Isotherm frig ICT removal and test results

[booster]

Finishing up on the ICT removal and mechanical thermostat reinstall on our 3.0cf Cruise Elegance frig. I also added a power on/off switch to remove all power from the frig so it can be ventilated without the light staying on, and put on a compressor speed 6 position selector switch. Long haul and expensive to get rid of the ICT after the temp sensor failed after one trip. The ICT reprogrammed the compressor control module so it had to be replaced, of all things. Totally ridiculous to make a product that way as it prevents using a simple thermostat as backup or if you just don't like the ICT as it is a kind of not great performer also.

Here are the power switch by the side of the frig door, and speed control in the kitchen above the frig along with our digital wireless frig thermometer.







The speed control is a 6 position selector switch in the thermostat wiring to the compressor module. One no resistance jumper and 5 different resistor values to give 6 speeds from 2000rpm to 3500rpm. The mounting is a piece of PVC drain line pipe and two discs of PVC sheet. Bottom is bigger to give the flange and is cemented on with pipe cement, and the top is the access and is screwed on. Two bullet connectors on the wiring in the mount.

Based on our old frig of the same size and brand we knew that 2000rpm is good almost all the time and finding the right combo of things to get the desired frig and freezer temps along with slow speed, could save a lot power use. The old frig freezer door did not shut tightly and new one does fit tightly and a different shroud on the freezer box and different drip tray meant starting from scratch to get the right temps.

I quickly found out the thermostat was also different on the new frig, and could only get to 20*F as the highest freezer temp even after max ranging the calibration screw adjustment. That was good for us though as don't do ice cream or long term storage in it. Stock the freezer ran a 6*F so used a lot more energy because of the colder evaporator. Stock it also ran at a bit under 3000rpm so that is less efficient.

After some messing around with the drip tray position, I found that the frig got to 37/39*F with the tray in place, but pulled away from the back of the frig as far as possible. Freezer held at 19-21*F. Both very good for how we want it to run.

It appeared to me that the frig was hardly running much, but did run a 24hr test on it to see what the actual energy use was.

Test conditions were the above frig temps, ambient 67*F steady, inside the shop so no wind or sun. Most of the test was run on shore power float charge at 13.1v and some on battery at high 12v range. Voltage didn't matter as I was measuring cumulative watt hours on a Wattsup hardwired into the power wire at the frig. Watt hours were converted to amp hours at 12.4v which would normally be a worst case average for us as we have a lot of battery and moderate use, plus solar holding up the voltage for nearly half the time if decent sun.

The results were very surprising to me.

24 hour watt hour usage was 177.7 watt hours.

At 12.4v that is 14.33 amp hours and very low for any frig. It is about 1/2 of what the frig in stock form and what on the ICT in the same conditions, even with the ICT in economy mode. It is also about 20% lower than similar testing I did on our old frig.

Of course real world use will be substantially more as we commonly saw 30-50% more power use in real life than controlled optimized testing, but even at 50% higher it would be very low power use for any frig. It will be interesting to see how it does in real life. I did set up the wiring with Delphi connectors so the Watts up is very easy to put in and out, and it can be reset by cycling the on/off frig switch so easy to use.

I am very glad to see the ICT and it's 6* temp swings and high energy use gone for good. Should never have believed the literature claims.


I probably will run a shorter timed energy use with the drip tray pushed all the way in to it's normal place as that should give 40-41* in the frig, which is the normal spec point for Isotherm. I will also turn up the shop heat to 77* for the test as that is also there standard test point. The lower frig temp should save some energy, but the warmer ambient should cost some energy so it will be interesting to see how that balances out.

[GeorgeRa]

Thank you for this data. Excellent efficiency. These are much better results than you got previously. 177.8Wh vs previous best 290Wh.

With my SEC thermostat the freezer temperature hit [-15.8] *F on max setting but the swing was huge. The thermostat I purchased has temperature range allowing me to switch sensor location from freezer to fridge, I should run this experiment. Just got a better picture of this new thermostat and hope it will fit in my place, could be too tall.

A couple of questions:

- Did you use DC or AC watthour meter?
- Is the sensor bulb touching the evaporator plate?
- What resistors did you use, 1/2W?

[booster]

Originally Posted by GeorgeRa

Thank you for this data. Excellent efficiency. These are much better results than you got previously. 177.8Wh vs previous best 290Wh.

With my SEC thermostat the freezer temperature hit [-15.8] *F on max setting but the swing was huge. The thermostat I purchased has temperature range allowing me to switch sensor location from freezer to fridge, I should run this experiment. Just got a better picture of this new thermostat and hope it will fit in my place, could be too tall.

