What is a Three-Way Fridge? How to Use.

Just about every motorhome I have come across has something called a three-way fridge. But what is a three-way fridge?

 

A three-way fridge is able to run on three different types of power sources. These are mains electricity (240V AC in the UK), 12V DC from a battery and gas, using absorption technology. This makes them very versatile for having in a motorhome or caravan.

 

A fridge that can run on gas may be a bit weird to people, it was for me. Took me a while to understand how the burning of gas can cool a fridge. The three-way fridge is quite different from the average household fridge. A household fridge works with compression, whereas the three-way fridge works with absorption. The differences are explained in a bit more detail below.

 

Why Have a Three Way fridge?

Having the three-way fridge allows you to have the fridge on while you are driving. It allows you to have the fridge when you hook up at a campsite or to any mains power and it allows you to have a fridge if you are off-grid with no external power system.

If you tried to run the fridge from the leisure battery (we only have one) it would last no time at all. That is why the gas side of the fridge is so useful. A fridge is generally a power-hungry luxury. It uses a lot of power over time.

 

The three-way fridge is different from most domestic fridges. A domestic fridge is usually a compressor fridge, a three-way fridge uses absorption technology. This means that the three-way fridge is almost silent while a compressor fridge will have the noise of the compressor which can be really loud especially in a small motorhome. It must be said, the noise level of the compressor fridges are dropping and they are becoming very efficient.

 

A three-way fridge is almost maintenance free, mainly due to having no moving parts, and tends to last twice as long as a compressor fridge, about 20 years. Ours is getting close to 30 years old and is still working well. The cooling part of the fridge has no moving parts apart from the actual coolant circulating through the pipes.

On the gas the three-way fridge can run for about a couple of weeks on an 11kg gas bottle (depending on the ambient temperature), so you can free camp for quite a while and still have a cool fridge.

 

Is a three-way fridge better than a two way?

As with most choices for the motorhome, there does not seem to be a clear winner. Both the two way and three-way fridges have positive and negatives and it basically comes down to what you can live with.

 

A two-way fridge is a normal compressor fridge designed to run on 12 volts and mains voltage. They can be very efficient and can be run off a decent solar/battery set up. They can be noisy but the more modern ones are getting quieter all the time.

The 2-way fridges are very good at keeping things cool while the three-way fridge finds it more difficult the hotter the outside temperature is.

A three-way fridge has to be level to work properly while a compressor fridge can cope with being off level, although we have not had a problem with this so far with our three-way fridge.

The main advantages of the three-way fridge are – its almost completely silent. I say almost silent, sometimes I can hear the burner going in the middle of the night if I listen closely with my ear on the fridge, so pretty much silent.

The three-way fridge can run on gas. This is excellent if you are free camping in the wilds in the summer. You don’t have that drain on the battery or run the engine.

 

If you already have a good battery/solar setup or are considering getting one, a 2-way fridge may be worth considering if your three-way has died on you. The 2-way fridges tend to be a lot cheaper but you need the power to run them.

 

How to Use the Three Way Fridge

The 12 volt Side of the Three Way Fridge

This is connected to the alternator. Once the engine is started a relay clicks on and allows power through the 12-volt side to the fridge. Our fridge has a switch specifically for the 12-volt side in case you don’t need it during a journey.

If you want the fridge to run on 12 volts switch off the mains and the gas switch. Switch on the 12-volt switch and make sure the indicator is lit. The engine has to be running for this to happen.

You can select how cold the fridge gets with the dial next to the switch, the higher the number selected the colder the fridge.

The Mains Part of the Three Way Fridge

The mains on the fridge, on our fridge, is a large green switch. This lights up when the switch is on and we are connected via electrical hook up. You can select how cold the fridge gets with the same dial used for the 12 volts.

 

The Gas Side of the Three Way Fridge

The gas part of the fridge is on the opposite side from the electrical switches.

To use the gas part you have to make sure the gas is on, the gas isolator valve for the fridge is on and the electrical switches are off.

Once you are ready, turn on the switch on the gas side. It flashes yellow when the gas is lighting and you will hear the igniter clicking. Once its lit the switch light will go out.

