compressor fridge efficiency

[GallenH]

Originally Posted by themexicandoctor

I keep my Novakool R3800 at 29% average. Fridge works perfectly...

Glad you responded. You're in LA, right? Your screenshots show c.80º ambient temp. How did your 3800 work out in the hot summer? Were you able to keep it that cold?

gallen

[themexicandoctor]

Originally Posted by GallenH

Glad you responded. You're in LA, right? Your screenshots show c.80º ambient temp. How did your 3800 work out in the hot summer? Were you able to keep it that cold?

gallen

My Truck is super modified however the Novakool was one of the most significant & inexpensive upgrades I ever made.

3 months a year, the 3 Way was fine.

9 months a year it was a Juggling Act.

The Novakool has been so liberating in terms of being able to park almost anywhere, on any reasonable grade, in the Sun, whatever.

And the fridge will hold whatever I put it to, the only negative might be the lack of a digital setting versus a know.

But I do have a Sensorpush unit in the Freezer compartment & one on the wall of the Fridge - get readouts in Real Time, Hourly, Daily, Weekly & by Month without opening the door.

As for the 80% you saw, that was an internal reading from the Living Room - I have 7 Sensorpush installed;

Front Cab
Hallway*
Living Room*
Underneath the full time Bed where the Inverter is & other special work equipment
Fridge
Freezer
Outside the Rig, in an empty Battery Box

*6 feet from each other

The Novakools are simple, bulletproof & work fine for me - I could set it for 20% if I wanted or even 5%, no problem.

I could do what Booster does & make it even more efficient but during the last two summers of ownership, apart from temp changes due to opening the door& taking my time selecting whatever, the unit performs flawlessly.

They just don't fail until like a Dead Horse, one day they won't work & there are a few people here who have had them for 20 plus years with zero issues.

For Class B's, unless like MsNomer you can build a kitchen from start & design an In Counter Chest Fridge Freezer,* we are relegated to Novakool, Vitrifrigo/Isotherm which in most places, simply slide in without any woodworking, especially the Novakools.

*if I was to design a rig from start up, a Chest Combo unit like an Engel would be my choice, nothing else. They are bulletproof & extremely efficient.

But to retrofit a Chest Combo unit in a Class B (and by golly I tried every which way), typically requires not just the space for the unit (formerly occupied by a Class B fridge unit), but then you need a Slide unit so you can access the contents & most rigs are too narrow.

My R3800 or a R4500 slide into the Roadtrek space vacated by the Dometic, etc with no need for carpentry work at all.

[themexicandoctor]

PS. Regularly it is 110% in the Summer, in the Rig.

Here are two screenshots of my 7 Sensorpush;

[booster]

Originally Posted by Ken Allan

booster...
Remove drip tray... I took note of that when you first mentioned it. It will for sure be removed in the future. It should allow more cold to flow downward AND now I added a battery fan for a bit more air flow. The tray only needs to be there after a shutdown and thaw anyway.

Now I can hardly wait to take another 106° trip to try it out!

Up to about 90° this fridge works pretty well. See'in as how we mainly travel to hike or kayak, we generally avoid the heat anyway.

If you can get at the area behind the frig, it might pay to take temp reading of the air back there. What you see in hot weather could also be made worse by marginally ventilation of that area. We know that probably a very high percentage of factory, and DIY, installs don't have optimum venting. Add on fans to clear heat behind the frig are very, very common on the Novakools with the big coils on the back of the frig, so you may have similar issues.

[avanti]

Originally Posted by booster

If you can get at the area behind the frig, it might pay to take temp reading of the air back there. What you see in hot weather could also be made worse by marginally ventilation of that area. We know that probably a very high percentage of factory, and DIY, installs don't have optimum venting. Add on fans to clear heat behind the frig are very, very common on the Novakools with the big coils on the back of the frig, so you may have similar issues.

I would go one step further and recommend proactively adding active ventilation back there whether you think you need it or not. Adding a pair of small computer fans at the exhaust vent (the top one) is cheap and usually pretty easy. Control them with something like this:

fan controller.jpg

They are intended for computer and audio cabinets. They modulate the speed of the fans according to temperature. As a result, the noise and energy consumption are generally negligible. (The particular unit shown above is likely no longer available, but there are many others).

I would be very surprised if there were very many compressor fridge installations that would not benefit from such as setup.

