Author Topic: Archive 7  (Read 3513 times)


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Archive 7
« on: May 03, 2012, 10:27:57 am »

Archive 7

With Richard's book, I was able to re-insulate my ice box and install a dual holding plate, 120VAC powered system without a single mistake. No kidding. Richard: I'm up against one problem now, which has nothing to do with the install. The guy I bought this used system from sold it to me knowing that the refer holding plate has a refrigerant leak. It had cracked a weld and leaked eutectic solution. He actually went through the trouble of charging it up and demonstrating to me that the system "worked." It's no wonder he suggested we leave the boat and get some food while it was bringing down the plates in his "demo" of the system. Anyway, I'm now operating with a 3cu. ft. freezer (working fine) and a 3cu.ft refer (holding plate installed, but not active - I disconnected it from the system). I pulled down the system yesterday to achieve a 20deg freezer, and then used a little DC fan to try and do a makeshift spillover setup. As you probably already know, this resulted in a 40 degree box all around. The freezer had dropped to 40 degrees and the refer is at 42 degrees. Neither a proper freezer or refrigerator. I have a month of back to back charters starting on Thursday this week. So... I'm writing to see if you have any ideas on how I can use my single 0deg freezer plate to carry me through the next month of heavy usage. Ideas thus far are: 1) Get 1 or 2 gallon jugs of glycol and freeze it in the freezer when I'm pulling down the freezer plate, then transfer it over to the refer side at the end of the pull down. I'll likely lose a lot of room from this setup. 2) Get peanuts in ziplocs and lay these over the frozen items, but continue using the spillover setup. I think given this setup, I'd probably have to run the unit 2x per day... not an attractive proposition since we have charter guests aboard who would not like to hear the genset that often. Any tips on how I can make it through the next month on just a 0deg freezer plate designed for a 3cuft space? I just don't have enough time between now and the start of this busy month to take out the broken plate, crack it open, and put new copper in. I would have to use a welding service, since we don't have a welder aboard. PS: Thanks for the advice re the vacuum pump. They don't rent them anywhere, but I did find a nice Robinair unit (5CFM, 40microns) which did a great job on the system. Surpisingly, with your book and that one question, I was able to get a system up and running in one shot even though this was my first time. Thanks for a grea book and a great forum here! Capt Sean

110 volt poor performance
I am confused you said the freezer worked OK, then said without the spillover the freezer dropped to 20 degrees. For a high temperature, short storage time freezer the temperature must always stay below +22 degrees F. With good insulation and the correct holding plates a one hour compressor run should drop freezer temperature well below +20 degrees. Forgetting the refrigerator spillover I dough that the freezer will make a tray of ice in 24 hours forget ice to cool refrigerator. There are a lot of open questions: Is refrigerant system setup correctly? Does it come close to the Fine tuning chart in my book? How long does the freezer temperature hold below 20 degrees? What is the size of the plate? Who made the plate? How do you know it is a Zero degree plate? How large is the refrigerator. The only suggestion I have that will help for a Thursday deadline is to buy a Engel portable 12 volt 45 or 60 qt. freezer then use the existing system for a refrigerator and cooler. Spending $600 now may get these charters and others back next year. Having done consulting on refrigeration for three different Bareboat charter companies I know how important it is to have cold drinks and ice cubes available all the time.

