Fixing up some old marine refrigeration

[old_salty]

Richard,

Could you please describe a bit more about the dual plate system, ie the pipe sizes; did they use TX valves etc. I'm going to have a go at TIGging one up.

Pete

[Richard Kollmann]

Originally Posted by old_salty

Richard,

Could you please describe a bit more about the dual plate system, ie the pipe sizes; did they use TX valves etc. I'm going to have a go at TIGging one up.

Pete

Pete, the layout of engine drive components on sketch is correct. Liquid line from condenser all the way to expansion valves would normally be 3/8 OD copper tubing. Low pressure side of system from the two expansion valves through holding plates all the way back to the flexible link at compressor is ½ inch copper. Because of compressor vibration both compressor lines must be flexible and are usually refrigerant hose several inches long.

When there are two separate boxes with evaporator holdover plates separate temperature control systems are required, this can be done several ways:
1 Use only one solenoid and expansion valve connected to refrigerator box controlled by a single thermostat allowing freezer box temperature and compressor running to be controlled by the low pressure switch and not a thermostat.
2. I have seen boats coming from Australia that control refrigerator area box temperature with a Evaporator Pressure Regulator (EPR) and dual TXV and two thermostats to control box temperatures separately.
3. My recommendation is components as you have shown them and electrical circuit connecting two box thermostats to respective box’s solenoid and using diodes so either thermostat can start and run compressor when that box needs refrigeration.

Many of these engine driven compressors have a history of failing because of excessive refrigerant flow when compressor clutch first engages this is why I keep compressor speed low, use small TXV orifices and use suction line accumulators no larger than ½ ton. Systems with low pressure cut off will also help prevent compressor failures. All my engine designs have always included a low refrigerant switch. If you follow this conceptual design compressor should operate 25 plus years as mine and others have.

[RaymondR]

I have pondered a system similar to what you propose with an engine driven Sanden paralleled with a Danfoss BD50 a number of times and have decided it is impractical. The Sanden system uses a fairly high capacity TX valve and the Danfoss BD50 generally uses a 0.6mm metering tube. Would the tx valve handle the comparatively small volume of refrigerant generated by the BD50? Two separate systems with two coils in the eutectic tank appears a more practical arrangement to me.

Your panels/batteries don't have enough capacity to run a cycling 12V refrigeration system unless you are happy to keep buying batteries however if you retain the eutectic system and install a timer which allows the refrigeration compressor to run only during daylight hours to freeze the tank then rely on it for night time carryover you might get away with the existing electrical system or only require a small increase in capacity.

[RaymondR]

There is a company in Victoria which supplies hydrocarbon based refrigerants which are claimed to be compatible with both types of refrigeration oils and do not require any licensing. I use their products and have found them to be just as good as the orthodox types of refrigerants.

There are arguments that hydrocarbon based refrigerants are dangerous in boats but since I already have a 9kg bottle of hydrocarbons hooked up to my gas stove I figure the stove is far more likely to do me harm than the relatively small amount of hydrocarbons in the refrigerator.

The hydrocarbon based refrigerant comes in 300 gram cans which I believe are about $20 a can but you need an adapter which the distributors will provide for about $40. These prices are a couple of years old. The adapter is reusable and screws into the R134 fitting on the compressor.

I have used propane from the small bottles you can buy from camping stores for camp stoves in an emergency however this is not advisable as the stuff they put into the hydrocarbon gas to make it smell causes corrosion.

[SV THIRD DAY]

Originally Posted by Suijin

Rich, why is that? I'm curious because I've been contemplating converting mine to a keel cooler, which I just assumed was more efficient. Can you elaborate?

Sure. There is a common myth that water cooling is "better" than air cooling. I think what helps keep this myth going is that the water cooling option is an upgrade and adder to the Cold machine or super cold machine. Then there are the engineers that will go on and on about how many BTUs of heat a water condensor can pull out compared to an air condensor. What they are missing is the design. But since most air condensors are undersized for warm climates and then require water cooling as a secondary way to dump heat...well poor design from the start makes people think that water cooling is better than air cooling. I've spent 4 yes cruising the northern sea of Cortes where the water temp is 90-degs a d I've seen the collapse of the keelcooled systems, right along side the air cooled systems that didn't have a large enough condensing unit to handle the heat load.