A couple of questions:

- Did you use DC or AC watthour meter?
- Is the sensor bulb touching the evaporator plate?
- What resistors did you use, 1/2W?

Yep, I was very surprised by the results as I expected a best case would be if it broke 245 watt hours.


I used a DC Wattsup accumulating meter, which is very small and with the Delphi connectors and a snap to hook up. I don't even have AC hooked up to the frig, even though it is in the cabinet already from the absorption frig the van came with.


Yes, the bulb is on the inside, top, rear of the freezer box and is clamped to the surface of the box, which is the evaporator. I don't know where it is in relation the stamped in tubes in the box itself.


I will have to look up the values I used, but they were 1/2 watt. Even 1/8 watt would be big enough based on the tiny amp draw they say is in the thermostat wire, but the 1/2 watt were a more robust which really helps because they are soldered directly to the switch terminals.

[booster]

To finish up, I decided to run a couple of shorter tests at the 77*F that Isotherm rates at to see how much that affects the energy use. Answer, I think, is quite a bit and more than I thought 10 degrees ambient would do.


Test 1 at 77*F


Drip tray pushed all the way to rear, OEM position. Freezer at 20* as in previous tests as the mechanical thermostat controls that and wasn't moved. Frig temp at 40-41*F which has historically been the Isotherm test point, also.


24hr watt hour use was 233.5 watt hrs or 18.8ah at 12.4v. About 24% more energy than the previous best test with 67* ambient but colder frig at 34-36*. It appears ambient changes energy use more than frig temp if kept at the same evaporator temp.


Test 2 at 77*F


Drip tray pull forward as far as possible as in best result test. Freezer still at 20* off thermostat. Frig temp drop was less than in best result test with all the same except ambient, at 38-40*F. This is kind typical of the small amount of drift we see with ambient temp changes for the frig temp with mechanical thermostat in place.



24 hr watt hour use was 250.8 watt hours so about 7% higher because of the lower frig temp.


Of note is that all of these power use numbers are lower than the 265 watt hrs per 24 hrs that I saw in initial testing with the frig so getting off of the colder freezer to 20*F freezer temp made a significant difference.


Isotherm rates this model with mechanical thermostat and OEM speed resistor at 368 watt hours per 24 hours so much higher than I am getting. They would be running at about 2750rpm compared to my 2000rpm on the compressor and have a 6*F freezer temp at 77* ambient and 41* frig temps. Our best results at 77* ambient like the rated ambient is only 63% of the rate power use, so I am certainly just fine with that. I do seen to remember the old frig, with the unshrouded freezer box being rated at lower power use, like maybe 285 watt hrs per 24 hours, but I don't have a spec sheet for it to confirm that. That freezer ran warmer than the 6* the new frig did stock.


Bottom line, I think, is that of the things you have some control over the freezer temp is probably the biggest influencer of energy use. This almost certainly why Novakool states they setup for "non rock hard" ice cream as they want to save energy. They also list lower running amps which would also be a benefit because of lower compressor speed. Their energy use then comes out closer to the unitized cooling unit frigs. The rear mounted coils with no fan cooling probably are less efficient than the fan cooled unitized Secop compressor/condenser units.


All very interesting, and I think on our annual two week spring trip to Custer State Park I will leave the Watts up hooked up and monitoring the whole time to get a real world, varying conditions, test of power use. Now that it is on Delphi connectors it should be able to travel Ok without issue.

[avanti]

In our new van, I am probably going to put a dedicated shunt on the fridge and feed it to the home automation system. I would then know for sure how much power I am using. Will be interesting to correlate it with ambient temperature.

[booster]

Originally Posted by avanti

In our new van, I am probably going to put a dedicated shunt on the fridge and feed it to the home automation system. I would then know for sure how much power I am using. Will be interesting to correlate it with ambient temperature.

That would be very interesting to see what you get, I think. Have you decided on a frig size and brand at this point?

[avanti]

Originally Posted by booster

Have you decided on a frig size and brand at this point?

Debating that right now. I may well end up with what we have now, which is a NovaKool RFU6800. Safe but unglamorous choice. We are also looking at some of the Vitrifrigo units, maybe:

https://www.vitrifrigo.com/us/us/dw2...er-compartment

Quite a bit nicer, but pricy. More importantly, as far as I have seen, all the ones I have looked at a bit bigger. The extra capacity would be nice, but it would cost me 2" of extra width, and I am already scrounging for the 11" that going to the Transit is costing us.

Anybody have any other suggestions?

[GeorgeRa]

Originally Posted by avanti

..........................

Anybody have any other suggestions?

Have you considered Isotherm, well known in the marine world.

