Refrigeration Email I have no good answer for.

[Bowdrie]

Originally Posted by RaymondR

I may be justified in edging towards an opinion that overall the refrigeration circuit using a TXV could be the more durable of the two systems when used in pleasure vessel marine applications.

Cap tubes are not "bad", per se, but systems using a TXV can be somewhat more tolerable of "parts mixing" than cap-tube applications.
Now, and this is only my opinion; The biggest downfall of the 12V package units, as built by several companies, is not the Danfoss compressor, nor even the electronic module, a spare module is an easy enough part to have on hand, and the couplings are not all that bad either.
The weak link is, and has always been, and always will be, the miserable and wretched pressed aluminum evaporators.
Many years, (decades,) ago the Standard Refrigeration Co. manufactured a range of pressed evaporators that were made of Stainless Steel, and they were used by the thousands, (perhaps 10s of thousands,) in many brands of domestic refrigerators/freezers.
Alas, they went by the wayside, replaced by "modern" engineering.

[Richard Kollmann]

Bowdrie, you are correct in that these small electronic refrigeration modules have demonstrated in some cases poor reliability. Danfoss has changed module designs several times modules fail on a number of refrigeration units. I have tested large numbers of these modules at no charge over the last twenty years and conclude the module that fail are on systems overloaded beyond their original design limits. There is one exception other than poor application and that is lightning strike direct or nearby.
Companies that sell icebox conversion refrigeration units incorrectly advise customers as to how large a box their system will operate as a refrigerator or a freezer. What about advise as to amount of insulation the box needs. One manufacturer’s catalog in small print calls for three times more insulation if it is intended to be a freezer. One manufacturer on this forum stated his unit with a Bd50 compressor can handle a 20 cubic foot box. My 12/24 volt Book is no longer available but the Slide Show ,what works and what does not, my web site is a twenty year old, generic view of selecting refrigeration hardware. If one is concerned about module failures take action on reducing compressor temperature. If you can not keep the palm of your hand on dome top of the compressor the control module may be at risk.

I did a study on evaporators service life some years ago that also included eutectic evaporators and copper tubing as a replacement.

[OzeLouie]

Originally Posted by Richard Kollmann

Bowdrie, you are correct in that these small electronic refrigeration modules have demonstrated in some cases poor reliability. Danfoss has changed module designs several times modules fail on a number of refrigeration units. I have tested large numbers of these modules at no charge over the last twenty years and conclude the module that fail are on systems overloaded beyond their original design limits. There is one exception other than poor application and that is lightning strike direct or nearby.
Companies that sell icebox conversion refrigeration units incorrectly advise customers as to how large a box their system will operate as a refrigerator or a freezer. What about advise as to amount of insulation the box needs. One manufacturer’s catalog in small print calls for three times more insulation if it is intended to be a freezer. One manufacturer on this forum stated his unit with a Bd50 compressor can handle a 20 cubic foot box. My 12/24 volt Book is no longer available but the Slide Show ,what works and what does not, my web site is a twenty year old, generic view of selecting refrigeration hardware. If one is concerned about module failures take action on reducing compressor temperature. If you can not keep the palm of your hand on dome top of the compressor the control module may be at risk.

I did a study on evaporators service life some years ago that also included eutectic evaporators and copper tubing as a replacement.

Yes, the earlier MDMs (motor driver modules) were a PITA! to say the least. Over the years as they 'evolved' (Evolved = nice way of saying we haven't got this right but we are working on it!) And they did. The MDMs now have soft start and have been further improved in recent times. They are now very reliable and with excellent 'fail-safe' protection.

Regards matching a suitable system to cabinet size, insulation, ambient etc. This is most important and more often ignored resulting in disappointing results.
Any application of refrigeration can only be confidently applied if the requirements are known so that suitable equipment is chosen. Things like the daily heat load specific to the project , power consumption etc,. can easily be obtained by using a 'Heat load, Power consumption and Duty cycle' estimator.

Consider this: A system that maintains a cabinet at +2c running 60% duty cycle in a +20c environment will fail miserably in a 35C environment. (Just when I needed you most! )

[OzeLouie]

Originally Posted by RaymondR

I have learned a lot from participating in these refrigeration threads over the past few years and feel that whilst I have a lot more to learn yet. I may be justified in edging towards an opinion that overall the refrigeration circuit using a TXV could be the more durable of the two systems when used in pleasure vessel marine applications. However this is from a limited experience base as yet limited to only capillary tube systems and may change if I can implement a TXV controlled system and gain some operating experience with it.

