Fridge Electrical Efficiency

[vandevsr]

As I switch over to solar powered boondocking, I'm wondering which is more efficient on my three-way fridge (assuming I'm not using propane): AC (through an inverter with it's losses) or DC? My fridge is a Norcold N300X. The manual shows these rough specs (AC120V- 1.4A; DC12V-12A), but it says quite strictly the DC isn't meant to cool things initially. It's only meant to keep cool while in transit. Which should I go with, AC or DC?

[tnchuck100]

Just my opinion that neither of those options are practical for boondocking/solar. Just for my own curiosity why are you rejecting propane? That is the very best option for boondocking.

[vandevsr]

Two things:
Being out of range (far north) for up to a month, limits the availability of propane, and leaves me prone to extreme prices for a refill.
Also, propane can't run every single appliance. Electricity can. I'm putting all my eggs in one basket without throwing out the other basket, because as far as propane goes, it's hard to beat. (One day, I may be running a propane fuel cell, or a propane fueled eu1000i generator).

[tnchuck100]

Even so using one 20# bottle of propane to run only the refrigerator would be a better choice. That one bottle would likely run just the refrigerator for over a month.

Electric and the refrigerator for boondocking is not the way to go. Efficiency? Very poor.

[Todd Klassy]

Given how much propane the refrigerator uses I'm told it is much more efficient than using the batteries. HOWEVER, one should know, even when using propane it is still using SOME electrical power.

[vandevsr]

I've considered the propane. I'm wondering which is better, AC or DC? If someone knows whether DC uses the Peltier effect and the AC a compressor, even that helps, but I have no clue.

[tnchuck100]

Originally Posted by vandevsr

I've considered the propane. I'm wondering which is better, AC or DC? If someone knows whether DC uses the Peltier effect and the AC a compressor, even that helps, but I have no clue.

Neither type. These are absorption refrigerators. They work by heating an ammonia/hydrogen solution and allowing to circulate though the system absorbing heat from the interior of the refrigeration. There are no moving parts or a compressor.

Whether you use 120VAC, 12VDC or propane the refrigerator operates the same way. You are merely selecting a heat source.

Since you seem to be intent on electric 12VDC would be the least detrimental to the electric supply. At least you would avoid the losses incurred by the inverter.

However, I full well believe you will find your solar will not be able to keep up with the demand using this method. Take into consideration as well you don't want to deplete the batteries more than 50% if you can help it. Battery life takes a hit discharging below 50%.

[vandevsr]

Thanks tnchuck! It's helpful to know it's the same principle behind AC and DC. That helps me predict they will have a similar duty cycle, so that my 500W of solar (2x250W panels) will take care of the approx 170W (or so) of the fridge. A few golf-cart batteries do the buffering. Somewhere in here, there's a plan to run a 5k-BTU AC unit too. It's no small plan.