Upgrade from Norcold to Dometic CR-1110 E/F-S (compressor fridge)

[davlin]

Originally Posted by scrubjaysnest

When I tested the new solar system, the load I used was the fridg on DC at the highest setting. Amps drawn at the start were 11.6 and by the end of the load testing was down to 11.1 amps. I would run the fridg until the Trimetric showed ~a 10% drop in SOC. The fridg was then turned off and the batteries rested two hours. This was continued until battery voltage was ~12.4 which according to Exide is 50% SOC. The Trimetric showed 60 %, the Trimetric bases it's % on Ah used and Ah capacity of the batteries. This all took about 6 hours of run time on the fridg. This current draw also represents about 11 % of the battery bank capacity.
Bottom line a single battery in the TM will be dead in about 4 hours of continuous running without some charging source.

Scrubjay,

Are you talking about the Norcold or the CR-110?

[scrubjaysnest]

Sorry, should have mentioned it was the Norcold. Haven't convinced DW to make the switch. She is concerned about those times we go a week without sun for the solar panels.

[davlin]

My experience with the Norcold on 12vdc was about the same as yours. The Dometic seems much more efficient on 12vdc. I do need to modify my statement about the "test" that I ran. It was only for 41 hours, not 48. Sometimes I get bad sectors in my hard drive.

[tentcamper]

So has anyone collected the hourly amp draw for the 12v DC compressor fridge?

[scrubjaysnest]

Originally Posted by davlin

My experience with the Norcold on 12vdc was about the same as yours. The Dometic seems much more efficient on 12vdc. I do need to modify my statement about the "test" that I ran. It was only for 41 hours, not 48. Sometimes I get bad sectors in my hard drive.

From full charge to about 50% SOC in 41 hours isn't bad at all.

[davlin]

Originally Posted by tentcamper

So has anyone collected the hourly amp draw for the 12v DC compressor fridge?

From the Dometic manual. That draw would only apply when the compressor is running, so the variables would be ambient air temp, amount of already chilled food in fridge (more is better), number of times and duration that the door is opened, etc.

[rickst29]

Originally Posted by tentcamper

So has anyone collected the hourly amp draw for the 12v DC compressor fridge?

Not hourly, but I can calculate that at less than 4AH (from ~50% "on" versus "off" ratio and 7.2A continuous while running, @ 95F ambient). Power consumption varies a bit, according to the temperature of refrigerant.

As Davlin said, the most important factor, by far, is the ratio of "on time" to "off time". In a hot driveway, 95F, and Fridge unloaded, the duty cycle was barely 50% (SWAG, less than 4 AH).
- - - - -
But reduced "electric power consumption" is the worst of 4 reasons to do this upgrade. The better reasons are:

1. It actually works great in extremely hot weather;
2. it's provides far more storage capacity within the same space; and
3. it looks really fancy (with "Stainless" door - the only way to go).

[scrubjaysnest]

Looking at the ratings there is a little difference between 50 watts at 12 volts vs 5.9 amps at 12 volts. Still worst case is half what the Norcold draws and as had been said it will cycle where as the Norcold is on until you shut it off.

[ChefLamont]

It sounds like the thermostat works ok in the compressor fridge, but I will throw in some experience in one of my other hobbies. They do make controllers that have "anti-short cycling" protection settings. One that I have used on fridges and freezers is the Johnson Controls A419. It works great and you can set a minimum number of minutes that it has to wait before cycling back on. If you have enough thermal mass in the fridge and good placement of the thermocouple, that really should not be an issue. However, its a nice feature to have to protect the unit.

[rickst29]

Originally Posted by scrubjaysnest

Looking at the ratings there is a little difference between 50 watts at 12 volts vs 5.9 amps at 12 volts. Still worst case is half what the Norcold draws and as had been said it will cycle where as the Norcold is on until you shut it off.

Originally Posted by ChefLamont

They do make controllers that have "anti-short cycling" protection settings.

The Fridge includes an enforced Delay between compressor cycles - something between 60 seconds and 2 minutes. It also does the other usual things - running the fan for some extra time after the compressor shuts off (and some unusual things - switching to the 120V power converter whenever 120V is present). The amount of power consumption in the Fridge varies with temperature and pressure of the refrigerant gas, and also with the running rotational speed which has been set for the Compressor (using "tuning" resistors). It's definitely not "constant" like the Norcold.