[Bud]

Originally Posted by avanti

I would go one step further and recommend proactively adding active ventilation back there whether you think you need it or not. Adding a pair of small computer fans at the exhaust vent (the top one) is cheap and usually pretty easy. Control them with something like this:

Attachment 12384

They are intended for computer and audio cabinets. They modulate the speed of the fans according to temperature. As a result, the noise and energy consumption are generally negligible. (The particular unit shown above is likely no longer available, but there are many others).

I would be very surprised if there were very many compressor fridge installations that would not benefit from such as setup.

Much like the ones in our houses, mine has a fan.

[GallenH]

Originally Posted by avanti

I would go one step further and recommend proactively adding active ventilation back there...

I did this on the upper vent of my 1997 PleasureWay to draw air in through the bottom vent and push it out the top. I can feel the warm air exiting when I put my hand at the upper vent. Worth noting that there are several sizes of computer fans. 120mm is common but you can get a slightly larger 140mm which I did for my install. Mine aren't thermo controlled. I just switch them on when it is warm (most of the time in the SW) manually. Amp draw is minimal.

[Stovebags]

Can you tell us which NovaKool unit you ordered that was too big?

[W9TR]

We have a NovaKool 4500 in our Thor Tellaro. Stock installation. Our experience is that if we turn the temp down to get solid ice cream in the freezer then the lettuce in the refrigerator freezes. I have looked at ways to reduce airflow between the two and will try some things out this summer.

Great info on adding a thermostatically controlled fan. Makes sense.

[joelm]

We have an isotherm cruise 130 and it kept ice cream solid and enjoyable in Death Valley at 106. We have 200W of solar which more than covered the fridge draw so it was essentially a non issue.

Having a good fridge and decent battery means you don’t have to micromanage it

[booster]

Originally Posted by W9TR

We have a NovaKool 4500 in our Thor Tellaro. Stock installation. Our experience is that if we turn the temp down to get solid ice cream in the freezer then the lettuce in the refrigerator freezes. I have looked at ways to reduce airflow between the two and will try some things out this summer.

Great info on adding a thermostatically controlled fan. Makes sense.

You might be able to change the temp ratio by speeding up the compressor. You would have to pull the frig normally to change the resistor in the thermostat wiring to the compressor module. Not particularly hard to do.


Another way would be to move the sensor probe from inside of the evaporator box of the freezer, it is built that way, and put in on evaporator box outside.


Starting with reducing airflow will be the easiest to do, though.

[JML]

I replaced my Dometic 3-way. My isotherm does get frost more than I like. I have just spent time making sure it is level and the door shuts better. I have not yet had it out to test on a trip after doing this, but it was fine after a five day home test. Regarding Ice cream, I have taken ice cream bars on trips with no problems, even after two weeks. Regarding efficiency, here a FB post I submitted after I installed the fridge:

Today I installed an Isotherm Freeline Elegance 115 AC/DC Compressor Refrigerator into my 2013 Excel TS. It was pretty straight forward but it was an extremally tight fit because of the sink. I had to take the feet off of the fridge and cut channels into the floor to accommodate the door hinges. A few years ago I installed a 100 AH LiPo battery and a 100 watt solar panel on the roof and I have a 100 watt suitcase for added input if needed. I also have a generator.

I had to take out some side molding and the lip in the compartment. I also had to cut the bottom front of the cabinet frame. There was also a thin strip of laminate behind the sink that I had to cut a piece and remove – that is how tight the fit is. There was some sheet metal at the top of the compartment that I had to bend back but not remove. I ended up putting some tape and insulation there.

There is a two inch gap at the top of the fridge. I haven’t figured out how I’ll cover this but it should not be much of a problem.

In the first three hours the following DC power consumption has occurred: 60 degrees ambient air temperature and a completely empty fridge at power level 3. In the first hour and 20 minutes the battery used 2% of power lowering the temperature from 60 to 40 degrees. I then switched to power level 4. In the next hour the temperature went to 33. Two hours later the temp was 33 and an added two % battery use. In five hours of use, the temperature was 33, the ambient air temp was 54 degrees and battery use was a total of 92 %. Bear in mind that the normal draw for the CO2 detector, etc. was also taking place. In the first six hours on DC only the fridge used 7% of the battery. This included the initial cool down. I turned the power level back to level 3 and I’ll post additional DC power consumption in the comments.

15 hours after starting the fridge, the temp in the fridge on power level 3 is 28 degrees, The low last night was 37, the ambient air temp in the coach was 42. Battery use in the 15 hours was 12%.

