Who provides the best 12 volt refrigeration systems?

[john61ct]

How is that different from TXV?

which I believe both ColdEh and CoolBlue use exclusively on theirs?

[a64pilot]

TEV is probably more correct than TXV, cause the word expansion starts with an e, not an x.
It’s sort of like xmsn, if you aren’t familiar with that being a transmission, it won’t make much sense.

All automobiles or nearly all use TXV’s due to the flexibility needed in an automotive air conditioner, heat loads are hugely variable.

In the US in 2006 the min SEER for a house air conditioning system was raised to 13. In order to meet the higher requirement nearly all new systems are TXV equipped.
The use of TXV’s due to ever increasing demands on efficiency is skyrocketing. They are complex, not cheap and another thing that can break of course. They are not magic.
The TXV functions to maintain the superheat within a narrow range, thereby increasing efficiency.
Now I’m sure if you can control other variables, then you can dial in a cap tube system to where it’s superheat is within a narrow range anyway, and likely systems that the whole thing, box and all are manufactured to a spec can do that.
However any Boat ice box conversion system is fighting an uphill battle at best, cause it has to work in a hugely differing set of circumstances.
My box for instance, you likely couldn’t come up with a worse case than mine, it’s old, not really well insulated to begin with, its 14 cu Ft. and some fool put the galley stove on one of its walls, and the engine on the other.
Contrast that with a better insulated smaller box that doesn’t have an engine and stoves heat to worry about, and you have to vastly different circumstances, but a system needs to be able to work in both.

The TXV functions as refrigerant cruise control if you will, if the demand is there it opens up and allows more refrigerant in, and of course loads down the compressor, once your evaporator gets close to the correct temp, it throttles back refrigerant flow, reduces the load on the compressor and that is when you get a jump in efficiency, then later you hit set temp and the compressor cycles off of course.
My BD80 for instance, if I turn my system on with the evaporator at room temp, it draws 15 amps I think for a long time until it freezes down the eutectic fluid, but like right now the system is close to set point, we haven’t added a gl of milk, or ice tea or a watermelon to cool down so when it’s on it’s draws under 6 amps, it’s power consumption is about equal to a BD35.

However these are general observations, and I’m sure there are ways to engineer systems to get good efficiency in other ways, there is always more than one way to skin a cat.

[newhaul]

I'm after every watt savings I can get . If I can run on the solar and keep 200 ah of Lfp between 75% and 90% I will be a happy camper if it goes much below that I will be looking to shave usages .
The only real power user will be the refer so it needs to be as efficient a system I can get .

[OzePete]

Originally Posted by john61ct

How is that different from TXV?

which I believe both ColdEh and CoolBlue use exclusively on theirs?

Hi John, Both a TX valve and a capillary tube do the same thing in as much as they restrict the flow of refrigerant into the evaporator. A throttling device.
A capillary is simply a length of very small bore copper tubing, very simple. A TX valve is a more complex mechanism that also requires additional components like receiver and sight glass.

Both have their issues:
TX valves are more complex and have more to go wrong like gas leaks via the O ring sealing the orifice adjuster, or from the evaporator side flare nut (if not welded) caused by the constant temperature variations. TX valves also have a capillary from the valve to the sensor.
A 'stuck open' valve, although rare, can flood the compressor causing irreparable damage.
TX valve orifices are easily blocked if the correct filter dryer type is not used, as the orifice is smaller than a similar capacity capillary tube. The valves strainer can also block although rare.
A TX valve inside such a tiny cabinet is cumbersome and ugly!

Capillary tubes can easily block also if the correct filter dryer type is not used.
Capillary tubes can easily block or have a restriction if the capillary used has a bore less than 0.8mm.
Capillary tubes can easily break specially at the ends where welded, unless the are strapped.
Capillary tubes can retain oil in loops when the unit is being evacuated making it essential to evacuate both low AND high side of the system.
Capillary tubes require a more precise refrigerant charge.

