Danfoss AEO controller

[SV THIRD DAY]

Originally Posted by a64pilot

Nothing I can find can explain my tremendous drop in amperage as the fridge gets close to set point, there is no data to support 60 watts draw at 4400 RPM,

I’m not complaining about cooling a 14 cu ft spillover on so little power, just trying to understand how.

You're not finding anything cuz you're looking in the wrong place it has nothing to do with the controller it's all about the TXV. It's injecting more refrigerant and asking the compressor to do more work at startup with a warm plate and it's injecting less refrigerant as you approach the temperature set point thereby asking the compressor to do less work.

[SV THIRD DAY]

Originally Posted by a64pilot

It sounds like just to me that this fridge controller and an AEO module is for a thin plate evaporator and not so much a hold over plate?

Yep....apples and oranges.

[SV THIRD DAY]

Im confuzed....
If you want to dead balls accurately track the refrigeration power usage....do what I do and install a dedicated link 10 lite Amp & Amp Hour meter on the power lead to the compressor. Bingo, data flowing with no guesswork.

[Richard Kollmann]

Quote:
Originally Posted by a64pilot View Post
Another thing I’m wondering, is once the plates are cooled down close to set point, maybe reducing compressor RPM to match load may be beneficial to power consumption and compressor life?

You are correct reducing compressor speed improves the compressor's Volumetric efficiency generally expressed in COP. Randy of Technautics set new energy savings records with the Cool Blue holding plate refrigeration by running Danfoss BD35 compressor at minimum speed. Of course there is a limit to the size and heat load on refrigerated box when operating at minimum speed.

[Richard Kollmann]

Sorry Richard, but the actual compressor origin is commercial and quite frankly none of your business!

Pete, What more do I need to explain. I contribute to this industry with free assistance and respect all boat refrigeration manufactures and boat owners. I can only say good luck with your unusual business plan.

[a64pilot]

Originally Posted by SV THIRD DAY

Im confuzed....
If you want to dead balls accurately track the refrigeration power usage....do what I do and install a dedicated link 10 lite Amp & Amp Hour meter on the power lead to the compressor. Bingo, data flowing with no guesswork.

Not really trying to track consumption, not really. I can get close enough on that with my amp counter, system is about as efficient as it can be I think, However it would be nice if I could automatically “turn it up and drop the set point” during times of excess power, and let it coast on thawing the plates overnight, I think with my dual plates maybe I could actually use almost zero energy from my bank, most days. I wasn’t trying to increase efficiency, I was trying to shift compressor run times.

I’m trying to understand the compressor system better is all.

I bought a “system” that upon reading the literature sounds logical, really seemed to be an intelligent way to manage a refrigeration system.
However after using it for only a very short time, have bumped into reality and theory don’t match up, it made assumptions that I believe are just not the case in the majority of Marine refrigeration systems. That got me wondering at what was causing the huge swings in power consumption I was seeing from initial cool down of the system to when it was running in equilibrium. It seems to automatically use more power when it was needed, but less when it wasn’t. Secop data seems to indicate that power consumption is flat based on evaporator temp and compressor RPM, so I got to thinking maybe my controller is an AEO controller, the huge drop in power draw that corresponded with demand, could be explained by an AEO controller slowing down the compressor. Sounded logical and the Secop data sheet seemed to indicate it was indeed an AEO controller.

Now John calling the TXV a cruise control I understand, actually I understand the functioning of a TXV better than you may think, but I didn’t think it could account for a 300% reduction in power consumption, that is huge.

So after having a good look at this “system” I have purchased, it’s essentially useless from what I can tell on likely any hold over system.
Further after really digging into its operating theory, while there are good reasons for why it does what it does, it makes it even less useful in any system with extended cycle times.
Gives you a pretty screen to look at though, but even the data on the screen is incorrect, cause it is calculated on the Secop data sheet on power consumption, and apparently the TXV changes that, drastically.

However as I see it, it’s designed for a small thin plate evaporator refrigeration, not freezer, and may well be the ticket there, just is not applicable to a hold over system.


As I have said from the beginning, I am not complaining about being able to run a BD80 dual hold over plate system cooling a 14cu ft half freezer, half fridge on a 5 amp draw, actually was trying to figure out how you could run such a large and poorly insulated system on only 5 amps if you really want to know, it seems to be way more efficient than possible, I was prepared and expected it to consume at least twice the power it does.

TXV must be how, if the controller is not dialing down the compressor RPM.

