Fridge

Most people now have a fridge freezer as their main machine, but fridges are still useful for supplemental space.

A fair bit of the information here also applies to fridge freezers.

Larders & frost free fridges

Standard fridges have an icebox, which will ice up and require periodic defrosting.

Larders contain no icebox, and don't frost up, so are frost free.

Brands

Pretty much all brands of fridge have a good reliability record. (This is less true of fridge freezers.) Liebherr and Miele are generally reckoned to be among the best makes.

Faults

Fridge faults can be caused by external factors.

Damp and water splash cause case rusting.

Liquid oozes inside the fridge can penetrate interior lining junctions and saturate the insulation at the bottom, leading to external dripping, rusting, increased power consumption and sometimes smells.

Inadequate ventilation

Too high a temp at the rear causes overheating of compressor, with consequently much reduced life.

An indoor/outdoor thermometer can be used to tell if the temp behind the fridge is getting too high, but its generally quicker to just place a hand on the hext exchanger at the rear. Warmth is to be expected, and hotness at one end, but if its hot all over then the compressor isn't getting the cooling it needs. In this situation, the refrigerant gas is delivered to the expansion line hot, so energy consumption increases, further increasing average compressor temp and reducing life expectancy.

The solution is more ventilation. Where its problematic to provide this, a quiet 3" or 4" fan can be used to move air upwards behind the machine.

Dripping

Modern fridges route interior condensation on the cooling plate down a pipe to a plastic tray on the compressor. The water evaporates from this due to the heat.

External dripping can be caused by the drainage tube becoming unattached from the plastic tray on the compressor. Some fridges have used metal evaporation trays, and these rust enthusiastically, eventually causing external dripping.

Interior dripping can be caused by blockage of the entry point of the pipe. Removal of any debris and a poke with a bit of wire should clear this. If it blocks repeatedly, mould growth is the usual culprit. This can usually be stopped by cleaning the interior spotlessly.

Exterior dripping can also be caused by saturated insulation. Replacing the insulation is the only cure, which isn't worthwhile unless the appliance is of high value. Insulation saturation usually occurs at the bottom of the fridge.

Thermostat

A thermostat stuck off will make the fridge play dead.

If stuck on, the compressor will run all the time, consuming excessive energy. Icing up of the cooling plate will occur in many cases.

Thermostats can be DIY replaced, but its not worth it for the average fridge. The capillary tube on the stat usually passes through the fridge's insulation, and the whole assembly must go in without being cut. The old one can be cut if necessary, as it doesn't need to work again. Generic replacement stats are available.

Compressor runs but not cold

This is caused by loss of refrigerant, which is caused by a leak. A gas refill will only leak out again.

Compressor dead

Compressors can be replaced, but again most fridges aren't worth it.

Partial short

A compressor with a partial short will overheat very quickly and cut out. Or it may blow fuses. Its posible to make these run by adding a high power series resistance to limit the short current, but the increased energy consumption and low cost of replacement fridges makes it not usually worthwhile. A 240v 3kW heater makes a suitable series resistance.

Noise

Fridge noise is usually caused by something touching the compressor or failure of the rubber suspension under the compressor. The latter can be fixed by inserting chunks of rubber under the compressor, making sure it can still move slightly.

Refrigerant loss

When a gas leak occurs, repairers may offer to refill. However if it leaked out once, it will do so again, so this will only ever be a temporary repair. Locating a very slow leak to fix it is extremely difficult.

The situation is different with belt driven in-car compressors. These leak refrigerant as a normal part of operation, and eventually require refill.

Seal alignment

Test effectiveness of the door seal by checking it will grip a till receipt all the way around. A failed seal allows air to leak through, which results in excessive condensation formation on the cold plate, more rapid icing of icebox models, and increases energy consumtion.

If the seal looks OK but isn't sealing, check the fridge is standing squarely and level on the floor with the feet adjusted correctly. The cabinent is easily jarred when not supported correctly on all feet, which can prevent the door fitting the frame. Secondly, check the door adjustment (where present). This should be correct when supplied, but can be misaligned when reversing the door.

Seal damage

Door seals can be replaced on some fridges. Peel the seal back to locate the screws.

Cleaning

Be sure to avoid all scented cleaners. Avoid scourers which will make the interior lining harder to clean in future. Avoid bleach too. Cream cleaner and a cloth are normally effective, with a brush for any residue buildup. Stubborn dirt should be soaked to loosen.

Smells

Smelly fridges are usually sorted out with a thorough clean. Do not use bleach or any scented cleaner.

Where smells are persistent, wiping the interior with dissolved bicarb (and not rinsing) sometimes clears the last of the smell.

If the fridge is in such a state that stinking oozes have gotten into the insulation, nothing but a new fridge will remedy this. For a valuable fridge, replacement of the insulation is the solution.

