Author Topic: Archive 21  (Read 3993 times)

Richard

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Archive 21
« on: May 02, 2012, 06:50:45 pm »
Leak Testing     Archive 21 
Nitrogen is the only high pressure gas I have used with a pressure regulator set at 150 psi and the required safety relief valve set at 200 psi. It may be expectable to use other non flammable inert gases but I can not recommend it. There are two proven ways to find leaks add enough refrigerant to a static system to achieve 60 to 80 psi. Follow up with a soap and water leak test. Use one once of water to one once of liquid dish washing soap, the secret is to stab a brush of the mixture onto each connection until shaving cream type foam is created, then watch for bubbles for at least one minute. The other method is to add florescent dye to the refrigerant and run the system for several hours. The leak area can easily be detected by use of any type of black light.

Compressor resistance values
The compressor terminal resistances between 1 - 2 = 4.1 ohms vs. 0.2 2 - 3 = 4.0 ohms vs. 3.5 3 - 4 = 0.3 ohms vs. 0.2 With the plug removed from the compressor the condenser fan starts and a low amp draw at the source. With the plug reinstalled the amp draw goes immediately to 40 amps. Thank you again for your valuable insight.


Richard since I have ordered your book I will review the same prior to asking any more questions. I did get the following response from the info center at Frigoboat regarding the use of their speed controller with my holding plate unit. Their response is contrary to my understanding of speed settings and efficiency. " Whats the point? With a holdover system you want the condensing unit to be as powerful as possible, and not necessarily efficient, so you want the compressor to run at max speed even though it is the least efficient. Friogboat Info"

Bad Module
The compressor is good the module is bad. Module failures are common due to heat or voltage spikes.

Conversion to 134a.
Sea Frost has a good engine drive refrigeration system but when the older Freon 12 units are converted to other refrigerants there is a risk of compressor failure. Their seawater condensers ability to keep high side pressure down in warm waters is a problem even with R12 refrigerant. Another concern with changing refrigerants on old system is the condition of the Swedge Lock line connection fittings they use. All you have said about this system is it has three holding plates and a small 110 volt shore power compressor. How does it perform in the five and two foot boxes now? I have connected a BD3 compressor to a Sea frost holding plate before which had 3/8 OD tubing coil. I dont think adding a second or third plate with 3/8 tubing will work as they will trap too much oil. The hybrid systems I built for BD compressors all used inch OD tubing. As to converting the engine drive over to 134a I have had good success draining oil from compressor, replacing only the filter/receiver/dryer and adding Castrols Polyester conversion oil. This means following the correct servicing instructions, leak testing, vacuuming and not over charging with 134a refrigerant. The trick in one of these conversions is to know how much conversion oil to add because in most cases there will be very little oil that is drained from compressor, so unless the complete system is flushed a larger percentage of mineral oil is left in system. If the major percentage of oil is not Ester the compressor will fail.


The skin temperature of holding plate, if that is the sense point of thermostat, should be at least 10 degrees F colder than the eutectic freeze point of solution to take full advantage of a holding plate. If the compressor speed is energy efficient the daily amp-hrs consumed will be fewer. Holdover plate systems are less efficient when it comes to heat energy transfer so without an amp-hour meter it is difficult to measure daily power consumption.

Parts for Crosby Refrigeration
Hi, I am trying to find a source for parts for the compressor. The system is a crosby 12vdc holding plate system. It has both freezer and reefer. The system was not working for probably most of its life. With some help, I re-wired it and charged it with R12 and it is working well, though I believe it will need another plate in the freezer. The plates are approximately 16" L X 15" W X 2 7/8" D. It draws around 25 amps on start up and 20 while running. The problem is the head gasket is leaking some oil. I am looking for a source of parts and maybe the explode parts diagram of the compressor. The compressor is a belt driven , Blu-Cold model number E435a, serial number 1d455. on the back is F-897-R4. The boat is a 1980 365 Pearson. I am lead to understand that Frick(?) bought out Blu-Cold, but I am unable to find a place that I can query in reference to parts and manuals. I would GREATLY appreciate light you could shed on a source. I just discovered your forum and find it an excellent source of info. Thanks in advance, Chris