However I was trying to find out the theory of operation of an AEO, since I couldn’t find out squat on the Internet.
I understand the flexibility of a variable speed compressor as long as the system manufacturer can select compressor speeds, it allows them to more closely match speed to demand and allow fewer sizes of compressor to be manufactured if you can fine tune output, but that brought up further questions. Would a larger compressor running slower be more efficient than a smaller one running faster, BTU of both being the same, but maybe it’s not much more efficient, my gut thinks it would be though.

However what I think of as graduate level of thinking would be a truly self adjusting variable speed compressor one that could match output to demand and essentially run at low RPM continuously, but at low power consumption. That seemed to be what I was seeing in my system as it was delivered, without any “systems” added to it.

Seemingly that can be done manually with a TXV

My house heat pumps each had two compressors, whenever set point was more than two degrees off of actual temp, the small compressor turned off and the big one kicked in, dropped the temp to set point and then reverted back to the little compressor, which on hot days, ran continuously, but extremely efficiently as it had way oversized evaporator and condenser and of course really did well dehumidifying.
A true variable speed compressor could operate in a similar principle, I think.


Perhaps a simple 12V timer is what I want, adjust the on and off times to correspond to daylight and acceptable temps swings, or just leave it alone

[Richard Kollmann]

Originally Posted by a64pilot

Not really trying to track consumption, not really. I can get close enough on that with my amp counter, system is about as efficient as it can be I think, However it would be nice if I could automatically “turn it up and drop the set point” during times of excess power, and let it coast on thawing the plates overnight, I think with my dual plates maybe I could actually use almost zero energy from my bank, most days. I wasn’t trying to increase efficiency, I was trying to shift compressor run times.

I’m trying to understand the compressor system better is all.

I bought a “system” that upon reading the literature sounds logical, really seemed to be an intelligent way to manage a refrigeration system.
However after using it for only a very short time, have bumped into reality and theory don’t match up, it made assumptions that I believe are just not the case in the majority of Marine refrigeration systems. That got me wondering at what was causing the huge swings in power consumption I was seeing from initial cool down of the system to when it was running in equilibrium. It seems to automatically use more power when it was needed, but less when it wasn’t. Secop data seems to indicate that power consumption is flat based on evaporator temp and compressor RPM, so I got to thinking maybe my controller is an AEO controller, the huge drop in power draw that corresponded with demand, could be explained by an AEO controller slowing down the compressor. Sounded logical and the Secop data sheet seemed to indicate it was indeed an AEO controller.

Now John calling the TXV a cruise control I understand, actually I understand the functioning of a TXV better than you may think, but I didn’t think it could account for a 300% reduction in power consumption, that is huge.

So after having a good look at this “system” I have purchased, it’s essentially useless from what I can tell on likely any hold over system.
Further after really digging into its operating theory, while there are good reasons for why it does what it does, it makes it even less useful in any system with extended cycle times.
Gives you a pretty screen to look at though, but even the data on the screen is incorrect, cause it is calculated on the Secop data sheet on power consumption, and apparently the TXV changes that, drastically.

However as I see it, it’s designed for a small thin plate evaporator refrigeration, not freezer, and may well be the ticket there, just is not applicable to a hold over system.


As I have said from the beginning, I am not complaining about being able to run a BD80 dual hold over plate system cooling a 14cu ft half freezer, half fridge on a 5 amp draw, actually was trying to figure out how you could run such a large and poorly insulated system on only 5 amps if you really want to know, it seems to be way more efficient than possible, I was prepared and expected it to consume at least twice the power it does.

TXV must be how, if the controller is not dialing down the compressor RPM.

However I was trying to find out the theory of operation of an AEO, since I couldn’t find out squat on the Internet.
I understand the flexibility of a variable speed compressor as long as the system manufacturer can select compressor speeds, it allows them to more closely match speed to demand and allow fewer sizes of compressor to be manufactured if you can fine tune output, but that brought up further questions. Would a larger compressor running slower be more efficient than a smaller one running faster, BTU of both being the same, but maybe it’s not much more efficient, my gut thinks it would be though.

However what I think of as graduate level of thinking would be a truly self adjusting variable speed compressor one that could match output to demand and essentially run at low RPM continuously, but at low power consumption. That seemed to be what I was seeing in my system as it was delivered, without any “systems” added to it.

Seemingly that can be done manually with a TXV

My house heat pumps each had two compressors, whenever set point was more than two degrees off of actual temp, the small compressor turned off and the big one kicked in, dropped the temp to set point and then reverted back to the little compressor, which on hot days, ran continuously, but extremely efficiently as it had way oversized evaporator and condenser and of course really did well dehumidifying.
A true variable speed compressor could operate in a similar principle, I think.