Storage

Unused fridges should be stored with door ajar to avoid bad odours. When the door may get closed, placing a couple of clean dry teabags inside will help.

Cooling arrangements

There are 3 common cooling arrangements:

1. Heat exchanger at back. Requires rear ventilation, but no side ventilation.
2. No external heat exchanger. These have cooling tubes built in under the outer skin, and require side ventilation for cooling.
3. Less common is cooling underneath the fridge, with warm air expelled at the front at the base. Such fridges require no ventilation to sides or rear.

Side gap

Its traditional to leave a small gap each side of a fridge. This gap makes moving the appliance easier, avoids the door catching, avoids vibration noise and increases rear ventilation. Newer fridges with no external heat exchanger need side ventilation for cooling.

There's also a condensation issue. You need enough ventilation at the sides to prevent the side panels dropping below the dewpoint and generating condensation, which would rust the fridge & run onto the floor. The other alternative is to seal the side gap so there's no flow of air to form condensation -- this is the approach used by linking kits for linking adjacent appliances.

Wire vs glass shelves

Glass shelves are wipe cleanable, and minimise spills of meat juices etc onto foods below. Glass and wire are both dishwashable.

Glass shelves can't always be retrofitted into a wire shelved fridge. Glass blocks air circulation, and this can sometimes result in inadequate cooling in fridges designed for wire. If retrofitting you'll need to check the temp on each shelf afterwards.

Energy efficiency

The energy efficiency of fridges has improved substantially since the 1970s. A free 70s fridge will generally cost more in total over its lifetime than a new one.

Refrigerants

Until recently nearly all fridges used the CFC R12, also known as freon. New fridges use any of several HC and HFC refrigerants. Some of these are believed to affect the ozone layer as well, some not.

Propane

Fridges in third world countries normally use propane (or similar gases) as the refrigerant. These gases are cheap and efficient, but leaks are potentially explosive. Despite this, data indicates that real world risk is negligible. A very few fridges here also use such gases, and with these one should ventilate well if gas is smelt.

Propane is also sometimes used by DIYers to repair fridges and a/c systems that were designed for R12, R-22 or R-134a. Its cheap, readily available, a plug-in replacement, and 9-15% more energy efficient than R12, but its also highly flammable.

Propane refrigerant is labelled as R-290. Note that bottled propane is a propane butane mix, not pure propane.

Butane is R-600 and works at low enough pressure to be contained in reinforced plastic hose.

Pentane is another low working pressure refrigerant gas.

Ammonia

Ammonia has long been used in a small percentage of fridges using the ammonia absorption cycle. These fridges are almost totally silent, with just the thermostat's click and the occasional quiet gurgle. They are easily spotted:

• the equipment on the rear looks quite different to compressor fridges
• They are completely silent when first plugged in

There are 2 issues with these fridges.

1. Power consumption is relatively high, due to low thermal efficiency
2. Even a mini fridge contains over 1kg of ammonia, which would be fatal if released.

One advantage of these fridges is they can in principle be run off any source of heat, such as 240v, 12v or bottled gas. Hence they are standard equipment in caravans. The other is they're silent, so are used in bedrooms, hotel rooms, and so on.

Antique fridges

R12

Safe R12 refrigerant was introduced in the mid 1930s. Old fridges using R12 and a sealed compressor unit will behave much like modern fridges, albeit with relatively poor energy efficiency, and without all the other modern refinements such as wipe clean linings, safe door latches, even temperature, low noise level and so on.

Belt drive

Earlier fridges used a separate motor and belt driven compressor. These are less efficient, and the compressor gradually leaks refrigerant, so needs refilling in time. The belt can slip or break.

Some belt driven fridges didn't use R-12, and are a safety problem - see below.

Pre- R-12 fridges

These all used a belt driven compressor, along with assorted nasty refrigerants. Belt diven compressors leak gas as a normal part of operation. The refrigerants used vary from toxic to very toxic, and some are explosively flammable. Such fridges are not suitable for use in inhabited spaces, and never were.

Refilling with modern refrigerants is problematic, as the working pressures of these old systems are often too far removed from those of modern equipment to produce a workable refrigeration cycle. Some of the old refrigerants (eg SO2) are sufficiently safe to use if the location is well ventilated and isolated from the main building. Some are absolutely not.

Butane and pentane work with lower pressures than R12, and may be usable in some cases. Ventilation is necessary when using a highly flammable gas in a belt drive compressor.

Peltiers

New mini fridges usually use peltier heat pumps instead of the ammonia absorption cycle. Like ammonia, these are silent and have poor energy efficiency, but the very remote risk of ammonia release is not there.

