The Worst pleasure boat refrigeration.

[rslifkin]

For the COP thing, I'm experimenting for this season with a tiny fan blowing across the evaporator in my fridge (Novakool RFU9000, so fridge / freezer combo, 6.6 / 2.5 cf with a BD35 and dual evaporators). There's a 1/2" of added foam insulation on most of the box.

Out of the box, it struggled a little if the cabin got over 85 degrees or so. I improved the fan setup for more airflow over the condenser and added the small evap fan this winter. Previously, until the cabin got over 85, it would keep about 0 - 5* F in the freezer and 37 or so in the fridge with no issues. The evap fan should run the evap at a higher temp, giving a bit better COP and also more total heat extraction capacity.

My only concern (which I'll found out when we launch in ~2 months) is what I'll get for freezer performance with appropriate fridge temps. Worst case, I'll see if I have room to add any more freezer insulation.

[Pete7]

Originally Posted by Uncle Bob

Pete, I have a 40 litre portable that I only use as a freezer and I have found that the travel cover supplied with it made a small improvement in power consumption, then I bought a 10 mm thick high density foam camping mattress roll and cut it into panels that fit snugly inside the travel cover, leaving all vents open of course, it's a bit of a squeeze but works well. Reduced power consumption and run time duration.

Thanks, it's on the to do list We only installed it in the Fall, (Gee, using American words now, been on the forum too long) and only used it whilst staying on board over Christmas. So the bath towel was the only thing handy. I did notice that condensation built up under the towel on the outside of the fridge, suggesting that it was cool and needs a helping hand with extra insulation.

[nilespf]

Originally Posted by GILow

Actually, I am not advocating one system or the other. I have no horse in the race as I don’t sell or service this stuff for a living. All I care about is that the systems are represented accurately without a whole lot of emotive words and expressions with no factual backing.

This whole thread is dotted with silly phrases trotted out in the absence of hard facts. I would have ignored it completely if it were not for the clear invitation for anyone who’d had a good experience of the Ozefridge systems to step forward. I provided not only my positive experience but a couple of simple numbers for comparison, with no idea if those numbers are good or bad. They are good enough for me, but for all I know I may be using twice as much power as another system of the same size and function.

Those numbers have been ignored and instead a bunch of banal phrases and hackneyed adages have been trotted out to try to imply that there is something fundamentally wrong with a system that works perfectly.

This thread feels like a bit of gaslighting disguised as a real discussion, and with the leading questions in the opening post I am not surprised.

It’s a pity, because it was a good idea to collect the bad experiences as a way of helping others avoid the same pitfalls.

Amen to what you just stated, I know I have been shouted at but for me the bottom line is DC. Give me the DC and AH consumed over a period of time that is all that is needed. If the system will keep ice cream frozen (if you cannot keep ice cream frozen then it is not operating properly IMHO) and some consideration to operational environment (tropics vs up North). My power budget tells me what the maximum AH's can be, the Admiral tells me the size and that's it. Much of the discussions seem to banter about all the different ways to improve or enhance systems but no actual data that is given in terms of DC and AH's consumed. For the purist among us DC is not even needed if a user can state the system will not be on at night and one only needs to worry about recharging the plates/tanks or what ever you want to call them. If you do not mention that then DC helps to determine depth of discharge during the night. I can tell you that any system that has a DC of <28% AND can freeze ice cream ( yea that ice cream again) AND has a AHr consumption of 50 gets my attention. Now if that system happens to be eutectic so be it. That is one data point among a lot (according to this thread) of happy users. Take a couple of measurements and tell us about what we can expect. I can assure you a bell curve will form for each type of system. We'll know if we exist too far out then we have a problem.


Pn

[GILow]

Originally Posted by nilespf

Amen to what you just stated, I know I have been shouted at but for me the bottom line is DC. Give me the DC and AH consumed over a period of time that is all that is needed. If the system will keep ice cream frozen (if you cannot keep ice cream frozen then it is not operating properly IMHO) and some consideration to operational environment (tropics vs up North). My power budget tells me what the maximum AH's can be, the Admiral tells me the size and that's it. Much of the discussions seem to banter about all the different ways to improve or enhance systems but no actual data that is given in terms of DC and AH's consumed. For the purist among us DC is not even needed if a user can state the system will not be on at night and one only needs to worry about recharging the plates/tanks or what ever you want to call them. If you do not mention that then DC helps to determine depth of discharge during the night. I can tell you that any system that has a DC of <28% AND can freeze ice cream ( yea that ice cream again) AND has a AHr consumption of 50 gets my attention. Now if that system happens to be eutectic so be it. That is one data point among a lot (according to this thread) of happy users. Take a couple of measurements and tell us about what we can expect. I can assure you a bell curve will form for each type of system. We'll know if we exist too far out then we have a problem.