Operating:
Either will provide near identical performance if engineered correctly.
Both systems are effected by variations in the temperature which they operate in although the TX system is less effected as the valve can modulate to reduce the effect to some degree.

Both systems are less efficient once operating in temperatures outside their engineered parameters. This can be in lower or higher temperatures than what is optimum.

To address the high / low temperature performance issues completely, Ozefridge condensers operate within a controlled temperature range, a range engineered to provide optimum efficiency in all possible environments be it hot or cold. TX valve systems would also benefit from this control method as it is commonly used on most large commercial TX systems.

Blockages:
Both are susceptible to blockage. It is not the TX or capillary that causes a blockage, it is gunk in the system that is not captured by a proper filter dryer.
Spun copper so called filter dryers should be banned IMO as they are strainers at best. Only the proper filter dryers like the Sporlan 030 or 050 also have a felt filter to capture fine particles. Something that is essential with these micro systems.

I hope this ramble on helps, but at the end of the day its half dozen of one and six of the other provided the capillary systems condenser temperature is controlled as it is with Ozefridge.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[OzePete]

Originally Posted by newhaul

I'm after every watt savings I can get . If I can run on the solar and keep 200 ah of Lfp between 75% and 90% I will be a happy camper if it goes much below that I will be looking to shave usages .
The only real power user will be the refer so it needs to be as efficient a system I can get .

Power efficiency! you want Power Efficiency?
Check here at Why Eutectic | Ozefridge (the last article called ECO2, bottom of page )

Cheers, OzePete

[a64pilot]

Not that what I think matters, but Pete’s post is I believe is a very fair and honest comparison of the different orifices, and that is all they are, an orifice, one is adjustable, one is not.

[newhaul]

Originally Posted by OzePete

Power efficiency! you want Power Efficiency?
Check here at Why Eutectic | Ozefridge (the last article called ECO2, bottom of page )

Cheers, OzePete

Pete you don't need to sell eutectic to me. I have installed many systems and for my boats its the only way to go I'm just on the fence as to cap tube or txv I'm running solar and wind.
The biggie is I will be operating from the 65°north or south to the tropics . I refuse to put any more holes in my boat and I only have a 30 gallon potable water tank at the opposite end of the boat from the condenser location. So water cooling is out.

[OzePete]

Originally Posted by newhaul

Pete you don't need to sell eutectic to me. I have installed many systems and for my boats its the only way to go I'm just on the fence as to cap tube or txv I'm running solar and wind.
The biggie is I will be operating from the 65°north or south to the tropics . I refuse to put any more holes in my boat and I only have a 30 gallon potable water tank at the opposite end of the boat from the condenser location. So water cooling is out.

Sorry about rambling on about eutectic, guess I was preaching to the converted!

Yes, I had noted you wanted an air-cooled system, that is why at post 90 I suggested the A480 Ozefridge condensing unit which has a triple pass air-cooled only condenser with twin two speed fans. Provided the condensing unit can be in a reasonably well ventilated area, this air cooled unit is quite adequate even for the tropics as it is only refrigerating one eutectic plate.

Cheers OzePete

[a64pilot]

Very few Eutectic systems actually are. I see Pete’s is, but most are not.
This is a reason why.
A eutectic solution freezes and thaws at the same temp, so we will just say we have a solution that freezes at 10 degrees, once frozen it will stay at 10 degrees for a long time, until it is completely melted, where a thin evaporator plate begins heating up immediately and soon is at the box temp.

However a true eutectic system is tough to have, the reason is what if a 10 degree plate gets the box too cold, or worse doesn’t get it cold enough?
Well you have three options then as I see it, increase the surface area of the plate until you get the box temp you need, usually meaning dual cold plates or maybe just a larger one.
Or you can drain your eutectic fluid and replace it with a fluid that now freezes say at 0 degrees, and of course adjust your thermostat to get the cold plate to zero instead of 10 degrees.

