100 Modern Refrigeration and Air Conditioning Copyright Goodheart-Willcox Co., Inc. Not all refrigeration systems have accumulators. Most small systems do not require an accumulator. Commercial system accumulators are explained in Chapter 22, Refrigerant Flow Components. 6.6.3 Suction Line A suction line is tubing that carries refrigerant vapor from evaporator to compressor. A suction line must be large enough to carry the vaporized refriger- ant with minimal flow resistance. It should slope from the evaporator down to the compressor. If it does not slope, pockets of oil will collect. A suction line is commonly made of copper tub- ing. It should be insulated in order to prevent moisture from the air from condensing on the cold tubing. An insulated suction line keeps a system balanced and running smoothly, Figure 6-14. Thinking Green Suction Line Condensation Condensation on the suction line means that more heat is being absorbed by the refrigerant vapor. The problem is that the vapor may be taking heat from spaces that are not intended to be conditioned. This additional heat absorption means that the system would be bearing a heavier load than it should. This causes reduced efficiency, extra work for the sys--s tem, and higher power bills for the owner. Insulating the suction line can improve system efficiency. The vapor refrigerant moving through the suction line is superheated. This means that the temperature of the refrigerant is above its condensation (saturation) point. This additional heat content can be measured in degrees because it is sensible heat. Be aware that the term superheat refers to the difference in temperature between the actual temperature of the refrigerant and the temperature that corresponds to the pressure of the refrigerant. Measurement and calculation of superheat will be covered in later chapters. A refrigerant that is superheated must first decrease in temperature before it can begin to condense into a liquid. Remember that it is the compressor’s suction of vapor refrigerant through the suction line that pro- vides the low pressure necessary for the low boiling point in the evaporator. This means that the refrig- erant inside the suction line is a low-temperature, S uction Line C ondensation C ondensation on the suction line means that more heat is being absorbed by the refrigerant vapor. The problem is that the vapor may be taking heat f rom spaces that are not intended to be conditioned. Thi s additional heat absorption means that the refrigerationrefrigeration system wou ld b e bearing a heavier l oa d th an i t should. This causes reduced efficiency, extra work f or the sy tem, and higher power bills f or the owner. Insulating the suction line can improve system efficiency. low-pressure superheated gas. Although the term superheated sounds like something hot, the suction line in which the superheated refrigerant flows is cool or cold to the touch, because the boiling point of the refrigerant is so low. 6.6.4 Suction Line Filter-Drier Some systems include a suction line filter-drier between the evaporator and compressor. A suction line filter-drier performs the same function as a liquid line filter-drier, but it is designed for low-pressure use on the low side of the system. Suction line filter-driers may be a part of the original system or added during system service for a particular purpose. Some filter- driers are temporarily placed in the system to clean the refrigerant. Certain system failures, such as compres- sor motor burnout, require the addition of specialized filter-driers to protect the system from circulating acid and contaminants. Figure 6-15 shows a typical suction line filter-drier. A filter-drier used in the suction line should offer little resistance to vaporized refrigerant flow. The pres- sure difference between the evaporator and the inlet to the compressor should be small. If a suction line filter- drier is causing a large or noticeable pressure drop, it should be removed from the system. Suction line filter- driers are also called low-side filter-driers. DiversiTech Corporation Figure 6-14. Insulation is placed over a copper suction line to prevent the formation of condensation on the line and prevent reduced system efficiency from heat absorbed outside the conditioned space.