Frigoboat Keel Cooling Refrigeration in Temperate Cold water?

[Cheechako]

Anyone else getting real tired of listening to these two guys try to prove who knows the most about refrigeration? Why dont you go out in the parking lot and resolve it?

[Frigoboat Info]

My responses in blue.
Frigoboat info, As I said before I will leave Compressor capacity versus insulated box sizes to the refrigeration industry and boating community without changing my recommendations

I do have problems with the lack of interest in solving the costly leaking O-ring problem and blaming the installer and boat owner for refrigerant leaks. This is no lack of interest, as I have shown in my previous posts. Yes the keel coolers location may cause two of the line disconnects to reach or exceed 130 degrees C ( 266 F ) Please explain to myself and others how temperatures at a coupling could reach 266Funder normal working conditions
A. Your figure quoted earlier in this thread is compressor vapor gas temperature 130 C from Danfoss Spec sheet.
I found two references to condensing temperature in my early postings: "130F condensing temperature, which is the figure used for air cooled condensers", and "From the Danfoss specs, capacity of a BD50 at 10F evap temp and 130F condensing temp = 464 Btu/hr " I'm sure that you know that the ASHRAE standard condensing temperature is 130F, not 130C.

but there are 134a refrigerant O-rings available that are advertised to handle much higher temperatures. There are also extended shelf and in service life O-rings available. Yes, we are well aware of what o-ring materials are available. As to your comment refrigerant leak must be proven beyond a doubt as leaking before questioning O-rings. What about compressor is running and evaporator has frost cover missing on half of evaporator’s surface. There are several reasons for that to happen besides refrigerant loss, and if there is a leak it should not automatically be assumed that the o-rings are the culprits. I can understand why a technican might confuse refrigerant flow blockage on keel cooler systems for O-ring leakage. You see, there’s one reason right there! Finding traces of oil at a leak in any small system is unlikely Totally incorrect Mr. Kollmann! Oil is always circulating with the refrigerant and will almost definitely been seen at a leak location. Ask any technician, or even some of our customers that have found such traces.
A. I ask this question to boaters in trouble with refrigerant loss on small systems containing less than 5 ounces of refrigerant and they rarely finding leaks. I believe there are better ways for a DIY boat captain to find leaks. On your keel cooler system I recommend testing all line connectors first then keel cooler inside boat through hull where refrigerant lines inter cooler.
Jedi has just answered that one .......

and besides two line connecters are located in hot gas line before keel cooler. This is irrelevant. Traces of oil at leak locations will invariable be found on both gas and liquid lines/components. Very few people even technicians can not adjust the level of refrigerant in one of these very small systems to match a well designed factory charge. Actually, the refrigerant charge of a component-style marine capillary system adjusted on-site will be the ideal. The factory charge will normally be close to ideal. Chances are even a technician will not get refrigerant volume correct with in 5 grams on first service call. It is impossible to use weight to accurately charge these small systems in the field.
A. I agree

Maintenance on any refrigerator after initial first year’s product improvements were made should be limited to only cleaning skills. I’m not I understand what this means.

A. Warrantee information feedback leads to product improvements. Refrigerant systems are believed to be maintenance free once bugs are worked out. Oh, if only that were true in a marine envronment, especially where the manufacturer has no control over application, installation, and operation.

It is true that in the past other icebox refrigeration conversion companies have had line connecter leak problems. Remember a satisfied costumer will help you sell 3 more units and a dissatisfied costumer will cause you to lose 13 sales. Another marketing tip is sales improve by a liberal warrantee policy as good as or better than others in this industry.

Having had technical equipment problems over 50 years ago with a foreign manufacturer I made several trips overseas to meet with good very proud engineers who would not consider improving their products reliability. I understand what you must be up against on O-rings and Filters. Fortunately this several million dollar contract I refer to contained maintenance cost and performance language similar to a construction performance bond. A sizable cash settle was made then later equipment was disposed of. I have no idea what relevance this has to this discussion unless it is to take a shot at foreign manufacturers in general.

A. Having supervised for years a department with Mechanical,Electrical,and Industral engineers in this country I know it is difficult to change their minds on a pet project. It is even more difficult overseas if you do not speak their language.

e cash settle was made then later equipment was disposed of.[/QUOTE]

[Frigoboat Info]

Jedi:
I'd really like to get some specifics here to see what's going on.
1) What o-rings are you changing? Just the main, large o-ring on the male coupling half when the coupling is disassembled, or all three.
2) Are these replacement o-rings supplied by Frigoboat?
3) Apart from the trace of oil, what did the system show any symptoms of being low on refrigerant?.

[s/v Jedi]

Originally Posted by Frigoboat Info

Jedi:
I'd really like to get some specifics here to see what's going on.
1) What o-rings are you changing? Just the main, large o-ring on the male coupling half when the coupling is disassembled, or all three.
2) Are these replacement o-rings supplied by Frigoboat?
3) Apart from the trace of oil, what did the system show any symptoms of being low on refrigerant?.

1) three? Oops, I only knew of two. One is obvious which must be the main one you talk about. That is the only one I replaced as it was clearly malformed (flattened). I saw another one in the female fitting I think, but it looked fine so I did not change that one. I don't recall seeing a third one at all so obviously missed that. I was close to cutting the connectors off and soldering everything, especially when I learned about the price of the extra filter drier with the quick connect fittings. I can buy just that filter drier for $10 locally.

