New Isotherm energy use testing results

[booster]

I have never gotten around to looking at this stuff carefully. Am I correct that if @Michael added the ability to control the compressor speed to his awesome project, he could do pretty much anything he wanted wrt efficiency/cooling tradeoffs?

The less ambitious of us could use a tiny microprocessor--just enough to flip the speed inputs, measure temperatures, and maybe a little display. It would essentially be an Isotherm that could be made to work exactly to one's taste.

Is this in any way harder than it looks?

To a large extent yes.


For @Michael, controlling compressor speed probably would allow him to do some things to improve the temp control and energy use, although the major issue on his appears to be the ventilation. By slowing down the compressor to lowest practical speed possible, the heat load to clear in the cavity above the frig would be a lower amount per minute spread out over a longer time, so could probably use less fans at lower speeds, but on longer. The probably would decrease power use numbers to some degree. In a discussion quite a while ago I showed the Danfoss literature that had the power use per power used numbers at different speeds for the compressor and also the very large gains that can be had by raising the evaporator temp if you can do so without being unhappy with warmer freezer temps. I looked at some pix online of the setup in the crossfit and it does have an upper vent to the inside, but it is smallish for sure. I could not tell how they have the fresh air going in, but in many cases that can be a major issue. If it is an issue it looked like it might be possible to open an extra opening into the rear under seat area that already has one vent to the inside of the van (electronics?) to get more air with less resistance to the flow. We also don't know what the back of the frig is shaped like and where the coils and compressor are, but the frig is tall, so a close fitting chimney to force all air to go over the coils and also gain velocity from the chimney effect might help.


Actually, we are doing similar to what you describe but without the microprocessor with a 6 position speed switch the runs different resistors to control the speeds, and on/off switch for main power to kill all power including the light so we can keep the door open when not in use, and a wireless thermometer. The problem with such a system is that it tells you very little about actually energy use as the running amps are certainly going to be lower at lower speeds, but run times go up so you can't relate directly to power use even with a time accumulator because of startup amp variations. Our system, or the microprocessor, would require a totalizer to be able to run controlled, multihour, test runs to know the real benefit. Once you do those tests you don't need the totalizer any more for the most part, from what we have seen. I used a Wattsup in the frig power line to do the totalizing testing.


And yes, with some testing and trial and error, I think nearly all the setups could be made to run on less energy. Really 3 things are big influences.


* Ventilation and if fans, both inside and outside cost you power or save you power, once you get to adequate cooling levels


* Compressor speeds for best efficiency and adequate cooling


* Evaporator and freezer temps to get decent freezing with the warmest running evaporator



Our tests got our frig to run at 265whr/day vs the 380wh/day that Isotherm rates the frig at, so not small gains. Our frig ran at the 380wh/day on the ITC when we got it.


Our original frig, when first installed with poor ventilation and totally stock, ran at nearly 500wh/day.

 

[avanti]

The problem with such a system is that it tells you very little about actually energy use as the running amps are certainly going to be lower at lower speeds, but run times go up so you can't relate directly to power use even with a time accumulator because of startup amp variations. Our system, or the microprocessor, would require a totalizer to be able to run controlled, multihour, test runs to know the real benefit.

Easy enough to continuously monitor current draw. I am picturing a little display with maybe five numbers: fridge temp, freezer temp, instantaneous current, cumulative power, and duty cycle.

Hmm. Another project to add to my ever-lengthening ESP-32 project list.

 

[booster]

Easy enough to continuously monitor current draw. I am picturing a little display with maybe five numbers: fridge temp, freezer temp, instantaneous current, cumulative power, and duty cycle.

Hmm. Another project to add to my ever-lengthening ESP-32 project list.

That would certainly tell you pretty much all you would need to know, but still would need to get a way to vary the compressor speed. Easiest would a 0-1.5K potentiometer as it would only be a couple connections. For traveling I prefer the fixed, so repeatable, settings but a pot for setup would be nice. Just remember what percent it was at for the settings you liked and then take it off and measure the resistance at those points and make the fixed setting on the way you would want it.


It does sound like a good project. I was kind of under the gun because ours had failed and needed to be replaced, but luckily a lot of the stuff was the same so I just copied it. Would have been done much sooner if I knew how bad the ITC would be.

 

[avanti]

still would need to get a way to vary the compressor speed. Easiest would a 0-1.5K potentiometer as it would only be a couple connections.

Easy enough to have the board control a digital pot, which would be repeatable. Maybe directly feeding a voltage from a D-to-A would work, depending on the voltage being fed to the resistor. I'll have to take a look.