Or you can do what just about everyone does, turn the thermostat down until the cold plate is at 0 degrees and not actually have a true eutectic system, cause if you wait until it melts, then your box temp is higher than you wanted. You still have a large thermal mass, just you don’t get to take advantage of that huge latent heat you get from a phase change.
Now if you can get a true eutectic system, that is the ideal, cause that way you ought to be able to shift your freezing times by different methods to the time when there is excess Solar, or when your motoring etc.
Ideally you could get a system that uses none or almost no battery power, but can store excess Solar that will get it through all or almost all of the night, if you have enough mass in your holding plate and good enough insulation.

You still will have a system that say has an almost 50% duty cycle, just instead of running 30 min out of every hour, it runs for nearly 12 hours straight , then off for 12 hours.
Ideal is less than 50% of course.
Either way, for a boat that gets its power from Solar, you should be able to tremendously reduce the AH you need to get from your battery bank for refrigeration, I’d guess than cutting it in half wouldn’t be too hard, but that is a guess.

On edit, your not necessarily increasing efficiency over a thin plate evaporator, your still going to use say 100 AH in a 24 hour period, just you get to use it when there is an excess and “store” the excess Solar power that is normally wasted in your cold plates.

[OzePete]

Originally Posted by a64pilot

Very few Eutectic systems actually are. I see Pete’s is, but most are not. Thank you Pilot! What a delight to see your comment here and so true. The vast majority of so called Eutectic Systems are not operating through phase change as you say, and so easy to detect... If more than two cycles per day are needed then it most likely is not. I have been bashing my head against a virtual brick wall trying correct incorrect statements from many who claim to understand latent heat / phase change but simply don't!

This is a reason why.
A eutectic solution freezes and thaws at the same temp, so we will just say we have a solution that freezes at 10 degrees, once frozen it will stay at 10 degrees for a long time, until it is completely melted, where a thin evaporator plate begins heating up immediately and soon is at the box temp. Absolutely correct! and what a delight to discuss these issues with someone who understands

However a true eutectic system is tough to have, the reason is what if a 10 degree plate gets the box too cold, or worse doesn’t get it cold enough?
Well you have three options then as I see it, increase the surface area of the plate until you get the box temp you need, usually meaning dual cold plates or maybe just a larger one.
Or you can drain your eutectic fluid and replace it with a fluid that now freezes say at 0 degrees, and of course adjust your thermostat to get the cold plate to zero instead of 10 degrees. We overcome this issue by settling on two phase change 'brews'. One with a phase change at approx -5C for refrigerators and the other at -20C for freezer plates. So we initially set the fridge plate to cut out at -10C with an 8C hysteresis and freezer plates to off at-24C and 8C Hys. Note we are sensing the core of the eutectic mass (Sure-Thaw) so as to enable proper phase change control. If this results in the cabinet needing to be warmer or colder, simply altering the SET point up or down is usually enough with such a wide hysteresis. F

Or you can do what just about everyone does, turn the thermostat down until the cold plate is at 0 degrees and not actually have a true eutectic system, cause if you wait until it melts, then your box temp is higher than you wanted. You still have a large thermal mass, just you don’t get to take advantage of that huge latent heat you get from a phase change. Exactly, to benefit from the phase change the controller must only shut off the compressor after the eutectic mass has frozen then only restart once the mass has mostly thawed.
Now if you can get a true eutectic system, that is the ideal, cause that way you ought to be able to shift your freezing times by different methods to the time when there is excess Solar, or when your motoring etc.
Exactly and that is why every Ozefridge system has ECO2 power management standard. This device monitors voltage presented and 'tricks' the controller into 'On mode when voltage abve 13.6 is detected.
Ideally you could get a system that uses none or almost no battery power, but can store excess Solar that will get it through all or almost all of the night, if you have enough mass in your holding plate and good enough insulation. Absolutely, we have many clients reporting that most of the year there is sufficient refreeze done when power is abundant that no battery power is needed.

