How to Prevent Frost in Refrigerant Lines: HVACR Tips

Doing these preventive measures could save anyone from experiencing a hot summer day with a broken AC due to frozen refrigerant lines.


There is no engineered product or system that is perfectly designed to the point that they do not need repairs or fixes. In the HVACR & MEP industry, there are several, especially in the air conditioning part.

One of the most common problems in air conditioning systems is the formation of frost in the refrigerant lines, which leads to loss of cooling. Especially if it happens in a location where the weather is sweltering, the situation can really get into the nerves.

But not when one knows how to prevent it.

For starters, the refrigerant lines are the two copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil. This is visible and not enclosed to the system, so one could see if the refrigerant lines, in any of its external parts, get frozen.

To be able to prevent it, the reasons why this phenomenon happens should be identified first. There are essentially four:

Blocked air flow.

This happens when there is restrictive air flow through the cooling coil, caused by either a dirty air filter, collapsed duct insulation, or a crimped flex-duct, among others. Heat exchange cannot take place when the air conditioning system is not properly blowing inside air over the evaporator coil, which, over time, can cause the freeze up.

Improper refrigerant charge.

The air conditioning system, including its refrigerant lines, can freeze if it runs low on refrigerant – due to lower pressure inside the system itself – or the fluid is improperly charged. When parts rub together or vibrate over time, leaks, especially in loose fittings and shoulder joints, could also cause refrigerant problems.

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Malfunctioning refrigerant metering device.

One such device is the thermal expansion valve, which, when not working properly, could lead to ice formation in the refrigerant lines due to misreading.

Bad defrost timer control.

When defrosting cannot be controlled due to a malfunctioning auto-defrost system, icing in the refrigerant lines could form.

While the last two cannot be prevented since components have a limited service life, there is something that can be done to prevent the first two from forming frost in the refrigerant lines.

The simplest, most cost-effective way to ensure the refrigerant lines do not freeze is to change the air filters regularly, usually about every three months or so. Once the evaporator coils are seen to be dirty, it needs to be cleaned by a professional to ensure that all the dust is vacuumed out, allowing smooth air flow.

It is also recommended that the owners should not close supply vents, or the ones that blow air out, even in unused rooms as doing this reduces airflow over the evaporator coil.

When it comes to the HVAC refrigerant charge, it takes a technician to test the air conditioning system for potential problems like leaks, weakened parts, and insufficient coolant. The owner does not have to worry about the icing in the refrigerant lines if the testing is done regularly.

Moreover, frost in refrigerant lines can be prevented if the air conditioning system is run only when the outside temperature does not go below 62 degrees Fahrenheit.

Such is a technique which is common sense. But it is worth mentioning that below the mentioned temperature, the pressures inside the air conditioner could drop, which can cause a freeze up. Plus it would not only prevent the HVACR system from freezing, it saves the owner energy and money on utility costs by just opening the windows.

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If the owner does not want to experience another hot day without a working air conditioner due to frozen refrigerant lines, the preventive measures above should be done. But if all else fails, it is best to call a technician to fix it.

And when it comes to technicians, some of the world’s bests are working for Rubber World Industries (RWI). Their specialty are in the products for HVACR in the Middle East, with much focus on rubber insulation.

Other than the quality technicians working for RWI, the company is considered to be one of the leading HVACR suppliers in UAE and the Middle East region, with service offices in 90 countries globally.

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How to Prevent Frost in Refrigerant Lines: HVACR Tips

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