ISOTHERM "vs" ARB Fridge Efficency?`

[So Cal Adventurer]

Hey Guys and Gals

Anyone have real world comparisons of the 2?

Looking mainly for differences in efficiency... ie, is the ISOTHERM as efficient (or at least close) to the ARB

I currently have the ARB 65qt and with a group 31 and 200 watts of solar, i havent even shut it off in over a year! My truck isnt my daily, and all my trips are last minute, so its always fully stocked.

Do the ISOTHERMS in the newer FWC perform the same?

I know the specs are available, but i am looking for real world opions.

Norcold, Engel, and ARB all have close to the same specs, but perform very differently. I am guessing due to insulation differences?

Anyone?

Thanks
Kevin

 

[Pax2525]

I don't know spec differences but I do know real world usage of a traditional door fridge vs top loader and the door is awesome!!! So from a convenience only perspective the camper fridge is killer!

 

[So Cal Adventurer]

I don't know spec differences but I do know real world usage of a traditional door fridge vs top loader and the door is awesome!!! So from a convenience only perspective the camper fridge is killer!

Thanks, i edited my post a little to clarify, its been a longggg day

 

[rollinrollinrollin]

I will admit that I have never used a top loader fridge but I do agree with the Senior Member in SoCal that a traditional door fridge has to be more convenient. I currently have a new Hawk with a large 130 liter ac/dc ISOTHERM running off two deep cycle 6 volt batteries plus a 160 watt rooftop solar panel. Although I've only had the camper a few months I have used it many times and always with a full fridge. My most recent trip was a week in Yosemite Valley and it worked flawlessly. I've read reports that a top loader maintains the cold temperature better. I believe that the convenience of a front door fridge and being able to just reach in and get what you need and close the door quickly vs the time it takes digging through a top loader, taking things out to get what you need and then having to put all the stuff back defeats any supposed advantage of the top loader as it relates to temperature maintenance. Just one happy unscientific FWC opinion.

 

[camper rich]

We have an Isotherm 130 in our 2016 Grandby powered by two 6 volt Lifeline batteies and the 160 watt solar panel on top. We also have an ARB 50 qt in our Ruger Trailer powered by 2 12 volt 85 ah Costco flooded batteries and a 130 watt panel mounted on the trailer. We also have a 100 watt portable to use as needed. The Isotherm seems to work well, but looses a lot of cold when the door is opened. The freezer is relatively small, but keeps things frozen quite well. We sometimes find the freezer door opened up and things have fallen out when driving rough roads. We also have to defrost it occasionally.

We use the ARB set on 0 degrees as a dedicated freezer. The sensor is wrong by 7 degrees, so it is actually 7 degrees rather than zero. When I use it in my VW Van, I set it on 28 degrees which give me 35 actual degrees to use it as a refridgerator.
We also have a Honda 2000i generator which we rarely use, especially in Baja, but we used it a lot in Alaska this summer as we had a lot of rain and cloudy skies.

 

[ckent323]

The amount of heat and energy lost opening a refrigerator door is minimal compared to the energy required to cool a warm can or bottle that is put into the refrigerator.

Consider that all the cold items in the refrigerator have much more thermal mass than the little bit of cold air that spills out. Those cold items will stay cold and will keep the interior cold even after the door has been opened and once the door is closed the interior air temp of the refrigerator will recover quickly. The fuller the refrigerator is the better this works.

My advice is to decide on a door or lid configuration based on the convenience not some notion of energy loss.

Regards,

Craig

 

[Durango1]

So I don't want to hijack this thread but is the current Isotherm that much better/more energy efficient than the largest Dometic (was it 130 liter too) that FWC was using back in 2015?

 

[So Cal Adventurer]

I will admit that I have never used a top loader fridge but I do agree with the Senior Member in SoCal that a traditional door fridge has to be more convenient. I currently have a new Hawk with a large 130 liter ac/dc ISOTHERM running off two deep cycle 6 volt batteries plus a 160 watt rooftop solar panel. Although I've only had the camper a few months I have used it many times and always with a full fridge. My most recent trip was a week in Yosemite Valley and it worked flawlessly. I've read reports that a top loader maintains the cold temperature better. I believe that the convenience of a front door fridge and being able to just reach in and get what you need and close the door quickly vs the time it takes digging through a top loader, taking things out to get what you need and then having to put all the stuff back defeats any supposed advantage of the top loader as it relates to temperature maintenance. Just one happy unscientific FWC opinion.

Perfect! Thanks!

Curious.. why 2 6v instead of 2 12v?

 

[So Cal Adventurer]

We have an Isotherm 130 in our 2016 Grandby powered by two 6 volt Lifeline batteies and the 160 watt solar panel on top. We also have an ARB 50 qt in our Ruger Trailer powered by 2 12 volt 85 ah Costco flooded batteries and a 130 watt panel mounted on the trailer. We also have a 100 watt portable to use as needed. The Isotherm seems to work well, but looses a lot of cold when the door is opened. The freezer is relatively small, but keeps things frozen quite well. We sometimes find the freezer door opened up and things have fallen out when driving rough roads. We also have to defrost it occasionally.

We use the ARB set on 0 degrees as a dedicated freezer. The sensor is wrong by 7 degrees, so it is actually 7 degrees rather than zero. When I use it in my VW Van, I set it on 28 degrees which give me 35 actual degrees to use it as a refridgerator.
We also have a Honda 2000i generator which we rarely use, especially in Baja, but we used it a lot in Alaska this summer as we had a lot of rain and cloudy skies.