This would be a nice little open-source project. Pretty straightforward.

 

[GeorgeRad]

We stay about 2 weeks in very quiet campgrounds in Olympus and Mount Rainer national parks. The refrigerator was extremely quiet, one reason was no mechanical clicking during starts (the result of the SEC electronic controller), quiet fan and perhaps compressor’s low RPM. Fridge was always cold and we only touched 80% SOC one morning (low SOC in the evening, about 2 hrs. 100W projector, D2/5 heating). Difficult to judge fridge energy drain among other drains from the Hydronic D5 for 15 min. a few times a day, the Airtronics D2 as needed and the projector.

I am at the point that 3 gauges are sufficient during camping, SOC, very accessible for viewing voltmeter +/- 1% BS-1733 and ambient temperature. While driving I monitor house batteries charging current.

 

[booster]

We stay about 2 weeks in very quiet campgrounds in Olympus and Mount Rainer national parks. The refrigerator was extremely quiet, one reason was no mechanical clicking during starts (the result of the SEC electronic controller), quiet fan and perhaps compressor’s low RPM. Fridge was always cold and we only touched 80% SOC one morning (low SOC in the evening, about 2 hrs. 100W projector, D2/5 heating). Difficult to judge fridge energy drain among other drains from the Hydronic D5 for 15 min. a few times a day, the Airtronics D2 as needed and the projector.

I am at the point that 3 gauges are sufficient during camping, SOC, very accessible for viewing voltmeter +/- 1% BS-1733 and ambient temperature. While driving I monitor house batteries charging current.

In the real world, yep, if the beer is cold and batteries not dead in near worst case, not big issue. We have way more battery and charging that we need for all we do. We could go a week with no no charging at all including no solar without much issue. I have always been an optimizer of things, both in my 50 years of work and at home, so making stuff as good as it can be is just kind of the normal, right, thing for me to do. Having everything running smoothly is very nice to have on a trip, and the knowledge of how the old frig reacted to things let us ding and tweak it enough to not ruin the trip by nursing it through nearly two weeks of semi normal use after it went bad.



Hopefully, all we learn in this stuff can help those that can't get the beer cold or they kill a smaller battery bank too easily, as we were there a long time ago and it isn't pleasant.

 

[@Michael]

IAm I correct that if @Michael added the ability to control the compressor speed to his awesome project, he could do pretty much anything he wanted wrt efficiency/cooling tradeoffs?

The less ambitious of us could use a tiny microprocessor--just enough to flip the speed inputs, measure temperatures, and maybe a little display. It would essentially be an Isotherm that could be made to work exactly to one's taste.

My fridge has a Secop 101N510 compressor controller, for which there are lots of technical docs, including how to connect to their 'One Wire' (Modbus??) interface on pins D/I and C. Presumably one could either use resistors or the One Wire interface to control compressor speed. Start at most efficient speed, wait 5 min, if temp not decreasing, speed up compressor.

For @Michael, controlling compressor speed probably would allow him to do some things to improve the temp control and energy use, although the major issue on his appears to be the ventilation.

[...]

I looked at some pix online of the setup in the crossfit and it does have an upper vent to the inside, but it is smallish for sure. I could not tell how they have the fresh air going in, but in many cases that can be a major issue.

[...]

We also don't know what the back of the frig is shaped like and where the coils and compressor are, but the frig is tall, so a close fitting chimney to force all air to go over the coils and also gain velocity from the chimney effect might help.

I re-did the insulation behind the fridge to create an insulated, sealed chimney and opened up both bottom and top vents more than what comes from the factory. The chimney effect works most of the time, but not when the sun is hitting the roof. Hence the fans.

Here's an early version of my 'chimney'. I've re-done it since, with more insulation and an inward facing reflective layer.

Easy enough to have the board control a digital pot, which would be repeatable. Maybe directly feeding a voltage from a D-to-A would work, depending on the voltage being fed to the resistor. I'll have to take a look.

Might be easier than hacking the 1-wire interface.

 

[booster]

My fridge has a Secop 101N510 compressor controller, for which there are lots of technical docs, including how to connect to their 'One Wire' (Modbus??) interface on pins D/I and C. Presumably one could either use resistors or the One Wire interface to control compressor speed. Start at most efficient speed, wait 5 min, if temp not decreasing, speed up compressor.



I re-did the insulation behind the fridge to create an insulated, sealed chimney and opened up both bottom and top vents more than what comes from the factory. The chimney effect works most of the time, but not when the sun is hitting the roof. Hence the fans.

