Refrigerant Piping DESIGN and FABRICATION GUIDELINES Corp
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Refrigerant Piping DESIGN AND FABRICATION GUIDELINES Corp. 9351 −L9 Revised July 26, 2011 APPLICATION AND DESIGN GUIDELINES TABLE OF CONTENTS Refrigeration Piping, both available from ASHRAE. In addition, the procedures and limits outlined in this manual Introduction . 1 do not supersede local, state or national codes under any circumstances. P iping Limits . 1 Piping Limits R ecommended C omponents . 3 All expansion valves (TXV) listed in the following tables can Liquid Line Quick S elect . 3 be used in either air conditioner or heat pump systems. These TXVs incorporate a check valve for heat pump Vapor Line Quick S elect . 6 system applications. Long Line R equirements . 6 Unit Size Catalog Number Fundamentals and Theory . 7 2−Ton Y0498 3−Ton Y0499 Line S izing in Detail . 9 4−Ton Y0500 S ystem C ontrol . 21 5−Ton Y0501 6−Ton Y0502 S ystem Operation . 23 Appendix . 24 Unit Size Catalog Number G lossary . 31 2−Ton Y0512 Introduction 3−Ton Y0513 4−Ton Y0514 The piping design of any air conditioning system will aect 5−Ton Y0515 the performance, reliability, and applied cost of that system. 6−Ton Y0516 The design of refrigerant piping systems involves capacity and eciency, reliability, oil management, refrigerant charge, sound level, liquid refrigerant control, modulation COOLING SYSTEM eectiveness and cost. Therefore it is essential that the HFC−410A installing contractor understand the eect of piping and be able to make intelligent decisions in order to do the best job Total equivalent length = 240 feet (Piping and all possible on the installation. This material below will clearly ttings, etc). explain the basic eects on system performance of the Length is general guide. Lengths may be more or piping design. less, depending on remaining system design factors. In most typical installations with lines less than 50 feet, the Maximum linear (actual) length = 200 feet. line sizes will match up to the connections on the outdoor Maximum linear liquid lift = 60 feet. unit. However, with installations involving long line sets or Maximum lifts are dependent on total length, elevation dierences between the outdoor unit and the number of elbows, etc that contribute to total pressure drop. indoor unit, the piping must be sized carefully. System Maximum length vapor riser = 125 feet. performance may be im proved even in a typical installation by optimizing pipe sizes. Up to 50 linear feet: use rated line sizes listed in unit specications or installation instructions. The intent of this manual is to represent generally accepted If 51 to 80 linear feet: Crankcase heater required, safe engineering practices. Specications and limits non−bleed port TXV (see TXV note ) preferred (RFCIV outlined in this manual are subject to change. System acceptable with maximum vertical of 25 feet). design should conform to all codes, laws and regulations applying at the site at the time of installation. Additional If 81 − 200 linear feet: Crankcase heater and non−bleed documents that should be followed include The Safety port TXV (see TXV note) required. Code for Mechanical Refrigeration and the Code for Over 200 linear feet: not recommended. Page 1 TXV NOTE: TXV NOTE: a) Indoor Factory Installed non−bleed, non−adjustable a) Indoor Factory Installed non−bleed, non−adjustable TXV can be used on the system if it can maintain TXV can be used on the system if it can maintain superheat lower than 25°F at outdoor unit service superheat lower than 25°F at outdoor unit service valve. (Superheat is critical to compressor operating valve. Superheat is critical to compressor operating conditions) conditions. b) If indoor unit does not have a factory installed TXV, b) If indoor unit does not have a factory installed TXV, or factory installed TXV needs replacing due to or factory installed TXV needs replacing due to system match, up or the factory TXV is not capable system match, up or the factory TXV is not capable of maintaining low enough superheats, use table 2 of maintaining low enough superheats, use table 1 for ordering the correct TXV for specific size indoor for ordering the correct TXV for specific size indoor unit. All of these are indoor non−bleed adjustable unit. All of these are indoor non−bleed adjustable thermostat expansion valves. Superheat adjustment thermostat expansion valves. Superheat adjustment procedures can be found in the TXV kit instructions. procedures can be found in the TXV kit instruction. S If not factory provided, high and low pressure switches are recommended S If not factory provided, high and low pressure S switches are recommended If not factory provided, a liquid line filter drier is required S If not factory provided, a liquid line