How do they work?
Frost free fridge freezers are very popular and auto defrosting fridges are a great convenience. In a frost free appliance the cold air is blown round the freezer using a fan. On modern refrigeration the evaporator (which is the plate that gets cold) is hidden behind the plastic wall inside at the back of the food shelves. When working correctly you can usually see small beads of ice randomly scattered on the back wall unless it’s in a defrost cycle when you may see water.
Heater inside
the 
Believe it or not most modern refrigeration has a heating element inside. This heater is used to defrost the appliance automatically. During the defrosting cycle the ice on the back wall melts and runs down the back wall into a channel. It is then directed through a hole out through to the back and runs into the evaporator tray. The evaporator tray is on top of the compressor which gets pretty hot and evaporates this water into the air.
Because the evaporator is behind a back panel the cold air has to be blown around the compartment with a fan motor. The defrost cycle also needs sensors and a timer and combined with several sensors throughout and PCBs to control everything the result is there is a lot more to go wrong than there used to be in old-fashioned conventional fridges. However, they are still fairly reliable.
Common problems with frost free fridge freezers
If the door is left open for too long (especially in humid conditions) the evaporator freezes over and the unit will not keep the food cold. This problem (unlike the older machines) has a greater impact because you can’t see the amount of ice built up around the back of the panel hiding the evaporator.
In many frost free fridges the ice can form all the way round the fan and cause it to run slowly or even seize up. Prior to seizing up the fan may catch on the ice and make a high pitched noise. This will of course result in the fridge or freezer not getting cold. If you hear a strange noise from your frost free fridge freezer which sounds like something is catching on a rotating fan it could be due to ice forming around it.
If it stops working due to ice forming behind the evaporator and round the fan then defrosting the unit manually can fix it but it involves unplugging the unit for at least take 12 hours or so.
You may not see much frost as it would be behind the back wall or behind the fan unit.
You can’t really use a hair dryer on modern units because they may have a thermal fuse which protects the defrost cycle.
Also, even just getting to the evaporator to defrost it can be a mammoth task especially with some of the new American-style fridges.
If a fault re-occurs later it could be due to faulty sensor but if the fault was only due to the door been left open for a few hours accidentally then a total defrost could work. This demonstrates the type of problem many people have when confronted with these larger bulky hoses with specific fitting instructions as described in the main article on the left.
Water or sheet of ice inside fridge
If your fridge has two sloping channels at the back wall and a hole in the middle this is designed to channel the water created on the defrost cycle through to the back of the unit where it runs onto an evaporator tray which can get blocked. More details on this here- Ice or water in base of fridge or freezer.
Whilst we are on with American style frost free fridge freezers, because the doors are so big and can store so much, the opportunity to overload them is greater. This too causes warm air to pass into the unit and frost it up.
Remember a frost free unit will not cope with too much ice on the evaporator so greater care must be taken to use it correctly and check the door seals regularly.
Summary
It’s common knowledge that most people rarely read the instruction book supplied with their new appliance. This is particularly true with something like a fridge or freezer. It’s easy to imagine most people thinking you only need to plug it in, leave it plugged in, and fill it with food – what’s to know?
I would advise anyone with a modern refrigeration appliance, especially the American-style fridge freezers, to carefully read the instruction book. Modern frost-free refrigeration units work very differently to a conventional fridge or freezer. It’s even important to learn how to stack them properly otherwise you can prevent the air from circulating inside and cause warm spots.
You would be surprised at what you can learn from reading the instruction book of an appliance you already know how to use. Many User instruction manuals can be downloaded here.The page concentrates on washing machine manuals but links to appliance manufacturer sites where users such manuals for fridges, freezers and other appliances should also be available.
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I am considering on buying a fridge freezer. On some of them there is a sign “No Frost” and on some “Frost Free”. Is that the same? And another question: Is it better the freezer to be on top (freezer top), or on bottom (freezer bottom)?
Thank you in advance
Hello Gjorgji: It’s possible some manufacturer’s are using the different phrases to describe the same product. Logically the terms “no frost” and “frost free” should mean exactly the same thing. You need to check with the sales people if there is any difference. If there is I’d like to know and would write an article specifically about it to clear things up.
Regarding the position of the freezer as far as I know it would be just down to personal preference. Most people are likely to prefer the fridge on top as they are likely to use it frequently each day but maybe someone frail might prefer the freezer on top if they found it easier to load and unload. Come to think of it I didn’t even know you could get one with the freezer on top. If it was a tall one you’d need step ladders to get to the top drawer.
My fridge has two channels at the back leading to hole in the centre. This hole tends to get blocked with ice frequently why is this. Do items in the fridge that touch the fridge walls make the back wall and hole ice up, if so why is this. Why does it ice up if things touch the walls, making sure food items are not touching the sides sevrely reduces the amount of space I can place items on each shelf. I would see this as a design flaw. Can’t something be done in the design of the units that makes it ok for items to be touching the side walls.
Please can you return your answere to me via email. Many thanks Neil.
I have a Zanussi ZI 920 integrated F/F which is frost free and has been working for about 6 years OK. Symptom is the common one of Freezer works OK, but fridge warm.
Fitted new defrost timer and now the freezer temp is uncontrolled. It hits the stop on the manual gauge.
There is a fan in the freezer compartment above the evaporator, but no fan and no ducting for the fridge. I am toold that there must be a separate evaporator for the fridge.
Thermostats near the evap. OK, fan and timer OK.
The condenser behind the unit gets quite hot in the first quarter, but the rest is just cool.
Any suggestions please as I am at my wit’s end.
Thanks and regards,
John
Neil: I don’t reply by email as that wouldn’t help anyone else reading this in the future. The channel is there to allow water from the back wall, which runs down after a defrosting cycle to be channelled through to the back of the appliance and run into a drip tray on top of the compressor. This tray gets hot from the compressor and the water evaporates. Items should be kept away from the back wall and is one of the disadvantages of frost free fridges as you can’t pack too much in them which restricts the cold air flow.
If the hole is icing up it can cause water to flow into the base of the appliance and form a sheet of ice. This can happen if the hole is blocked somehow and the water doesn’t run through to the tray at the back.
John: Sorry I can’t try to solve specific faults but the fan should be in the freezer compartment. The fan then blows the cold air around the fridge compartment. If the fan was in the fridge it couldn’t circulate any cold air.
H Neil, I found out that this fridge freezer has a separate cooling coil with a fan hidden under all the foam sound proofing. The diagnosis is that there is insufficient gas (due to leakage) to cool the fridge section. It would need all the insulation to be removed and even then it woul dbe difficult to find the leak to repair and recharge the system.
So I was advised to switch off it’s life support machine and replace it with another Unit.
Many thanks for your assistance.
John
The User Handbook supplied with our new Zanussi fridge freezer advises cleaning the dust off the condenser annually.
The condenser is however concealed by a backplate and not accessible by a long handled dusting brush! as advised by Zanussi Customer care. Should we leave well alone! Thanks in anticipation!
Jopaco: Do they not mean the black condenser at the back of the machine which is open to the air and gets very dusty? The gas passes through and loses heat there and attracts a lot of dust. I wouldn’t have thought a part concealed under a backplate would get any dust.
That is our point , Dear Washerhelp, there is no exposed condenser on the rear of our new Zanussi fridge freezer ZRB227XO, just a flat back from the compressor opening at the base to the plastic top plate which is also without vent openings.
Hi Andy,
We think our Zanussi fridge freezer ZRB227XO is of the ‘Flat Back’ type of design as per Googled spec. sheet and therefore the condenser is not exposed or accessible at the rear of this unit. The User Handbook is at fault advising annual cleaning of the condenser on this model. Please accept our apologies for wasting your time. Unit performance seems satisfactory.