[booster]

Originally Posted by JML

I replaced my Dometic 3-way. My isotherm does get frost more than I like. I have just spent time making sure it is level and the door shuts better. I have not yet had it out to test on a trip after doing this, but it was fine after a five day home test. Regarding Ice cream, I have taken ice cream bars on trips with no problems, even after two weeks. Regarding efficiency, here a FB post I submitted after I installed the fridge:

Today I installed an Isotherm Freeline Elegance 115 AC/DC Compressor Refrigerator into my 2013 Excel TS. It was pretty straight forward but it was an extremally tight fit because of the sink. I had to take the feet off of the fridge and cut channels into the floor to accommodate the door hinges. A few years ago I installed a 100 AH LiPo battery and a 100 watt solar panel on the roof and I have a 100 watt suitcase for added input if needed. I also have a generator.

I had to take out some side molding and the lip in the compartment. I also had to cut the bottom front of the cabinet frame. There was also a thin strip of laminate behind the sink that I had to cut a piece and remove – that is how tight the fit is. There was some sheet metal at the top of the compartment that I had to bend back but not remove. I ended up putting some tape and insulation there.

There is a two inch gap at the top of the fridge. I haven’t figured out how I’ll cover this but it should not be much of a problem.

In the first three hours the following DC power consumption has occurred: 60 degrees ambient air temperature and a completely empty fridge at power level 3. In the first hour and 20 minutes the battery used 2% of power lowering the temperature from 60 to 40 degrees. I then switched to power level 4. In the next hour the temperature went to 33. Two hours later the temp was 33 and an added two % battery use. In five hours of use, the temperature was 33, the ambient air temp was 54 degrees and battery use was a total of 92 %. Bear in mind that the normal draw for the CO2 detector, etc. was also taking place. In the first six hours on DC only the fridge used 7% of the battery. This included the initial cool down. I turned the power level back to level 3 and I’ll post additional DC power consumption in the comments.

15 hours after starting the fridge, the temp in the fridge on power level 3 is 28 degrees, The low last night was 37, the ambient air temp in the coach was 42. Battery use in the 15 hours was 12%.

Door fit is critical for both efficiency and frost buildup. When putting the frigs in it is a good idea, if you can get to the area from the back or under from the front, to check all four corners at the feet or wherever it hits the floor otherwise. You need to make sure it is not being twisted at all by binding on the sides or top and that all four corners contact the floor so it won't flex with bouncing. I have our isotherm lightly pulled down with screws next to where the rear feet would be as ours are also removed. I have ours set on two aluminum angles and it did need a bit of shimming. Ours also uses the 4 through the side mounts in the front instead of a flange mount so those need to either be shimmed or not pulled too tight as they will bend the sidewalls.


A good test of door seal is to lift the latch and then slowly pull the door open and see how much suction you get holding it shut. On our Cruise 85 it is substantial and increases the effort quite a bit.


If you are reading a battery monitor to get %, you are really better off to look at the amp hours out after a full charge, assuming it reset to true full based on the volt and amp settings. % readings are not all that reliable in many cases. Of course both % and AH readings will be thrown off by solar output so for testing the solar should be disabled. In the conditions you listed, I would expect a 115 to use very few AH per day, perhaps in the teens even. Once you get up above 70* power use increases pretty quickly at least on the two 85s we have had.

[JML]

Regarding the battery, percentages are taken directly from the internal BMS. I used percentage for ease of understanding as it its a 100 AmpHr battery. I'm putting in a 270 AmpHr LiPo this winter, so your advice will be well taken. Actual amps used averaged 1.1 to 1.4 an hour for the fridge depending on temps and how often we open the door. All our travel so far has been in the SW.

Originally Posted by booster

]
If you are reading a battery monitor to get %, you are really better off to look at the amp hours out after a full charge, assuming it reset to true full based on the volt and amp settings. % readings are not all that reliable in many cases. Of course both % and AH readings will be thrown off by solar output so for testing the solar should be disabled. In the conditions you listed, I would expect a 115 to use very few AH per day, perhaps in the teens even. Once you get up above 70* power use increases pretty quickly at least on the two 85s we have had.

[booster]

Originally Posted by JML

Regarding the battery, percentages are taken directly from the internal BMS. I used percentage for ease of understanding as it its a 100 AmpHr battery. I'm putting in a 270 AmpHr LiPo this winter, so your advice will be well taken. Actual amps used averaged 1.1 to 1.4 an hour for the fridge depending on temps and how often we open the door. All our travel so far has been in the SW.

