What Does Liquid Slugging Have to Do with Frozen AC Coils?

You've probably heard that your air conditioning evaporator coils can freeze. You may have even experienced this condition in the past. In many cases, a frozen air conditioner will exhibit numerous negative symptoms, eventually stopping altogether as the compressor shuts down to protect itself from further damage.

Unfortunately, many homeowners assume that freezing is normal or something that may occur if your air conditioner is working too hard. In reality, your air conditioner's coils should never freeze, and this situation indicates a potentially severe underlying problem. Understanding why coils sometimes freeze and how this relates to a condition known as "slugging" can help you avoid some expensive repairs.

The Basics of Frozen AC Components

An air conditioner that's functioning properly pushes cold, low-pressure refrigerant through a component in your air handler known as an evaporator. The evaporator contains many coils that allow the refrigerant to absorb heat energy from the surrounding air. As the air near the coils cools, water condenses into droplets.

These droplets normally drain away because your refrigerant isn't cold enough to cause them to freeze. However, some situations can restrict the refrigerant pressure levels in your evaporator. Lower pressure results in lower temperatures, and the water condensing from the surrounding air will eventually form ice on the evaporator coils. You may also see ice forming on refrigerant tubing.

Ice creates several problems for your air conditioning system. For example, you'll often notice increased humidity since the condensation is freezing instead of draining away. More seriously, the ice will insulate the evaporator, eventually preventing it from absorbing heat. If the evaporator can't transfer heat to your refrigerant, the refrigerant may remain in liquid form.

How Freezing Leads to Slugging

The heat transfer in your evaporator converts the liquid refrigerant into a compressible vapor for its return trip to the compressor. When refrigerant remains liquid for this journey, it can form "slugs." Since liquid refrigerant is not compressible, these slugs can potentially cause severe damage to the compressor. Liquid refrigerant can also wash away the oil your compressor needs for lubrication.

Slugging usually produces a variety of unpleasant symptoms, including loud banging or knocking noises from the condenser unit. Repeated freezing and slugging can cause substantial damage and, if left unaddressed, will eventually destroy your compressor. While relatively rare, this situation can ruin your entire system and force a replacement.

Freezing can have numerous causes, from refrigerant leaks to line restrictions, but it's always a serious problem. If you suspect your AC may be freezing, you should stop using the system immediately and contact a professional for an evaluation. Repairing the underlying problem before it progresses can save you from a drastically higher bill in the future.

For more information, look to a company such as Metro Express Service.

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