Whilst simpler and with fewer moving parts and possible leakage points, the capillary flow control system is dependent upon a very fine balance between compressor output and system refrigerant volume. With the corrosive marine environment and high vibration levels and often extended periods of remote operations common in pleasure vessels this may prove difficult to maintain.

In contrast the extra volume of refrigerant in TXV systems with an accumulator provides some leak tolerance and the compressor speed independent control of flow into the evaporator provided by the TXV being more responsive to flow variations which may occur with low DC voltage compressors and better design to ensure optimum refrigerant volumes in the evaporator could prove the more appropriate system for pleasure vessel usage.

Hi Raymond, Regards the old debate TX valve verses capillary. Each have their merits and its that which has seen their application popular world wide, fall into two groups.
Firstly capillary systems are by far the most used worldwide with near all fractional HP systems employing them. They are simple, reliable and efficient if engineered correctly for the application.
Everyone of us has or had many fridges, freezers etc that were capillary fed and who has ever had the capillary cause a problem? My bet bet is no-one!

Engineering a system for capillary throttling is more complex than using a TX valve. It must be correctly sized, a proper filter dryer and a suitable suction accumulator used. This tool is handy for sizing: https://dancap.informer.com/1.0/

The only weakness of capillary is due to softening where it is braised each end to larger copper tubing. This can be avoided by simply applying a shallow S of the capillary back onto the larger copper tube and tying to same.

TX valves are commonly used for larger systems especially systems with multiple evaporators and when using the best refrigeration method known.. pump down system! Being 'adjustable' they allow more freedom of application which may suit the one off marine fridge maker.
TX valves also have their issues like gas leaks! Plus they are downright ugly / cumbersome in small cabinets but hey, what ever rocks your boat!
If building with TX valve, use only a *correct sized liquid receiver followed by a proper filter dryer and sight glass. (* Don't use a car air con receiver!)
With a TX and operating as a pump down system, you could engineer the system to service a second cabinet.

[RaymondR]

Originally Posted by OzeLouie

Hi Raymond, Regards the old debate TX valve verses capillary. Each have their merits and its that which has seen their application popular world wide, fall into two groups.
Firstly capillary systems are by far the most used worldwide with near all fractional HP systems employing them. They are simple, reliable and efficient if engineered correctly for the application.
Everyone of us has or had many fridges, freezers etc that were capillary fed and who has ever had the capillary cause a problem? My bet bet is no-one!

Engineering a system for capillary throttling is more complex than using a TX valve. It must be correctly sized, a proper filter dryer and a suitable suction accumulator used. This tool is handy for sizing: https://dancap.informer.com/1.0/

The only weakness of capillary is due to softening where it is braised each end to larger copper tubing. This can be avoided by simply applying a shallow S of the capillary back onto the larger copper tube and tying to same.

TX valves are commonly used for larger systems especially systems with multiple evaporators and when using the best refrigeration method known.. pump down system! Being 'adjustable' they allow more freedom of application which may suit the one off marine fridge maker.
TX valves also have their issues like gas leaks! Plus they are downright ugly / cumbersome in small cabinets but hey, what ever rocks your boat!
If building with TX valve, use only a *correct sized liquid receiver followed by a proper filter dryer and sight glass. (* Don't use a car air con receiver!)
With a TX and operating as a pump down system, you could engineer the system to service a second cabinet.

Hi Louie, good to hear from you mate.

I had a lot of problems getting on top of the TXV valve as a functioning device which problem Richard provided a lot of help in overcoming. I later realized that the problem was my perception of the device as a temperature rather than flow control device. However the up side was that because of the perceptual problem I had actually learned a lot about them whilst overcoming it.

One of the reasons I became so interested in the TXV was that I was pondering on how one might exploit the variable speed capability of the small DC compressors we use in these systems to better exploit the wind and solar power commonly available on boats and decided that the TXV might work better than cap tube in this type of application, particularly since a much higher service factor is imposed when eutectic systems are employed.

I eventually came to the conclusion that a high side float valve, to ensure liquid to a TXV at the lowest possible head pressure and consequent current draw, without an orifice restriction, to optimize the fill of two state refrigerant in the evaporator with the lowest possible pressure drop across it was probably the best overall solution.

