 R2 Four Basic Components of a Refrigeration System #4 Metering Devices

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 2 Metering Devices Feed refrigerant to evaporator Provide pressure drop From high side to low side

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 3 Thermostatic Expansion Valves TEVs can vary the amount of refrigerant Responds to suction line temperature

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 4 Courtesy of Sporlan Valve Co. Sweat connections External equalizer Inlet Outlet Head Body Cap for Adjuster Thermostatic Expansion Valve (TEV)

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 5 SPORLAN Wire from electronic controller Motorized head Body Outlet Inlet Courtesy of Sporlan Valve Co. Electronic Expansion Valve

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 6 Fixed Metering Device Provides consistent pressure drop Condensing pressure to evaporator pressure

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 7 Fixed orifice capillary tube Courtesy of Supco Sealed Unit Parts Co. Fixed orifice capillary tube (cap tube)

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 8 Courtesy of Rob Dohse Carrier Training Center Valve body Metering Device End cap Carrier’s Accurator® Fixed orifice nozzle

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 9 TEV Cut-Away View Shows internal parts of a TEV

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Valve Construction Valve Construction: Diaphragm, tube, and sensing bulb Valve body Needle and orifice Inlet Screen Spring, adjuster, and packing gland

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v TEV Operation Meters refrigerant Maintains superheat Opening force: Bulb pressure Closing forces: 1. Evaporator pressure 2. Adjustable spring

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Expansion Valve Detail RETURN AIR 75 o EVAPORATOR 40º 50º Typical A/C Using R22 69 psig 278 psig SPORLAN

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Expansion Valve Detail RETURN AIR 75 o EVAPORATOR 40º 50º Typical A/C Using R22 69 psig 278 psig 50º = 84 psig Pressure on diaphragm Evaporator 40º = 69 psig closing pressure Spring pressure to maintain equilibrium is: 84 psig – 69 psig = 15 psig

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Adjusting Superheat To lower superheat: Decrease spring pressure Increases refrigerant in evaporator

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Lower Superheat from 10° to 6° RETURN AIR 75 o EVAPORATOR 50º 40º 46º 69 psig 278 psig Superheat Adjustment Back out adjuster one full turn

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Adjusting Superheat Increase superheat: Increase spring pressure Decreases refrigerant in evaporator

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Raise Superheat from 6° to 14° RETURN AIR 75 o EVAPORATOR 40º 46º 54º 69 psig 278 psig 40º Superheat Adjustment Screw in adjuster two full turns

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Identifying the Valve Connections: Flare, sweat, and flanged Evaporator Pressure Equalization: Internal equalizer External equalizer

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Flare Sweat Flanged External equalizer Internal equalizer External equalizer Expansion Valve Connections

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Sensing Bulb Placement Must sense true suction temperature –Not bottom of pipe –Not top of pipe Following are Sporlan’s recommendations

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v ≥ 7/8” Factory Recommended TEV Bulb Placement If pipe OD is greater than or equal to ( ) 7/8” then bulb should be placed at 4:00 or 8:00 (≥)

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Factory Recommended TEV Bulb Placement If pipe OD is less than (<) 7/8” then bulb can be placed anywhere between 8:00 and 4:00 < 7/8”... but never on the bottom!

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Simplifying bulb location Following is a simple rule for bulb placement

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v “Rule of Thumb” TEV Bulb Placement Warmer vapor on top Oil insulates bottom Bulb mounted on side works well on all pipes

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v More suggestions on bulbs Make sure it is on a flat surface of pipe Use stainless steel hose clamps: –Easier to install –Easy to service

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Picture of bulbs and clamps TEV Bulb Straps Coupling Braze Joints No Bulb Contact Good Bulb Contact Radiato r Clamp

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v More on Mounting TEV Bulbs Best on horizontal line If you must put on vertical line: Oil in line may affect operation Cap tube must come out top of bulb

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v TEV Bulb on Vertical Line SPORLAN

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v TEV Bulb on Vertical Line System Off Start Up Oil pushed up sides of pipe Oil collects in P-trap SPORLAN

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v TEV Bulb Mounted Upside Down Liquid Flows to Head of Valve No Liquid In Bulb to Boil Off SPORLAN

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v “Reading” a Valve Understand the numbering system, and you will know the valve. Following are examples of Sporlan valves

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Picture of SVE-2-GA valve “S” style valve “V” R22 “E” externally equalized “2” Two Tons (24,000 Btu) “G” Air Conditioning

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Picture of GV-1/2-C Valve “G” type valve “V” R22 “1/2” ton (6,000) Btu “C” Commercial (medium temp.)

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Capillary tubes (cap tubes) A fixed metering device Regulates refrigerant flow by pressure drop Pressure drop is based on: Cap tube length Internal diameter of tubing

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Hose Pressure 25’ of hose 200’ of hose 75 psig 25 psig 100 psig 100 psig

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Picture of Supco capillary tube.040” I.D. Courtesy of Supco Sealed Unit Parts Co.

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Plugged cap tubes Beaded desiccant in most filter driers Desiccant can plug cap tube inlet Solution: Cut off some cap tube Replace filter drier

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Correcting Plugged Cap Tube Beaded Desiccant Powder flakes off beads Clogs inlet of cap tube Replace Drier Cut off an inch or two of cap tube to remove clog

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Cap tube guidelines Following is an information sheet from J/B Industries Interesting points are highlighted in yellow

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Factors Affecting Refrigerant Flow capillary tubes depend on their length as well as their diameter to determine their total restriction. changing the diameter by.005" as between.026" I.D. and.031" I.D. can double the flow. The longer the tube, the slower the flow, the shorter the tube, the faster the flow.

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Cap tube sizing J/B has charts for sizing cap tubes The following example is a 1/3 H.P. unit Operating at a 15° evaporator The cap tube size is.o36” I.D., 6’ long

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Refrigeration Application Chart (R-12 & R- 22) R-22 H.P.REF +5 to Ft TC-36 1/3

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Cutting cap tubes  Do not use tubing cutters  Use a file to score it, then snap it  J/B also makes special cutters

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v Cap tube file and Cutter A10972 CAP TUBE FILE Specially designed to cut and open tube. File notch around tubing at desired cutting point. Snap tube by bending at notch. Clean burrs by reaming out with special file tip. In cleaning or deburring, always hold tube downward to keep small particles from entering tube. A10973 CAP CUTTING TOOL Specially designed to cut all sizes of soft and many sizes of hard drawn cap tubes. WORKING WITH CAPILLARY TUBING Every precaution possible should be taken to prevent chips, dirt, flux, moisture, filings, etc. from entering the system when changing the cap tube. Cap tube is sealed and dehydrated from the factory. Remember, most cap tubes have very small holes... it doesn't take much to plug them. The A10972 Cap Tube File and A10973 Cap Tube Cutter are specifically designed tools for working with cap tube.

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v What is existing cap tube size? J/B has a tool to check cap tube size

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v The A10971 Cap Tube Gauge accurately measures a full range of capillary tube sizes. Correct tube size is determined by using both the I.D. and O.D. dimensions. Check OD of tube in "V" slot. Compare OD with reference chart printed on back of gauge to determine probable ID. Use pin gauge to confirm actual size of ID. This same means of cross referencing can be used whenever two standard I.D.'s are very close or OD's are the same. DETERMINING CAP TUBE SIZE

 © 2004 Refrigeration Training Services - R2 Subject 4 Metering Devices v1.2 47