You still will have a system that say has an almost 50% duty cycle, just instead of running 30 min out of every hour, it runs for nearly 12 hours straight , then off for 12 hours.We use much more powerful
compressors than others so as to take best advantage of abundant (free!) power All ozefridge systems are rated for far less than 50% duty cycle in 40C ambients
Ideal is less than 50% of course.
Either way, for a boat that gets its power from Solar, you should be able to tremendously reduce the AH you need to get from your battery bank for refrigeration, I’d guess than cutting it in half wouldn’t be too hard, but that is a guess. Absolutely, then there are the other power efficiency benefits of a eutectic system like a better COP factor and far less power wasting start ups per day!

On edit, your not necessarily increasing efficiency over a thin plate evaporator, your still going to use say 100 AH in a 24 hour period, just you get to use it when there is an excess and “store” the excess Solar power that is normally wasted in your cold plates.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[rgleason]

I heartily second this endorsement.

[Neptune's Gear]

Pete, of course, has it right. Phase change is the key. My own ozefridge is now about 8 years old, never been switched off. Keeps ice cream, even in the tropics, right on the equator. Now back in NZ, with the boat at the back door dock, we use it as excess freezer space for the house. The quality of the Ozefridge units, and Pete’s great support, is why I resell these in NZ. Have done for about 5 years, and never regretted it. Great product made by someone who really understands his business. :-)

[Richard Kollmann]

Electrical energy delivered to refrigerator is converted to Btu energy more efficiently in some compressors than others defined as higher Coefficient Of Performance COP. To believe that inside any type evaporator eutectic or thin plate additional energy is created is against the laws of creating or destroying energy. You can store energy in a battery or eutectic plate but you can not create it there as some would like you believe. Pete has confirmed in his own test that his eutectic cycling plate over a thin plate evaporator will save some boaters 1/3 of an amp per hour.

If by now you are not sure which evaporator will result in the refrigerator box temperatures you are looking for either a true eutectic holding plate where compressor runs only once or twice a day, or a cycling compressor eutectic plate, or the many standard sizes of thin plate evaporators you will never have your answer.

Remember the first refrigerator component selected when considering an Icebox conversion refrigeration system is the evaporator as it establishes the various box temperature zones and what type refrigerator you will end up with. Drink cooler evaporator coolers are easy to design while refrigerator two and three temperature zone boxes are more challenging.

Other major component you must select for an icebox conversion refrigerator are the size and configuration of condensing unit which includes the compressor. One of these air cooled small system manufactures recommends their condensing unit should be installed in a large area of at least 100 cu feet. Large compartments avoid heated refrigeration process air from reducing condensing unit’s efficiency. Most popular brands of marine refrigeration condensing units are designed to draw cooler ambient air from one large area and through differential pressure deposit warm process air to another area. Adler Barbour and Isotherm offer duct adapters for condensing units.

The last component that generally is chosen by the system manufacture is the refrigerant flow control device, Capillary tube or TXV or suction pressure regulator. All holdover type eutectic holding plates use the TXV unit with a liquid refrigerant receiver tank to more efficiently control evaporator superheat so that refrigerant completes its heat absorption inside evaporator. Capillary tube designs have always worked well for refrigeration designed to operate at normal standard day temperatures. Cap tube controls do not react to the diminishing or expanding changes of liquid refrigerant volume when temperatures change in mobile refrigeration. Fortunately almost all refrigeration technicians around the world understand maintenance of cap tube and TXV refrigerator system. Low pressure regulator control is not as forgiving as Cap tube or TXV at controlling refrigerant flow.

[john61ct]

Originally Posted by Richard Kollmann

All holdover type eutectic holding plates use the TXV unit

Who else besides Rich's CoolBlue?

[a64pilot]

Originally Posted by OzePete

Capillary tube, the only way to go!

I should add that uniquely the Ozefridge unit operates within a controlled condenser temperature range thus eliminating concerns about varying environment temperatures.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

It would seem Pete’s system is the odd ball operating with hold over plates, but without a TXV?