12 volt refrigeration repair or replace?

[Jill on Maya]

Question: Seeking advice on the usual lifespan of an Isotherm Compact Classic with a water cooled SP (self pumping) condenser. Is it time to just replace the whole or worth trying again to find and fix a very slow leak?

Background:

We have an Isotherm Compact Classic 12v refrigeration system that runs a 100 litre upright fridge. (The fridge can also be run from an engine driven eutectic system). Best guess is that the system was fitted when the yacht was built in 1994. On board records show installation of a new SP water cooled condenser kit in 2007 in preparation for an extended long term voyage which included some months in the tropics. The system was re-gassed in 2014 then ran without concern until December 2020 when it showed reduced cooling, the compressor (Danfoss BD35F) was running but not cycling in the usual way. Refrigeration mechanic tested for leaks (using helium gas I think he said), unable to find any leak, tightened loose connections on flare nuts on gas lines, evacuated lines to remove any moisture then re-gassed with the small amount (70ml) of R134a that the system holds. We concluded that this type of refrigeration system might just need to be re-gassed every 5-7 years. It then ran as usual for about 4 months until it again showed reduced cooling and the compressor started to run more often but at lower amps. We assume it has again lost gas. In Australia access to refrigerant gas is restricted to certificated tradesmen so each re-gassing is a more costly exercise. Because it has a water cooled condenser (fitted in the galley sink outlet), a leak at this component can't be found until next haul out in about 7 months. If that is where the leak is, what is likelihood that it will be repairable? If we decide on a complete replacement, are air cooled systems cheaper or more reliable than water cooled? Not complaining about longevity of the system we have but just don't want to spend time and money trying to fix something that is better replaced.

[Richard Kollmann]

Originally Posted by Jill on Maya

Question: Seeking advice on the usual lifespan of an Isotherm Compact Classic with a water cooled SP (self pumping) condenser. Is it time to just replace the whole or worth trying again to find and fix a very slow leak?

Background:

We have an Isotherm Compact Classic 12v refrigeration system that runs a 100 litre upright fridge. (The fridge can also be run from an engine driven eutectic system). Best guess is that the system was fitted when the yacht was built in 1994. On board records show installation of a new SP water cooled condenser kit in 2007 in preparation for an extended long term voyage which included some months in the tropics. The system was re-gassed in 2014 then ran without concern until December 2020 when it showed reduced cooling, the compressor (Danfoss BD35F) was running but not cycling in the usual way. Refrigeration mechanic tested for leaks (using helium gas I think he said), unable to find any leak, tightened loose connections on flare nuts on gas lines, evacuated lines to remove any moisture then re-gassed with the small amount (70ml) of R134a that the system holds. We concluded that this type of refrigeration system might just need to be re-gassed every 5-7 years. It then ran as usual for about 4 months until it again showed reduced cooling and the compressor started to run more often but at lower amps. We assume it has again lost gas. In Australia access to refrigerant gas is restricted to certificated tradesmen so each re-gassing is a more costly exercise. Because it has a water cooled condenser (fitted in the galley sink outlet), a leak at this component can't be found until next haul out in about 7 months. If that is where the leak is, what is likelihood that it will be repairable? If we decide on a complete replacement, are air cooled systems cheaper or more reliable than water cooled? Not complaining about longevity of the system we have but just don't want to spend time and money trying to fix something that is better replaced.

If you are able to access the through hull SP inside boat and see if the zinc attached is still in good condition, if not leak may not be repairable. Some models of SP's did not have zincs.

A system like yours may only contain three ounces of refrigerant. A leak after 4 months small enough to case performance problems is impossible to detect with normal leak detector. When was the last time you went under boat and cleaned inside the SP. Reports like yours are generally caused by oil collecting inside drain. It is easy to test performance of SP by temperature change of refrigerant lines going to and returning from SP. From compressor to SP line is normally hot. line from SP towards evaporator is no more than 15 degrees F. Compressor amp draw is another method of testing SP and confirming loss of refrigerant. Above 5 amps could indicate poor condenser or too much refrigerant in warm seawater. Amperage below 3 amps and no frost on evaporator is normally normal except in cold seawater.

If you have confirmed a loss of refrigerant then proceed first at the line connections and servicing connection. I recommend equal parts of water and dish washing soap applied with a one inch paint brush. The secret is to stab brush tips into the small area to create shaving cream foam which breaks down the surface tension so leak will display a bubble. For leak test to work the complete system in including evaporator must be warm and and have enough refrigerant for a pressure over 50 psi. Do one suspect area at a time and watch each one for at last 5 minutes.

