Author Topic: Archive 1  (Read 4159 times)


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Archive 1
« on: May 03, 2012, 10:57:57 am »

Archive 1

Selecting refrigeration
If you have not seen the slide show on my this site you should spend time reviewing it. A twenty year old boat will not have the best insulation do to the aging process of foam insulation so you can expect to consume more daily energy than a box with new insulation. A warm climate with warm sea-water is another problem that will require additional daily power. I do not know enough about your boat and how you are going to use it to give a recommendation for refrigeration. After you have studied the slide show let me hear from you again. I would suggest: BD50 condensing unit with some type of compressor speed control. 15 inch chamber evaporator if it will fit into box. The storage capacity of six group 27 batteries. Anywhere from 180 to 300 watts of solar panels. High output alternator with smart voltage regulator. Add additional insulation inside and outside the box or remove it and start over. I know you probably can not fill all of the above wish list, but see what you can do and then I can give you an idea of the performance under those conditions as well as which companies having a refrigeration system to fit your needs.

Refrigerant and oil
If everything in the system is new except the holding plate and it was at least blown out I would use Ester oil (POE) and not PAG oil. When the refrigerant of choice is 134a the only pure refrigerant available without a license thats the one to use. I have had good luck in engine driven compressors with Castrol Ester conversion oil sold by many auto parts stores.

Refrigerant Level
Since my last post, the CoolBlue unit has been running continuously but has not cooled the cold plate significantly, and the compressor has shut down occasionally on compressor overload, then restarted. The suction pressure remained at about 25 psig, and the discharge pressure varied with air temperature from 88 to 98 psig. Persuant to your suggestion, I adjusted the TEV to two turns from full closed, and removed R-134a until it ran at 13.4 psig suction. At this point, the discharge settled at 63 psig. There is no indication of liquid in the sight glass, and, since this discharge pressure, at saturation (64 degrees F), is less than ambient air temp. (85 degrees F), I assume the unit is running totally in the gaseous state. I do not think the plate will ever freeze at this condition of under charge.

Refrigerant pressure problem
Not knowing the complete history of this system and the size of the expansion valve orifice I have to believe that the refrigerant is contaminated. The next step is to use a refrigerant vacuum pump to draw out what ever is in the system then add new 134a. There is always a possibility that the compressor valves are leaking but I have never seen this on a BD compressor. I have found refrigerant contaminated with nitrogen, propane, and large amounts of air. In each case of contamination the pressure readings resemble those that you are seeing. I had one case where the orifice was missing in a Danfoss expansion valve, later to be found in the bottom of the box.

CoolBlue is still uncool
I am beginning to think there is a problem with the BD-35 compressor, and as you suggested, specifically the valves. I removed the refrigerant from the system, vacuumed it down to 250 microns, and refilled it with new R-134a. The pressures were identical to my last posting. In addition, I checked the current draw and found 4.75 amperes. The owner says neither the expansion valve nor any other part of the system has been tampered with since the unit worked correctly. It had been shut down for a period of time, while he was off the boat and, when he turned it back on, it did not cool down. He did say that once in the past he had added refrigerant and briefly added it as a liquid. He inverted the can, then quickly turned it upright. Do you think, if he slugged the compressor with liquid, it damaged the valves, even though it worked fine for a period of months thereafter? Thank you so much for helping me with your thoughts on this matter. Don (Mayball)

