Geothermal Alliance of Illinois TXVs – Theory and Fundamentals John Haug – Senior Application Engineer Emerson Climate Technologies - Flow Controls Thermal Expansion Valve Topics Anatomy Operation Terms & Features Superheat Emerson Flow Controls Thermal Expansion Valve Anatomy Valve Power Sensing Packing Bulb Element Metering Diaphragm Pin External Valve Inlet Equalizer Valve Outlet Internal Check (Optional) Pin Carrier Superheat S.H. Adjusting Spring Stem (Optional) Emerson Flow Controls Thermal Expansion Valve Power Assembly ThermalThermal BallastBallast Stainless Steel P.E. Diaphragm Stainless Steel Buffer Plate Emerson Flow Controls Thermal Expansion Valve Metering Pin & Port Metering Pin Valve Inlet Valve Port Pin Carrier Valve Outlet Emerson Flow Controls Thermal Expansion Valve Topics Anatomy Operation Terms & Features Superheat Emerson Flow Controls Why Do You Need A … TXV “It regulates the flow of liquid refrigerant into the coil to match the heat load on the coil”. This is accomplished by controlling the superheat temperature of the refrigerant vapor leaving the coil. Emerson Flow Controls Purpose Of A TXV Controls Evaporator Superheat – Responds To Temperature And Pressure Only Does Not Control: – Space Temperature – Head Pressure – Capacity – Suction Pressure – Humidity Emerson Flow Controls Thermal Expansion Valve Valve Operation (Separates high side from low side) High Pressure Low Pressure Liquid Liquid and Vapor Emerson Flow Controls Thermal Expansion Valve Valve Operation 100100°F °F Low Pressure High Liquid Pressure and Vapor Liquid 40°F40°F Emerson Flow Controls Thermal Expansion Valve Valve Operation Remote Bulb And Power Assembly P1 Pressure (Only Opening Evaporator Pressure Force) (Closing Force) P2 Valve is in P Balance When 3 Superheat Spring (Closing Force) P1=P2+P3 Emerson Flow Controls Thermal Expansion Valve Topics Anatomy Operation Superheat Terms & Features Emerson Flow Controls 1 pound of + 140 BTU = 1 pound of Water 72˚ (Sensible Heat) Water 212˚ 1 pound of + 970 BTU = 1 pound of Water 212˚ (Latent Heat) Steam 212˚ 1 pound of + 8 BTU = 1 pound of Steam 212˚ (Sensible Heat) Steam 220˚ Emerson Flow Controls Superheat Is A Temperature Difference Not Just A Temperature + 40 - 40 + 50 - 30 10°F Superheat 10°F Superheat Emerson Flow Controls Superheat Measurement R-22 68.5 PSIG = 40 F Actual Temp. 65.6 PSIG = 38 F 40°F 58.5 PSIG = 33 F P T Saturated CHART 33°F Suction Pressure 58.5 PSIG Note: Turn Clockwise Actual Superheat = 7°F To Increase S/H Emerson Flow Controls Thermal Expansion Valves Normal Superheat Settings High Temp = 10 to 12 F (>30°F Evap. ) Medium Temp = 5 to 10 F (0 to 30°F Evap.) Low Temp = 2 to 5 F (Below 0°F Evap.) Follow System Manufacturers Recommended Superheat Emerson Flow Controls Thermal Expansion Valves Superheat Adjustments Turn Adjustment Stem Clockwise To Increase Superheat. Adjustment (Superheat NXT Change) Varies By: – Valve manufacturer – Valve family – Refrigerant – Evaporator Temperature Emerson Flow Controls Thermal Expansion Valve Topics Anatomy Operation Superheat Terms & Features Emerson Flow Controls Thermal Expansion Valve Fixed Vs Adjustable Superheat Emerson Flow Controls Thermal Expansion Valve Internal Vs External Equalizers Internal Separate Equalizer Equalizer Connection Outlet Connection External Equalizer Emerson Flow Controls Thermal Expansion Valve Internal Bleed Option A Bleed Port Is An Internal Passage Directly Between The Valve Inlet And Outlet. Allows High And Low Side System Pressures To Equalize During The Off Cycle Thereby Allowing The Use Of Low Start Torque Compressors Adds To Total Valve Capacity 15% To 20% Typical Bleed Rate Emerson Flow Controls Water Source HP Bi-Flow Cooling Emerson Flow Controls Water Source HP Bi-Flow Heating Emerson Flow Controls Thermal Expansion Valve Internal Check Option Flow Flow Forward (Closed) Flow Reverse (Open) Flow (Low Leak) (High Flow) Emerson Flow Controls Water Source HP Dual TXVs Cooling Emerson Flow Controls Water Source HP Dual TXVs