[Jill on Maya]

Thank you Richard for information filled response.

At every annual haul (last done December 2020) we cleaned out the inside of the SP. No oil noticed.
The fridge technician gave the impression that his leak detector was the most effective way to find leaks. You say not so and we will try the soapy test method but may have already lost too much refrigerant for soap test to find the leak/s. When running now it uses about 2 amps (compared with 3 - 3.5 amps prior to problem) and the evaporator plate (flat 360mm/14.2" x 386/15.2") only gets frost on the end closest to outlet to compressor. Does this tell you whether that will be enough gas pressure to find the leak? If not enough pressure we will soap test after re-gassing next week.

When working normally (prior to the leak) the plate gets slightly frosty all over. We are in colder waters of southern Tasmania where summer average temp ranges between 17-24'C (63-75'F) and sea water temp ranges 11-18'C (52-64'F).
The SP condenser is both skin fitting and drain for galley sink. There is no zinc anode inside the Isotherm SP condenser. Its not part of the design. There was a zinc anode attached to the outside of the SP condenser/skin fitting. We replaced it in 2015 and over the next 4 years it slowly corroded at the fastening points but body of zinc showed very little wear. In 2019 haul out, when fastening points no longer usable we decided not to replace based on the instructions that came in the anode kit for Isotherm SP. "In normal conditions it is not necessary to mount the zinc anode on the Isotherm SP through hull fitting." "If the anode looks good after a season, the fitting can be left without the anode ..." We decided zinc did not appear to be necessary and it reduced the water flow around the condenser coil. We found no signs of corrosion at the outlet at either of the next annual haul outs.

Have temperature tested the in and out tubes at the SP and the evaporator. Line from compressor to SP condenser tests at 27'C (81'F) and the line from SP condenser to evaporator is 15'C (59'F). Temperature at evaporator is in at 15'C (59'F) and out at 3'C (37'F). We interpret this to mean that compressor, condenser and evaporator are working which adds more evidence that the problem is a refrigerant leak.

We will tighten all fittings ourselves before fridge technician re-gasses tomorrow.

[OzeLouie]

Electronic leak detectors often fail to find small leaks so you are best to do the bubble test as advised above, but will need some refrigerant first as your system is definitely short of gas.
As you are in Tassie I would suggest having the raw water condenser removed and a cross finned, fan forced condenser fitted. This would eliminate the most likely area of gas leak and gets you away from the problems that raw water cooling causes.

[Jill on Maya]

OzeLouie said:

"As you are in Tassie I would suggest having the raw water condenser removed and a cross finned, fan forced condenser fitted. This would eliminate the most likely area of gas leak and gets you away from the problems that raw water cooling causes."
I have searched for but not found threads on CF regarding problems with raw water cooled condensers but your reply says they are problematic. If the gas leak is at the SP condenser, rather than at a line or servicing connection then am I right to think we won't be able to find the leak? If so we could well already be chasing a not repairable system - another technician visit to test and re-gas, then we bubble test all connections, find no leak, test in and out temperatures at condenser and find they are within correct range but in a few weeks or months have lost refrigerant again because there is a leak in the condenser. That would indicate its time to replace either the whole system or just the condenser. Your reply suggests we just replace the condenser. Is that because evaporators and compressors are best left alone until they fail and its best practice to just replace each component of a 12v evaporator type system as each component fails rather than replace the whole system at once? Boat records show payment of NZ $1200 in 2007 for SP Condenser kit (kit only not labour to install). That seems like too much to pay for just a Condenser kit so perhaps included a new compressor which would mean that the Danfoss BF35F compressor is now 14 years old. Do these compressors have a usual lifespan?

[Richard Kollmann]

Special interests in areas around the world have used air quality regulations to their financial benefit. Some countries are more friendly with abating small quantities of refrigerant 134a with regards to small boat refrigeration.

Finding a small leak in system in question is very difficult because it can be a very small electrolysis pin hole in SP coil or interior pin hole in thin plate evaporator. Micro leaks in other areas are normally found by the bubble foam test I gave you. An experienced tech would add 200 psi of Dry nitrogen to a small amount of refrigerant and close the refrigerator box for 12 hours. Bobble test questionable lines and connections. After 12 hrs placing an electrical leak test probe down low in box will confirm leak is in there or not. If leak is in evaporator or its line joint where copper is bonded to aluminum the evaporator assembly must be replaced as there is no permanent repair.

Unless you can not acquire necessary tools including vacuum pump and materials needed it would be smart to buy a complete new fan air cooled simple gadget free system using no form of water cooling.

