KEEP IT COLD
We talk different kinds of fridges and compressors, and how to get the best out of your fridge
COMPILED BY CARAVAN AND MOTORHOME
Most of us understand the benefits of having a fridge when you’re out exploring the country. The ability to keep food and drinks cold and fresh for a long period of time is a huge benefit us modern day explorers are blessed with. But there are a lot of things worth considering before you add the convenience of a 12V fridge to your setup.
We brought you the huge 12V Fridge Comparo a couple of issues ago, now we bring you the very best tips and tricks for getting the most out of it. Apart from the initial purchase price of the fridge, what hidden costs are associated with setting your camper trailer up to cater for a fridge? How do you ensure your fridge lasts the distance, and how can you improve its overall efficiency? We answer these questions and more in this piece full of essential information to help you choose the right fridge and ensure it lasts a lifetime.
ARE ALL FRIDGES CREATED EQUAL?
NO! Don’t spend your money on a fridge that won’t do what you want – here’s a closer look at what fridges are available and how much you should expect to pay.
Often the cheapest type of fridge on the market, thermo-electric fridges work by passing current through two dissimilar metal conductors to either cool or heat the inside of the fridge.
Sure they’re cheap, but most are only able to cool to about 20°c below the ambient temperature; so on a 30°c day the coldest most thermo-electric fridges will get is down to 10°c. They’re also power-hungry by nature and will quickly drain your battery if left on without the engine running.
EXPECT TO PAY: $150-$300
12V COMPRESSOR FRIDGES
A compressor fridge uses either 12V or 240V power to drive a small internal compressor which pumps refrigerant through a series of cooling tubes. As the refrigerant flows through the evaporator elements inside of the inner walls of the cabinet, it removes heat from your food and drink and disperses it into the outside air via the condenser.
Compressor fridges have an excellent cooling ability in high ambient temperatures (some units can cool up to 60°C below ambient), use 12V power efficiently and can be operated in rough terrain and on angles of around 30°C, making them perfect for us 4WDers.
EXPECT TO PAY: $600-$1,600
What makes a 3-way fridge unique is that they can be run off 12V power, 240V, and mostly efficiently off gas. That’s because instead of using a conventional compressor, they use a heat source to boil a furnace. The furnace kick-starts a sequence of chemical changes promoting the flow of refrigerant around the cooling circuit. As the refrigerant flows through the evaporator inside the fridge, it removes heat from your food and drink and disperses it into the outside air.
While most 3-way fridges will do alright to maintain temperatures on 12V or 240V power, they work best when running on gas because a naked flame is more efficient at boiling the furnace than an electric coil, thus the flow of refrigerant is greater. Thing is, though, that means you can only run them in a wellventilated area around camp – this is bad news for the milk and butter if you’re shifting camp each morning – and what you save on the initial purchase price you end up spending on gas to keep it running.
EXPECT TO PAY: $300-$700
With Collyn Rivers – Caravan and Motorhome Books
• When installing a fridge wiring harness, the connecting cable must have low voltage drop – ideally no more than 0.2V. Almost all fridge wiring harnesses have cable that’s only a quarter of the essentially needed size.
• Never connect your fridge via the vehicle’s cigarette plug/ socket. The cable used between the main battery and 12V socket by the vehicle manufacturer is often not designed to be used with aftermarket 12V fridges.
• A fridge is designed to transfer any heat from inside the unit to the outside. This heat must be free to escape, meaning some ventilation is vital. Cool air must also be able to enter from the base.
• When possible, refrain from setting the fridge colder than 4°C, or the freezer to below -180C. The extra work required to maintain these temperatures causes the fridge to work much harder.
For more information, check out Collyn’s articles and books at www.caravanandmotorhomebooks.com
Primarily used for marine applications, eutectic fridges use a similar cooling method to a compressor fridge, only instead of constantly running the compressor to pump cool refrigerant, they only use it to pre-chill unique eutectic pods (similar to ice bricks) inside the fridge’s inner walls to keep your food and drink cool. The plus side is that once it’s down to temperature it can be switched off and still keep your food and drink cold for days. Manufacturers claim eutectic fridges use less power on average, but most consumers are put off by the hefty price tag that usually accompanies a eutectic fridge.