Perhaps a simple 12V timer is what I want, adjust the on and off times to correspond to daylight and acceptable temps swings, or just leave it alone

If you are seriously interested in true and factual performance analysis or your system get a small temperature Data logger with computer soft wear and place it in refrigerated box or on holding plate for at least a week. When Logger is set to take readings every five minutes mine will take 8,000 temperature readings. When connected to a computer the complete story is displayed graphically, Compressor start times, box temperatures, visual changes in compressor speed change, and holdover box temperatures when compressor if not running. When matching this information with your Amp-hr meter for the same period you will be able to answer all your own questions about best performance for your refrigeration system.

I mailed my data logger out to boaters in the states many times testing systems and insulation. The logger was also used on over 100 test box comparisons along with a Link E amp-hr meter.

[a64pilot]

I’m curious, but not that curious.
I think I have a handle on what is going on, it’s the TXV unloading the compressor, must be, cause I don’t think it’s changing speed, but I do get a rather large variance in current, making anything that uses a set value in an attempt to calculate AH usage, essentially worthless.

[Richard Kollmann]

Originally Posted by a64pilot

I’m curious, but not that curious.
I think I have a handle on what is going on, it’s the TXV unloading the compressor, must be, cause I don’t think it’s changing speed, but I do get a rather large variance in current, making anything that uses a set value in an attempt to calculate AH usage, essentially worthless.

It is too bad that others do not follow your lead and recognize that when something is in satisfactory state and there is no reason to change it why add an additional reliability risk gadgets. The simpler one of these mobile refrigeration systems are the more dependable they are. The smart thing to do is purchase reliability and save money.

[Stu Jackson]

Originally Posted by a64pilot

>>>>>>>>>>>>>but I do get a rather large variance in current, making anything that uses a set value in an attempt to calculate AH usage, essentially worthless.

I've enjoyed reading this thread and learning, thanks.


But, but, but...a64, you for sure know there are two variables: load and time. In all my energy budgets (anchored, daysail and offshore) even if the loads are known the hours are estimates, too. I know you know this, and that you have a batt mon. I've done energy budgets and then when I installed my Link 2000, simply "proved" my estimates.


My Record of Daily Energy Use of 100 ah per day:

"Breaking In" New Wet Cell Batteries


Interesting material about the fridges.

[a64pilot]

Stu, it’s in theory a lot more complex than that.
This gadget promised a couple of very interesting possibilities. First it would run in “boost” mode whenever a user adjustable voltage set point was exceeded, meaning of course when your panels were making more power than your bank could accept this unit would change the resistance to the thermostat pins on your controller kicking it into high speed.
It would also if you chose lower the temp set point, so you would both increase the output of the fridge and lower the temp with “free” energy, energy that would otherwise be wasted.
Couple that with the flywheel effect if you will of the cold plates and I thought it may well be logical that my fridge could sit overnight at a higher temp set point and slowly warm overnight, but when it hit the higher set point, of course come on and maintain temp.
It ought to significantly reduce power required from my bank. It’s not increasing efficiency, if anything it’s less efficient, but it would be shifting the cooling to the period when I had excess power anyway.
Sounds great in theory, but in practice there were a few problems.
1. If I had done my homework or even really thought about it much, I would have realized my system was already in “boost”mode, and it couldn’t have been sped up.
2. The system works by looking at set points only when the compressor is powered on, it does this for a logical reason, if for example you program it so that you consider charge to be 14 volts, you hit 14 volts with the compressor off, then it comes on and voltage drops due to load, so set point increases, compressor turns off, voltage increases, compressor cycles on, your in a loop. So to prevent this the system only looks at new settings when the compressor is first powered on. The downside of this is a cold plate has extended runs, mine are many hours long, so the timing of when the compressor should be cooling to lower temps wasn’t going to be correct, it is as likely to not cycle back on until afternoon, get a lower set point and then run all night trying to achieve the lower set point.
So it in effect can easily do just the opposite of what it is attempting to do, that is it can easily increase consumption.

Couple that with it’s supposed to tell you how many AH you use, but as I found out power usage if you have a TXV is widely variable, so that their number is most often way off, for instance the number they use for “boost” which is normal ops for my system, and I suspect most cold plates, is 168 Watts, the number Danfoss quotes, so they used a good valid number, but it’s just not even close for a TXV system, mine pulls about 65 Watts on average, or 1/3 the number.

If you could find a thin plate system that normally ran the compressor at its lowest speed, then I think you have found the machine that this gadget is meant for and would work well with, and a fridge, not a freezer or a spill over.
Just it can’t operate as intended with a TXV cold plate system, it’s just the wrong tool for the job.
The people who made it are well intentioned, return emails and will bend over backward to try to help you, just it’s the wrong tool for a TXV cold plate system, in my opinion.