Cycling 12 volt BD Compressors and holding plates
Whoever you talked to about compressor efficiency and holding plates is correct when compressor running time is more important than energy used. Holding plates are for storing of energy when it is only available some of the time but this means it may take more energy to produce a frozen plate. Most boat refrigerator holding plate systems rely on the engine to provide energy to freeze plates. To shorten engine run time a much larger compressor is used than deeded for the average plates. A lot of energy is wasted when a one ton compressor is used to freeze a 50 pound holding plate this is like putting a 400HP engine in a VW. When the onboard DC power grid is also used for refrigeration away from the dock its daily System Coefficient Of Performance (SCOP) is going to determine the daily energy consumption. The Danfoss BD compressor has better COP at slower speeds so if maximum speed is not necessary to satisfy box temperature a slower compressor speed can be more efficient and improve the overall SCOP. Automatic variable speed control is a major breakthrough with standard thin plate evaporators, by compensating for daily ambient temperature changes. The problem with holding plates is they are slower to respond to heat transfer especially with capillary tube expansion devices and fixed high temperature eutectic solutions. This means they are not the best candidates for either Danfosss AEO or Frigoboats automatic compressor speed controller. Isotherms ASU speed controller does work well with holding plates in small boxes as it uses plate temperature to control compressor speed, although it has a limited control range for large boxes. As I said before daily amp-hrs consumed per day is the only way to compare which speed is the most efficient with holding plate evaporators. Over capacity is not more energy efficient, if it was we would not have higher gears in our cars to slow engines down. Going the other way slow speed or under capacity could mean the compressor runs so long it uses too many daily amp-hrs, this is the case when compressor on a balanced system runs more than 70% of the time.


Excellent explaination, I will run some tests at different speed settings and determine daily consuption via my Battery monitor. Just for general information my 2 64 watt Unisolar amphorus solar panel powered the boat without trouble in ambient temps of 85 degrees and water temp in the high 60's at 49 degrees North Latitude with the BD50 3500 RPM. If memory serves me correctly my overnight consuption from everything on board was around 28 amps 8PM to 8Am. We could have stayed at anchor indefinitely under those conditions.

Looking for energy efficiency in the wrong place
At 28 amp-hrs per day I would not worry about reducing compressor speed unless you were to move the boat to my location in Ft Lauderdale. Adjusting your ambient temperatures to mine would more than double your daily power usage and only then would better compressor speed management be worth the effort.


I believe my total daily consuption from the compressor to be in the 45 Amp hour range. I have only 240 amps of Battery bank so I tend to be cautious. thanks again for the info.

Norcold Will Not Run On DC
Running on AC and not on DC would indicate the problem is inside the electrical component box if you are sure there is 12 volts to the component box. Some Norcold models have a small red button circuit breaker in DC wiring on the back or on bottom at front. What ever you do when checking unit do not disconnect compressor wire when DC power is connected, as this can destroy DC to AC pulsating inverter. My 12/24 volt boat refrigeration manual has information on Norcold systems but it will not help you anymore than this message. Norcold used more than twenty different electrical component box configurations so the best solution is to contact a shop that is set up to repair the box you have. To purchase a new plug in electrical box if you can get the correct one is around $330 hopefully the repair cost would be half that. The most likely items inside the component box that will be causing your problem are the switching relay, the small pulsating inverter or the step-up voltage coil inside the multi circuit transformer. There are a number of companies that repair these components on the web just Google search Norcold with model number, I know Electricboat is one and there is another in Alabama most are set up to do RV refrigerators. The compressor actually runs on either 22 or 26 volts AC depending on compressor size, from a dual purpose step-up and step-down transformer. If the unit did not run on AC but ran on DC it is usually the transformer that has failed do to heat. If all else fails or is too expensive you could purchase a $39 three hundred watt inverter to power the AC portion from the batteries when not connected to shore-power. This would mean you would need to have a manual switch over when shore power is connected.

Norcold works on Shore Power but not on DC
Hello I have a Norcold SCQT-6406 s/n RKN0051 But no manual. Is there a place I could download a manual .....any suggestions? My Norcold works fine on Shore Power but not on DC volts. Any Suggestions? Thanks

Tecumseh Parts
Richard- I was checking out an old CA tecumseh compressor at Sailorman today. I was wondering if parts for these are still available. I am thinking of getting rid of my AC Seafrost system and adding a 1/4 horse DC on that side. Do these type of systems continue to be more efficient than the Danfoss one. It seem like I can build one for less than one Danfoss system, yet have the power to cool all three plates in both boxes with the one compresor running maybe 3 hours per day Going back to my R12 question, Seafrost uses an additional control valve on the R-134 systems that is not on the R-12. Do you know what that is? I really would like to keep the engine drive as well as it can't be beat for speed on the days the engine is running. What type of condnesor would you recommend the Seafrost one that is claimed to be fairly ineffient. Also as an FYI the boxes the boat has are totally gone to be gutted so I have alot more space now than I will eventually. I haven't even tried to evaluate performance of the current setup. Thanks, Jeff