I assume you are saying 1.1-1.4 amp hours per hour which would put your 24 hour use at 26-34 which would be on the low side for a 115 but possible, I think. It would have to be quite cool to get to 23 in a frig that size. They rate it at closer to 19ah per day which is a lot lower than their other frigs that are smaller. Our Cruise 85EL is rated nearly 50% higher than that by Isotherm so kind of confusing. I would be a bit surprised if it is really that low. Was there some solar contribution at that time?



I think your frig has the sliding piece under the upper lip of the frame so you set it to ventilate when in storage. Be sure that is in the position all the way so the latch is holding it shut tight or it may be not staying full shut all the time.

[JML]

Or around 22 Amp hours. My use was averaging 26 to 33 Amp Hrs. I'll be sure to double check the latch when using, thanks!

Originally Posted by booster

I assume you are saying 1.1-1.4 amp hours per hour which would put your 24 hour use at 23-34 which would be on the low side for a 115 but possible, I think. It would have to be quite cool to get to 23 in a frig that size. They rate it at closer to 19ah per day which is a lot lower than their other frigs that are smaller. Our Cruise 85EL is rated nearly 50% higher than that by Isotherm so kind of confusing. I would be a bit surprised if it is really that low. Was there some solar contribution at that time?



I think your frig has the sliding piece under the upper lip of the frame so you set it to ventilate when in storage. Be sure that is in the position all the way so the latch is holding it shut tight or it may be not staying full shut all the time.

[booster]

I fixed my Ah typo.



At 26AH per day, you would be at 351 watt hours per day using 13.5v for the lithium battery feeding it or float voltage on a lead acid. They rate it at 265 watt hours per day, which is very low. You would be at 19AH at that power use. They rate at 41* in the frig and 77* outside temp. You would be at about 28ah with lower voltage lead acid batteries at 12.5v


From what we here about frigs on the forum, most don't get below 30ah per day with most closer to 40 so if you are that low or close to in warmer weather, you will be doing very well. For comparison in 70* weather and cooler at night we will get to 25ah quite a bit of the time, but our frig is smaller and freezer warmer, plus we have added insulation.



Our 85 is rated at 365 watt hours for comparison. With extra insulation and turning down the compressor speed we can beat that rating at similar conditions by a some. If I remove the drip tray and can get substantially lower but not to 265 watt hr, IIRC. Removing the tray increases the freezer temp form 6* to 20* and improves efficiency a lot.


It will be very interesting to see how your use comes in over longer times and varying conditions, but with solar contributing it will be kind of hard to tell how much the frig is using.

[ChicagoTom]

I have the 3-way, 2009 Pleasureway Lexor. Ice cream stays frozen solid, drinks ice cold and often in temps above 100. I think the reason so many have issues is not understanding how to load it, airflow and proper position of my rechargeable inside fan. Ex HVAC Tech, many years ago, so maybe that is a plus for me. As a side note, I lived full time 99% boondocking and it was on 24/7 for well over a year.

[themexicandoctor]

Originally Posted by ChicagoTom

I have the 3-way, 2009 Pleasureway Lexor. Ice cream stays frozen solid, drinks ice cold and often in temps above 100. I think the reason so many have issues is not understanding how to load it, airflow and proper position of my rechargeable inside fan. Ex HVAC Tech, many years ago, so maybe that is a plus for me. As a side note, I lived full time 99% boondocking and it was on 24/7 for well over a year.

I have read your posts before. Not only are you super proficient but you are one of four people in North America who not only do everything right but also got a Monday made machine.

I have the transcript from Dometic's Head of Customer Service in the days before she was fired, just short of being fully vested/20 year deal.

"The RM line of 3 Way Fridges are a customer service disaster for us & owners during the summer months ..."

"The RM line is the most problematic of all ..."

"Dometic's new ownership is a disaster for both the Employees, the Dealerships, the Installers & the Customers ..."

"We haven't made a quality product in 10 years*..."

*was stated in 2020

"Our interest is now purely profit centered ..."

[Rlum]

Originally Posted by ChicagoTom

I have the 3-way, 2009 Pleasureway Lexor. Ice cream stays frozen solid, drinks ice cold and often in temps above 100. I think the reason so many have issues is not understanding how to load it, airflow and proper position of my rechargeable inside fan. Ex HVAC Tech, many years ago, so maybe that is a plus for me. As a side note, I lived full time 99% boondocking and it was on 24/7 for well over a year.

My hats off to you. I have never been able to get my RML8330 to cool properly in 90 plus temps. I have multiple fans inside and on the vents.

Even on one camping trip. I attempted to level my van 5 plus times. Finally gave up and moved to another site.

My experience with 3 way refrigerators has compelled me to switch to a compressor model.