EXPECT TO PAY: $2,500
5 TIPS TO HELP YOU FIND THE PERFECT FRIDGE
1 Spilling your food or drink is bound to happen when you’re camping (particularly if you have kids), so buying a fridge that’s easy to clean saves hours of hard work down the track. Look for handy features such as removable baskets, rounded corners, smooth walls without lips or joins as well as a drain plug to make cleaning easier.
2 3-way fridges might seem cheaper to buy on face value, but with the ongoing cost of gas, their higher 12V power consumption and their need to be perfectly level and well ventilated while running – you’re often limited in where and how you use them.
3 Look for a fridge with a digital display and controller. They’re better able to maintain an accurate set point, and most can vary the compressor operation to reduce power consumption.
4 Insulation bags are worth their weight in gold if the fridge you’re looking at comes with one. They not only improve the overall efficiency of the fridge, but they add an extra layer of protection from water, dirt and dust as well as protect the fridge from direct sunlight which drastically affects the fridge’s performance.
5 Most new buyers are so caught up in how good the fridge is they forget to check the power adaptors that run it. A dodgy power supply or connection will bring even the best fridge to its knees – so only invest in a fridge with a good quality power supply and connectors
ARE ALL COMPRESSORS THE SAME?
SECOP (DANFOSS) BD35F
The Secop compressor (formerly branded Danfoss BD35F) is found in a number of portable camping fridges including the ARB, Ice Cube, Powertech and Primus units.
Using their 35+ years of refrigeration experience, Danfoss have finetuned their compressor technology and earned themselves a reputation for reliability, performance and efficiency. In 2010, Munich-based company Aurelius AG bought out Danfoss, and soon after, the Danfoss name was changed to Secop.
The Secop compressor uses an electric motor to move a piston up and down a cylinder via a crankshaft and connecting rod. This reciprocating motion pumps refrigerant around the cooling circuit, enabling the cooling cycle to take place.
The Secop compressor employs a variable electronic controller to determine the best rotating speed for the compressor. This controller allows the compressor to run at slower speeds as the unit first starts up and closes in on its temperature set point, reducing current spikes and average power consumption over long periods of use. Designed to operate at angles up to 30°, it’s an obvious choice for 4WD fridge manufacturers.
Crack one of the new WAECO CFX fridges open and you’ll find WAECO are now using their own compressors. WAECO have been developing compressors for mobile applications for years. In fact, they worked together with Danfoss in the 1970s to develop what would become the Danfoss BD series compressor. Now some 35 years later they have co-developed a new compressor in collaboration with a high volume compressor manufacturer that they’re keeping very tight-lipped about, this time carrying their own stamp.
At the heart of the WAECO compressor is an electronically driven reciprocating piston design that pumps refrigerant around the cooling circuit. The electric motor and pump assembly are mounted on calibrated springs inside a thick steel shell to isolate noise and vibration.
Design elements such as material selection, surface finish, oil and lubrication paths and spring calibration have all been tailored to suit Australian road conditions.
Variable Motor Speed Optimisation (VMSO) is also featured in the WAECO CFX range. VMSO taps into the variable speed functionality of the compressor to optimise the cooling speed through automatic selection between ‘Soft Start’ and ‘Turbo’ modes, reaching the set temperature faster, and then maintaining the temperature. The WAECO units can also operate efficiently at angles up to 30°.
SAWAFUJI SWING MOTOR
The Japanese made Sawafuji Swing motor is used by Engel in their range of fridge/freezers. The Sawafuji Swing motor doesn’t use a traditional crankshaft or connecting rod to drive their piston.
Instead it uses a combination of springs and electro-magnets that move the piston up and down when it’s needed. By utilising this technology, it eliminates the need for wearing parts like bearings, cranks or connecting rods.
Efficiency is also a key benefit of Sawafuji Swing motor. Because it has only one moving part, less friction helps lower current draw.
The Sawafuji Swing motor uses rubber mounting bushes that are then suspended between shock absorbent springs to ensure the motor is completely isolated from harsh knocks or vibrations – great if you’ve ever hit a cattle grid at speed. Like the other compressors, it’ll also run at angles of up to 30°. The difference is the Swing motor is designed to run almost constantly, so while it has less hour-for-hour power draw than the other compressors, it still draws more overall as it’s running for longer.