Can I Mix MO99 With R-22? (Must Read Before Doing Anything)

Due to several circumstances, many refrigerators owners face the choice of mixing different refrigerants.

For instance, refrigerator owners may want to mix MO99 and R-22 because these refrigerants are isotopes and are more accommodating to the other.

The main reason why a homeowner, contractor, or technician might mix refrigerants is to cut the replacement cost.

First, however, you must be sure of certain things before you begin and ascertain if it is possible.

No, it would help if you never mixed MO99 alias Freon MO99 and R-22. However, it will result in some AC problems that you will find rather unpleasant. First, your electricity bill will increase because it will require more energy for the AC to function. In addition, the Environmental protection agency has strict guidelines against mixing refrigerants.

Details on How to Mix MO99 with R22?

Can I Mix MO99 with R-22

Mixing refrigerants is wrong and unsuitable during AC repairs; it also applies to the Freon MO99 and R-22. Each refrigerant is unique and operates at a particular temperature and pressure.

For example, R-22 is one of the most common refrigerants but is more expensive and scarce.

Consequently, homeowners may want to purchase the most accessible or mix it with another to increase the refrigerant’s volume.

Unfortunately, this action strains your compressor and leads to a burdened system. There are several reasons why you cannot mix Freon MO99 and R-22.

Consider the following reasons below.

#1. It Is Illegal

The United States Environmental protection agency says that it is illegal to mix different refrigerants.

This concern is from the outcome of consistent errors from illegal mixing of refrigerants which is dangerous to the environment.

When you mix refrigerants, it results in the depletion of the earth’s ozone layer. Therefore, it is unhealthy for our health, water, and air.

Refrigerants contain chlorofluorocarbons or hydrochlorofluorocarbons, which are the leading causes of ozone layer depletion. 

#2. It Alters the Pressure and Temperature

ACS refrigerants require a specific temperature and pressure to cool effectively. These factors vary depending on the type of refrigerant and its composition.

If you still combine Freon MO99 and R-22 despite the warning, you risk your AC compressor.

The reason is that the mixture alters the pressure and temperature of the cooling system, making it slower.

Consequently, it will require more energy to cool and hence take a longer time to function normally. Since you know the dangers of mixing, it is best not to embark on the course.

Is MO99 a Drop in Replacement for R22?

MO99 is not necessarily a drop-in replacement for R-22; it is the most suitable.

Although the most preferable between the two is R-22, it does not mean that Freon MO99 is inferior. R-22 came into existence before MO99.

One primary reason why the MO99 is a suitable replacement is that it shares some similarities with the R-22.

For example, it works in both commercial and personal air conditioning systems. In addition, the refrigerant in MO99 is R-438A, and any system that can support the R-22 will automatically accept it.

Therefore, as long as you are not mixing the two refrigerants, there is no reason to worry.

In addition, Freon MO99 is more affordable than the R-22 and helps the air conditioners’ compressor life span.

Many folks prefer the R-438A because of its affordability; this is a huge advantage it has over the R-22.

Also, in recent times, companies that produce R-22 are packing up, which is becoming a problem. Subsequently, the price is tripling, and it is not easily accessible. 

Even though it has high energy efficiency, the Freon MO99 has a similar efficiency. Furthermore, Freon MO99 has no negative impact on the earth’s ozone layer. This reason may lead to it being a healthier choice than R-22.

After all, when you have the environment at heart, EPA becomes your friend, and you will be on the right side of the law.

Can You Top off R22 with MO99?

No, you cannot top off R-22 with MO99, as any form of mixing the two refrigerants is not advisable.

It is impossible to top off one with the other without them, resulting in a combination. Before you can replace R-22 with MO99, you must purge the air conditioning system. 

You can only top off R-22 with more R-22 if it depletes any other refrigerant. Therefore, this procedure is only possible when servicing the system or carrying out routine checks.

Usually, you ought to service your AC once every twelve months. In addition, you do not need to top off the refrigerant often unless there is a leak.

Therefore, you should consider topping off the refrigerant only when there is a gas leak. Another thing is knowing when there is a gas leak since you cannot assume, but you need to be specific.

Here are some signs that your air conditioning system is experiencing a leak, and you need to top it off.

  • First, if your split unit takes a long time to cool, it shows gas leakage.
  • Next, if your air conditioner uses more energy than it cools, it is another sign of a gas leak.
  • Also, one of the most obvious signs of gas leakage is if you hear a shrill sound around the split unit.

It would be best to call the technician once you notice these signs.

How Do You Convert R22 to MO99? 

As much as it is impossible to mix Freon MO99 and R-22, you can convert the latter to the first.

One crucial reason why R-22 is suitable for MO99 is that it requires no oil change for the compressor. To carry out this procedure, all you need to do is to replace the filters after the gas.

Here is a step-by-step procedure on how to convert R-22 to MO99.

#1. Step One- Check For Retrofitting Capacity

Before converting one refrigerant to the other, you must confirm if it allows retrofitting. Wikipedia defines retrofitting as adding or updating new technology to an older system.

Consequently, you must check their compatibility before you embark on the procedure.

You can only convert two similar refrigerants, like R-22 to MO99 or R-11 to R-12. So, once you discover a suitable replacement, you can go ahead with the conversion. 

#2. Step Two- Purge the System

Since R-22 and Freon MO99 mustn’t mix, you must purge the system before replacement. The purging involves removing any remnant R-22 in the cylinder before you add the Freon MO99.

Then, you can collect the gas into another cylinder to weigh the residual amount. You can proceed to the next step once you finish the purging process.

#3. Step Three- Change the Filter Dryer and Gaskets

The filter dryer is responsible for cleaning the gas entering the unit. So, there will be residual R-22 in the dryer, and since we do not want a mixture, you must replace the old one.

Also, the gaskets seal the outlets to prevent leaks. Therefore, it would be best if you replace the gasket to be on the safer side.

#4. Step Four- Check the System for Leaks

When you finish the replacement, check the system for leaks or passing. You can do this by listening to any hissing sound.

#5. Step Five- Confirm the Oil In the Compressor

Since Freon MO99 uses the oil in the compressor method, it would help if you checked the oil.

This action is to confirm the availability of the oil level and efficiency of the compressor. After all these steps, you can relax and ensure that the AC unit runs perfectly.

What Refrigerant Can be Mixed with R22?

There are no suitable refrigerants to mix with R-22 because the process is illegal and hazardous to the environment.

However, you can convert the R-22 to Freon MO99 and a few others. Most refrigerants in the R- series are suitable conversions for the R-22.

For example, most chlorofluorocarbons like R-11, R-12, R-13, and HCFC are compatible replacements for the R-22. Although most CFCs are not environmentally friendly, they are great refrigerants.

Pros And Cons of Mixing MO99 with R22

There are more than a few pros and cons to mixing MO99 with R22; here is a table that highlights them.

It may save you some cost.It is outrightly illegal to mix refrigerants.
Since R-22 is scarce, it will benefit the manufacturers of Freon MO99.You are at risk of apprehension by the EPA since it is against their law.
There will be no oil change requirement.The environment is at risk because of the harm that CFC causes.
MO99 is a suitable conversion for R-22.


In conclusion, it is not advisable to mix R-22 and Freon MO99, even though they are both refrigerants. Their similarities are not a license to create a cocktail of the two gasses.

Furthermore, it takes a long time for your split unit to cool and consumes so much energy.

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