Did a First Article Test on my Propane Fridge...

[SidecarFlip]

On another forum we have been discussing the virtues and drawbacks of ammonia fridges versus compressor fridges.

I wanted to see just how efficient mine was on fuel usage so, having my unit sitting in the side yard, I took a full propane bottle and set the fridge to run on propane, I want to see, 1. How much of as internal temperature swing I had from daytime to nighttime use and 2. How much fuel the unit consumed as well as the amp draw.

Here is my findings:

It took a month to deplete a full 20 pound bottle of propane.
The temp swing daytime / nighttime was less than 4 degrees overall (I used a digital recording wireless recording thermometer)
Amp draw averaged 2/10 amp without the external cooling fans operating, 2 amps with both FDB fans running and cooling the external condenser.

My Dometic is a typical slide out mount, intake low, exhaust high, so no natural convection in the fridge cavity, necessitating artificial induced convection (internal cavity air movement) via 12 volt cooling fans.

My fridge is modified with extra insulation between the fridge unit and it's exterior cabinet (FR see fit to install a minimal amount of insulation), I added 1/2 roll of R13 unfaced and filled the cavity.

I replaced the single Dometic OEM sleeve bearing fan (noisy), with 2 Fluid Dynamic Bearing 120mm computer muffin fans (quiet), wired through the OEM snap action thermostat (60 off, 80 on) affixed to the outside fin on the external condenser and wired through the Dometic control board (OEM).

Compared to a residential style (compressor fridge), power consumption is very low. A trypical compressor fridge pulls 4-6 amps running. While it might not be an issue when shore powered in a campground, it's a big issue when no shore power is available.

The unit was leveled within 1/2 bubble on my every present torpedo level.

You can basically run an ammonia fridge for 30 days continuous on one 20 pound bottle. Pretty economical in my view and the power consumption is within reason as well.

[SeaDog]

I don't think anyone has said they would not run a long time on propane and only sip DC that was a good test to bear that out, with that said I think the big difference besides the power required would be in recover rate after opening and closing door during day with the residential being faster to recover