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Old 29-01-2015, 11:31   #16
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Re: Refrigeration Problems

Quote:
Originally Posted by Dockhead View Post
Thank you!! Very useful advice.

I can't really evaluate the evaporators -- they are behind the stainless steel walls of the Isotherm-made boxes.

The through-hull condensors seem fine. I inspect and clean them every time I lift out (every 3 or 4 months), but they are never really dirty, and the anodes don't wear. I wire brush them to expose fresh zinc.

It sounds like you are recommending replacing everything, the entire system, and not just the compressor. That is far more serious than what I was thinking, but what you say makes a lot of sense. How stupid would it be to replace the compressor if the through hull unit has pinhole leaks.

So maybe there's no easy way out just replacing something -- maybe I'd better start tracking those leaks. So, I'd be grateful for your procedure.

Thanks again.


I have given advice on do it yourself technical advices form a remote location for 61 years. For the first 35 years I was employed to supervise and provide technical services by phone now I do it on web to stay busy. And in the last 26 years I have concentrated on pleasure boat refrigeration. I now find mechanical problems where a unit is designed to be replaced (expendable) rather than repairable.


Dockhead, these are the logistic problems that you are faced with if you are to restore this Isotherm refrigerator to reliable condition:
  • If your boat is in a country where refrigerants and servicing is limited by regulations are you able to purchase the necessary materials and do the work yourself?
  • The actual size of refrigerant leak is a problem also. Your system contains a very small quantity of 134a refrigerant, somewhere from 2 to 4 ounces ( 57 to 114 grams). My experience would indicate that if one ounce of refrigerant were to leak out in one month it could be detected easily if it is in an accusable spot using a mixture of liquid soap and water 50/50%. With leaks this small electronic detectors are not easy to use. Soap and water agitated into shaving cream foam will break down surface tension at leak area so a one ounce leak per year might even be detected.
  • The standard procedures I would recommend are similar to RONDO’s advice except I use refrigerant pressure for testing by a DIY person on all line connection and line wear points.
  • Your clarification that this is an Isotherm cabinet refrigerator and not an icebox conversion unit means it may not be possible to isolate condenser from evaporator by switching quick-dis-connects around. With evaporator hidden behind box liner the only way to check it for leaks is to isolate it from the rest of system and then pressure test it.
  • Leak testing through hull condenser is another problem but maybe because you feel the zinc indicates lack of metal discharge it is OK. But if leak can not be found elsewhere condenser will need a nitrogen high pressure test also. With such a slow leak testing condenser lines must be disconnected and one end capped and a pressure gauge on the other.
The one overlooked place that causes leaks is the servicing refrigerant cap seal. The valve core by itself is not a tight seal most caps today have a rubber seal inside cap.

My belief at this point is to add refrigerant and check for leaks at all line connection including at through hull solder joints. Then operate system long enough to determine leak rate. If performance after a month shows again loss of refrigerant add more refrigerant. If after operating unit adding refrigerant several months and leak rate increases you will know that there is probably additional or larger corrosion leakages.

If refrigerant leak loss is greater with system turned off than when left cycling on thermostat this would indicate leak was in low pressure side of system including evaporator.
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Old 29-01-2015, 12:57   #17
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Re: Refrigeration Problems

Quote:
Originally Posted by Richard Kollmann View Post
I have given advice on do it yourself technical advices form a remote location for 61 years. For the first 35 years I was employed to supervise and provide technical services by phone now I do it on web to stay busy. And in the last 26 years I have concentrated on pleasure boat refrigeration. I now find mechanical problems where a unit is designed to be replaced (expendable) rather than repairable.


Dockhead, these are the logistic problems that you are faced with if you are to restore this Isotherm refrigerator to reliable condition:
  • If your boat is in a country where refrigerants and servicing is limited by regulations are you able to purchase the necessary materials and do the work yourself?
  • The actual size of refrigerant leak is a problem also. Your system contains a very small quantity of 134a refrigerant, somewhere from 2 to 4 ounces ( 57 to 114 grams). My experience would indicate that if one ounce of refrigerant were to leak out in one month it could be detected easily if it is in an accusable spot using a mixture of liquid soap and water 50/50%. With leaks this small electronic detectors are not easy to use. Soap and water agitated into shaving cream foam will break down surface tension at leak area so a one ounce leak per year might even be detected.
  • The standard procedures I would recommend are similar to RONDO’s advice except I use refrigerant pressure for testing by a DIY person on all line connection and line wear points.
  • Your clarification that this is an Isotherm cabinet refrigerator and not an icebox conversion unit means it may not be possible to isolate condenser from evaporator by switching quick-dis-connects around. With evaporator hidden behind box liner the only way to check it for leaks is to isolate it from the rest of system and then pressure test it.
  • Leak testing through hull condenser is another problem but maybe because you feel the zinc indicates lack of metal discharge it is OK. But if leak can not be found elsewhere condenser will need a nitrogen high pressure test also. With such a slow leak testing condenser lines must be disconnected and one end capped and a pressure gauge on the other.
The one overlooked place that causes leaks is the servicing refrigerant cap seal. The valve core by itself is not a tight seal most caps today have a rubber seal inside cap.