Here's an early version of my 'chimney'. I've re-done it since, with more insulation and an inward facing reflective layer.



Might be easier than hacking the 1-wire interface.

Our new frig has the same compressor and wiring diagrams on it show the same speed control resistor location as the old one did. You can vary the speed of the compressor from 2000 to 3500 rpm by using resistors between 0 and 1.5K ohms. Not important to be in steps or anything like that as it is continuous, but the literature does give you the values for 200,2500 3000, and 3500 rpm that I can list if you would like. The resistor still goes on in the thermostat connection wiring attached to C and T on the compressor controller, so very, very easy to do, especially with a pot.

 

[booster]

@Michael, you may have seen this thread, as I think you were here then, but I will mention it anyway.


https://www.classbforum.com/forums/f5/compressor-frigs-and-specs-9459.html


The Danfoss charts shown show just how much the compressor speed and evaporator temp influences the energy use of the frig. I have found this information as a very good reference for determining what to test and try.

 

[eric1514]

My fridge has a Secop 101N510 compressor controller, for which there are lots of technical docs, including how to connect to their 'One Wire' (Modbus??) interface on pins D/I and C. Presumably one could either use resistors or the One Wire interface to control compressor speed. Start at most efficient speed, wait 5 min, if temp not decreasing, speed up compressor.

Here's a speed controller that I think accomplishes what you want

Merlin II Smart Speed Control

 

[booster]

Here's a speed controller that I think accomplishes what you want

Merlin II Smart Speed Control

Coastal Climate had nice controllers in several models, but they are dropping them quickly as the don't work with the latest AC-DC controllers and it appears the at least Isotherm is dropping all the DC only versions. They even had a very nice digital temp readout one that had a manual speed selection knob. The Merlin is more of an automatic one that touts efficient speed choices, but I wonder a bit considering the bad results from the ITC.

 

[@Michael]

The Danfoss charts shown show just how much the compressor speed and evaporator temp influences the energy use of the frig. I have found this information as a very good reference for determining what to test and try.

Thanks - very interesting.

I found a newer version of that doc on the Secop web site (attached). It has updated EER ratings for various temps and RPM's. Is the temperature in those charts the temperature of the evaporator?

Here's a speed controller that I think accomplishes what you want

Merlin II Smart Speed Control

Yep - that's the idea.

 

[booster]

Thanks - very interesting.

I found a newer version of that doc on the Secop web site (attached). It has updated EER ratings for various temps and RPM's. Is the temperature in those charts the temperature of the evaporator?



Yep - that's the idea.

I had also run across that one when I went searching to see if the resistors were the same for the newer compressors. Numbers are really close so I didn't bother to print it at the time and had my answer on the resistors.


I think that they are evaporator temps as the talk about those temps earlier in the documents, and that is the only temps they have as they are only testing the cooling unit not a frig box or freezer.


AFAIK, the Merlin II will not work with our compressors, like the other Coastal models won't, and personally prefer just selecting a speed occasionally as it rarely needs to be changed on ours. The old frig sat on the slowest speed for years at a time. Ours is will be, once converted back to manual and mechanical, totally no parasitic load, and I have often found it interesting at how hard it is to find the parasitic ratings on the the automatic and digital units. The fact that they are LED displays instead of would probably mean that aren't really low. The ITC lights up the whole van at night and you can't dim it or shut it off, and it never self dims or goes off either, so it will need to be taped over at night. We have one trip left where we will be using it for the first time, and then it is going away.

 

[GeorgeRad]

When you run your efficiency tests comparing the ITC with the capillary thermostat was your SECOP OK to run on capillary after ITC tests. What is that poison cookie ICT drops into SECOP?

 

[booster]

When you run your efficiency tests comparing the ITC with the capillary thermostat was your SECOP OK to run on capillary after ITC tests. What is that poison cookie ICT drops into SECOP?

I wish I knew for sure on that very question. I have tried and tried to reconstruct the order it all was done without success. Logically, it certainly would be something I would do as a standard test procedure so if I didn't, I should have. My assumption all along is that I did do that and that certainly contributed to my amazement when told the ITC made that impossible.


Since I am very, very skeptical of anything manufacturers tell you when are having problems it certainly has crossed my mind that the reprogramming is smoke and mirrors to keep people from going back to mechanical and staying with the ITC. I still can't believe the guy that I was in contact with went dark as soon as I asked him if I could just change the module and go back to mechanical.

 

[@Michael]

Since I am very, very skeptical of anything manufacturers tell you when are having problems it certainly has crossed my mind that the reprogramming is smoke and mirrors to keep people from going back to mechanical and staying with the ITC.

