Sudden explosion, one dead and one injured! The air conditioner has become a "time bomb"?! Can we still use it with confidence...

In the past two days, a short video has been widely circulated on the Internet. It shows two workers unfortunately having an explosion accident while installing an air conditioner, which is very distressing to watch.

The picture comes from the Internet

Some accounts only spread the video and did not mention the location at all. As a result, many netizens thought it happened in China, but in fact the accident happened in Vinh An, Vietnam.

The picture comes from the Internet

This accident is so shocking that it has made many people very worried. Can our air conditioners still be used normally? Is the outdoor unit a big bomb? There are also some WeChat chat screenshots that point the finger directly at the commonly used refrigerant R32 .

The picture comes from the Internet

So, as the temperature rises and the hot summer is approaching, can we still use air conditioners with confidence? Is the refrigerant R32 really that unsafe?

Let me first state the conclusion: the air conditioner should be turned on and can be used with confidence.

Let’s have a good chat about it below.

01

What is refrigerant?

Let me explain refrigerant first.

The reason why the air conditioner can cool down the room is that the liquid refrigerant vaporizes in the evaporator to absorb heat and cool down (the main function of the indoor unit) . After the refrigerant vaporizes, it will pass through the compressor and condenser, and after being pressurized and cooled, it will liquefy (the main function of the outdoor unit), and then return to the evaporator to vaporize.

The refrigerant vaporizes and liquefies over and over again, and the heat in the room is "transported" to the outside little by little by the refrigerant, and the room temperature drops.

In this process, the refrigerant is equivalent to a "porter", and the efficiency of this "porter" is closely related to important factors such as the energy consumption and cooling effect of the air conditioner. Efficient refrigerant can improve the energy efficiency of the air conditioner and reduce the energy consumption of the air conditioner.

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So what are the refrigerants?

When you mention refrigerants, your first reaction is probably Freon, and your next reaction is that this thing is not environmentally friendly and will damage the ozone layer. In fact, Freon is a general term for three types of substances. Among them, chlorofluorocarbons are the ones that damage the ozone layer, while hydrochlorofluorocarbons and hydrofluorocarbons have little or no damage to the ozone layer.

Like the small air conditioners we usually use at home, most of the refrigerants come from the Freon family.

So how safe are these refrigerants?

02

How is the refrigerant selected?

Whether the refrigerant is flammable depends on the specific type. For example, chlorofluorocarbons are very safe. They have stable chemical properties and will not burn. However, hydrochlorofluorocarbons and hydrofluorocarbons are flammable and may even explode. For example, the R32 mentioned above is a hydrofluorocarbon.

So the question is, if it is dangerous, why choose such a refrigerant?

The reason is actually quite complicated.

First, the choices are limited . The refrigerant must be able to be compressed into a liquid state at room temperature by the compressor at the lowest possible pressure, and the boiling point must be low, so that it can boil and vaporize at room temperature to absorb heat. There are not many substances that meet these conditions, and the refrigerant's ability to "carry" heat must also be considered, so the choices are actually very limited.

Secondly, environmental issues . As mentioned above, CFCs are non-flammable and have good cooling effects, but once they leak, they will damage the ozone layer, and the greenhouse effect of CFCs is much stronger than that of carbon dioxide.

Finally, there are some cost considerations, including both production costs and the costs when users add refrigerant.

In short, the common refrigerants used in our home air conditioners are mainly the following.

The lower the GWP and ODP values, the more environmentally friendly they are, and safety level A1 is the safest. Excerpted from "White Paper on Trends in Green and Low-Carbon Refrigerants and Carbon Dioxide Refrigeration Technology and Applications"

We can see that in terms of comprehensive performance, R32 is a very good choice.

Some friends may ask, doesn't the R290 below look more environmentally friendly? The problem is that the main component of R290 is actually propane, which is the fuel filled in many fuel tanks. Because it is more flammable, there are more restrictions on the use of this type of refrigerant, and it has higher requirements for machinery and construction. Therefore, at present, in the field of household air conditioning, R32 refrigerant is becoming the mainstream.

The problem with R410A is that, unlike other single-component refrigerants, it is a mixture of R32 and its inhibitor. The ratio of the two needs to be strictly controlled. Therefore, if air-conditioning users need to refill the refrigerant, they cannot do so directly like other refrigerants. They can only drain out all the old refrigerant and refill it with new one, which costs a lot more money. Moreover, the global warming coefficient of R410A is much higher than that of R32, and it is a refrigerant that is prioritized for elimination in the Kigali Amendment.