Sorry for the confusion, Richard. The freezer works ok and pulled the freezer compartment down to 20 degrees before I put in the spillover. It did this in about an hour, which is normal. The unit does seem to match your figures for the 1/2hp 120VAC unit mentioned at the back of your book. It builds a high side pressure of 80PSI (water is cold here, and temps have been in the 60's). The low side is often in a slight vacuum when running. The freezer holds below 20 deg for maybe 18 hours or so... I don't have a lot of data on this yet due to the amount of time it takes to test. The freezer plate is 20"x14"x3", and is in a 3cu.ft. area, surrounded by 4" of R6.5 per inch insulation with aluminum reflective surfaces. Also, the insulation is bagged (for water vapor), encased behind some fiberglass, and all of this is inside of the old, existing ice box, which had a 2" foam all around it. The plate is made by Rich Beers of Ft Lauderdale (Technicold) The only way I know it's a zero degree plate (and now that you mention it, it probably isn't) is through speaking with the folks at Rich Beers and the previous owner. When he demo'd the freezer, it pulled his box down to 10 deg, if I remember correctly. I could be forgetting, as this was some time ago. Today, during my hour run (from genset), frost failed to form on the small amount of copper tubing between the expansion valve and the cold plate. I could still hear a hiss of refrigerant vaporizing through there, but it didn't do the trick. I was unable to do more than cool down the plate. I hooked up the manifold and checked... same pressures as before - no leak. So... based on your book, I'm assuming I have some water vapor still in the system as well. In a last ditch effort, I will try and pump this thing down for a couple hours again with the 5CFM/40 Micron pump. Apparently, the refrigerator section's holding plate is a "dual coil", so I am going to attempt to hook in such as way as the refrigerant doesn't leak out, enabling both holding plates. Anything I should watch out for, given the background above? If this doesn't work, it's off to buy and Engel. :)

Repair or Replace
I do not have any information of the older Isotherm 250 model refrigeration unit. If the seawater condenser failed and allowed salt water to enter the refrigerant which is a common failure on that type unit, it is best to replace the complete system. If the condensing unit failed do to external water damage then the holding plate and its capillary tube is not contaminated. The air cooled Isotherm 3701 condensing unit has the larger BD50 compressor and will pull the plate down faster, but the tubing connections may not match those on the old plates tubing. There are a number of things to consider when buying only the condensing unit; chances are there will be no warranty, The mineral oil should be flushed from the old plate, and the system will need to be evacuated and serviced with refrigerant. Because the new compressor may be too large for the capillary tube expansion device I recommend you also buy their ASU unit to improve efficiency.

Isotherm holding plate
Several years ago my water cooled/md. plate, '91 Isotherm 250? died due to salt water corrosion. Until then, I was satisified with the cooling performance in my <3 ft, 4" insulated box. I'm now contemplating a replacement and am leaning towards Isotherm's air cooled 3701 and installation would be simplified if I could use the existing holding plate. Any thoughts/suggestions? cruising area - SW FL, Keys, Bahamas 500 a/h 12v 100w solar 100a alternator w/smart regulation

Compressor replacement for a freezer
I have a unit that no longer freezes. It uses 409 refrigerant. I would like to up grade to unit using current refrigerant. My system is 110 volt water cool system. The wate pump does work. Would be able to recommend a source of replacement?

Refrigeration replacement
When you say it no longer freezes do you mean the compressor has failed? Your unit is already up graded to the current refrigerant 409a. If you have made up your mind to buy something new I will need to know the size and type of your current unit before I can recommend a replacement system.

charging VD-160 coldplate
We have a VD-160 coldplate (8 months old) and just had to replace the old compressor by a new unit. The new one is a BD-50, brand Vitrifrigo In the manual of the VD-160 coldplate is stated that the charging of freon is adequate when the low pressure shows -4 psi after 7 hours running. I am wondering if the charging should be the same with our new different kind compressor. Another question is when is the best moment to remove the low pressure hose, when I am ready with charging? With the Compressor on or off? I know the low pressure should not be in the vacuum because that will suck moistre in the system. Can you help me with that? Thanks in advance Michel ten Bosch

BD 50 and AB Power Plate
The old system must have been an Adler Barbour and the plate is a stainless steel evaporator called a power plate. If you purchased the complete Vitrifrigo condensing unit it will have a mutable speed resistor spade connector attached. If the refrigerated box is small or you are cruising in a cool climate I would run compressor at the slowest speed 2000 rpm for best efficiency. This is what Vitrifrigos instructions say; A system with a volume of 30 litres for example, will be able to use a compressor that runs at 2000 rpm, thereby consuming an extremely limited amount of power. However, a system with a volume of 200 litres requires a compressor that operates at around 3000/3500 rpm according to the type used. I would start with a suction of 8 to 10 psi adjusting only at 10 to 20 minutes after start up. Then follow their instructions but monitor the frost line on the return line. Too much refrigerant wastes energy and it should not reach compressor. With a suction pressure of +4 psi it indicates there is still a good flow and evaporator temperature at seven hours has reached -5 degrees F. with 134a refrigerant. Always connect the suction gauge with compressor Off. It is OK to disconnect suction gauge when compressor is running if suction pressure is reading a positive pressure.