Secop Parameters (Section 4.2.6) - the doc is for a difference series of controller, but IIRC the 5xx's are similar.

Seems like one can flip a parameter and force a particular thermostat type. I have no idea how one would do that without their software and gateway hardware. Isotherm can though. It would be nice if they'd offer to de-program your original one.

 

[booster]

Secop Parameters (Section 4.2.6) - the doc is for a difference series of controller, but IIRC the 5xx's are similar.

Seems like one can flip a parameter and force a particular thermostat type. I have no idea how one would do that without their software and gateway hardware. Isotherm can though. It would be nice if they'd offer to de-program your original one.

I think someone mentioned earlier that Secop has a programmer available to sell so OEMs can reprogram the modules. It can't be too complicated to do if the minimal electronics available on the ITC board can do it. Of course, they could have reprogrammed the module before sale to be easy for the ITC to switch it, also. Nobody mentions that, but if they did any modules not bought from Isotherm would not work with the ITC. Not a lot of ITC users out there yet, so not much information on them yet.

 

[GeorgeRad]

I wish I knew for sure on that very question. I have tried and tried to reconstruct the order it all was done without success. Logically, it certainly would be something I would do as a standard test procedure so if I didn't, I should have. My assumption all along is that I did do that and that certainly contributed to my amazement when told the ITC made that impossible.


Since I am very, very skeptical of anything manufacturers tell you when are having problems it certainly has crossed my mind that the reprogramming is smoke and mirrors to keep people from going back to mechanical and staying with the ITC. I still can't believe the guy that I was in contact with went dark as soon as I asked him if I could just change the module and go back to mechanical.

My contact didn’t go dark after I asked the question about using capillary as a back-up to ITC.

George,
Unfortunately, you cannot switch between the two, once the module is programed to the ITC it saves the information and would have to be reprogramed.
Kind regards,
Mike Cusare
OEM Sales
Technical Support
Isotherm Marine Refrigeration

 

[GeorgeRad]

SECOP removal

Finely I go my fridge on the bench to replace SECOP controller and decide on thermostat. It seems as my compressor is attached with 4 posts and snap rings, no screws, reasonably easy. But.

Replacing the SECOP controller was another r story, remind me a story from Claudio Zampolli Lamborghini shop in LA how Lamborghinis were built. Large floor, engine hanged from the ceiling and all components were added to it. Maintenance required a reverse process.

I thought it shouldn’t take more than 15 min on the bench to remove the SECOP, unfortunately took 2 hours to remove one screw, screw had to be drilled out in very limited space. Screw supposed to be screwed in to remove the controller but after removal I realized the screw was fully in by the factory. I should have force the SECOP out, seems easy in the hind side.

Booster, was your screw also completely in?

See at 1.00.

 

[booster]

Finely I go my fridge on the bench to replace SECOP controller and decide on thermostat. It seems as my compressor is attached with 4 posts and snap rings, no screws, reasonably easy. But.

Replacing the SECOP controller was another r story, remind me a story from Claudio Zampolli Lamborghini shop in LA how Lamborghinis were built. Large floor, engine hanged from the ceiling and all components were added to it. Maintenance required a reverse process.

I thought it shouldn’t take more than 15 min on the bench to remove the SECOP, unfortunately took 2 hours to remove one screw, screw had to be drilled out in very limited space. Screw supposed to be screwed in to remove the controller but after removal I realized the screw was fully in by the factory. I should have force the SECOP out, seems easy in the hind side.

Booster, was your screw also completely in?

See at 1.00.

Been there, done that, and lost all the skin to prove it........


Until, of course I finally figured out how to do it.


Like yours, ours is insulated with extra foilboard so I missed the fact that there are two screws facing the rear that hold the back of the entire compressor module in place through the sheet metal base. The end of the base that faces forward has two "spades" coming out the end that slide into slots in the front wall, and they are nearly invisible because of sealer. Take out the two rear screws and the one on the top and then slide the whole thing to the rear to clear the spades and the whole assembly is loose.



I then was able to twist where it was sitting, still on the box, just enough by bending the tubes a small amount to get access to the controller end. You don't need to remove the two screws, only turn them in supposedly, but I still couldn't get the controller to come out so had to take them out. I put the screws back in very far in before sliding the new controller in place it would go back together with them in place.



I had taken some of the clips off also, which is not necessary to do if you move the whole base and they were a bugger to get back on as they got distorted.


I was very concerned about bending the tubing, but it was necessary I think.