The most important part of your fridge is the compressor. It is the ‘engine’ and should not be overlooked when buying a recreational fridge. There are 2 main types, the Danfoss and the Sawafuji. Both are purpose built compressors designed specifically for mobile refrigeration. Almost all fridge brands now use the Danfoss compressor however Engel uses the Sawafuji swing compressor. We outline the main features of the two compressor types and some typical pros/cons of 2 big fridge brands, Waeco and Engel.

Danfoss Compressor & Controller

Made in Germany, the Danfoss BD35F uses an electronically commutated permanent magnet with variable speed brushless DC motor. These compressors are capable of operating from 2,000 rpm to 3,500 rpm. The controllers also feature built in diagnostics by way of a flashing LED. There five fault conditions which can be identified by counting the number of consecutive flashes. It is a simple matter to vary the compressor speed to enhance cooling performance. In Waeco fridges, the speed is usually set to 2,500 rpm in normal use, but this is increased in the ‘Turbo mode’ of some Waeco fridges. At 12V, the BD35F can consume a minimum of 1.5A @ 2000 rpm to a maximum of 6.5A @ 3500 rpm.

Sawafuji Compressor & Controller

Made in Japan, the Sawafuji compressor is driven by a reciprocating piston, connected to an electro dynamic device which is powered by magnetic fields. On start-up, the piston moves down just a fraction then returns. It slowly increases the distance the piston travels each stroke until it reaches a full stroke. This means it doesn’t have a high start up current draw. The real secret of how they work lies with the electronics. The compressor is driven by an AC voltage with the power supply's waveform, frequency and timing being critical for the correct operation. The power signal needs to ‘agree’ with the natural resonance of the compressor under varying load conditions. This is an entirely different approach to the more conventional Danfoss.

Which Compressor Is Better?

The below summary of findings is made after viewing many test results, ignoring results coming from test done in ‘less accurate’ environments. 

Warranty: 5 years on the Waeco’s Danfoss. 3 years with the Engel’s Sawafuji.

Durability: The Engel, has been running well for over 30 years. Thirty years from now, maybe we can look back and say the same for the newer 2005 Danfoss powered compressor.

Noise & Vibration: The Danfoss is quieter and almost free of vibration in contrast to the Engel, this is a significant factor if you are trying to sleep nearby. Vibrations can often be felt in motorhomes, caravans or boats fitted with built-in Engel fridges.

Temperature limits: Many test have found that in the higher temperatures (around 45-50 deg) the Sawafuji performance is not as good as the Danfoss. The Danfoss was able to bring the fridge temperature down to a lower temperature.

Power: The Danfoss is more powerful - around 20% more. This is reconfirmed in many tests showing Sawafuji compressors are much slower to lower the fridge temperature than Danfoss powered fridges.

Efficiency: Waeco is the clear winner. The 4WD Action Magazine recently tested and compared a range of fridges against each other. A test was to determine average current consumption in a 'Real World' situation rather than a laboratory.

How the test was done. Fridges were placed in the chamber together, connected to 12V, 40A DC power supply. Each fridge was then packed with 2L milk, one loaf of bread, 250g butter, six cans of soft-drink, 1.25L water and 450g sausages. Fridges with freezer compartments had a bag of frozen peas added to ensure it was cooling more than just hot air. The fridges were set to 4°C and left to run over night to ensure even temperature saturation. The temperature chamber was then set to run from 25°C down to 0°C over 10 hours, at which point 0°C was held for two hours before ramping back up to 25°C over another 10 hours. From here, the fridges were allowed to stabilise at 25°C for two hours before ramping up over 10 hours to 60°C which was then held for 2 hours, before returning back to 25°C over ten hours again allowed to stabilize for another two hours. Current draw was measured every half second and temperature was constantly measured.

Cold Climate Test Results: 25°C > 0°C > 25°C (Avg 17°C)
Waeco CF50  = 3.95A over thr 24hr period.
Engel MT45F = 5.20A over the 24hr period.

Hot Climate Test Results: 25°C > 60°C > 25°C (Avg 37°C)
Waeco CF50  = 38.33A over the 24hr period.
Engel MT45F = 45.25A over the 24hr period.

For more details please see 4WD Action's full Fridge Comparo report here.

The Pros And Cons Of Both Brand’s Mid Sized Portable Fridges

Waeco CF40 & CF50

Pros:

• Good control panel. It is easy to use and the most sophisticated.
• 3 stage battery protection - set on digital display.
• Error codes displayed.
• Light weight.
• Good warranty (5 years on compressor & 3 years on the rest).
• Excellent value for money.
• Great service technician support network.

Cons:

• Has a flimsily cord used to prevent the lid from opening too far.

Engel MT45 & MT60

Pros:

• Rugged & Solid.
• Separate fridge and freezer.
• Been around for many years.

Cons:

• More expensive than the Waeco.
• No low battery cut-out.
• Less substantial warranty compared to Waeco.
• Noticeable vibration and on a lesser extent noise.
• In hot weather, performance is not quite as good as the Danfoss.

For more details on the Waeco portable range, see our "Waeco CF Fridges" guide.