Contaminant Controls System Clean-up With Filter Driers w/ Jim Jansen

The basic refrigeration circuit includes an evaporator, compressor, condenser, metering device (which comes in many varieties), and the tubing between those main components. Even large DX refrigeration systems have those components (though often with multiple evaporators or compressors and other ancillary components).

Contamination happens when we get unwanted material in an unwanted location; it can happen in many different ways and often disrupts the proper operation of the controls in a refrigeration system. Filter driers in various locations can help protect the system components from contamination.

A filter drier on the liquid line is often positioned close to the metering device (and liquid line solenoid in circuits that have those). These filter driers catch contaminants to ensure that only oil and refrigerant circulate through the system, not acids, wax, or varnish. Moisture is a common source of contamination, and acids can form from it as well. Catch-All is Sporlan’s brand of liquid line filter drier.

As a result, filter driers contain a desiccant core to remove moisture, acid, or wax from the system via adsorption; the desiccant material will dictate what the desiccant can remove, and these materials include molecular sieve (water), activated alumina (acid), and activated carbon (wax or oil). Different desiccant types also have different pore structures, which also contribute to contaminant removal. Sporlan makes replaceable cores of all materials.

Filter driers are often used to help clean up a system after a burnout. When you suspect a burnout, an acid test kit (manufactured by several companies, including Sporlan) will let you compare an oil sample to a color chart that confirms or denies the presence of acid. Using moisture indicators can also help prevent the formation of acid before the system experiences a burnout.

Suction filters go on the suction line and may offer optional bypass; these can protect your compressor and stay in the system for an extended period of time. Suction filter driers, on the other hand, tend to be used immediately after burnout for cleanup and are not permanent components.

Liquid line filter driers will need to be added or replaced when there is a new system installation or replacement, the system is opened, the pressure drop exceeds 5 PSI, there is moisture or acid in the system, and after burnout cleanup. An oversized liquid line filter drier should be installed during cleanup, and severe compressor burnout should also warrant the installation of a suction filter drier. To remove a filter drier, use a proper tubing cutter whenever possible, and you’ll want to use the typical brazing best practices when brazing a new one in.

Many filter driers can remove contaminants as small as 20 microns in diameter; being able to remove these tiny contaminants will have a significant impact on the lifespan of the bearings in the compressor. Abrasive particles as small as 5 microns in diameter can reduce bearing life. Sporlan also makes oil filters to protect reciprocating and scroll compressors from contaminants in the oil. However, we don’t want to remove moisture with the oil filter because that could dry out the oil, so we want to make sure we’re removing system moisture from the refrigerant in the liquid line.

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