Experience: ARP Controller For RV Absorption Refrigerators

[gbrinck]

Some of you who attended Indio this past winter saw a presentation by Paul Unmac on the ARP (Absorption Refigerator Protection) controller he invented. Quite a few people bought one as a result. I've had an ARP installed in my Norcold 1200 since September, 2013, as part of a field test and I've had the opportunity to discuss ARP operation and use personally with Paul. My own experience is that ARP does exactly what it claims (see http://www.arprv.com/), monitoring the boiler temperature in the fridge cooling unit and managing it to stay within a safe, normal range. To me, this represents a fundamentally different and much better approach to the problem of keeping the fridge safe and healthy over the long term. The temperature device built in by the fridge manufacturer is a fail safe device, letting the boiler run amok until it nears catastrophic failure and then shutting it off permanently (or at least until a technician can replace the fail-safe module).

As part of the ARP field testing, I have a data collection package installed on mine, so I can see and capture the actual boiler temperature changes as I drive down the highway or park the coach. It's educational to see how much and how quickly the internal temperatures change as a result of fairly innocuous events such as stopping in traffic, lunching in a rest area, or parking outside a campground office for 15-20 minutes to register. It doesn't take a whole lot of tilt to send the boiler temps climbing, but the direction of the tilt makes a difference. A moderate lean toward the boiler recovery tank is not a problem, but a slight tilt in the opposite direction can quickly inhibit refrigerent flow and send temperatures climbing. I've watched Paul Unmac demonstrate this in his presentation using an actual Dometic cooling unit and it's amazing how quickly it reacts.

We all know RV owners who have had their fridges fail in just a few years of use and everybody swears they never operate off-level. The fridge makers tell us that we are OK as long as the fridge is level to within 3 degrees side-to-side and 6 degrees front-to-back, but that doesn't take into account the slow but inevitable degradation that occurs when temperatures go out of normal range for even brief periods. Even moderately high boiler temperatures cause the sodium chromate corrosion inhibitor in the refrigerant to crystalize, reducing its effectiveness and contributing to clogs in the tiny tubing of the cooling unit coils. To my way of thinking, that's a recipe for premature failure.

My Norcold 1200 has always worked well, but I felt that installing an ARP controller was a way to make sure I wouldn't have the sort of failure that I see happening to others.