So in the end it all goes back to proper design for the application. A poorly designed water cooled system is as much disaster as a poorly designed air cooled system. Water isn't intrinsically better than air and if you want some basics why I think water cooling sucks....well read Skips water cooling system disasters and other posts about keel cooler corrosion. Sea water is evil....so I like to keep it out of the system and save the head ache.

But Rich....but Rich....air cooling won't work in the tropics....my dock expert friend told me so
Well tell that to the hundreds of mobil air cooled food service 12v units we have sold to the US Military rated for 135-degs F over the last few years.

[old_salty]

Originally Posted by Richard Kollmann

Pete, the layout of engine drive components on sketch is correct. Liquid line from condenser all the way to expansion valves would normally be 3/8 OD copper tubing. Low pressure side of system from the two expansion valves through holding plates all the way back to the flexible link at compressor is ½ inch copper. Because of compressor vibration both compressor lines must be flexible and are usually refrigerant hose several inches long.

Current pipe sizes were discharge 1/4" and suction 3/8". Would I be better to change?

Originally Posted by Richard Kollmann

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3. My recommendation is components as you have shown them and electrical circuit connecting two box thermostats to respective box’s solenoid and using diodes so either thermostat can start and run compressor when that box needs refrigeration.

Yep, there were 2 thermostats wired in parallel so that either could turn ON the compressor, but both had to be open circuit to turn the compressor OFF.

Originally Posted by Richard Kollmann

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Many of these engine driven compressors have a history of failing because of excessive refrigerant flow when compressor clutch first engages this is why I keep compressor speed low, use small TXV orifices and use suction line accumulators no larger than ½ ton. Systems with low pressure cut off will also help prevent compressor failures. All my engine designs have always included a low refrigerant switch. If you follow this conceptual design compressor should operate 25 plus years as mine and others have.

Richard, did you note the Danfoss KP15 HiLo pressure switch in the diagram? It had a manual Hi reset. The original instruction sheet for the unit said to limt compressor revs to 1500rpm. You've bee spot on all the time!

I have sourced a replacement for the KP-15 with a an automatic reset HiLo pressure.... I assume that takes the guesswork out?

[old_salty]

Originally Posted by RaymondR

There is a company in Victoria which supplies hydrocarbon based refrigerants which are claimed to be compatible with both types of refrigeration oils and do not require any licensing. I use their products and have found them to be just as good as the orthodox types of refrigerants.

Thanks Raymond,
I have actually spoken with Hychill a number of times, but the negativity that surrounds HC's is overwhelming. And, I think that it is illegal to charge a system above 300g??? Is that correct?

[old_salty]

Originally Posted by Richard Kollmann

Old salty,
Ester ISO 100 POE conversion oil is my choice for 134a refrigerant.

Hi Richard,
I was just looking at the technical specs of the Sanden SD7H13 compressor and they recommend a PAG oil, not an ester for R134A. Is it safe to change a whole system to a different oil?

If so, how do you flush the compressor? From my reading, compressors should not be flushed.
Your recommendations much appreciated.

[Richard Kollmann]

Pet, I was just looking at the technical specs of the Sanden SD7H13 compressor and they recommend a PAG oil, not an ester for R134A. Is it safe to change a whole system to a different oil?
If so, how do you flush the compressor? From my reading, compressors should not be flushed.