filter drier is S For HFC−22 systems with suction lines over 50 feet required with lines that are 7/8" or smaller, add three ounces S For HFC−410A recommend adding oil to system of oil every 10 feet of line over 50 feet. For systems based on the amount of refrigerant charge in the with 1−1/8" and larger suction lines, add four ounces system. No need to add oil in systems with 20 of oil every 10 feet of line over 50 feet. pounds of refrigerant or less. For systems over 20 HEAT PUMP SYSTEM pounds − add one ounce of every five pounds of refrigerant. HFC−410A S Total equivalent length = 240 feet (Piping and all HCFC−22 fittings, etc) Total equivalent length = 240 feet (Piping and all fittings, NOTE Length is general guide. Lengths may be more or less, depending on remaining system design factors. etc). S Maximum linear (actual) length = 200 feet. NOTE Length is general guide. Lengths may be more or S Maximum linear liquid lift = 60 feet. less, depending on remaining system design factors. NOTE Maximum lifts are dependent on total length, S Maximum linear (actual) length = 200 feet. number of elbows, etc that contribute to total pressure drop S Maximum linear liquid lift = 50 feet. plus when the outdoor unit is above the indoor unit. S Maximum length vapor riser = 60 feet. NOTE Maximum lifts are dependent on total length, S Up to 50 linear feet: use rated line sizes listed in unit number of elbows, etc that contribute to total pressure specifications or installation instructions. drop. S If 51 to 200 linear feet: Crankcase heater required, S Maximum length vapor riser = 125 feet. non−bleed port TXV (see TXV note) required. S Up to 50 linear feet: use rated line sizes listed in unit S If 81 − 200 linear feet: Crankcase heater and non−bleed specifications or installation instructions. port TXV (see TXV note below) required. S S If 51 to 80 linear feet: Crankcase heater required, Over 200 linear feet: not recommended. non−bleed port TXV (see TXV note) preferred (RFCIV TXV NOTE: acceptable with maximum vertical of 25 feet). a) Indoor Factory Installed non−bleed, non−adjustable S If 81 − 200 linear feet: Crankcase heater and non−bleed TXV can be used on the system if it can maintain superheat lower than 25°F at outdoor unit service port TXV (see TXV note below) required. valve. Superheat is critical to compressor operating S Over 200 linear feet: not recommended. conditions. Page 2 b) If indoor unit does not have a factory installed TXV, S If not factory provided, high and low pressure or factory installed TXV needs replacing due to switches are recommended. Low pressure switch system match, up or the factory TXV is not capable bypass switch will be required on units that do not of maintaining low enough superheats, use table 1 have provision to ignore the switch when unit is for ordering the correct TXV for specific size indoor operating in ambient temperatures below 15°F. unit. All of these are indoor non−bleed adjustable S If not factory provided, a liquid line filter drier is thermostat check expansion valves. Superheat required. adjustment procedures can be found in the TXV kit S For HFC−22 systems with suction lines over 50 feet instructions. with lines that are 7/8" or smaller, add three ounces S If not factory provided, high and low pressure of oil every 10 feet of line over 50 feet. For systems switches are recommended. Low pressure switch with 1−1/8" and larger suction lines, add four ounces bypass switch will be required on units that do not of oil every 10 feet of line over 50 feet. have provision to ignore the switch when unit is Recommend Components operating in ambient temperatures below 15°F. S If not factory provided, a liquid line filter drier is PRESSURE TAPS required. Should be installed at the inlet and outlets of indoor coils to S For HFC−410A recommend adding oil to system allow field measurement of saturated pressures for based on the amount of refrigerant charge in the calculating superheats and sub−cooling values. system. No need to add oil in systems with 20 pounds of refrigerant or less. For systems over 20 ANTI−SHORT PROTECTION pounds − add one ounce of every five pounds of Systems should have anti−short cycle. refrigerant. S ON − usually four minutes. S Timed OFF − usually five minutes and timer HCFC−22 NOTE A number of electronic thermostats contain these S Total equivalent length = 180 feet (Piping and all features) fittings, etc). OPTIONAL SIGHT GLASS NOTE Length is general guide. Lengths may be more or less, depending on remaining system design factors. A glass window type device placed in a liquid line and used for visual inspection of the liquid. It can also be used to S Maximum linear (actual) length = 150 feet. determine the point at which all gas bubbles are removed S Maximum linear liquid lift = 50 feet.