My belief at this point is to add refrigerant and check for leaks at all line connection including at through hull solder joints. Then operate system long enough to determine leak rate. If performance after a month shows again loss of refrigerant add more refrigerant. If after operating unit adding refrigerant several months and leak rate increases you will know that there is probably additional or larger corrosion leakages.

If refrigerant leak loss is greater with system turned off than when left cycling on thermostat this would indicate leak was in low pressure side of system including evaporator.
OK, thanks. As usual, very useful. I will order your book.

I can buy R134a in the UK, although apparently the little cans all have leak sealer, which I know is a no-no. I can buy this: Refrigerator Fridge Refrigerant Gas Fluid: R134A Disposable 1kg cylinder: Amazon.co.uk: Kitchen & Home

1kg for a reasonable price.

Do I need to add oil?

I will scrounge around for the gauges and the adapter for Schraeder valves.

I guess the first thing to check is the Schraeder cores and caps. I guess if the cores need replacing, that's good news. If I solve the problem like that, then I won't mind hiring a pro to evacuate the system and recharge it.
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Old 29-01-2015, 15:19   #18
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Re: Refrigeration Problems

Quote:
Originally Posted by Dockhead View Post
OK, thanks. As usual, very useful. I will order your book.

I can buy R134a in the UK, although apparently the little cans all have leak sealer, which I know is a no-no. I can buy this: Refrigerator Fridge Refrigerant Gas Fluid: R134A Disposable 1kg cylinder: Amazon.co.uk: Kitchen & Home

1kg for a reasonable price.

Do I need to add oil?

I will scrounge around for the gauges and the adapter for Schraeder valves.

I guess the first thing to check is the Schraeder cores and caps. I guess if the cores need replacing, that's good news. If I solve the problem like that, then I won't mind hiring a pro to evacuate the system and recharge it.

You will not need to buy my book as there is much more info on this type problem on my web site at http://www.kollmann-marine.com then click on REFRIG CHARGE and servicing. Use my web procedures to charge system. The only mistake you can make is by putting too much refrigerant in unit causing module to stop compressor from running. When you are satisfied there is no leak then it might be a good idea to vacuum and dehydrate system. I no longer provide my help to sell books, in this case read the web sections on too much, too little and refrigerant servicing .

Your link on Amazon refrigerant 134a bottle containing no oil or leak detector is what you need plus hose set is what you need except many manufactures do not have 134a to R12 adapters on compressor. The adapter converts a standard mail ¼ inch male flare service fitting to the 134a spring loaded connector on the Amazon hose end.

You do not want or need oil. Nor do you need to replace Streator type valve core although if you need to install Freon adaptor to 134a the old valve core is removed. This adaptor will come with a valve core and a Blue cap with its own seal inside.

I will repeat again ALL valve cores leak small amounts of refrigerant over time this is why a cap with its own permanent seal is important. Valve cores are to prevent leaks when cap is removed for servicing only...
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Old 21-02-2015, 11:40   #19
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Re: Refrigeration Problems

Thanks to everyone, especially Richard, who gave me all this good advice.

While I was in the U.S., I acquired a hose and gauge with Schraeder fitting and can tap, and a couple of 12oz cans of R134a.

I followed the instructions on Richard's website. Purged the hose with refrigerant and then attached it to the freezer service port (I left a little bit of gas flowing as I attached to exclude air). Then I started the compressor, and the pressure dropped all the way into vacuum. So I added refrigerant slowly until the pressure stabilized at about 6 pounds. I could see that the freezer box was now nicely frosting all around, instead of just in one spot, which according to Richard is how you tell the quantity of refrigerant is enough. So I let it run until the thermostat shut it down. Pressure fell to 5 pounds or so as the box got cold. After shutting down, the pressure rose to over 10 pounds, but I guess that doesn't mean anything. Seems to be running normally and cooling well now.