These fridges don't generally have the same cooling power as standard fridges, with the ability to only cool by upto 15°C being normal. Thus they are not safe to use as a main fridge from a food poisoning point of view, as food stored at 15°C in a hot 30°C room will spoil rapidly. This is why they are usually described as drink chillers only. If wanted to store food, the interior temp should be monitored and the machine only used for foods requiring refrigeration when sufficiently cool. Foods that don't require refrigeration (such as chocolate) are safe to store in them.

The peltier pumps used in these are usually rated at 12v 5A, but can run on anything upto 16v for maximum cooling. Some of these mini fridges also have a fan or a second peltier, doubling power use.

Temperatures

5°C or below is the recommended fridge temp for food storage.

Temperatures in fridges tend to vary from one location to another. The salad crisper operates at high RH and slightly higher temp, keeping salads firm for longer and avoiding any risk of freeze damage. Enclosed spaces mounted on the door also run at slightly higher temp, and are good for keeping butter, making it not quite so hard.

Areas close to the cooling plate run colder, and foods such as salads can be damaged by frost if put there.

TCO

Annual Total Cost of Ownership depends on purchase cost, life expectancy and energy cost. Hence the most energy efficient models aren't necessarily the best value ones, but are more likely to be if all other factors are equal. Naturally all other factors aren't equal in practice, since maximising energy efficiency costs money.

Life expectancy is an important factor when seeking to minimise TCO.

Fridges using fans often need a replacement fan fitted at some point in their life. This is a cost and reliability issue to bear in mind when purchasing.

Having said all this, there is no single simple strategy to minimise TCO, and no hard reliability or life expectancy data to base calculations on. News:uk.d-i-y and expert websites sometimes discuss TCO reduction strategies, but opinion remains divided.

Food safety

1. Check the fridge temperature is correct.
2. Inspect contents regularly, removing anything that is beginning to spoil.
3. Avoid arranging foods so that meat juices could drip onto other food types.
4. Keep the fridge interior clean.
5. Glass shelves reduce cross contamination by reducing drips.
6. Don't pack a fridge full, this blocks airflow and results in unsafe temperature rise on some shelves.
7. Don't store meat or fish above other food types, as drips could contaminate them.

Disposal

Most local councils take fridges and freezers away free. Local dealers will purchase or collect the very few types of fridge they could repair and sell profitably, but this only applies to high ticket items.

Most other disposal options are now illegal for R12 fridges, since it is no longer permitted to release R12 to the atmosphere. There's R12 in the insulation as well as the coolant circuit.

Compressors

Compressors removed from fridges have their uses. They provide compressed air at high pressure but low flow rate, and require an oil catcher if they're to last.

The dial

Fridge dials are usually marked with numbers unrelated to actual temperature. The only way to determine temperature is to leave a thermometer in the fridge.

A few fridges also have an insulation sheet between icebox and the main fridge space. The position of this can be adjusted in conjunction with the thermostat dial to achieve the desired temperatures in both fridge and icebox sections. The sheet is moved to adjust the relative temps of fridge and icebox; when blocking all airflow there will be maximum temp difference, and when opened there will be less temp difference.

Improving energy efficiency

For most of us the simple way to improve energy efficiency is to replace the 1980s fridge with a modern A rated one.

Energy saver plugs

File:Savaplug 828-4.jpg

Energy saver plugs reduce energy consumption in older fridges, but are incompatible with a lot of new fridges, some of which have this technology built in.

Energy saver plugs pass full power to the compressor during starting, then throttle the power back once running.

In many places a 10 year old fridge can be bought for the price of one of these plugs, and will deliver more performance improvement, so even for older fridges their use isn't very popular.

More aggressive methods

People running fridges on small solar electric systems sometimes wish to reduce energy consumption. Any of the folowing can help:

• Add more polystyrene insulation on the outside of the fridge (watch for condensation on the metal cabinet, which can rust it)
• Use an energy saver plug when compatible
• Put frozen items in the fridge overnight when defrosting them
• Write contents on a wipe clean board on the front, then decisions can be made with the door closed.

Location

Domestic refrigeration is designed to operate indoors at around 20C.

Fridges will work at lower temps, unlike many fridge freezers. But cold rooms tend to cause condensation on the case, leading to rust and the risk of insulation saturation.

When put in a very hot room, such as a conservatory or shed in summer, a fridge is likely to fail to be able to cool enough to keep food safe. If any doubt, check the fridge's internal temp.

RCDs

RCDs can cause nuisance trips. If this occurs when out for the day the fridge will warm up, making some of the food unsafe to eat. Food poisoning claims orders of magnitude more lives than electrocution by fridge, so ideally a fridge should be run from a non-RCD circuit. This is even more true for freezers.

See Also

• Wiki Contents
• Wiki Subject Categories
• Refrigerant history