All you have to do now is select the temperature you want the fridge to go to and that’s it.

Simple.

Took us ages to work this out!

 

How Does the Three Way Fridge Work?

A three-way fridge works using absorption technology but what does that actually mean?

It is quite simple chemistry but difficult to explain in simple language but I will give it a try.

 

A refrigerant is used in the system, Ammonia solution. It is heated by a flame or electrical element and the ammonia evaporates out of the solution as a gas, The ammonia gas has a low boiling point and the gas condenses in the heat exchanger cooling the fridge. The condensed ammonia is then reabsorbed back into a liquid and the process repeats. Simple. Maybe too simple, but good enough for me.

 

The three-way fridge is best described on this web page. Have a look, it’s the best I can do.

What is the Power Consumption of the Three Way Fridge

We have an old Electrolux Rm275. On 12V this fridge will use about 150W which is about 12.5 amps every hour. The three-way fridge uses a good chunk of power which would quickly drain down a leisure battery.

Consuming 12.5A would kill most batteries in about 6 to 7 hours. So it is not practical to run the fridge on the battery. This is why the fridge will only run on 12volts when the engine is running.

 

How Much Gas does the Three Way Fridge Use

With our fridge on most of the time, we have managed to get about 15 days from the gas bottle – 11kg. That would also include cooking as well as heating and some hot water. We do a lot of cooking but if you had a dedicated gas bottle for the fridge you should get a few weeks out of it. Obviously, this is just a ballpark figure as the ambient temperature would make a big difference. If you are in the middle of a heat wave the fridge will be using way more energy.

 

From the manual the three-way fridge uses about  0.27kg per 24 hours – this should, in theory, give around 40 days use on an 11kg bottle which seems quite good but you will be using that same bottle for cooking, heating and hot water which all help to eat up the gas.

 

Three-way Fridge in Hot Weather

As the heat outside increases, it gets harder for the fridge to keep things cool. An absorption fridge has to get rid of excess heat for it to work. The hotter it gets the more difficult it is to get rid of that excess heat.

An absorption fridge, the same type as ours should work up to the high 30s (degree C). Above around 36 it will start to struggle and above 40 will not work. There are absorption fridges that are rated for higher temperatures – these are rated for use in the tropics and can work at higher temperatures.

 

Do you Have to Keep a Three-Way Fridge Level?

You do have to keep a three-way fridge level. We never use levellers for the motorhome and always try to park on flat ground. It’s never completely level but we have never had a problem with the fridge. Saying that a lot of people do seem to have problems with the fridge not being level. So if you are having problems with the fridge you might want to eliminate this problem first by getting the motorhome level.

 

Three Way Fridge Modification

As a three-way fridge relies on getting rid of excess heat in order to cool down. Once the temperature gets to a certain level the fridge becomes less efficient.

A few people have had success in improving the efficiency of their three-way fridge by fitting exhaust fans at the top vent of the fridge. A three-way fridge has two vents one at the top and one at the bottom. The vent at the bottom allows air to flow into the fridge area for the gas burner and the top vent allows the heat to escape from the fridge. The gas burner has its own separate exhaust.

The top vent is where fans would be fitted to help vent the heat to the atmosphere. This, in theory, should help the fridge cooldown as long as the air temperature is lower than the heat coming from the fridge – for ours, this is almost 40℃. Above this temperature, the fridge will stop working.

In practice, many have reported good results and have given their old three-way fridges a new lease of life.

The only thing I would say about this is don’t be tempted to put fans on the bottom vent as you will disrupt the gas flow of the gas burner and it could cause the gas to burn inefficiently giving off carbon monoxide. Not good,

I will probably do this modification and see if it makes a difference (on the to-do list).

Do You Actually Need a Three-Way Fridge?

This is the question many classic motorhome owners ask themselves. I am one of them. If this fridge breaks down would I replace it with a three-way fridge?

A three-way fridge is an expensive beast, changing like for like is about £800. I am sure that the fridge would be so much better but £800 is a lot of money for a fridge that is why when I have to replace the fridge I will weigh up the cost of a two-way fridge and the cost of upgrading the solar/battery system. If it’s about the same cost I will probably do that.