Obviously I have a leak, so I will start testing for that when the boat is hauled in April (so I can get to the Isotherm SP units).

This leak appeared fairly suddenly, because when I added refrigerant last June, I had never touched the freezer since buying the boat five years previously. And now already adding again.

I checked the valve caps; they look ok.

The only thing which causes me concern is that the compressor seems to run quite hot -- about 50C measured at the outside of the housing with an infrared thermometer. Is that normal? If not, what would cause it?
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Old 21-02-2015, 12:24   #20
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Re: Refrigeration Problems


Compressor dome temperature of 50 C (125 F) is normal.

The degree and rate of leak can be monitored by area of frost loss over time.

You are correct low pressure with system stopped has no real value except to indicate there is some refrigerant.
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Old 21-02-2015, 12:42   #21
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Re: Refrigeration Problems

Quote:
Originally Posted by Richard Kollmann View Post
Compressor dome temperature of 50 C (125 F) is normal.

The degree and rate of leak can be monitored by area of frost loss over time.

You are correct low pressure with system stopped has no real value except to indicate there is some refrigerant.
Thank you!

One last question:

I turned the thermostat to the medium position and let the unit run for an hour or so. This is a freezer, by the way. The box is frosty all around and temp inside seems to be about -13C. This is the way it used to perform.

The low pressure side pressure, however, has dropped to about 2 or 3 pounds. Is that normal, or am I still short of refrigerant?
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Old 21-02-2015, 14:05   #22
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Re: Refrigeration Problems

Most of these gauge sets are not real accurate in the 3 to 8 psi range. The lower the temperature of evaporator the lower the pressure. If evaporator surface has at least a 85% frost cover after cycling on thermostat for 24 hours do not mess with refrigerant. If less frost cover than 85% add a small amount of 134a. It is always more energy efficient a little low on refrigerant.

Your through hull condenser refrigeration unit probably holds less refrigerant than any other boat refrigerator, as the seawater temperature changes so will the refrigerant volume change. If seawater temp increases so will frost cover increase. Move boat into cooler water refrigerant volume and frost cover will decrease.
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Old 21-02-2015, 15:26   #23
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Re: Refrigeration Problems

A refrigeration pro should have a leak detector so if you suspect a leak and can't find it any other way, a call to the pro might be in order.
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Old 21-02-2015, 15:47   #24
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Re: Refrigeration Problems

I have four different electronic leak detectors with vacuum pumps inside that are of little value when looking for 1 to 2 ounces of refrigerant loss per year. The method of DIY leak detection I recommend on my web site will locate 1/2 ounce loss per year by breaking down surface tension at leak area with a brush.
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Old 21-02-2015, 15:50   #25
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A refrigeration pro should have a leak detector so if you suspect a leak and can't find it any other way, a call to the pro might be in order.
Various pros have said that looking for the slow leak is not cost-effective.
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Old 21-02-2015, 16:25   #26
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Re: Refrigeration Problems

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Various pros have said that looking for the slow leak is not cost-effective.
Only correct statement if failed water cooling system has let water mix with refrigerant. Yes, there are various pros from Hell out there. Evaporator replacement if you can not be accomplished as a DIY project might cost 50% of a new system.
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Old 22-02-2015, 08:55   #27
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Re: Refrigeration Problems

Quote:
Originally Posted by Richard Kollmann View Post
Only correct statement if failed water cooling system has let water mix with refrigerant. Yes, there are various pros from Hell out there. Evaporator replacement if you can not be accomplished as a DIY project might cost 50% of a new system.
OK, thanks again for all the excellent advice

Reefers now working perfectly; -20C in the freezer at half setting.

I've learned a lot from this, especially about watching the extent of frost to determine proper refrigerant content . I will look for the leak when the boat's on the hard in April. Meanwhile, I feel much more confident about refrigeration for my big cruise this summer
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Old 04-03-2015, 11:15   #28
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Re: Refrigeration Problems

Dockhead et. al

We may be in a similar learning environment. We purchased a 2003 Farr 50PH in October in Didim Turkey. We had a limited trip there so were only able to shake down the boat on a 20 day cruise. After that we put her back on the hard in Didim with YachtWORKS...who have been working on multiple items prior to our return in late April to our "new" boat.

Our refrigeration is Isotherm. A 150Lt stand-alone Refer and separate top-load freezer...both are Magnum water (pumped) cooled systems. The prior owner records show multiple leaks, topping off/reducing Freon, changing at least on compressor, potential compressor damage, voltage controllers being replace, one +? pumps...etc. On our cruise the Freezer would only get cold although we did see some frost. The frig would get cold but is working very hard. Records indicate never having replaced any zincs. Work was done in multiple countries around the Med.