Pn

Well, I haven’t done the ice cream test yet. I’ll just have to buy some and report back. :^)

[GILow]

Originally Posted by nilespf

Amen to what you just stated, I know I have been shouted at but for me the bottom line is DC. Give me the DC and AH consumed over a period of time that is all that is needed. If the system will keep ice cream frozen (if you cannot keep ice cream frozen then it is not operating properly IMHO) and some consideration to operational environment (tropics vs up North). My power budget tells me what the maximum AH's can be, the Admiral tells me the size and that's it. Much of the discussions seem to banter about all the different ways to improve or enhance systems but no actual data that is given in terms of DC and AH's consumed. For the purist among us DC is not even needed if a user can state the system will not be on at night and one only needs to worry about recharging the plates/tanks or what ever you want to call them. If you do not mention that then DC helps to determine depth of discharge during the night. I can tell you that any system that has a DC of less than 28% AND can freeze ice cream ( yea that ice cream again) AND has a AHr consumption of 50 gets my attention. Now if that system happens to be eutectic so be it. That is one data point among a lot (according to this thread) of happy users. Take a couple of measurements and tell us about what we can expect. I can assure you a bell curve will form for each type of system. We'll know if we exist too far out then we have a problem.


Pn

Just checking a theory. The “less than” symbol in a post seems to mess up the app on the iPad.

[a64pilot]

Originally Posted by rslifkin

For the COP thing, I'm experimenting for this season with a tiny fan blowing across the evaporator in my fridge (Novakool RFU9000, so fridge / freezer combo, 6.6 / 2.5 cf with a BD35 and dual evaporators). There's a 1/2" of added foam insulation on most of the box.

Out of the box, it struggled a little if the cabin got over 85 degrees or so. I improved the fan setup for more airflow over the condenser and added the small evap fan this winter. Previously, until the cabin got over 85, it would keep about 0 - 5* F in the freezer and 37 or so in the fridge with no issues. The evap fan should run the evap at a higher temp, giving a bit better COP and also more total heat extraction capacity.

My only concern (which I'll found out when we launch in ~2 months) is what I'll get for freezer performance with appropriate fridge temps. Worst case, I'll see if I have room to add any more freezer insulation.

I believe most end up with positive Fahrenheit numbers in their fridges on boat ice box conversions, say plus 10 or so. I can drive mine to slight neg numbers, but it’s pretty much a 100% duty cycle to get and stay there.

[ayates]

I ran numerous tests with a NovaKool RFU9000 fridge/freezer; 9.1 cu ft of which 2.5 cu ft was freezer. Normal thin evaporator plates.

This was the "best" scenario where the fridge did not freeze, but got a low as possible. Ambient temperature was 20C. The fridge was loaded with 4 litres of water at room temperature (20C). Power consumption was ~ 50 AH/24 hour period.

I could get a much faster cool down with a fan on the evaporator, the compressor would run continuously during that time, but the fridge would settle below freezing.


Allan.

[nilespf]

Originally Posted by ayates

I ran numerous tests with a NovaKool RFU9000 fridge/freezer; 9.1 cu ft of which 2.5 cu ft was freezer. Normal thin evaporator plates.

This was the "best" scenario where the fridge did not freeze, but got a low as possible. Ambient temperature was 20C. The fridge was loaded with 4 litres of water at room temperature (20C). Power consumption was ~ 50 AH/24 hour period.

I could get a much faster cool down with a fan on the evaporator, the compressor would run continuously during that time, but the fridge would settle below freezing.


Allan.

Interesting wave forms, do you know if the compressor is controlled by a thermostat, or processor.


Pn

[Q Xopa]

Originally Posted by nilespf

Amen to what you just stated, I know I have been shouted at but for me the bottom line is DC. Give me the DC and AH consumed over a period of time that is all that is needed. If the system will keep ice cream frozen (if you cannot keep ice cream frozen then it is not operating properly IMHO) and some consideration to operational environment (tropics vs up North). My power budget tells me what the maximum AH's can be, the Admiral tells me the size and that's it. Much of the discussions seem to banter about all the different ways to improve or enhance systems but no actual data that is given in terms of DC and AH's consumed. For the purist among us DC is not even needed if a user can state the system will not be on at night and one only needs to worry about recharging the plates/tanks or what ever you want to call them. If you do not mention that then DC helps to determine depth of discharge during the night. I can tell you that any system that has a DC of <28% AND can freeze ice cream ( yea that ice cream again) AND has a AHr consumption of 50 gets my attention. Now if that system happens to be eutectic so be it. That is one data point among a lot (according to this thread) of happy users. Take a couple of measurements and tell us about what we can expect. I can assure you a bell curve will form for each type of system. We'll know if we exist too far out then we have a problem.


