How to keep your cool

Picking the right RV fridge is not as easy as you think

One of the greatest inventions that make all the difference when camping in your home- away-from-home is the humble RV fridge.

You won’t find a caravan kitchen built since the 1970s that didn’t come with one fitted, and even the cheapest camper trailer today offers at the very least a slide-out for a portable one…

The problem is that not all RV fridges are the same. If you’re new to caravanning, motorhoming or camper trailering – or perhaps not so new – you’ll need to get to grips with how your fridge works and importantly, what type works best for you.

Which one?

Typically, there are two types of fridges used in mobile homes –absorption and compressor. Absorption fridges came first in caravans and, while still popular, advances in power generation and storage mean compressor fridges are gaining momentum.

There were absorption fridges available until the 1980s that ran on either gas or 240v but the most popular type since then has been the three-way fridge, offering the choice of running on gas or your choice of 12volt or 240volt power.

Without trying to make your eyes glaze over with technical stuff, it’s important to get the gist of how these fridges work. An absorption fridge has a sealed system with next to no moving parts. It has tubing snaking its way behind and through the cabinet which contains an ammonia solution (and hydrogen and water to keep the ammonia moving and complete the cooling process).

The action starts when the ammonia solution is heated up (either by gas, or a 12v or 240v heating element) and then cooled. It then mixes with hydrogen and evaporates; a process that ultimately cools down the interior of the fridge cabinet.

The beauty of this system is that it’s so basic – there’s little that can go wrong with an absorption fridge. The tubing can corrode (after many years), resulting in the ammonia solution leaking out and the fridge not cooling.

If the inside surfaces of the fridge cabinet have turned brown, it’s not because the previous owners smoked heavily in the van with the fridge opened – this is evidence of an ammonia solution leak. Absorption fridges can be repaired for roughly half the cost of a new one.

The main advantage of an absorption fridge when camping is that it’ll run pretty efficiently on gas – perfect if you’re free-camping. With smaller fridges, you’ll get two to three weeks running out of a full 9kg bottle of gas.

Problems with absorption

There are three potential problems with an absorption fridge, even if it’s in perfect working order.

Firstly, the fridge has to be close to level for the solution to work its way around the system – and therefore do its job of cooling the cabinet (although they seem to run fine when on the move). An absorption fridge often won’t work unless it’s within a couple degrees of level.

There are also issues relying on 12v power – an absorption fridge is heavy on the juice when it’s relying on 12v to power its heating element.

You need to be careful if you have power hooked up from your tow vehicle to run the fridge on 12 volts when on a transport stage; leave the vehicle hooked up and the fridge running overnight and you’ll most likely run your tow vehicle’s battery flat (although if you hook up a low-voltage shut-off switch it’ll avoid this).

This also becomes an issue when bush camping – you really have to run on gas rather than 12volt power, unless perhaps you’re using solar panels.

Lastly, absorption fridges don’t pull down temperature within the cabinet too well in hot ambient conditions. While newer absorption fridges are more efficient and do a better job of keeping your perishables fresh, at much more than 35 degrees ambient, they can all struggle.

Keeping the fridge cabinet down at four degrees (which is really the maximum temperature you want to keep fresh food from going off) is not a given with an absorption fridge running in high ambient temperatures.

To get your absorption fridge to cool more quickly before your trip, add frozen bottles of water or ice packs to the compartment (if you have the space) before heading off. In fact, if you’re only carrying a few items in your fridge, the fridge will have to work harder to keep temperature down – more perishables or bottles filled with frozen water will help.

Gas can be tricky

Level the van before you go and run the fridge on gas overnight to get it to cool the compartment. Although there’s no law to say you can’t run an absorption fridge on gas while towing, it’s not a good idea. If the gas flame extinguishes and the automatic gas cut-out fails, you could be faced with a gas-filled caravan interior just waiting for a spark to go boom.

At camp ensure you don’t cover the vents on the outer wall behind the fridge. For the absorption method to work, it needs air to circulate to cool the tubing.

Setting up a shade over the vents (but not so the vents are covered) can help reduce heat from a hot summer sun, and a solar-powered cooling fan is also an excellent idea, as is a thermometer to check how well the fridge is working.

The compressor option

Compressor fridges, a bit like an absorption fridge, have tubing running in and around the fridge with a gas that is pressurized, cooled (which turns it to a liquid) then evaporated, giving the cooling you need. The key element to this is the compressor, which compresses the freon gas (typically R134a as used in cars) to begin the process.

Compressor fridges can only be run on electricity and are noisier as the compressor cycles in and out, although they’re usually not noisy enough to wake you up at night (unless the fridge is ancient and the compressor motor is getting tired).

Unlike absorption fridges, being level isn’t critical and they can pull temperature down much more quickly and keep it there even when it’s a hot day.

The main disadvantage with compressor fridges has always been how to keep power up to them when free camping – they’re best suited to running off the tow vehicle’s battery on transport stages and then hooking up to 240v mains power at caravan parks.

Having said that, if you’re prepared to invest a chunk of money in a good battery and solar set-up – and cop the extra weight of these components and the storage space they take up – then you could potentially have weeks of refrigeration out in the bush.

You’ll still need a fair bit of solar input – 160watts of solar panels to keep the battery fed with enough juice just to keep the fridge running, and that’s with a small fridge. If you’ve gone for a 200 litre-plus compressor fridge, you’ll find it hard going to keep it running with enough power for a bush stay unless you’ve got a whole lot of solar panels, a generator as a back-up and don’t get a lot of cloudy days.

Using a generator to top-up the battery during the day is a good option to extend your compressor fridge’s running time off-the-grid. If possible, run the fridge on 240v power overnight before you head of on your trip so that it can pull down temperature and, as with an absorption fridge, filling it to capacity with cold food or frozen bottles helps.

While not as sensitive to performance as with an absorption fridge, a compressor fridge still needs adequate ventilation – don’t cover the external vents on the van’s exterior wall.

Cool heads required

Choosing between an absorption or a compressor fridge comes down to the set-up you are prepared to invest in (a compressor fridge set-up is usually a bigger outlay), and what camping you do and in what season.

Compressor fridges are better at getting temperature down and keeping it there while absorption fridges can be a lot more versatile in the bush with their ability to run efficiently on gas, just so long you can keep them level…

How to keep your cool

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