What is a Compressor Crankcase Heater?

what is a crankcase heater

The compressor crankcase heater was designed almost as an afterthought to solve a unique problem that affects certain compressors. The problem is that temperature variations inside and outside of the crankcase can cause the oil and refrigerant inside the compressor to change states, migrate, and even mix. In order to prevent this from happening, engineers had to find a way to regulate the temperatures inside the crankcase. Thus, the compressor crankcase heater was born.

The Problem

During normal operation, a compressor heats up and moves both oil and refrigerant under pressure. The pressure and heat created ensure that both the oil and the refrigerant stay in the proper state and separate from one another. However, when the compressor is not in use, there is no pressure or heat to maintain the two fluids. As the crankcase cools down, it is possible for the refrigerant to migrate through the seals and into the oil. In addition, the refrigerant may begin to condensate inside the crankcase. This mixing of fluids causes a number of problems for the compressor. First and foremost, the oil becomes less effective for lubrication because of the refrigerant, causing damage to the bearings and other wearable parts. Secondly, with less refrigerant in the coils, the compressor is unable to operate normally and will experience a serious loss of efficiency as well as possible damage caused by pockets of non-compressable air. In essence, you could end up with low refrigerant levels without even having a leak, so to speak.

How the Crankcase Heater Helps

Crankcase heaters were designed as an addition to existing compressor models. They use a simple electrical circuit to create heat within the crankcase when the compressor is not in use. The heat keeps the refrigerant from condensing and prevents refrigerant from migrating through the seals into the oil. Crankcase heaters may be either internal or external to the unit. In addition, many manufacturers now rely on crankcase heaters as part of the normal startup procedures for the compressor. By using a crankcase heater to bring all of the fluids up to operating temperature before starting, the compressor motor can start easier and pick up where it left off. Without the crankcase heater, these compressors would have to work a lot harder during startup, potentially causing excess wear on the parts.

With modern crankcase heaters, the user has even less to worry about. Internal sensors can now be used to determine whether or not the crankcase heater is needed, and automatically switch the heater on if necessary. This is a simple low-maintenance solution to a problem that many compressors faced. In fact, few consumers are aware that when they turn their HVAC systems off for the winter, their unit could be experiencing refrigeration migration. For homeowners and commercial building owners, the process of switching the AC back on in the spring may seem like a minor task, but by then the damage is already done. Adding a crankcase heater prevents spring-time breakdowns of otherwise healthy systems that simply got cold over the winter.

Today, crankcase heaters are very common on compressors of all kinds. They have proven effective for extending the life of a compressor, and especially for reducing the loss of costly refrigerant. They are used in both residential and commercial applications and can be added to existing systems that do not already have heaters installed internally. In the end, they help your compressor start up smoothly, year after year, without having to worry about checking the oil for contamination and other issues. For more information, visit Compressors Unlimited today and ask about the various parts we carry for compressors over the size of 7.5 tons.


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