I think now I have one of two choices.
1. Leave the fridge alone, run it as it was designed, it is actually a Marvel in efficiency and seems to be simple and rock solid. It’s KISS.
2. Put it on a simple timer and have it automatically turn off during the night and back on during the day, thats cheap and pretty KISS.
I can’t be trusted to do it myself, I will forget.

[a64pilot]

I’m convinced that the only real way you will ever really drill down and know exactly what it happening is do do as John suggested.
However I’m interested, intrigued, but not that much, I’m not spending the $$ to find out.
See I’m sitting at a dock waiting for Hurricane season to begin and end, so I’m bored, and coming up with projects.

[Stu Jackson]

Originally Posted by a64pilot

>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

See I’m sitting at a dock waiting for Hurricane season to begin and end, so I’m bored, and coming up with projects.

HAHAHAHAHAHA


I really enjoyed and fully understood your #26, very well written. It was a good summary.


An indirect way of saying what I meant and why I linked to that photo of my Link 2000 may have been in the text. Once you do a BUDGET, the sure way of confirming that budget is to measure actual use. That's what I did there.


My stuff was pretty "static." In your case, you were thinking "How can I improve efficiency" given your coolant/fridge system compounded by the cold plate vs. thin evaporator systems most of the rest of us peons have. I understand.


Now that you've knuckled under to reality [I do like the timer idea though, betcha you can get one that resets itself daily...], could you please explain to us what the next complicated "Brain Spurt" is going to be while you're waitin' out dem hurricanes?

[a64pilot]

I don’t want a power budget, and I do understand what you meant, you mean track useage, a budget is a limit, we are on a financial budget for example, cause I can’t realistically increase earnings, we are Retired.
I can’t really decrease power consumption either without doing without things we want to have, however I was trying to take advantage of what is normally just wasted power. More of an experiment than a need actually, but the less you cycle a bank, the better, right?
Yes, I know likely the best way to do that is by going to a Life-PO bank, but I’m not ready for that yet, I keep waiting for that to not be a science experiment.
I doubt just in boats that there is enough sales to justify a complete real drop in solution, but maybe with these tiny houses popping up and with RV’s there may be enough business to justify it.
The tiny house thing has me confused to be honest, you can buy so much more for less in a mobile home or RV.

[OzePete]

Originally Posted by a64pilot

I don’t want a power budget, and I do understand what you meant, you mean track useage, a budget is a limit, we are on a financial budget for example, cause I can’t realistically increase earnings, we are Retired.
I can’t really decrease power consumption either without doing without things we want to have, however I was trying to take advantage of what is normally just wasted power. More of an experiment than a need actually, but the less you cycle a bank, the better, right?
Yes, I know likely the best way to do that is by going to a Life-PO bank, but I’m not ready for that yet, I keep waiting for that to not be a science experiment.
I doubt just in boats that there is enough sales to justify a complete real drop in solution, but maybe with these tiny houses popping up and with RV’s there may be enough business to justify it.
The tiny house thing has me confused to be honest, you can buy so much more for less in a mobile home or RV.

Hi, in response to your fridge / freezer issues.

At 14 Cubic foot (340 Litres, half fridge half freezer) your asking far too much of the system but I think you know that, as I recall you mentioning that Rich had advised you to use two systems which would have been ideal.

Also being under sized your system is not operating as a eutectic system.
A eutectic system needs to freeze the eutectic mass solid on a run cycle then remain off until the eutectic mass thaws before starting another cycle. (Phase change) This can only occur if temperature of the thermal mass controls the system run /off cycles. This ensures that the benefits of the eutectic system are actually delivered with each cycle.
Your reported 80% duty cycle indicates that because the system is way undersized, it is operating with efficiency only a little better than a cyclic system.

Before supplying systems we, like Rich from 'Cold Blue', do a heat load and power estimate. (See below)
I took the liberty of running your cabinet through our Heat load, Duty cycle & Power estimator (Guessed dimensions but to match your quoted capacity) and the results are very much as you are finding. This would suggest that your insulation is most likely ok and that your system is working as well as can be expected!.

If you look at the figures, add the fridge and freezer data (highlighted) then halve for an outcome for your combination cabinet, otherwise they separately relate to the whole cabinet operating as either a fridge or as a freezer.

Click on chart to read.




We are only too happy to run the numbers through our estimator and email the results back back should any member wish to have the heat load and consumption estimated for their cabinet or future project. Simply send a response to questions in the top panel (As seen in red)

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems