator pressure which results in a given evaporator temperature.

Technautics verus Frigoboat tradeoffs
I recently purchased and read your book (which was very helpful). I also spoke with a number of vendors and looked into their websites and literature. I have a 7 cubic foot icebox with the original adler barbour unit. I drilled some holes to check and the insulation (from 1982) varies from 3.5 inches in the bottom and side to about 2 inches on top. Its a hard brittle but dry insulation. I am modifying the icebox to add 2 inches of blue board to the inside and create a flat bottom reducing the size to between 4 and 5 cubic feet. My cruising varies between 4-5 day trips in the New England to several months in the Bahamas/carribean so the usage and needs vary quite a bit. I do not run the engine much except when needed. In New England when I'm not sailing the boat is at a slip with shore power. At the moment I am leaning towards the Technautics or Frigoboat (keel cooled or air) units with cold plates. I like the Frigoboat techtemp control which would make use of alternate or shore power whenever its available. I'm interested in your opinions on the following pros and cons: 1. I've been told the Frigoboat cold plate uses a true eutectic solution at 14F while techautics uses an antifreeze type solution. 2. Your book indicates the technautics has a unique design that makes it very efficient. 3. The Frigoboat unit with Keel cooler would be silent and in some situations maybe more efficient and would avoid heat transmission into the boat. But I am concerned bout if there is a problem in cold water (45f) at times. So my question is could you elaborate on your opinion of these tradeoffs? I do like the idea of using power to freeze the cold plate whenever its "free" like in the Frigoboat. Thanks in advance for your response. Alan