New Fridge Advice

[BroncoHauler]

I think the Isotherm ASU is really in its element when combined with solar. With an adequate solar panel, the power received during the day should be enough keep your house batteries charged up with extra going to provide the power necessary to freeze the thermal mass of the fridge, and then let the thermal mass provide the cooling assist during the night.

This should also help reduce the frequency of the fridge cycling on and off.


Herb

[coyotearms]

Don't know what all this fuss about varying power to a fridge depending when it is day and when it is night. If a fridge has a certain target temp inside and an certain ambient temperature exists outside, it will take the same electrical energy over a 24 hr period regardless of whether more electrical energy is used during the day and less at night. Exactly what conditions might exist for which ASU keeps a fridge alive when it wouldn't otherwise seems to stretch the imagination. One would be if battery capacity is just enough to make it through the night only because the cold plate was there to take some load off of the compressor. I don't think many people would size their house battery bank that small. I would think the money to do ASU would be better spent on better insulation, more mechanical efficiency and better reliability. To learn more about how one tests those things to REALLY find the best performing fridge is by reading the classic review of portable fridges in a 2010 issue of Overland Journal, http://expeditionportal.com/overland...fridge-review/. I doubt any of this stuff on ASU would be very important in such tests, although it might be somewhat entertaining to watch all the lights telling the audience what dance the ASU is currently performing. Relax, I'm just joking . . .

[Scalf77]

Reading the link, a couple of the units do exactly that, vary power and speed to the compressor. Just having a closed loop system will do wonders for power consumption, I am not sure about the TruckFridge but the Norcold unit I have does not even have temperature feedback. I am not sure that the cold plate part of the design is really worth it, as far as cost, etc, but that is just part of the overall system.

If you look at one of newer Isotherms Cruise Elegance, they have abandon the ASU cold plate but instead offer a smart energy controller and the use the mass of the contents in the fridge. It is a much cheaper add-on to the ASU package, and can be retrofitted into any of their Elegance line. I also expect that , it could be retrofitted on to other units also that have a the Danfoss BD35F compressor. if one was inclined to do so.


-greg

[coyotearms]

Originally Posted by Scalf77

If you look at one of newer Isotherms Cruise Elegance, they have abandon the ASU cold plate but instead offer a smart energy controller and the use the mass of the contents in the fridge. It is a much cheaper add-on to the ASU package, and can be retrofitted into any of their Elegance line. I also expect that , it could be retrofitted on to other units also that have a the Danfoss BD35F compressor. if one was inclined to do so.

From my two posts above it should be clear that I think ASU is nothing more than a sales gimmick, and I tried to explain in simple terms why it does not lower overall energy consumption. So I am not surprised if they dropped that feature. However, they still claim that using the food inside instead of a cold plate results in "Significant energy savings." http://www.webasto.com/int/markets-p...nergy-control/. In a table on the same site the claim is "Power consumption can be reduced by up to 50% with the use of an Isothmer Smart Energy Control Kit." Also on that same website they claim their frost free feature also saves energy! Oh well, every company has its marketing department.

[daveb]

I used to do the same with my Norcold. On the road or during the day (solar in sun) I'd crank it up to very cold temps, then lower it to a more mild temp at night. Problem with that was it froze some things I didn't want to be frozen. The power consumption was actually higher until I turned it down at night where it fridge didn't cycle nearly as much. Like I posted earlier, I don't really care because after adding a second house battery I have more power left over than needed. I now just leave the fridge temp set to keep the inside temp reasonable throughout the day. One might also factor the cost of the second house battery just like a ASU/fridge. I also agree with spending the money on insulation but thin panels will only do so much. A DC power fridge insulated like a Yeti would be nice but probably huge in size.

[BroncoHauler]

Originally Posted by daveb

... A DC power fridge insulated like a Yeti would be nice but probably huge in size.

Isotherm does offer their compressors with cooling units separately, so you could build your own custom, well insulated box, and turn it into a super efficient fridge.

http://www.isotherm-parts.com/index.php ... 4e75017919


Herb

[coyotearms]

Ditto for build-your-own Danfoss-based units through Sure Marine in Seattle. See Pg6: http://www.suremarineservice.com/cat...on_Catalog.pdf.