[Richard Kollmann]

Raymond you are 100% correct the positive control of and performance of a TXV flow control is a must in mobile refrigeration as it has the ability to compensate for design flaws and as ambient temperatures changes. It is true there are maybe a billions of capillary tube
in stationary environment's but they are less desirable in mobile refrigeration. Car liquid receivers with over pressure blow out plugs work well in managing evaporator supper heat, Servicing refrigerant is simple on TXV systems and extremely difficult on cap tube systems, It is true pump down the first time but only the fist time will take 10 minutes, there after only seconds. The only way to justify a cap tube over a more reliable TXV with receiver and sight glass is Cap tube is less expensive.

[Bowdrie]

In many respects, the ideas/practice of having refrigeration on small to medium sized boats has been a "Boatload of Irony".
What we have today in the small-package 12V units is what was needed when reefer systems were just getting started.
In the '60s>'70s, and even into the '80s, about the only hope of having a freezer/reefer on a smallish sailboat was an engine drive unit.
A Tecumseh HG 850/1000 running some Dole plates was the most common, later the Sankyo/Sanden compressors became popular because of space/mounting advantages.
The boats of the time were thought to be "Well equipped" if they had 3 group 27 batteries, one for starting, and 2 for the house,, and a typical 12V system used a Tecumseh CA/CB belt drive compressor hooked-up to an evaporator, not an ideal situation for power management concerns,, and they used a LOT of valuable space that smaller boats just don't have.
The use of 120VAC units, (the most popular was the Tecumseh AE2410AC,a true "low temp" unit,) with the emerging inverter technology was a first step, but the problems of power generation and power storage was still the issue to overcome, in a way, the use of 1/4,>1/2HP 120VAC units was ahead of its time.
Fast forward to today; The small/smaller boats can have enough solar and deep-cycle batts to enable the use of the 12V package units.
Here's where I tend to "part ways" with some of the prevailing thinking;
Today, even medium sized boats, with their acres of solar and big batt banks really have no reason to be "locked in", if you will, with the fragile/under-powered 12V units, with their constant on/off cycling.
With their efficient inverters/big batt banks, and availability of large amounts of solar, they have the resources to effectively use a 120VAC unit with eutectic plates.
Also, you can have a system that is easily serviced and parts obtained, in any part of the world,, you don't end-up having emails and phone calls to some person/company who may be thousands of miles away, and then go thru the expense/problems of shipping, to get some "proprietary" part.
And, the average sailor can "see", (a sight glass with a moisture indicator is a wonderful thing,) what's going on with his system.
The systems are "intuitive", any problem is readily deduced, and you don't have to be an "expert" to work on them.
Now,, if we could just get Dole Refrigeration Co. to bring back the superior line of eutectic plates in suitable sizes,, the smallest one they make now is 20x24 in.,, but it's rated at well over 4,000BTUs at +18F, and ~3,500 at -10F.

[OzeLouie]

Originally Posted by Bowdrie

In many respects, the ideas/practice of having refrigeration on small to medium sized boats has been a "Boatload of Irony".
What we have today in the small-package 12V units is what was needed when reefer systems were just getting started.
In the '60s>'70s, and even into the '80s, about the only hope of having a freezer/reefer on a smallish sailboat was an engine drive unit.
A Tecumseh HG 850/1000 running some Dole plates was the most common, later the Sankyo/Sanden compressors became popular because of space/mounting advantages.
The boats of the time were thought to be "Well equipped" if they had 3 group 27 batteries, one for starting, and 2 for the house,, and a typical 12V system used a Tecumseh CA/CB belt drive compressor hooked-up to an evaporator, not an ideal situation for power management concerns,, and they used a LOT of valuable space that smaller boats just don't have.
The use of 120VAC units, (the most popular was the Tecumseh AE2410AC,a true "low temp" unit,) with the emerging inverter technology was a first step, but the problems of power generation and power storage was still the issue to overcome, in a way, the use of 1/4,>1/2HP 120VAC units was ahead of its time.
Fast forward to today; The small/smaller boats can have enough solar and deep-cycle batts to enable the use of the 12V package units.
Here's where I tend to "part ways" with some of the prevailing thinking;
Today, even medium sized boats, with their acres of solar and big batt banks really have no reason to be "locked in", if you will, with the fragile/under-powered 12V units, with their constant on/off cycling.
With their efficient inverters/big batt banks, and availability of large amounts of solar, they have the resources to effectively use a 120VAC unit with eutectic plates.
Also, you can have a system that is easily serviced and parts obtained, in any part of the world,, you don't end-up having emails and phone calls to some person/company who may be thousands of miles away, and then go thru the expense/problems of shipping, to get some "proprietary" part.
And, the average sailor can "see", (a sight glass with a moisture indicator is a wonderful thing,) what's going on with his system.
The systems are "intuitive", any problem is readily deduced, and you don't have to be an "expert" to work on them.
Now,, if we could just get Dole Refrigeration Co. to bring back the superior line of eutectic plates in suitable sizes,, the smallest one they make now is 20x24 in.,, but it's rated at well over 4,000BTUs at +18F, and ~3,500 at -10F.

