Welcome to Manins' truck camper project

The Refrigerator

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The Camper was supplied with a 230 V Westinghouse 120 litre Bar Fridge, WIM1200SC (550W x 570D x 845H) modified by Caravan Refrigeration Service in Brisbane. They replaced the compressor with a Danfoss BD35F unit that runs off 12 V DC and changed the refrigerant from R600a (isobutane: ODP of 0, GWP of 3) to R134a (an HFC with ODP of 0, GWP of 1430! — see: Linde Group), which must have been done to be compatible with the Danfoss unit's lubrication needs.

Due to an unfortunate occurrence, the fridge died and its death was made terminal by a local refrigeration service agent. Not really such a tragedy since 230 V power is available in the camper, a 230 V fridge is much lower cost than a 12 V conversion yet consumes much the same energy, and the change of refrigerant was a retrograde step. Further, although the 12 V version of the fridge performed better than the Vitrifrigio we had in a previous motorhome, it still had a mind of its own, performing well for weeks at a time but then refusing to hold temperature until fully defrosted and restarted. In really hot weather the fridge proved to perform poorly with large variations of temperature from day to day and large variations within the fridge. Frozen vegetables at the back, cool at the front. An internal fan would have helped with the latter problem and this has been done (see below).

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View in the left drawer carcase. Cooktop above, 15 A surface mount socket for the cooktop. Below is a 10 A surface mount socket for the fridge.

I have replaced the fridge with the same model Westinghouse Bar Fridge but this time unmodified and running off 230 V. The fridge has an energy rating of 1 Star, and has 117 litre capacity in the fridge, 3 litre in the freezer. Importantly, the condenser cooling fins are at the back so the fridge can be built into a small space. Achieving any energy star rating must be a good thing. Its coolant, isobutane (R600a), is butane "with added vitamins and minerals"; it has low environmental impact and excellent thermodynamic performance (10–20% better than R134a) and it is now the refrigerant gas of choice in domestic and small commercial refrigerators. The result is a fridge that uses less energy than one running R134a or any of the R40 range of numbers.

Performance

The specified enegy consumption of the WIM1200 is 282 kWh/yr, which works out at 32.2 Wh/h or 2.4 A/h @ 13.2 V. This is about the same as a Danfoss BD35F fridge running half the time, but is for real-world conditions. Unlike the 12 V version, the unmodified fridge makes proper use of the rear "wet wall" feature and does not build up ice. So defrosting is not necessary – a real bonus when travelling. The user manual says the ice box should be defrosted when ice builds up to 4 mm thickness but this seems to take several months.

In service, the fridge draws 74 W when running but startup briefly requires up to about 660 W. These are much higher figures than for the Danfoss version of the fridge. A test over 12 hours with the fridge at 1..2°C and freezer at -12°C showed a consumption averaging 13.7 W or 1.05 A at 13.2 V. The fridge actually ran for 2 h 2 min of the 12 hours. I would have expected the 12 V fridge to run about half the time and average a little over 2 A at 13.2 V. The performance of the 230 V fridge is excellent.

That the fridge performs well in practice was confirmed in a five-month trip (May..October 2016) through the Northern Territory and Cape York Peninsular where the temperatures were over 30°C every day and sometimes well into the night.

The only negative with using the fridge on 230 V is that the inverter must be on all the time, and this overhead is 2 A or 26 W, or 48 Ah over 24 hours — perhaps more than the fridge over 24 hours! Some people use a separate inverter just for the fridge; but since this is not an "inverter fridge" the startup current requirement is high and this means a largish inverter, most of which have poorer overhead than our Victron. Of course the inverter is used for other things too, particularly the cooktop, so it's convenient to have the inverter on all the time.

Temperature Monitor

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To monitor the performance of the fridge and the freezer I am using an AcuRite 00986 Refrigerator/Freezer Wireless Digital Thermometer purchased through Amazon.

The sensors are located away from the cold plates. The display is centred on the wall behind the fridge so it is easily seen. The wireless setup is very convenient, providing the necessary assurance that all is well in the fridge. Alarms for over-temperature can be set and I have used this sometimes.

Internal Fan

An internal fan, running all the time the fridge is on, was somewhat successful in my previous motorhome in keeping fridge internal temperature variations small, but there were problems with items interfering with the fan and the fan taking up too much space. In the present fridge the shelves have a gap of 18 mm from the rear "wet wall" cooling plate to allow air circulation. This gap is ideal for a fan, if only such a thin one could be found.

Cooling pads for notebook computers have exceptionally thin fans, and the "Partlist NCPPL05 Stylish Quiet Slim Laptop/Notebook Cooler Pad" from MSY for $9.00 is remarkably cheap (Apr17: $4.00 clearance!) and very suitable. It is less than 20 mm thick, runs off a USB port and has a metal mesh guard. It is a slow speed (1200 rpm) 200 mm dia. fan and consumes less than 1.75 W (133 mA at 13.2 V).

I disassembled the Cooler Pad, discarded the plastic base and attached the fan to the metal mesh. Six 17 mm high wooden dowels were hot-melt glued to the mesh to act as standoffs. A USB cable was threaded into the fridge compartment up the existing drain hole and connected to the fan. The whole fits snugly behind the shelves, and runs very quietly off a 5 Volt USB port.

Cooler Pad fan installed in/on the mesh; standoffs glued on.

The 5 Volt connector is on the outside of the mesh.

The fan is held in position by the shelves. The LEDs give some comfort.


The internal fan has now run for just over six months continuously and has proven to be a great success. The air circulation has ended earlier issues with items freezing at the rear cool plate and has probably helped with the automatic defrosting feature which also worked well.

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