Refrigeration Problems

[Dockhead]

I have two separate Isotherm SP systems cooling a fridge and separate freezer.

When I bought the boat 5 1/2 years ago, the fridge was not cooling well, and I had gas added to it, whereupon it performed flawlessly for another 4 1/2 years. Then, last summer, cruising in Sweden on my way to Finland, the fridge just about stopped working, and the compressor became very hot as well. I found a marine refrigeration guy who added gas, and it worked ok again. Then just a few weeks later, the freezer stopped cooling well -- if only I had thought to have that checked at the same time the guy did the fridge .

The problem seems to be a slow leak of refrigerant, and last summer, I thought, if I only have to top it off once every four years, it's really not a problem.

But now the freezer is cooling weakly again, a little over half a year after it was topped off

What is the right thing to do in this case? The Swedish refrigeration guy told me that small leaks like this are almost impossible to track down -- is that true? Are there any likely places to look?

Or should I just buy cans of refrigerant and a hose kit, and just top it off myself as often as it needs it?

Or give up, and replace it all?

Advice gratefully received as always.

[IdoraKeeper]

Before you give up, try the soapy water trick. It seems to be getting worse. If both systems are separate you could be reaching the end of life for seals in the compressors.

[Stu Jackson]

Get in touch with the guru of refrigeration: Richard Kollmann. He has an excellent website. One of his points has always been than 99% of frdige problems are electrical (unless you're sure it's a leak). Good luck.

[RONDO]

Hi i service a lot of small marine systems and have found the surest method of leak detection for me is to remove all refrigerant from the system and then pressure the system with approx 125 lbs pressure of dry nitrogen.Then i would also remove hose and cap service valve.Now brush and spray soapy water onto all tubing and parts.

[Dockhead]

Thanks for all the good advice!

Now one more question -- is it worth chasing these leaks? Is there a reasonable chance of success?

These units are now 14 years old -- what is their normal useful life? These Danfoss compressors are not all that expensive -- maybe it make sense to just replace them? I can well imagine that some hours of screwing around with the old ones will soon add up to the same money, with no guarantee of a good result, whereas replacing them will give me a new system. What do you guys think?

[sailorboy1]

I would try a pressure test to find the leak since the system works fine otherwise. Otherwise maybe it is time for you to get a recharge kit.

[GordMay]

Originally Posted by Dockhead

... These units are now 14 years old -- what is their normal useful life? ...

You're probably approaching the unit's end of life.
The “standard” life expectancy of a domestic household refrigerator typically varies between 10 & 18 years, with 14 years being considered “average”.

[Dockhead]

Originally Posted by GordMay

You're probably approaching the unit's end of life.
The “standard” life expectancy of a domestic household refrigerator typically varies between 10 & 18 years, with 14 years being considered “average”.

Thanks -- does that also apply to marine refrigeration, which is shut down most of the time?

My previous boat had an air-cooled reefer which was about 30 years old when I got rid of the boat, and still worked ok. Unlike this system, I never had any leaks and never needed to service it.

I don't know anything about these much more modern Danfoss units, except that they fry their electronic control boards from time to time. Are they mechanically weaker than the old ones? Do they wear out? Does the fact that they are shut down most of the time extend their life, shorten their life (seals drying out?), or doesn't matter?

Could it be that running mine with low gas, which made them run very hot, hurt them last summer?

Is it a good idea to replace them at this age? I'll have another 4 month, 3000 mile cruise this summer, like last summer, sometimes with a lot of people on board, and the refrigeration is pretty important.

Grateful for all advice.

[a64pilot]

Originally Posted by Dockhead

Thanks for all the good advice!

Now one more question -- is it worth chasing these leaks? Is there a reasonable chance of success?

These units are now 14 years old -- what is their normal useful life? These Danfoss compressors are not all that expensive -- maybe it make sense to just replace them? I can well imagine that some hours of screwing around with the old ones will soon add up to the same money, with no guarantee of a good result, whereas replacing them will give me a new system. What do you guys think?

