Post actualizado el día octubre 25, 2026 by DeiviSanzPlay
A refrigerator doesn’t «cool.» That’s what all the manuals repeat, and it’s a half-truth that confuses anyone. What a refrigerator does is move heat: it takes it from inside the box and throws it outside, into your kitchen. If you understand it that way, everything else falls into place. And if you don’t understand it, you end up calling the technician for things you could have solved yourself in ten minutes.
Let’s dismantle the myth from scratch, without thermodynamics mini-courses, and with the data that really matters when your fridge starts making strange noises or doesn’t cool as it should.
The compressor: the motor that moves the cold (and the one that breaks most often)
The compressor is the heart of the refrigeration system. It’s a sealed motor that draws in the refrigerant in gaseous state, compresses it, and pushes it under pressure through the entire circuit. When it’s compressed, that gas heats up enormously —it can come out at over 70 ºC— and that’s where the magic begins.
When that hot gas reaches the condenser, that black grille you see on the back or the sides of the fridge, it releases the heat into the environment. That’s why the back of your refrigerator is hot: it’s not a fault, it’s working. If you’ve ever noticed that the wall behind it burns, now you know why.
A fact almost no one mentions: the compressor is the piece that consumes the most energy in the entire house in summer. In an average apartment, it can account for between 15% and 20% of the monthly electricity bill. And that’s without counting whether it’s poorly sealed or overloaded.
Condenser, evaporator and expansion valve: the real circuit
After the gas cools and turns into liquid inside the condenser, it passes through the expansion valve (or capillary tube in the cheaper models). There, a sudden drop in pressure occurs and the refrigerant expands. As it expands, it cools down instantly. Very cold.
That cold liquid enters the evaporator, which is the coil inside the freezer or at the back of the cold compartment. There it absorbs the heat from the interior air and turns back into gas. And the cycle starts again.
This cycle repeats non-stop as long as the thermostat allows it. There’s no magic, no magic ice: just a fluid that changes state over and over again to steal heat from where you don’t want it and release it where it doesn’t bother anyone.
An important nuance: in No Frost models, the evaporator isn’t inside the main box, but hidden behind a panel. A fan distributes the cold air throughout the compartment. That prevents frost, but it also dries out food more if you don’t cover it. It’s the price you pay for never having to defrost.
Thermostat and fan: the ones that keep the temperature stable
The thermostat is what decides when the compressor starts and when it stops. If it’s poorly calibrated, either the compressor never shuts off, or it doesn’t start when it should. And that’s where the real problems begin.
The ideal temperature of the cold compartment is between 3 and 5 ºC. The freezer’s, at -18 ºC or lower. If your fridge is at 8 ºC because «that way it uses less,» you’re breeding bacteria like Listeria or Salmonella like royalty. It’s not an opinion, it’s basic food safety.
The fan, in No Frost models, distributes the cold air evenly. Without it, you’d have frozen zones and warm zones inside the same fridge. And that, even if you don’t notice it, shortens the shelf life of what you store.
Common problems: what you can diagnose yourself
When a fridge fails, it’s almost always due to one of these four things:
- Ice buildup in the freezer: it’s usually a problem with the door seal or the automatic defrost system. If the gasket is hard or dirty, humid air gets in and freezes inside. Check the gasket with your hand: it should give and return to its place.
- It doesn’t cool enough: it could be a lack of refrigerant (a leak), a faulty compressor or an uncalibrated thermostat. If the freezer does cool but the lower compartment doesn’t, suspect the fan or the air damper.
- Strange noises: a constant humming could be the compressor working overtime. A squeal is usually the fan motor. A knocking, something loose inside.
- The fridge is hot on the outside: if the side walls burn more than usual, check that it isn’t pressed against the wall or exposed to the sun. The condenser needs ventilation.
Before calling anyone, check two things for free: that the door closes properly and that the fridge has at least 5 cm of free space around it. Many «expensive» breakdowns are fixed with that.
How to use it so it lasts longer and uses less
Don’t overload it. When you put all the supermarket shopping in at once, the compressor works twice as hard for hours. And if the shelves are so full that the cold air can’t circulate, the motor struggles in vain.
Location matters more than you think. A fridge next to the oven or the dishwasher consumes up to 15% more. And if you put it in a place without ventilation, the condenser can’t release the heat and the whole system becomes inefficient.
Another detail almost no one applies: don’t put hot food in. Wait for it to cool on the counter. By putting in a steaming stew, the compressor has to sweat to compensate for that extra heat.
And check the door gasket every six months. Run a piece of paper along the edge and close it: if the paper comes out without resistance, the gasket is failing. Replacing it costs little and prevents the compressor from starting up every other minute.
What almost no one tells you: the refrigerant matters too
Years ago, fridges used CFCs and HCFCs, which destroyed the ozone layer. Today isobutane (R600a) or R134a is used, much more eco-friendly, but also more flammable in case of a leak. If you smell something strange near the compressor, don’t ignore it: ventilate and call a technician.
And beware of the «tricks» of recharging refrigerant yourself. It’s not like adding water to the windshield washer. It requires a vacuum machine and measuring exact pressures. Doing it wrong can blow the compressor and turn an 80-euro breakdown into a 400-euro one.
Understanding how your fridge works isn’t an engineer’s curiosity. It’s the difference between paying a reasonable electricity bill and changing refrigerators every five years. And between throwing food away or not. That’s the real saving.