Runs on 110 volts but not on DC
There are two basic designs for this size refrigerator, those that use Swing vibrating compressors and brands that use Danfoss compressors. Norcold units use Swing compressors, WAECO and Isotherm and others use Danfoss compressors. So knowing the type system you have is important. Assuming you have a Norcold refrigerator then the swing compressor vibrates at a pulsating current of from 22 to 26 volts. The AC powered side has a step down transformer to provide the lower voltage at 60 cycles that causes the compressor to vibrate and pump refrigerant. When 110 volts powers the refrigerator it also operates a transfer relay disconnecting the 12 volt power from refrigerator. When A/C power is not available to refrigerator but 12 volts power is, it is directed to a voltage increasing transformer coil that raises the voltage to 22 to 26 volts, depending on compressor model. To get the Swing compressor to vibrate there is an isolator control module in the 12 volt circuit. SWING Compressor System If you have a Swing compressor system about all you can do is check to see that 12 volts is actually at the refrigerator. On Some models there will be a small circuit breaker box with a very small red button down low or at the back of refrigerator. There may be a red button on the thermostat if this is a very old model. DANFOSS Compressor System On a Danfoss systems there will be a control module attached to compressor, on your unit it is OK as the unit does run when A/C power is available. There is a separate small inverter that produces 13+ volts when powered by A/C. Because your unit runs OK on A//C I would look for a resistance connection in the boats electrical wiring.

12v versus AC - 12v side won't work
Small pleasure boat (1997 Sea Ray 280 bowrider) with 12v/AC refrigerator. The frige won't come on under battery but does when connected to shore power (AC). I read on another board that it could be due to low voltage of the batteries. However, I left my boat connected to shore power over night and the batteries became fully charged. Even that next morning, the frige won't work on DC. I've checked the switches, fuses and breakers. All check out ok. Any ideas would be great - or if you can point me towards any information.

Thanks for the help. I have the wiring diagram for the boat and it doesn't show any separate devices in the DC circuit (such as a separate inverter). I have not seen how to remove the refrig. It is of course on deck but in a fiberglass housing (with sink and transhcan) and I don't see any places where the frige is bolted down. I believe it would have to pull straight out but I'm not sure. Is there any available information on how to pull the frige out? Thanks a bunch.

If the refrigerator is AC/DC and is an Isotherm or WAECO their will be a small invertor as part of refrigerator beside the compressor. Most of those slide in refrigerators have a flange on both sides with two or three screws holding unit to vertical members of the cabinet. There will be trim covers that cover up the screws that need to be removed first.

Condenser size
I am changing my refrigeration unit from a water cooled to an air cooled condenser. The unit has a BD35 compressor and a box type evaporator. The condenser that I am considering is 8 by 8 by 4 and has four separate copper coils that join into one. Are there any problems associated with a larger condensers? Thanks Dan

Air-cooled Condenser for BD35 Compressor
I believe the best condenser temperature range for these small BD compressors in all climates is 90 to 131 degrees F. Over sizing an air-cooled condensing unit is not a problem as air flow can be reduced in cool climates by restricting a portion of air cooling area with cardboard. With condenser temperatures in this most efficient range the high side pressure will be between 105 and 125 psi. The design information section in my 12/24 volt manual recommends that condenser tubing not be too large as smaller tubing will increase turbulent velocity for better heat transfer. Oil collecting in large or mutable tube coils is another problem with the size condenser you have. Most ice box conversion air cooled BD 2.5 through BD50 condensing units use 3/8 OD copper tubing with aluminum fins spaced at 1/16 inch. The total length of condenser tubing used in these application ranges from 84 to 112 inches. The normal flow within an air cooled condenser is, IN at the top and liquid OUT at the bottom to insure the phase change from gas to a liquid and oil movement through system.