Pn

DC AHs over a given period. Evaporator may, or may not be more efficient. I don't know as there seems to be conflicting opinions. I suspect there isn't much in it.

To me it's of little overall relevance.

I have a portable Engel and an installed Cool Blue cold plate unit. So I guess I have an each way bet.

These are different sizes and one is portable the other fixed with different insulation etc. So I can't make any apples to apples comparisons.

What I do like about Cold plates is that whether or not they consume more or less AHs than a comparable evaporator unit I really couldnt say.

It doesn't use them from the battery for half the time. This is the boon for me.

So they possibly? are less efficient, but they use otherwise wasted AHs. To me it's a 'making hay while the sun shines' deal. Of course it's not just sun, the concept works equally as well running the motor. Better than drawing so much from my battery overnight IMHO.

[ayates]

Originally Posted by nilespf

Interesting wave forms, do you know if the compressor is controlled by a thermostat, or processor.

This was with an OEM thermostat connected directly to the compressor controller.


Allan.

[nilespf]

Originally Posted by Q Xopa

DC AHs over a given period. Evaporator may, or may not be more efficient. I don't know as there seems to be conflicting opinions. I suspect there isn't much in it.

To me it's of little overall relevance.

I have a portable Engel and an installed Cool Blue cold plate unit. So I guess I have an each way bet.

These are different sizes and one is portable the other fixed with different insulation etc. So I can't make any apples to apples comparisons.

What I do like about Cold plates is that whether or not they consume more or less AHs than a comparable evaporator unit I really couldnt say.

It doesn't use them from the battery for half the time. This is the boon for me.

So they possibly? are less efficient, but they use otherwise wasted AHs. To me it's a 'making hay while the sun shines' deal. Of course it's not just sun, the concept works equally as well running the motor. Better than drawing so much from my battery overnight IMHO.

My box used to be 65% DC. If I started the evening hours with anything less than topped off batteries I had to turn off the reefer before retiring for the evening. After improvements to seals, a more sophisticated temp control system and an additional battery I can make it through the night. For me AH usage is everything because I use an evap plate. I can't count on any flywheel effect during the non solar times. Now the technology is irrelevant but only because improvements have yielded a lower DC and my battery bank has been increased. Current draw is identical.
Pn

[nilespf]

Originally Posted by ayates

This was with an OEM thermostat connected directly to the compressor controller.


Allan.

So is the top waveform some kind of test point you selected for indication of compressor operation? I suspect it is mapped to the time axis? The saw tooth behavior of the fridge and freezer test probes is interesting. It seems as if the freezer operates on temp demand (the fridge is along for the ride). If the delta between actual and desired is high it keeps the compressor running continuously but when inside of a range it switches over to a fixed rapid behavior??????. Hmm but it never stops, interesting.



Pn

[rslifkin]

On my Novakool RFU9000, the thermostat cycles on fridge evap temp. The freezer is along for the ride (with a significantly bigger evap than the fridge). That's why I'm concerned I may see higher freezer temps with an evap fan in the fridge (fridge evap will be warmer for a given fridge box temp, so t-stat set warmer to maintain, meaning freezer may be warmer).

[ayates]

Originally Posted by rslifkin

On my Novakool RFU9000, the thermostat cycles on fridge evap temp. The freezer is along for the ride (with a significantly bigger evap than the fridge). That's why I'm concerned I may see higher freezer temps with an evap fan in the fridge (fridge evap will be warmer for a given fridge box temp, so t-stat set warmer to maintain, meaning freezer may be warmer).

This is exactly what happens. With a fan on the evaporator in the fridge, the thermostat needs to be turned to warmer setting to prevent the fridge temperature from going below freezing. And the resulting freezer temperature is only just below freezing. In the attached graphs, the "OEM #2" line, is the setting on the OEM thermostat.


Allan.

[ayates]

Originally Posted by nilespf

So is the top waveform some kind of test point you selected for indication of compressor operation? I suspect it is mapped to the time axis? The saw tooth behavior of the fridge and freezer test probes is interesting. It seems as if the freezer operates on temp demand (the fridge is along for the ride). If the delta between actual and desired is high it keeps the compressor running continuously but when inside of a range it switches over to a fixed rapid behavior??????. Hmm but it never stops, interesting.

The OEM thermostat is on the fridge evaporator, and the freezer is along for the ride.

The top wave form is the current drawn by the compressor, against the secondary Y axis. The other two wave forms are the fridge and freezer temperatures, against the primary Y axis. All three wave forms are synced to the time azis.

Basically the thermostat continuously cycles the compressor, even when the temperature of the fridge is way too high. As soon as the evaporator gets cold, the compressor is turned off until the evaporator absorbs heat from the fridge. As it has little thermal mass, it doesn't take long to warm up. The duty cycle decreases as the fridge cools.


Alan.