[OzeLouie]

Originally Posted by Jill on Maya

OzeLouie said:

"As you are in Tassie I would suggest having the raw water condenser removed and a cross finned, fan forced condenser fitted. This would eliminate the most likely area of gas leak and gets you away from the problems that raw water cooling causes."
I have searched for but not found threads on CF regarding problems with raw water cooled condensers but your reply says they are problematic. If the gas leak is at the SP condenser, rather than at a line or servicing connection then am I right to think we won't be able to find the leak? If so we could well already be chasing a not repairable system - another technician visit to test and re-gas, then we bubble test all connections, find no leak, test in and out temperatures at condenser and find they are within correct range but in a few weeks or months have lost refrigerant again because there is a leak in the condenser. That would indicate its time to replace either the whole system or just the condenser. Your reply suggests we just replace the condenser. Is that because evaporators and compressors are best left alone until they fail and its best practice to just replace each component of a 12v evaporator type system as each component fails rather than replace the whole system at once? Boat records show payment of NZ $1200 in 2007 for SP Condenser kit (kit only not labour to install). That seems like too much to pay for just a Condenser kit so perhaps included a new compressor which would mean that the Danfoss BF35F compressor is now 14 years old. Do these compressors have a usual lifespan?

My previous suggestion was to replace the existing raw water cooled condenser as raw water and DC power are a recipe for electrical corrosion. But that would require the rest of the system, compressor, evaporator etc to be ok and given the age and previous work done on it, then maybe the best remedy and most likely the most economical long term, would be to replace the entire system.
If the new replacement condensing unit can be located in a well ventilated area and you are not planning on cruising up north in the tropics, then an air cooled system would be adequate, otherwise a system that is air cooled and backed up with fresh water recycling automatically as required would be the better option.

[Richard Kollmann]

Originally Posted by OzeLouie

My previous suggestion was to replace the existing raw water cooled condenser as raw water and DC power are a recipe for electrical corrosion. But that would require the rest of the system, compressor, evaporator etc to be ok and given the age and previous work done on it, then maybe the best remedy and most likely the most economical long term, would be to replace the entire system.
If the new replacement condensing unit can be located in a well ventilated area and you are not planning on cruising up north in the tropics, then an air cooled system would be adequate, otherwise a system that is air cooled and backed up with fresh water recycling automatically as required would be the better option.

When it comes to properly designed and properly installed small Danfoss BD compressor condensing units any form of unfriendly water cooling is not beneficial.

[purplesunrise]

Something to ponder - you can buy about 10 110 volt refrigerators for the price of one marine refrigerator. Or put another way, if you cruise for 5 years, that means you could have a brand new refrigerator every 6 months!

[Minggat]

After years of learning curve, I bought a stand alone military grade chest style unit. That was 2007. I couldn’t be happier with the neatly zero maintenance. I do have to defrost a couple of times a year, or it would be totally zero maintenance.

After getting that unit, I finally dialed in my built in unit. Bet I never use it. The “someday” factor has kept me from gutting the box of the thick insulation that robs the space for dry goods that is used for now.

Seriously much lower power draw, reliable.
I bought a Fridgefreeze, made in San Diego. But there are others out there. I have considered an Engle for an additional dedicated freezer. The two together my gut draw as much power as my Adler Barbour.

[skipgundlach]

Originally Posted by Richard Kollmann

When it comes to properly designed and properly installed small Danfoss BD compressor condensing units any form of unfriendly water cooling is not beneficial.

As one who Richard knows well, and saddled with an air-water SeaFrost, the water part being that the air part could not manage what a smaller (bd80 vs bd 50 based system) Frigoboat keel-cooled-only system easily managed (until a design flaw, since remedied, killed it), I can echo his comment.

Do NOT do water cooled unless forced to do so, and if so, reconcile your future need for access in order to clean out accumulations of whatever can reach it (mud, grass, critters, etc.) on a regular basis with the higher conductivity of heat via water compared to air benefit.

Still, having been forced into having that water, I wish I had pretty-cold water to cool with; it would drastically alter my amp burden.

PS I'm on my 3rd March pump (well, 4th, really, except the last one was nearly immediately after installation and under warranty); that's another grand or so blown trying to achieve cold that, at its best, isn't within 5°F of what the Frigoboat could achieve at a third less amps.

(Albeit I wouldn't want to snorkel or dive in your colder water as I do in the tropical water I'm normally cruising in. Tradeoffs...)

[kryg]

I agree, It cost me 7K, installed and repair many times a custom fridge 135 Litres and I still can get a cold beer.

