12v vs 3-way fridge energy consumption

Michael49

I previously owned and sold a 2018 400,  now thinking about a 320.

The newer 320's have a 12V fridge like the 400. We did a lot of boondocking and solar and lithium batteries I often found the fridge in the 400 to be a big energy hog and often challenging to keep cold.

How is the 12V fridge in the newer 320's in terms of boondocking? Have people found it to be a similar energy hog? 

pthomas745

The newer 2 way fridges are "compressor" fridges.  They are quite a lot more efficient than the "old" three way fridges on DC (battery) power.  The newer fridges are reported to use 21 amp hours (or so) per 24 hours.  Compare that amp hour use to my 2017 if I even could run it on 12V.  It would use 21 amp hours in an hour and a half.  The newer 3 way fridges would consume 21 amp hours in even less time than that.

Check the comment by "Elbereth" in this thread that discusses the power consumption of the newer fridges.

https://tab-rv.vanillacommunity.com/discussion/11483/field-experience-with-dc-refrigerator-power-consumption-and-factory-solar

The "downside" of the newer 2 way fridge would be inadequate battery capacity.  If "only' the stock 80 AH battery is in the trailer, that smaller battery capacity (only 40 amp hours usable) could be problematic, even with installed solar or portable panels.  A couple of lousy solar power days might have an owner having to juggle fridge power use to help preserve battery amp hours.  The usual "fix" is more battery power that will help you get through a couple of days of little solar input.

Denny16

The TaB320 has a newer, improved compressor fridge, which uses less battery power, but I would upgrade the 320 battery to at least a 100 AmpHr Lithium battery and have factory solar, which the Boondock models come with.

That said, I have found the original DC/AC fridge in our 2018 TaB400 very efficient and works well on battery, with the trailers OEM solar panel recharging our 200 AmpHr battery during the day, on a 4-day Boondock trip.
Cheers 

Sharon_is_SAM

@pthomas745 - Elbereth was referring to the old 2 way Norcold in the CSS.  The new 320 has the 2 way Isotherm Cruise Elegance - even more efficient than the Norcold.

Michael49

Sharon_is_SAM said:

@pthomas745 - Elbereth was referring to the old 2 way Norcold in the CSS.  The new 320 has the 2 way Isotherm Cruise Elegance - even more efficient than the Norcold.

I think our 400 had the Norcold, I've heard that the Isotherm is more efficient.

Mickerly

I have am older CSS. The old DC Norcold is not bad (NR751 in the 400, NR740 in the 320) . The new frige appears to have the same compressor. Door sealing and insulation have some space for improvement in the Norcold. This is probably how the Isotherm posts better numbers. All of these refrigerators are more efficient than the old absorption refrigerators; however, you need electricity. I think Denny16 has a good explanation of that part.

WayneW

We have the Isotherm fridge, 100ah lithium battery, rooftop solar and a 100 w Renogy solar suitcase in our 320S boondock. On a recent 3 day trip w no hookups we had ample power even with 1 day of clouds and showers. 

The weather was cool so the fridge didn’t have to work very hard, but we’re in northern Idaho and the sun angle is still quite low, and night still comes fairly early so we used the light quite a bit. 

Last year we still had the stock 75ah lead acid battery and I didn’t have nearly the confidence level that I do now with the current setup. This summer I think I’ll run out of beer before I run out of power to keep it cold. 

pthomas745

The Norcold and the Isotherm fridges both appear to be using a "Danfoss" compressor.  The power consumption for both fridges (according to the manuals, etc) are fairly close.  (I had the numbers yesterday, and I can' find them this morning....give me some time!) 

I still think Elbereth's numbers are in the ballpark for any of the compressor fridges.