We want improved reliability, low need for imminent repairs and lower operating energy needs. My reading suggests we would like to switch out
to Frigoboat keel cooling...and improve the controls/thermostats to auto/manual speed control and digital t-stats.


The fridge...has the evaporator behind the stainless sidewalls. The freezer is believed to be similar behind the "plastic" walls

We are debating the costs/reliability of "cobbling" together parts or wholesale replacement of the systems.

The yard and some local US friends believe we can marry up new Friogoboat Keel Coolers to the DB 50s with little difficulty. After reading your post and Richards remarks maybe this is more doable tha
n I thought. Any readers opinion on this would be very welcome. Also, did you investigate what it would take...IF...you needed to change the evaporators out? Can this be done by removing the units?

Thank you for any comments...

S/V Sea Change
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Old 10-03-2015, 11:29   #29
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Re: Refrigeration Problems

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Originally Posted by Brewer40 View Post
Dockhead et. al

We may be in a similar learning environment. We purchased a 2003 Farr 50PH in October in Didim Turkey. We had a limited trip there so were only able to shake down the boat on a 20 day cruise. After that we put her back on the hard in Didim with YachtWORKS...who have been working on multiple items prior to our return in late April to our "new" boat.

Our refrigeration is Isotherm. A 150Lt stand-alone Refer and separate top-load freezer...both are Magnum water (pumped) cooled systems. The prior owner records show multiple leaks, topping off/reducing Freon, changing at least on compressor, potential compressor damage, voltage controllers being replace, one +? pumps...etc. On our cruise the Freezer would only get cold although we did see some frost. The frig would get cold but is working very hard. Records indicate never having replaced any zincs. Work was done in multiple countries around the Med.

We want improved reliability, low need for imminent repairs and lower operating energy needs. My reading suggests we would like to switch out
to Frigoboat keel cooling...and improve the controls/thermostats to auto/manual speed control and digital t-stats.


The fridge...has the evaporator behind the stainless sidewalls. The freezer is believed to be similar behind the "plastic" walls

We are debating the costs/reliability of "cobbling" together parts or wholesale replacement of the systems.

The yard and some local US friends believe we can marry up new Friogoboat Keel Coolers to the DB 50s with little difficulty. After reading your post and Richards remarks maybe this is more doable tha
n I thought. Any readers opinion on this would be very welcome. Also, did you investigate what it would take...IF...you needed to change the evaporators out? Can this be done by removing the units?

Thank you for any comments...

S/V Sea Change
Hi Sea Change,

I'm not a genuine fridge expert but before a total rebuild of the system in my '84 Pearson I did a LOT of research including reading opinions from several actual experts and a number of internet "experts", plus I bought the books, consulted with a friend that's a certified AC and fridge tech and read several years of threads and discussions on this and several other forums.

So I can report what I did based on the above and the results in my first year of use.

First I went with the Frigoboat and have been very satisfied with that choice. I don't say it's the only good choice but seemed to have a good combination of quality, price, support, options, etc for my requirements.

I went with a straight air cooled model based on the BD50 for several reasons and it has worked out fine. I have a fairly large box, over 9 cu ft total including almost 2 cu ft of freezer section. Mid summer in FL, daytime highs approaching 100, lows high seventies I was using around 50-60 amp hours per day max. When I was on the boat to open the hatches and let it cool down inside it dropped to around 50 or less. Until I added more insulation around the freezer I was freezing stuff in the bottom of the fridge section so it was plenty cold in the box. I did completely rip out the old box and rebuild the whole thing with a lot more insulation which certainly helped. In cooler weather the power draw has been half that.

I considered the keel cooler but rejected it because it was more expensive, didn't seem to be necessary and I was concerned about corrosion on the keel cooler fittings. If the section exposed to salt water leaks due to damage or leaks or whatever you will get salt water into the system and according to the experts it will not be repairable and you will be buying a new system. That to me was a big downside. I understand the keel cooler system is quieter but I don't think significantly more efficient than the air cooled if at all. Some claim that you will pick up less heat in the boat with the keel cooled version (all the heat goes into the water and not the cabin air) but I didn't notice any difference with or without the fridge running. I measured the temp change over a couple of days in the area under the floor where the compressor is installed and even closed off the ventilation to see if that made any difference. Worst case I only saw a couple of degrees difference in a space of 5-6 cu ft.

So from me, one solid vote for a Frigoboat air cooled system.
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