Compressor test
I am confused a current draw of 4.75 amps is about right for a BD35 compressor running at 3500 RPM max speed and producing max cooling. Because you said when adding refrigerant the compressor stopped on high pressure but you did not indicate what that pressure was. I would like you to check your high pressure gauge for accuracy. Does the unit have a troubleshooting LED and when it stops how many times does it flash? An overload would show three flashes and repeated after four seconds. What comes next is to check the compressor valves and the Expansion valve: 1. With the gauge set connected install a self sealing cap on the center fitting of the gauge set. This cap will block off the fitting where the yellow servicing hose was connected. The blue hand valve is closed and the red valve is to be opened after hoses are connected. 2. You now need to block off the high pressure line. This I believe can be done by disconnecting the liquid line quick-disc-connect at either the condensing unit or the one near the expansion valve. It is important that the high pressure service fitting be on the condensing unit side of the disc-connect in order to read compressor output. If we are lucky both sides of the open disc-connect will hold the refrigerant in. Hopefully there is at least pound of refrigerant still in the system. 3. Now the unit is ready for test. The red hand valve on gauge set is open the center port is capped. Open the blue valve now turn and turn the compressor on. 4. The system is now running and the blue hand valve as the refrigerant expansion device. Very slowly close the blue valve to keep the suction between 0 and 5 psi. This takes a little practice but it can be done. 5. Gas should now be compressed and cooled by the condenser creating liquid in the receiver up to the blue hand valve. 6. This part of the test is to eliminate the expansion valve If the gauge manifold is getting cold and the high pressure is now reading over 115 psi it sounds like the expansion valve was the problem. 7. If the test in #5 failed to produce results when close the blue valve all the way blocking all flow, this will test the compressors reed valves. If there is to much refrigerant in the system an overpressure condition will occur so watch the high pressure to prevent pressure from exceeding 125psi. In a warm climate 80+ psi could be normal. Suction pressure should draw down to 20 inches of vacuum if the open disc-connect holds air out. 8. Stop the compressor and see how long these pressures will hold. If they equalize in a few seconds and if the expansion valve was eliminated as a cause I would replace the compressor.

I mentioned in my first post that the overload was accompanied by 3 flashes on the LED, but didn't mention that the discharge pressure was about 105 psig, with a suction pressure of 30 psig. I will check my guages and perform the compressor valve/expansion valve test at my next opportunity and let the forum know. Thanks Don (mayball)

I think the location of the high pressure tap will not allow the test to be conducted. This tap is located on the discharge line between the compressor and the condenser, so, when using the gage manifold as the expansion valve, the condenser and the receiver are out of the refrigerant flow. To make the test work, I would need to add a tap to the line after the receiver and before the disconnect or find half of a disconnect to which I can add a male 1/4 inch flare outlet. Don

Troubleshooting BD35 Compressor
Because of where the high pressure port is located the expansion valve can not be tested. The compressor can still checked. Close the expansion valve down by closing the superheat screw, maybe it is stuck in the full open orifice position. This may or may not close the valve. Then use the gauge set in the normal way both hand valves closed. Start the compressor and monitor the gauges. If the valve does close all the way the suction pressure should drop to a deep vacuum. If pressure does drop, open the valve a fraction of a turn until the suction pressure indicates 6 to 8 psi. This is of course assuming the holding plate is warm. With good airflow through the condenser, a suction pressure of 6 to 8 psi and a amp current draw from 3 to4.5 amps there should be a high pressure of 115+ if the refrigerant charge is correct. You did not reply to my questions: I am confused a current draw of 4.75 amps is about right for a BD35 compressor running at 3500 RPM max speed and producing max cooling. Because you said when adding refrigerant the compressor stopped on high pressure but you did not indicate what that pressure was. I would like you to check your high pressure gauge for accuracy. Does the unit have a troubleshooting LED and when it stops how many times does it flash? An overload would show three flashes and repeated after four seconds. For this compressor to shut down on overload it would need to draw over 7+ amps.

There were two postings in a row from me. Perhaps you missed the former one. Don

The Cause of the Problem
I checked with Randy at Technautics and he also thought the problem was caused by the setting on the expansion valve. He said the factory setting for the valve was 3 1/2 turns in from full open. The full range is 6 1/2 turns on this valve. I tried 3 1/2 turns with no change in the pressures. Then I tried your suggestion of full closed with also no change. So, thinking the valve must be jammed open, I opened the disconnect upstream of the valve and the suction pulled into a deep vacuum, indicating the compressor valves are OK. The TEV is Danfoss TF2 for R12, which I intend to replace. The orifice has two zeros, one above the other, which I assume is 00. I don't think the Danfoss TEV is available in Puerto Vallarta, so I will try to find the equivilent for R-134a in the more common Alco valve here in Mexico. Thank you for your valuable advice on this matter and I hope I did not take up too much of your time on solving this problem and with my further education. Don