Good to hear from another 'hands on member. Yes the industry has certainly come a long way helped by the application of improved 3 phase drive AC compressors, digital control devices, far better soft start MDM's, but unfortunately many makers still choose to use cheap materials in their systems. Aluminium refrigerant tubing, bundy tubing, and ineffectively coated / protected aluminium evaporators, spun copper dryers, etc., have NO place in a marine DC powered environment.

Only copper refrigerant tubing, stainless steel cold plates, proper filter dyers, and high & low refrigerant service ports should be the norm specially for marine application.
Regards eutectic plate availability, we manufacture eight eutectic plate sizes from 320mm x 290 x 60 through to 650mm x 530 x 100 that couple up to a range of condensing unit options starting with a 3.5cc air cooled unit. We believe that the primary objective is proper and adequate refrigeration ability with all else secondary.

@Richard... Using car air-con receivers can see the top of the receiver rust out from the inside due to moisture congregating there. The last one we heard of was only two+ years old and rusted through, besides they were made for car air cons with very different factors at play. Use a correctly sized receiver, then a proper filter-dryer and sight-glass if you want to do it properly.

[Richard Kollmann]

@Richard... Using car air-con receivers can see the top of the receiver rust out from the inside due to moisture congregating there. The last one we heard of was only two+ years old and rusted through, besides they were made for car air cons with very different factors at play. Use a correctly sized receiver, then a proper filter-dryer and sight-glass if you want to do it properly. Quote

Louie, It is difficult to understand your dislikes for the norms and advantages of hardware that provides the mobile refrigeration industry superior Super Heat in any size evaporator at any desired temperature. I think you are confused about liquid refrigerant receiver's designs to, as long as they are larger than needed to hold sufficient volume of refrigerant. The most popular and oldest marine companies Technautisc, Crosby, Grunert, SeaFrost not to mention my own company, all have used industrial receivers "you call car receiver's". If you have seen one of these popular companies refrigeration the steel and aluminum components are corrasion protected outside and do not trap moisture inside. The TXV designs advantages far out way the Cap Tube designed system when used in mobile boat refrigeration. This is a case where cheaper is not better.

[RaymondR]

I suspect that car receivers would probably be too big for the fractional horsepower systems we use in boats. Different matter when we were using auto aircon systems to implement the old style, engine driven eutectic systems with a high BTU capacity.

I was thinking that if I needed an accumulator I would use one of the small gas bottles (not the cans) used for refrigerant or propane. My muck-about condensing unit is fitted with a service valve so I can divert the refrigerant and isolate it from the rest of the system if I need to open it.

A short narrative on sourcing refrigerants in places with excessive regulation.

When I first came to the east coast I became friendly with another yachty named Roy.

Roy had an old style engine driven, eutectic system which he characterized as "a bit gas hungry".

I encountered Roy at the dingy dock on my way home after a late night out. He had a bucket with a cloth over the top in his hand:

Me: Where are you off to at this time of the night Roy?

Roy: I'm going to get some fridge gas.

Me: Where, at this time of night Roy.

Roy: In the basement car park of that big hotel there, they don't lock the utility room.

Me: They leave refrigerant gas bottles in there?

Roy: Nah but I've got a bunch of adapters in my pocket and I'll just tap into one of the service connections.

Me: It'll take you forever to fill that bottle like that.

Roy: Nah, that's what the dry ice is for.

This is the sort of mischief formerly honest yachties are driven to by over-regulation.

[Richard Kollmann]

Louie, you will notice I have followed the board's advice and ignored your insults. The industry supports my efforts so I will never retire. I just realized there are more of my designed systems in Australia than you have units in the US. Since I have never criticize your system designs.