Thank you!

Another person using (2) instead of 12s... Whats the advantage?

Thanks

 

[So Cal Adventurer]

The amount of heat and energy lost opening a refrigerator door is minimal compared to the energy required to cool a warm can or bottle that is put into the refrigerator.

Consider that all the cold items in the refrigerator have much more thermal mass than the little bit of cold air that spills out. Those cold items will stay cold and will keep the interior cold even after the door has been opened and once the door is closed the interior air temp of the refrigerator will recover quickly. The fuller the refrigerator is the better this works.

My advice is to decide on a door or lid configuration based on the convenience not some notion of energy loss.

Regards,
Craig

Thanks

 

[rollinrollinrollin]

To address So Cal Adventurer's battery question. I never asked why two 6 volts instead of one 12 volt. My new FWC Woolrich Edition Hawk came standard with two 6's instead of one 12. I assumed the manufacturer must know what they are doing. It certainly had nothing to do with cost. Based on some brief research I have done it seems that one twelve volt battery with the same total amperage of two 6 volts may have to be much larger, also two deep cycle six's in series may have more life cycles. Anyone with a more accurate answer please let me know.

 

[nikonron]

Only problem with the two 6 volts is if one goes bad you have nothing where as if they are 12 volt and you lose one you still have a useable 12 volt system/ battery. Ron

 

[ntsqd]

Same could be said for a 12VDC battery, loose one cell and you have nothing. Can't recall that last time I had a vehicle battery of any voltage loose a cell. It has happened to me, but not in recent memory.

The 6V batteries usually used are the 2GC golf cart batteries, which are a heavy plated, deep cycle design. I don't think that there is a comparable 12 VDC deep cycle battery made. Not to say that there aren't good 12 VDC deep cycles, just none that would directly compare to a pair of 2GC's (of any chemistry) in series.

 

[So Cal Adventurer]

Same could be said for a 12VDC battery, loose one cell and you have nothing. Can't recall that last time I had a vehicle battery of any voltage loose a cell. It has happened to me, but not in recent memory.

The 6V batteries usually used are the 2GC golf cart batteries, which are a heavy plated, deep cycle design. I don't think that there is a comparable 12 VDC deep cycle battery made. Not to say that there aren't good 12 VDC deep cycles, just none that would directly compare to a pair of 2GC's (of any chemistry) in series.

So is it a size/space thing or an amp hour thing?

 

[ntsqd]

Definitely different size-space requirements. Our camper came with 2 FLA 2GC's (Trojan T-125's) that unfortunately had been hurt beyond salvage and it took me a while to realize that. I went back with two AGM 2GC's because those fit.

I tend to think that 12 VDC deep cycles, with a few exceptions that can be located by their price tag, tend to be built as 'recreational' deep cycles while 2GC's (& similar) are built to an industrial standard. In a deep cycle the more lead the better. Look at the weight of the batteries under comparison too, not just the Ah rating and the rated number of cycles. At least that's my quasi-informed take on the topic.

 

[klahanie]

Both come into play.

So is it a size/space thing or an amp hour thing?


For size, if looking at 2x12v vs 2x6v battery bank, the 6v battery has half the cells per battery case so there is the opportunity to make the inside plates larger and more robust. From what I remember depth of cell is an important factor for deep cell performance. Certainly the electric forklifts we used to have had very deep cell dimension, like 30" deep/tall. And I think the 2GC would be taller than a typical size 27 or 31 12v. All the dimensions might be different, actually, but you could prob find a comparable total cubic volume for both a 6 and 12 v battery case.

For amp hrs, amp hours @ 20 hr rating is a good measure to use but minutes of discharge at a lower amp draw might be a more useful comparison for something like fridge use. Again take the 2x12v (using Lifeline agm GPL-31T) vs 2x6v (using Lifeline agm GPL-4CT). Amp hrs rating is 210 vs 220(12v). Minutes of discharge at 8 amps is 1376 vs 1692. Now, IDK what the voltage curve is for that draw down but I'm guessing it would still give a bigger advantage to the 6volts.

Note, Lifelines are premium batteries, each mfr might be different and as always, YMMV. I'll add that, marketing aside, there's prob a better chance of getting a true deep cycle battery when buying a 6v, whereas a 12v might be more of a hybrid rv/marine type.

With all that said I went with the 2x12v, in part because of what Ron said, in part because my application included use for inverter; winch and back up motor starter; and finally compartment fitment was an issue.

 

[nikonron]

My group 31 NorthStar 12 volt does also serve as a backup starter battery if needed. 2-6 volts would take up more space and weight for my install. Ron

 

[rando]

I have used both a top loader in my previous camper and the Isotherm in my current FWC. I have never made a direct scientific comparison between the two as I didn't have them at the same time, but I can say that the efficiency is similar - around 1.5A average draw under hot conditions with the Isotherm maybe being a hair more efficient. The convenience of the front loader far outweighs any small efficiency differences.

Another factor is the venting - with the top loader we kept it in the back seat of our Tacoma/wildernest then in the rear of our pop top Landcruiser. On a sunny day, the temperature inside the vehicles maybe 30 - 40F above ambient, and this is the temperature the fridge compressor is working against. With the built in fridge - the hot side coils are vented to the outside, so the fridge is working against ambient, not the temperature inside the vehicle/camper, which would likely overwhelm any slight efficiency advantage the ARB/top loader may have.