The Danfoss expansion valve has two points inside that can cause it to stick in the open position one on the stem below the diaphragm and the other in the removable orifice. By turning the superheat screw in would increase the spring pressure that moves the pin out of the orifice this might break that friction point loose, but this showed no improvement in pressure during your test. To check the orifice valve it self to see if it is stuck it must be removed from the valve. Remove the screen from the orifice than if you can blow through it, it is stuck open and only the orifice needs to be replaced. The orifice valve ball is always on its closed seat when removed from the body of expansion valve. A mark of 00 on orifice indicates it is sized for a maximum Btu capacity of .3 tons. I would be careful if you look for a substitute valve as you may not find one with a small enough orifice. As you can see even the 00 orifice is way too large for the maximum output of a BD35 compressor which has an output of less than .1 ton of cooling. An 0X orifice that is the size of a 00 orifice would have been a better choice. I have seen similar Problems to the one you are experiencing caused by conditions that are out of the expansion valves control range. Say the expansion valves control bulb is warm and the BD35 is set to run at slow speed 2000rpm ,( no resistor in the thermostat circuit) it could be that there is not enough cold refrigerant reaching the control bulb to kick start the valve into the valves control range for that compressors output. I believe I would try one more test; Place the expansion valves control bulb in a container of ice and turn the system on. If the pressures are close to where they should be and the return lines temperature drops the bulb can be returned to its original location. I have seen other boats with this problem and as long as the box stays cold the system will be fine. When you think you have seen it all there is another mystery to solve, Please let me know the final outcome.

Ester Oil Advice?
Hi Richard, Since gettting Ester Oil in a used 3M Adhesive can from Richard Beers (the owner of the company that produces Technicold systems), I am quite nervous about screwing up my compressor with it. Beers is extremely reluctant to say that the ester oil won't damage my compressor, and now that I've gotten into an argument with him, I am nervous about him adding something into any new Ester Oil I buy from him. The customer service is nill over there. I mean, the Ester Oil in the can can't be good because: 1) If he washed it out with water... and then put Ester Oil in - it's junk 2) If he didn't wash it out at all... it's full of contaminants. So, I need to find out where I can source some Ester Oil of the appropriate weight for my compressor. When you said you buy it locally in appropriate cans, do you know what the can should say on it? Do you know what weight I would need for the following Tecumseh compressor by Technicold? Also, what kind of shop do you find it at? Automotive? Thanks, Sean

110 Volt Compressor Oil
Only the compressor manufacture can recommend the best viscosity of oil to use in their compressors. Job shop refrigeration builders like Rich Beers will apply the manufactures recommendations when selecting the right viscosity for his systems design. The evaporators operating temperature as well as compressor design is what determines the viscosity of oil used in a refrigeration system. The oil viscosity must be miscible through the systems entire temperature operating range or the oil will separate from the refrigerant in the system causing poor heat transfer and inadequate lubrication. I believe only Rich Beers can tell you what viscosity oil he has found best for his system. I can only guess that a HP electric 110 volt Tecumseh approved for ester oil would use a viscosity of 150 SUS. These oils are available only from refrigeration parts outlets like United Refrigeration or WW Granger. If this system were a belt driven engine drive Tecumseh automobile compressor used in boat refrigeration, then the POE (Ester oil) sold at auto stores has been used successfully in these systems.

new frig/freezer
I have just purchased a Prout catamaran that had no icebox at all. I am in the process of building a frig/freeezer box. I have managed to get 6 inches of insulation around the frig and will have 6 + inches around the freezer. The box is sort of a T shape with the freezer in the leg of the T. The frig area is approx. 5 cubic feet and the freezer area is just over 2 cubic feet. It is narrower and shallower than the frig compartment. I plan on putting the holding plate or evaporater in the back of the freezer compartment and having a spillover into the fridg area. There are 2 seperate lids for the compartments, each aout 13 by 10 inches. Do you see any problem with this design? We are preparing the boat for the Carribean and will have solar and wind power, as well we haven't designed the battery bank yet so can design what we require. Tom L.

New Refrigerated box design
As for as box design the divider between the boxes needs to provide enough insulating quality to maintain low temperatures in the freezer, this will require a 1 to two inch thick divider. I prefer a one inch square muffin spillover fan that is powered full time by its own thermostat mounted in refrigerator. For your boat, for use in the tropics, I recommend a solar panel bank that is rated at a total of three hundred watts and a wind generator. As to the refrigerator evaporator location a good freezer needs an evaporator that can absorb heat in more than one area of the box. I believe you only have three choices a thin aluminum plate wraparound evaporator, two thin plate evaporators in series, or two holding plate evaporators in series. The size of the lid opening and interior wall size may dictate the type evaporator that can be used.