I would solicit industry email and forum PM for your comments.

[sailjumanji]

Originally Posted by Dougtiff

Charg to 10 PSI, don't overcharge, it's easy to do, frost line not to exit the box, you can also use a tempt. Pressure chart for correct charge.

I had a refrig guy recharge our compressor/holding plate system, after replacing the holding plate due to hole. Initially we had frost line almost back to the compressor. He removed some refrigerant, and frost line moved back toward the box/plate, but still about 4 feet of ice coated tubing. Should we remove a bit more? Is the target always to have all of the conversion back in the plate, i.e., no frost/ice buildup on tubing exiting the box?

[Uncle Bob]

Originally Posted by Richard Kollmann

Louie, you will notice I have followed the board's advice and ignored your insults. The industry supports my efforts so I will never retire. I just realized there are more of my designed systems in Australia than you have units in the US. Since I have never criticize your system designs.

I would solicit industry email and forum PM for your comments.

Richard, you have aroused my curiosity, how do know how many US sailors have made the choice to purchase an Ozefridge product?

[OzeLouie]

Originally Posted by RaymondR

I suspect that car receivers would probably be too big for the fractional horsepower systems we use in boats. Different matter when we were using auto aircon systems to implement the old style, engine driven eutectic systems with a high BTU capacity.

.

Raymond, you have nailed it exactly! Using a tall oversized receiver sees little activity in the top interior of same. Unlike a car air con system with ten times the refrigerant traffic / velocity, the little fridge unit's feed into the receiver is minute, comparatively sedate and rarely involves the top part of the receiver. This results in the raw metal top interior being void of activity hence no 'wetting' with refrigerant / oil as would be the case when used as intended as an air-con receiver.
Being a tall, warm area it is also inducive of being a storage area for any air / moisture in the system because as we know air being lighter than refrigerant, likes to occupy such areas. This was the conclusion of my mentor who was involved in investigating this phenomenon a few years ago. He was able to replicate the issue.

And again as quoted earlier... 'Use a correctly sized receiver, then a proper filter-dryer and sight-glass if you want to do it properly.' That being the correct industry recognised procedure.

Louie

[Richard Kollmann]

Originally Posted by sailjumanji

I had a refrig guy recharge our compressor/holding plate system, after replacing the holding plate due to hole. Initially we had frost line almost back to the compressor. He removed some refrigerant, and frost line moved back toward the box/plate, but still about 4 feet of ice coated tubing. Should we remove a bit more? Is the target always to have all of the conversion back in the plate, i.e., no frost/ice buildup on tubing exiting the box?

Frost on a refrigerant return line and how close frost gets close to reaching the compressor is always of concern. What is important is frost near the compressor indicates liquid and not gas vapor could damage the compressor. I prefer to know more about the design of this system and what else was done when the new plate was installed.before I give advice about tampering with refrigerant charge.
All refrigerator designs have a low pressure accumulator at the end flow of all types of evaporators to be efficient and to take advantage of refrigerant heat extraction liquid to gas phase change. Larger pleasure boat systems have a separate suction line accumulator to insure liquid phase change and allow small amounts of saturated liquid and oil to return to the compressor this then becomes the primary source of compressor cooling on many designs. Assuming the frosted line is not approaching the compressor at any time during the freezing of the eutectic plate compressor is safe but this condition needs to be corrected.
Again an experienced technician needs to know the type of refrigerant flow control device used on your refrigeration system Capillary tube, a Thermostatic Expansion Valve (TXV) or a low pressure evaporator temperature regulator:
Cap tube refrigerant flow is controlled by refrigerant volume in complete systems which change as ambient temperatures change, too much refrigerant on a warm day and not enough on a cold day.
TXV with its liquid refrigerant storage tank receiver needed to meter refrigerant flow to evaporator as conditions change ensuring the most evaporator heat removed per ounces of refrigerant flow.
Refrigerant flow of a Low Pressure Valve is preset manually to a desired pressure/evaporator temperature.
I prefer when adjusting refrigerant volume on most electrical refrigeration compressor to adjust volume of refrigerant based on compressor current amperage.
On volume of refrigerant in a TXV system with a sight glass keep small bubbles in sight glass until desired evaporator temperature is reached and only then add refrigerant till glass is clear. This method will keep you from over charging unit and allow you to verify later there are no leaks in the system.