 

Three Way Fridge Not Working

 

When we first go our motorhome the fridge would only work on the mains. The 12-volt side did not work and the gas igniter would not come on so wouldn’t light the gas. Remember to fix a three-way fridge you have to be comfortable with electrics and gas. If you are not please seek professional advice.

 

To try and pinpoint where the faults are it’s a good idea to have a little knowledge of how the fridge actually gets its power.

 

Mains Power

Our fridge has a direct cable to the fridge from a connector at the fuse box. This is what powers the fridge on mains and is a relatively simple connection from the mains to the fridge.

So, when you connect to the electrical hookup. Your fridge will have power.

 

If your fridge is not working on the mains make sure that the power is actually connected and you are getting power into the motorhome – sometimes a fuse can trip and although you are plugged in there will be no mains in the van.

 

Get the multimeter out (remember this is mains voltage you are testing. If you are not confident testing this get the help of a pro) and make sure there is power reaching the fridge. If there is you may have a dodgy fridge. If you are lucky you may just have a faulty switch.

 

12 Volt Power

The 12-volt power only comes on when the engine is running. The 12 volts for the fridge comes directly from the alternator.

If you are having difficulty with the 12-volt side this is what I did.

• Take off the bottom vent of the fridge – the vents are outside. There will be a top vent, bottom vent and the flue for the gas.
• The bottom vent should give you access to electrical connections. These are 12-volt. One for the gas igniter and one for the 12-volt power for the fridge. This is where I got lucky. Both these connections were completely corroded and I was able to replace the connections.
• Test the connections for 12 volts. One of them should have 12 volts – this will be for the gas igniter. The other connector should have zero volts.
• You have to start the engine and see if the connector with zero volts now shows about 12 (probably closer to 14V).
• If it does then you can rule out the relay as this will be working. If there is still no voltage with the engine running there is a good chance that the relay that comes on with the engine is faulty. This relay on our motorhome is at the rear of the fuse box.
• If there are 12 volts showing than the fridge should be on and the light should be showing.

As well as the corroded connectors we also had a problem with the 12-volt switch being a bit temperamental. I used some contact cleaner on that and it all seems to work perfectly.  

 

Gas Power

For the Gas side, there can be quite a few problems. For us, the problem was with the lighting. Once the corroded junctions were repaired the igniter started working again.

 

There are a few other reasons the fridge may not be working –

• No gas (simple fix – make sure you have gas and it is switched on and the valve for the fridge is open)
• Faulty gas regulator (this would affect more than just the fridge)
• Gas pipe blocked – rare but can happen
• Gas flue sooted up – years of use and not serviced
• Gas burner blocked – sometimes dirt gets in or rust
• Loss of coolant gas – usually terminal. These are sealed systems.

Most of these problems can be solved by going through the bottom vent and investigating in there. If you are a competent DIYer you should have no problem cleaning up the burner at the back of the fridge and while you are there a clean of the flue would be a good idea.

 

What if I Smell Ammonia Coming From a Three-Way Fridge?

The smell of ammonia coming from the three-way fridge is not a good sign. These fridges are completely sealed and use ammonia as the coolant. If you can smell it then the coolant is leaking. I have not yet come across anyone who has managed to have the fridge resealed and new coolant put in. Usually by the time this happens the fridge is at the end of its life.

 

Other Things to Take care of the three-way fridge.

Other things to watch out for is the door seal. Make sure the door seal is in good condition and the door closes properly.

Don’t let ice build up in the fridge. This greatly reduces efficiency. Not usually a problem in an absorption fridge but keep an eye on it.

Always make sure the vent covers are removed when the fridge is in use, especially when on gas. The airflow is required for the fridge to work well.

The motorhome fridge is another amazing luxury. It’s good to try and maintain the fridge to keep the efficiency high and to make sure that you get as long a life as possible from your fridge. The absorption type fridge is very reliable but you do have to take care of them.

 

Finding out about our fridge and understanding how it works has been a long journey. Hopefully, this blog will help you if you need to know about your fridge.