2) yes, they came with my units

3) I only replaced them after 6 years but leakage had been going on for some time. The obvious low refrigerant indication I found was that more and more of the evaporator didn't get any frost on it anymore. I now state 5 years so as to make this preventive maintenance.

I was wondering if more suitable O-rings are available to extend the service interval.

[Frigoboat Info]

Thanks for the info, Jedi. I really appreciate the input.
1) The other two o-rings are hidden, and are sealed in at the ends of the male and female halves of the couplings. These should never be disturbed unless it has been established without doubt that these are leaking.
We have managed to reduce the price of the pre-charged Filter/Drier recently by downsizing it, so it is now more reasonably priced. Unfortunately, the price of a simple filter/drier creeps up once you add on the cost of the couplings, the tubing, and the labor to put it all together and then to evacuate and charge it with a precise amount of refrigerant. Cutting out the couplings and soldering the lines together is perfectly acceptable if the correct precautions are made to ensure that no dirt whatsoever enters the system. Of course the refrigerant will first have to be recovered and then the system will need to be evacuated and recharged.
2) We include those o-rings primilary so that if one get's nicked during installation the installer has a replacement close at hand. But it's good to know that they can come in handy later.
3) I'm not sure I have an answer as to why an o-ring would leak so slowly over such a long time. Did you have to add refrigerant at any time before replacing the o-ring?

There really is no better or more suitable material for seals in a R134a system than the Buna M (Nitrile) as used in Frigoboat o-rings. There is another version of Buna M, Hydrogenated Nitrile, that has an even higher temperature tolerance, but that is way beyond anything we would see in our marine applications, and it has some drawbacks in other areas. Never use Viton o-rings (as we have found some customers have), as this material is not compatible with refrigerant R134a.

[s/v Jedi]

Frigoboat, i never had to add refrigerant before replacing the O-rings but at that time, I evacuated the system and did the precise fill by checking frost area. The reason I waited so long with the fix was that this box was a 7 cu.ft. fridge so plenty of over capacity (so still good enough undercharged), plus I had to buy a new vacuum pump.

I did this 2.5 years ago and all has been 100% since then.

On the O-rings: there is another set of spares mounted on the dust caps.

[Celestialsailor]

Originally Posted by Cheechako

Anyone else getting real tired of listening to these two guys try to prove who knows the most about refrigeration? Why dont you go out in the parking lot and resolve it?

...Having a bad day?...
Personally, after sifting through all the information, I have found some very useful information. If I wasn't into the thread in general, then I would just move on. To me these are two well versed individuals with a lot of knowledge.

[Tortuga's Lie]

How about those green o-rings that are for commercial refrigeration units? Just curious.

Here's a link to o-ring selection chart:
http://www.marcorubber.com/material_chart.htm

The Buna-N lists that it is only marginal for refrigerants/freon but does this chart does not specify 134-a..............Still curious........

[Tortuga's Lie]

OK, upon further research, R-134a is listed as "Tetrafluoroethane" and this chart:
Marco Rubber | Fluid Compatibility Guide

has the Buna-N listed as excellent for "Tetrafluoromethane" which I am assuming is chemically very similar??

[Frigoboat Info]

Buna N is perfectly safe for R134a and R12 and the oils used in these systems. That is why it is used extensively in marine refrigeration and automobile air conditioning (where incidentally the temperatures are much higher than marine refrigeration), but it is marginal at best for some other refrigerants.
Color is no reliable guide to material, unfortunately.

[Tortuga's Lie]

Thanks Frigoboat, I am sure you wouldn't use anything that would not be compatible. I am mainly interested in learning and furthering my education on materials and suitability.

[Celestialsailor]

Originally Posted by Frigoboat Info

Buna N is perfectly safe for R134a and R12 and the oils used in these systems. That is why it is used extensively in marine refrigeration and automobile air conditioning (where incidentally the temperatures are much higher than marine refrigeration), but it is marginal at best for some other refrigerants.
Color is no reliable guide to material, unfortunately.

I think the real question would be...is there a better o-ring material for the purpose.

[skipmac]

Originally Posted by Celestialsailor

I think the real question would be...is there a better o-ring material for the purpose.

Exactly. Frigoboat nixed the use of Viton but I have also used Teflon o-rings and EPDM o-rings for some specialty applications. What about one of these as a more permanent solution?

[Frigoboat Info]

There are many more considerations to be met when selecting the material for o-rings in a mobile refrigeration or air conditioning system than with, say, a hydraulic system. There is obviously the compatibility with both the refrigerant and oils, both as vapour and liquid, but also the extremes of temperature and the repeated temperature swings whether they are on the discharge or suction side. Then they have to perform reliably under high pressure and also in a vacuum, plus durability, hardness (we use 80 Shore), elongation, age hardening, etc.
Hydrogenated Nitrile is normally green in color and has even higher temperature tolerance than Buna N, but has lower elongation so is more difficult to handle. Temperatures in mobile refrigeration are comfortably within the limits of Buna N, and nowhere near those seen in automobile air conditioning where it is the material of choice.

[Frigoboat Info]

I really don't know what was going on with your system, Jedi. That's one heck of a slow leak! But glad changing the 0-ring fixed it.
Thanks for reminding me about the spare o-ring on the dust caps. I'd forgotten to mention that.