Answer: CFC and HCFC refrigerants are recommended to be flushed out along with mineral oil, I would try as best you can to remove all old oil.
Sanden compressors have been the most successful engine driven refrigeration compressor in pleasure boat refrigeration while using POE oil and 134a refrigerant. My position has always been that one must use only the oil and refrigerant the manufacturer requires. If it is a true statement from Sanden not to use POE oil in a low zero F. temperature refrigeration compressor of theirs you should follow there instructions and not mine.
Mineral oil does not mix well with newer refrigerants. My understanding of my countries standard is a warning that POE oils can tolerate more of a percentage of mineral oil contamination than PAG refrigerant oil as it is limited to no more than one percent mineral oil contamination. Hundreds of thousands of automobiles were converted from Freon R12 to 134a refrigerant by adding POE oil on top of existing mineral oil.

Refrigerant flush liquids available at auto or refrigeration supply stores.

Pet,. Q. I have sourced a replacement for the KP-15 with an automatic reset HiLo pressure.... I assume that takes the guesswork out?

Answer: as long as the high and low pressure switches are both adjustable then high pressure switch is better if it is not an automatic reset. When high pressure is set 30 to 50 psi higher than normal operating pressure it will only trip to alarm you of a dangerous condition like poor condenser cooling.


Pet, Question answeres, on volume of refrigerant in your one of a kind system can only be determined when it is
first operated using high pressure plateau leveling off when first seen, and watching sight glass changes and plate temperature of eutectic solution as plate moves through its phase change

[hellosailor]

Salty-
I have no idea what the rules are in Oz, but in the US you can take online training and for about $50 get tested & certified for an EPA license that allows you to work with 134a and "portable" systems, which would cover your boat. It might be worth your time to dig around and see if there's something similar in Oz.


And of course, you can pressure test your finished system with compressed nitrogen, no license required, and then just have someone come in to fill it afterwards. Pressure-vs-vacuum testing, and how you want to test it, and how long you want to let it stand, all being similar to choosing a religion.

[old_salty]

Oh, I wish...
In Australia I think the minimum time requirement includes a 3 year apprenticeship and about $1000 in course fees.

It sounds a bit ridiculous doesn't it?

We can't even purchase or import those small R134 cans to top up car A/C which leaves us paying a minimum of $100+ for a car A/c service.

[Richard Kollmann]

I can not believe that your law is as you say. I know the people in my country do not understand our own regulations regarding the requirements for handling refrigerants. Best you talk to repairmen in an automotive AC repair shop on how the law is really interrupted and what you are required to have for doing maintenance on your own boat refrigeration system.

The US law as written prohibits anyone from working on any system containing refrigerants including 134a refrigerants. This law directs our EPA to write regulations to be used in implementing and regulating the law. After these regulations go into effect there are always some abatement changes that diminish some rulings, one of these changes was in the purchasing of 134a refrigerants at least for now. Our regulation also requires training for those servicing refrigerant, by an EPA approved school. My first three licenses for Low pressure. High Pressure and 100 ton systems were provided by an EPA approved school after one days training. I later through the mail on line for $20 obtained a second license for mobile refrigeration. In the US to actually use this license you must have an EPA approved recovery pump and a special recovery cylinder.

My point is do not always believe what you read on the web or from others with their own special good intension interests in mind. The intent of the Montreal Accord many countries sign was to reduce damage caused by venting refrigerants into the atmosphere and not to stop the use of refrigeration in boats. Unfortunately governments do not publish the rules they abate like ignoring 134a refrigerant global warming for a while. Always do your own home work.

[old_salty]

I'm serious. It is exactly like I say. You know how eBay sellers offer the self-fix cans of R134A? Customs here in Australia will confiscate them at the border. It's actually written into law that it is a criminal offence to handle refrigerant gases without a license.

See here https://www.arctick.org/rhl.php

[old_salty]

I have cut open the old eutectic plate and there is about 20 foot (6 meters) of 3/8" copper tube inside in a rather un-organised way (I can post some photos if required).

My question is : when I re-make this plate, I will replace the 20' 3/8" copper pipe for the engine driven compressor, but, what would be the length and dimension of the tube for the second line to handle a BD-50 or 80 using a TX valve (Danfoss TN2 with a number 1 orifice I assume) ?

[SV THIRD DAY]

12 to 15ft of 1/2" will work with the set-up you are doing.