Last year I hired Summit Marine from Sydney to replace my failed compressor engine driven Frig system to electric power agreed Quote was $3,500 AUD. After a solid Q&A as agreed I removed all the old Fridge components to make space for the new installation. Outcome lots of promises, they never came to install it. I was told they were building it every two weeks, Nada. Three months evaporated with broken Instillation deadlines ever few weeks. By Xmas last year out of frustration I cancelled Summit Marine as a no show.

I was so incensed and frustrated by being jerked around I wrote to Marty You are fired!! Now 5 months later I had No reply or apology from Marty's Summit Marine, it's owner. (Because of my negative experience, my advice is stay away from Summit Marine).

Meanwhile, my interim solution, an Australia 2nd hand build Eva Kool portable fridge freezer cost $300. Keeps everything frosty. The problem is where to stow it under way! I would like to buy a 2nd one as they are excellent. Consume about 2.5 amps per hour for a 45 litre unit. After years of bad experiences, with fridge mechanics. I have totally given up on Marine Fridge installers. I will use my boats Nicely build fridge box for dry storage. What a man will do to enjoy a $2 bottle of a cold one!

Originally Posted by Minggat

After years of learning curve, I bought a stand alone military grade chest style unit. That was 2007. I couldn’t be happier with the neatly zero maintenance. I do have to defrost a couple of times a year, or it would be totally zero maintenance.

After getting that unit, I finally dialed in my built in unit. Bet I never use it. The “someday” factor has kept me from gutting the box of the thick insulation that robs the space for dry goods that is used for now.

Seriously much lower power draw, reliable.
I bought a Fridgefreeze, made in San Diego. But there are others out there. I have considered an Engle for an additional dedicated freezer. The two together my gut draw as much power as my Adler Barbour.

[Uncle Bob]

Originally Posted by kryg

I agree, It cost me 7K, installed and repair many times a custom fridge 135 Litres and I still can get a cold beer.

Last year I hired Summit Marine from Sydney to replace my failed compressor engine driven Frig system to electric power agreed Quote was $3,500 AUD. After a solid Q&A as agreed I removed all the old Fridge components to make space for the new installation. Outcome lots of promises, they never came to install it. I was told they were building it every two weeks, Nada. Three months evaporated with broken Instillation deadlines ever few weeks. By Xmas last year out of frustration I cancelled Summit Marine as a no show.

I was so incensed and frustrated by being jerked around I wrote to Marty You are fired!! Now 5 months later I had No reply or apology from Marty's Summit Marine, it's owner. (Because of my negative experience, my advice is stay away from Summit Marine).

Meanwhile, my interim solution, an Australia 2nd hand build Eva Kool portable fridge freezer cost $300. Keeps everything frosty. The problem is where to stow it under way! I would like to buy a 2nd one as they are excellent. Consume about 2.5 amps per hour for a 45 litre unit. After years of bad experiences, with fridge mechanics. I have totally given up on Marine Fridge installers. I will use my boats Nicely build fridge box for dry storage. What a man will do to enjoy a $2 bottle of a cold one!

Hi, sad to hear about the summit experience, did you contact Ozefridge in victoria, they manufacture a variety of units and ship virtually anywhere.

[Richard Kollmann]

Originally Posted by Uncle Bob

Hi, sad to hear about the summit experience, did you contact Ozefridge in victoria, they manufacture a variety of units and ship virtually anywhere.

Uncle Bob you keep advertising your Ozefridge but say nothing about your unit and details of your Ozefridge: size of box, age of unit. and daily energy consumption based on ambient temperatures. Pictures would also help.

[OzeLouie]

Originally Posted by Richard Kollmann

Uncle Bob you keep advertising your Ozefridge but say nothing about your unit and details of your Ozefridge: size of box, age of unit. and daily energy consumption based on ambient temperatures. Pictures would also help.

Richard I think you may be confused. Bob has never said he owns an Ozefridge system nor does he have any connection to our company. Bob is a Sydney based friend of ours, has seen many of our systems there and appreciates what we are building.
For the information you seek it may be best to check out this CF thread: https://www.cruisersforum.com/forums...ws-136455.html or www.ozefridge.com The web site describes the various systems in detail with pictures, data, diagrams and easy to follow commentary. I'm sure you will find it very interesting.

BTW, you mention posting pictures yet my attempts here at CF and elsewhere to find pictures, data or schematics to support you or your company as 'hands on refrigeration', failed!
Perhaps you could post some pictures etc depicting your past system building activities?