charging a bd35
Richard, First, thanks for all your help and such a great web site. Both your books have been a great help. I am trying to charge a new bd35 with an old box evaporator and oversized condensor per my last post. Ambient temperature is 80, pre-start pressure is 84psi, low motor speed. After three minutes, I reach a low side pressure of 8, high side 110. Within 5 minutes, the low pressure moves back up to 15psi and stays there. I get frost over the entire evaporator with an outside box temperature where the lines go in of 14 degrees. Your book and prior posts suggest that I should get to 6-8 psi and then after the box cools, the pressure should continue to go down. My pressure drops to 8 then back to 15. Any suggestions, Thanks again for all of the valuable help. Dan

Refrigerant Level For BD35
The correct procedure was to start up a warm system and let it run 10 minutes then adjust 134a refrigerant suction pressure to 6 to 8 psi in the next five minutes. From then on pressure will drop as the evaporator cools and no more adjustments are made. At 15 psi the evaporator will not get cold enough and power consumption will be twice normal. If you warm system up then reduce the suction pressure to 6-8, in a time window between 10 to 15 minutes the refrigerant level will be correct. I would expect at 80 degrees ambient and 2000 rpm the amp draw of a BD35 will be less than 3 amps.

Cool Blue Runs constantly
I have a Cool Blue 2000 yr model. Was working great. The unit sat for 1 1/2 yrs. Compressor runs constantly using 55 - 80 amps /day. Freezer unit is -2 degrees, holding plate has frost and temp is -13 on frost, -8 on the metal surface. The temp guage is set on 5 and no difference is noticed if it's set on 2. When set on 5 it will turn off when I move the temp gauge back to 0, cuts out at about 2. The unit runs and uses 3.9 amps noted after the box is frozen. What would keep it from cycling off? There are bubbles in the sight glass even when there is a good coat of frost on the plate. The high side tube is not hot, but the compressor top is very hot. I can hold my hand on it for no more than 3 secs. Due to an electric malfunction the module was replaced because it would not allow the compressor to start. We released the r-134 to empty but did not vacume, then recharged with two cans of R-134. It would not run after taking both cans and some was released until it ran. I'm new to all this and the forum, so thanks in advance for helping a rookie. Thanks, tom

Compressor runs continiously
When the Cool Blue holding plate reaches temperatures well below zero F, I think you can assume that the refrigeration unit is working correctly. When you turn the thermostat to the O position which should be the off position and compressor stops, this would indicate the thermostat or its control tube are at fault. As the far end of aluminum capillary tube coming out of thermostat gets cold it causes the thermostat switch to opens up and compressor will stop. For the thermostat to work correctly 2 to 3 inches of its capillary tube must be inserted into the bracket tube provided for it attached to holding plate. The numbers on refrigerator thermostats have no relative corresponding reference to box temperature. It is desirable to have the desired box temperature when the control is set between 3 and 4 on dial. It is easy to adjust the sensing range of thermostat by how much of the cap tube end is in contact with plate. If the thermostat is not full of ice and the capillary tube is correctly attached to plate I would replace the thermostat assembly.

Thank you. I have the thermostat set on 3 1/2, the t-stat wire is into the tube 3 inches, I'll see what happens tomorrow. Several strange things occurred today though. I observed the unit cycle off, and display 3 flashes indicating a pressure differential. I turned the t-stat dial to off and then back on and it began running again. Any idea what would cause this when the holding plate temp seems to be okay? I'm getting frustrated with this unit. Thanks, Tom

AB Super Coldmachine service fitting
I have an AB Super Coldmachine system on my trawler. It has been running since 2000 and is taking longer to cool. The minimum freezer temp used to get down to -4 degrees at the bottom of the cycle and now it doesn't get below 0. I think it needs a little charge. When i take the cap off the service fitting on the BD50, I don't recognize the fitting. Can you tell me what exactly is that fitting and what do I need to mate with it for my guages? Also, where can I get an adapter? I have just ordered your book "12-24 volt refrigeration". Does it contain the procedures/pressures, etc for recharging the Super Coldmachine or, if not, do you know where I can get them? I used to maintain my old R-12 system, but when it gave up the ghost, I installed this Adler Barbour system (r-134a)and have been pleased with it. However, fittings, etc are different on this one and I am not sure just how to proceed. Thanks for your help. b kaye