Heating Emerson Flow Controls http://www.emersonclimate.com • Emerson valves, controls and system protectors. • Other Emerson products including Copeland compressors and White-Rogers thermostats. • Additional training and educational material. TXV Troubleshooting Sensing Bulb Location Bulb Should Be Clamp On A Horizontal Run Bulb Should Be Locate On The Pipe At: – 12 O’clock On Less Than 7/8" Pipe – 8 Or 4 O’clock On Greater Than 7/8" Pipe In All Cases The Bulb Should Be Insulated From The Ambient 12 O’clock 8 O’clock 4 O’clock Emerson Flow Controls Sensing Bulb Location In Most Cases The Bulb Can Be Mounted In Any Position On A Vertical Run In Most Cases It Is Not True That The Charge Will Leave Bulb If OK Mounted With Cap Tube Down Why Not OK? Horizontal Position Is Preferred Not OK Emerson Flow Controls Proper Bulb and Equalizer Location The Bulb Should Be Located As Close As Possible To The Outlet Of The Evaporator Outlet The Bulb Should Be As Close As Possible To The Equalizer Tube The Bulb Should Be Located Up Stream Of The Equalizer To Prevent Being Effected By Any Liquid Leakage Through The Equalizer Tube Emerson Flow Controls Improper Bulb and Equalizer Location The Bulb Should Not Be Mounted On The Evaporator Suction Header The Bulb Can Not Measure The Temperature On The Bottom Runs – This Could Create A Possible Flood Back Situation Emerson Flow Controls Improper Bulb and Equalizer Location If The Bulb And The Equalizer Are Not On The Same Side Of The P Trap Poor Superheat Control Can Result – Equalizer On The Coil Side Can Result In High Superheat – Bulb On The Coil Side Can Result In Low Superheat WRONG Emerson Flow Controls Improper Bulb and Equalizer Location If A P-Trap Is Used The Equalizer And The Bulb Have To Be On The Same Side Of The Trap – Coil Side Is Preferred – If There Is Not Enough Room The Compressor Side Of The Trap Will Work Emerson Flow Controls Valve Doesn’t Feed Enough No Solid Column Of Liquid – Valve Can’t Make The Valve Must Have a Capacity Solid Column of Liquid Results at the Inlet – High Superheat – Loss of Coil Efficiency Corrective Action: Add Refrigerant Emerson Flow Controls Valve Doesn’t Feed Enough Cause: Flash Gas In The Liquid Line Diagnose By: Look For Flash Gas In The Sight Glass Listen For A Whistling Sound At The TXV. Results: Flash Gas – High Superheat Bubbles At 0 TXV Inlet – Loss Of Coil Efficiency Corrective Action: Remove Source Of Restriction Or Add Refrigerant Emerson Flow Controls Valve Doesn’t Feed Enough Cause: Incorrect Superheat Setting (High) High Setting Normal Setting Last Point Last Point of Liquid of Refrigerant Refrigerant Inefficient Corrective Action: Change Superheat Setting Emerson Flow Controls Valve Doesn’t Feed Enough Cause: Low or Lost Bulb Charge P1 The Loss Of P1 Means The Only Opening Force In The Valve Has Disappeared. This Means Little Or No Flow Through P2 The Valve - High Superheat Diagnose: Remove Bulb And Hold In Your Hand – If No Change In Valve Flow, Then The P3 Bulb Has Lost Charge Corrective Action: Replace Power Head Or Valve Emerson Flow Controls Superheat Is Erratic Or Hunts Bulb Location – Reposition Bulb Too Large A Valve – Replace Valve With The Proper Size Superheat Adjustment – Adjust Superheat To Correct Setting Don’t Jump to Conclusions to Quickly – If the valve has been operating properly for a lengthy period of time it’s probably not the conclusions listed above Emerson Flow Controls TXV Troubleshooting Problem Sympton Cause Fix Overfeeding Low Superheat S/H Setting Adjust Overfeeding Oversize TXV Replace Overfeeding Overcharge Remove Refrig. Overfeeding Bulb Location Relocate Overfeeding Dirty Evaporator Clean Underfeeding High Superheat S/H Setting Adjust Underfeeding Undercharge Add Refrig. Underfeeding Damaged Power Head Replace Underfeeding Clogged Drier Change Underfeeding Ice Forming Change Drier Hunting Fluctuating S/H Bulb Location Relocate Hunting Oversize TXV Replace Hunting S/H Setting Adjust (See catalog section for more) Emerson Flow Controls.