I think you know the answer, seems you have stated it pretty well to me.

[Dockhead]

Originally Posted by a64pilot

I think you know the answer, seems you have stated it pretty well to me.

I'm just speculating based on zero knowledge.

Maybe someone who really understands these systems will say:

"Those compressors are bulletproof and last 30 years. Find the leak and get it properly evacuated and charged and forget about it. But keep a spare control board on hand as those do go out unpredictably."

For example. Or maybe it could be:

"Those compressors are useless once they've been overheated once, so just replace them now."

or:

"They will be near the end of their useful life at that point in any case, so go head and replace them."

I just don't know.

[GordMay]

Originally Posted by Dockhead

Thanks -- does that also apply to marine refrigeration, which is shut down most of the time? ...

Good question(s) for Richard Kollmann.
➥ Cruisers & Sailing Forums - View Profile: Richard Kollmann
➥ Kollmann Marine

[Richard Kollmann]

Originally Posted by Dockhead

Thanks for all the good advice!

Now one more question -- is it worth chasing these leaks? Is there a reasonable chance of success?

These units are now 14 years old -- what is their normal useful life? These Danfoss compressors are not all that expensive -- maybe it make sense to just replace them? I can well imagine that some hours of screwing around with the old ones will soon add up to the same money, with no guarantee of a good result, whereas replacing them will give me a new system. What do you guys think?

Unless you want to take the project on yourself to find leak and correct it, complete replacement now may be your best decision. Air cooled Danfoss BD compressor refrigeration units are generally repairable at 14 years but the same unit water cooled is exposed to much harsher conditions. Tampering with refrigerant can cause interior acid corrosion over time destroying aluminum evaporators. Low voltage discharge from Danfoss compressor into seawater over time will damage condenser coil as well as galvanic corrosion damage from dissimilar metals in saltwater.

What is the present condition of evaporator? If evaporator’s exterior coating has blisters this can be caused by internal micro size refrigerant leaks do to a small moisture content in refrigerant.

What is present condition of through hull condenser's sacrificial zinc anode? And when was it last changed? Electrolysis here even with copper nickel alloy will cause very small leaks in the beginning and progress over time to faster leaks.

If you decide to find the leak yourself let me know and I will send you a step by step test procedure where all you will need is a small can or 134a a tap a can injector and two days of free time.

[skipmac]

If timing isn't good to buy/install a new one and you want to give it a try I do believe a good refrigerant leak detector can locate even tiny, slow leaks.

At least might help isolate the problem area and keep you in operation until you pick up a new system.

[Dockhead]

Originally Posted by Richard Kollmann

Unless you want to take the project on yourself to find leak and correct it, complete replacement now may be your best decision. Air cooled Danfoss BD compressor refrigeration units are generally repairable at 14 years but the same unit water cooled is exposed to much harsher conditions. Tampering with refrigerant can cause interior acid corrosion over time destroying aluminum evaporators. Low voltage discharge from Danfoss compressor into seawater over time will damage condenser coil as well as galvanic corrosion damage from dissimilar metals in saltwater.

What is the present condition of evaporator? If evaporator’s exterior coating has blisters this can be caused by internal micro size refrigerant leaks do to a small moisture content in refrigerant.


What is present condition of through hull condenser's sacrificial zinc anode? And when was it last changed? Electrolysis here even with copper nickel alloy will cause very small leaks in the beginning and progress over time to faster leaks.

If you decide to find the leak yourself let me know and I will send you a step by step test procedure where all you will need is a small can or 134a a tap a can injector and two days of free time.

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.

[colemj]

Isotherm sells everything in parts, don't they? You seem to have probable reason to believe that your problem is a leak.

If you think the most probable leak is the evaporator or lines to it (my guess), then replace that.

If the leak continues, replace the condenser, although I think if this is bad, you would have contamination showing far worse issues.

It is probably less likely that the compressor itself is bad if it is running fine now.

I'm assuming you have already done an easy leak check of the schrader valves, cap o-rings and exposed tubing.

Mark