[Davydd]

We had the Nova Kool RFU6800 in our last two Class Bs. It was OK except in warm temperatures. For design, space and weight issues we installed this. The Isotherm Cruise 115 Freeline Elegance. It is a one door but with a freezer big enough to hold four pizzas and a half gallon ice cream container if you want to imagine size. It was big enough for our needs coming down from a two door ref/frig. It keeps better temperatures than our Nova Kools and more energy efficient. I suggested this one to ARV and from what I can tell this was the only one they have installed.

https://www.indelwebastomarine.com/u...-115-elegance/

[booster]

Originally Posted by Davydd

We had the Nova Kool RFU6800 in our last two Class Bs. It was OK except in warm temperatures. For design, space and weight issues we installed this. The Isotherm Cruise 115 Freeline Elegance. It is a one door but with a freezer big enough to hold four pizzas and a half gallon ice cream container if you want to imagine size. It was big enough for our needs coming down from a two door ref/frig. It keeps better temperatures than our Nova Kools and more energy efficient. I suggested this one to ARV and from what I can tell this was the only one they have installed.

https://www.indelwebastomarine.com/u...-115-elegance/

I have been reading the manual for the 115 and it is interesting. It appears to have an electronic control that is a simplified version of the ICT for the most part.


A couple of things would make me hesitant based on my, very poor, adventures with the ICT. It states that when it is normal cooling mode where you choose the temp from only 3 or 4 buttons it will run in max speed to store "cool" in the contents of the frig. The ICT and I think GeorgeRa's older electronic control do the same. The biggest issue is power use, because the high speed is quite inefficient if it is used when not on charging voltage. The 115 instructions seemed to say they only get off of the high speed mode when battery voltage drops below 12.5v. Our AGMs are down quite a few amp hours by the time they get to that voltage and davydd's lithiums might never get there so will always waste energy. The instructions didn't say what parameters it goes to in ECO mode or if the temp controls still controlled box temperature. The ICT states that in ECO mode runs at the lowest compressor speed (but it doesn't as the lowest speed is 2000 and other materials say the ICT runs it at 2500) and the temp controls still work. Older electronic controls would go to max temp of 41* when in energy saving mode, so not certain what the 115 does. It also has not temp readout so you don't know what the frig temp really is.


As with anything electronic, it needs to be 100% sealed to survive in frig, especially right at the door opening where it will see temp swings and moist are. Condensation in electronics is not a good thing and with the big temp swings from in use and shut off, internal pressure will change and either bleed or the sealing made to hold it. If it isn't sealed that well in will get moisture inside it.


It will be interesting to see how it works out for davydd in his new van. I hope there is some way for him to see what the daily use for the frig is as that would be very informative.


Davydd, how do you like the center handle door opening lever? We have the same on our new 85 Elegance and the handle lifts to almost horizontal plus the pull to open is fairly high. DW needed to use two hands to open the frig which is very inconvenient when you want to put something into it. I have since found a way around it, but needed to add a handle and way to temporarily disable the positive latch when we are parked.

[GeorgeRa]

Good points, I agree it is like ICT, could be pre or post ICT development. One of main differences in Isotherm electronic (SEC/ICT) and electromechanical thermostats is sensor location. In fact, you could have electronic thermostat with probe located on cold plate and could behave similarly to a capillary one.

Dave did you see location of the sensor on 115?, back wall in a perforated plastic shroud. If it is invisible than it could be on the cold plate.

[Davydd]

I haven’t looked at anything on the Freeline but put a thermometer on the wire shelf you can see in the photo. It maintained about 37F on a 90F day. I was satisfied. My NovaKools didn’t perform as well.

The top latch is probably not the best design as I sometimes but not all have to use two hands or I feel like I’m going to pull the latch off. The left hand to break the seal on the non-hinged side.

As mentioned the one door design is efficient and that large freezer is the best I found on a one door RV frig/freezer combo. It does keep ice cream hard and items frozen. I haven’t checked the temperature.

[avanti]

Originally Posted by GeorgeRa

Have you considered Isotherm, well known in the marine world.

Yeah, good call.

Looks like the Cruise 195 may be a good compromise, both size-wise and cost. Looks like a nice step up from the NovaKool.

Are those handle latches OK when they are on the side rather than the center?

[booster]

Originally Posted by Davydd

I haven’t looked at anything on the Freeline but put a thermometer on the wire shelf you can see in the photo. It maintained about 37F on a 90F day. I was satisfied. My NovaKools didn’t perform as well.

The top latch is probably not the best design as I sometimes but not all have to use two hands or I feel like I’m going to pull the latch off. The left hand to break the seal on the non-hinged side.