As for R22, it is fading out of the market because of its damage to the ozone layer.

Some friends may start to worry after reading this: Stop for now, you said earlier that R32 is flammable, so is it really okay to pour such flammable materials into the air conditioner?

It doesn’t really matter.

03

Why are refrigerants not that dangerous?

We know that for combustion and explosion to occur, certain conditions must be met. There must be sufficient combustible materials and oxidizers (usually oxygen in the air), and the temperature must reach a sufficient level, and it must be in a small, enclosed space.

For R32, although it is flammable, it is not like many flammable materials that will ignite with a spark. Strictly speaking, it is a weakly flammable material (also called micro-flammable in some literature). It must leak out in large quantities and come into contact with an open flame before it can be ignited. Once ignited, it will go out if it is away from the flame. In the usage scenario of household air conditioners, even a small amount of leakage is difficult to ignite. Therefore , many self-media say that R32 is flammable and explosive, which is actually inaccurate.

Excerpted from Zhou Xiangyang, Li Feng, Liu Zhen, et al. Research on the application of R32 refrigerant in variable frequency air conditioners[J]. Daily Electrical Appliances, 2012(7):3.

But some friends said, you are wrong. If you search for "air conditioner explosion", there are obviously many news reports and there are also videos from the past few days as evidence.

In fact, if we look carefully at the news about these air conditioner "explosions", we will often find that these accidents are closely related to improper installation operations , and the cause of the "explosion" here is not necessarily the ignition of the refrigerant. It may also be due to improper operation, such as leaking a valve causing excessive pressure inside the air conditioner, or incorrect operation causing air to enter the air conditioner, and leaks in the copper pipe welding causing leakage and fire, etc.

Some accidents are caused by the installers ignoring the safety requirement of no open flames within 5 meters during installation and lighting cigarettes at the installation site. In addition, improper operation during the relocation of the machine leads to a large amount of refrigerant leakage, which may also catch fire or even explode when encountering open flames.

Some people try to install or move the air conditioner themselves, but end up with the following accidents...

The picture comes from the Internet

Therefore, air conditioning installation is a very professional matter. Even professional repairmen still need a lot of training to operate safely when encountering new refrigerants. As the saying goes, no matter how good an air conditioner is, "30% depends on the air conditioner and 70% depends on the installation." On the one hand, we must strictly require practitioners to operate in a standardized manner, and on the other hand, as consumers, we must not do it ourselves just to save money.

04

How should we view risk?

Before talking about air conditioning and refrigerants, imagine that there is a machine that is constantly exploding inside. At the same time, it also carries a large amount of flammable liquid. These liquids are extremely flammable and will ignite if there is a spark. Now, if you are asked to stay with this machine for a few hours, would you be happy?

Many people may be scared when they hear this, but in fact, what is described here is just an ordinary car - who hasn't sat in a car for a few hours?

There is also a kind of gas that is very flammable. A little electric spark will catch fire. Excessive leakage is enough to cause an explosion. Now let the pipeline filled with this gas pass through your home. Would you be happy? - No? Isn't this the natural gas pipeline connected to the stove at home?

What I want to tell you through these two examples is that as long as the design is reasonable and safe, flammable substances such as gasoline and natural gas will be obedient, and refrigerants are no problem.

In fact, Japan's household air-conditioning industry has been using R32 refrigerant in large quantities since 2012, and my country's household air-conditioning brands have also gradually used R32 in recent years.

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On April 8, 2023, the China Refrigeration and Air-conditioning Industry Association just released the "R32 Refrigerant Safety Risk Assessment and Application Technology". The research results show that the safety risks of R32 refrigerant are completely controllable when used in small and medium-sized air-conditioning fields, and it can be promoted and used on a large scale under the protection of limited and reasonable protective measures.

As consumers, what we should do is to ensure that the air conditioner at home matches the circuit, choose a qualified brand of air conditioner, and have the manufacturer come to your home to install it in a standardized manner. After that, you can rest assured to enjoy the cool breeze on hot summer days.

Author: Ding Zong Science Editor

Reviewer: Qin Zongmin, member of the Chinese Society of Refrigeration, Vice President of Technology of Huangshi Dongbei Compressor Co., Ltd.

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