As mentioned the one door design is efficient and that large freezer is the best I found on a one door RV frig/freezer combo. It does keep ice cream hard and items frozen. I haven’t checked the temperature.

The Isotherms are good frigs, no problem with that at all. They do set them up to keep the freezer at about 6*F yours behaves like ours does. IMO, they cool better than a Novakool for the most part and the freezer is much colder. The problems I had were with the ITC and the fact that they made them so you can't remove the ITC without buying a new several hundred dollar compressor controller. If yours it the same you will be out of luck if the controller dies as you would not be able to just put a mechanical thermostat on to save the trip you were on. George's older Isotherm electronic control doesn't mess up the compressor controller so your may not also. Availability on Isotherm parts and frigs has been very poor lately and was never great. You may want to ask ARV to check that out for you so could decide if you wanted to carry a spare electronic thermostat with you, or a spare compressor controller so a mechanical could be put in. IMO, better to think what you would do now rather than later as it can be allowed for.


All the testing I did was to find out if the Isotherm could be made more efficient as our new one used more power than are older model of the same frig did. I found out it could quite readily, be improved by changing the compressor speed and even more by running the freezer temp higher (would not keep ice cream rock hard but would keep food frozen fine). I don't think there would be any beef with Isotherm over doing those changes for personal taste, but when Isotherm made all the claims about how much more efficient the ITC was than the mechanical thermostat they were severely exaggerating at best. Even in stock form and stock compressor speed, the ITC in ECO mode was not noticeably better in daily running. In regular mode, like yours would appear to run most of the time unless you tell it otherwise, the ITC was much less efficient than the mechanical in stock form. The rest of the frig is good, no problems, and I would get another of them but with mechanical thermostat.

[avanti]

So, is there any particular reason one couldn't build a DIY fridge controller with an Arduino-class device and some temperature sensors? Does not look like rocket science.

[GeorgeRa]

Originally Posted by avanti

Yeah, good call.

Looks like the Cruise 195 may be a good compromise, both size-wise and cost. Looks like a nice step up from the NovaKool.

Are those handle latches OK when they are on the side rather than the center?

We have the handle latch on the side, works well in closing and opening. Wish to have partially open vent position latch.

[GeorgeRa]

Originally Posted by avanti

So, is there any particular reason one couldn't build a DIY fridge controller with an Arduino-class device and some temperature sensors? Does not look like rocket science.

It is not rocket science but good understanding of the new SECOP controller operating software is necessary unless you opt to just build an on/off electronic thermostat in lieu of a capillary thermostat. But if simple thermostat is the goal than there are ready to go options such as AKO 13112 or Inkbird.

It must be a reason why Isotherm folks decided to reprogram SECOP to work with their ICT, perhaps soft start, or variable speed, I have no clue. Unfortunately, this reprogramming nulls the option of electromechanical thermostat.

[avanti]

Originally Posted by GeorgeRa

It is not rocket science but good understanding of the new SECOP controller operating software is necessary unless you opt to just build an on/off electronic thermostat in lieu of a capillary thermostat. But if simple thermostat is the goal than there are ready to go options such as AKO 13112 or Inkbird.

It must be a reason why Isotherm folks decided to reprogram SECOP to work with their ICT, perhaps soft start, or variable speed, I have no clue. Unfortunately, this reprogramming nulls the option of electromechanical thermostat.

But couldn't one control the speed by simulating that speed resistor thing? Or is that not there anymore?

[Davydd]

Originally Posted by booster

You may want to ask ARV to check that out for you so could decide if you wanted to carry a spare electronic thermostat with you, or a spare compressor controller so a mechanical could be put in. IMO, better to think what you would do now rather than later as it can be allowed for.

With ARV I have a three year bumper to bumper warranty of everything they did or put in. I am not going to carry spare parts on the come for the first three years. For instance I had a VB air suspension bag leak and they overnighted the parts to a MB Sprinter dealer where I was at in Texas and the dealer installed it and I was out before noon. In Phoenix they did the same with the Nations second alternator replacement and I got in and out again before noon. I don't know how they do it but they do it and promptly.

[booster]

Originally Posted by avanti

But couldn't one control the speed by simulating that speed resistor thing? Or is that not there anymore?

Yes to all you questions on building your own control. Coastal Climate used to sell a lot that exact thing. Speed control, temp control. I think might also have had some energy program if wanted, but not sure.


The literature is still on their website, but they have updated the control to the newer compressor models.


I have the manual version of what you are talking about and none are tied into the Secop compressor control module program at all. All of them are strickly in thermostat loop except an on/off power switch for the entire frig. Electronic temp control, variable resistor of some sort for speed, master on/off switch should not be any issue at all. I don't do electronic controls, but I could build that as a relay control easily.