Geothermal Alliance of Illinois. TXVs Theory and Fundamentals John Haug Senior Application Engineer Emerson Climate Technologies - Flow Controls

Transcription

1 Geothermal Alliance of Illinois TXVs Theory and Fundamentals John Haug Senior Application Engineer Emerson Climate Technologies - Flow Controls

2 Thermal Expansion Valve Topics Anatomy Operation Terms & Features Superheat

3 Thermal Expansion Valve Anatomy Sensing Bulb Diaphragm External Equalizer Power Element Valve Packing Metering Pin Valve Inlet Valve Outlet Pin Carrier S.H. Adjusting Stem (Optional) Internal Check (Optional) Superheat Spring

4 Thermal Expansion Valve Power Assembly Thermal Thermal Ballast Ballast Diaphragm Stainless Steel Stainless Steel P.E. Buffer Plate

5 Thermal Expansion Valve Metering Pin & Port Valve Inlet Metering Pin Valve Port Pin Carrier Valve Outlet

6 Thermal Expansion Valve Topics Anatomy Operation Terms & Features Superheat

7 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.

8 Purpose Of A TXV Controls Evaporator Superheat Responds To Temperature And Pressure Only Does Not Control: Space Temperature Head Pressure Capacity Suction Pressure Humidity

9 Thermal Expansion Valve Valve Operation (Separates high side from low side) High Pressure Liquid Low Pressure Liquid and Vapor

10 Thermal Expansion Valve Valve Operation High Pressure Liquid 100 F 100 F 40 F 40 F Low Pressure Liquid and Vapor

11 Thermal Expansion Valve Valve Operation Remote Bulb And Power Assembly Pressure (Only Opening Force) P 1 P 2 Evaporator Pressure (Closing Force) Valve is in Balance When P 1 =P 2 +P 3 P 3 Superheat Spring (Closing Force)

12 Thermal Expansion Valve Topics Anatomy Operation Superheat Terms & Features

13 1 pound of Water BTU = (Sensible Heat) 1 pound of Water pound of Water BTU = (Latent Heat) 1 pound of Steam pound of Steam BTU = (Sensible Heat) 1 pound of Steam 220

14 Superheat Is A Temperature Difference Not Just A Temperature F Superheat 10 F Superheat

15 Superheat Measurement R PSIG = 40 F 65.6 PSIG = 38 F Actual Temp. 40 F 58.5 PSIG = 33 F Saturated Suction Pressure 58.5 PSIG Note: Turn Clockwise To Increase S/H P T CHART 33 F Actual Superheat = 7 F

16 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

17 Thermal Expansion Valves Superheat Adjustments Turn Adjustment Stem Clockwise To Increase Superheat. Adjustment (Superheat Change) Varies By: Valve manufacturer Valve family Refrigerant Evaporator Temperature NXT

18 Thermal Expansion Valve Topics Anatomy Operation Superheat Terms & Features

19 Thermal Expansion Valve Fixed Vs Adjustable Superheat

20 Thermal Expansion Valve Internal Vs External Equalizers Internal Equalizer Separate Equalizer Connection Outlet Connection External Equalizer

21 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

22 Water Source HP Bi-Flow Cooling

23 Water Source HP Bi-Flow Heating

24 Thermal Expansion Valve Internal Check Option Flow Flow Forward (Closed) Flow (Low Leak) Reverse (Open) Flow (High Flow)

25 Water Source HP Dual TXVs Cooling

26 Water Source HP Dual TXVs Heating

27 Emerson valves, controls and system protectors. Other Emerson products including Copeland compressors and White-Rogers thermostats. Additional training and educational material.

28 TXV Troubleshooting

29 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

30 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 Mounted With Cap Tube Down OK Why Not OK? Horizontal Position Is Preferred Not OK

31 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

32 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

33 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

34 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

35 Valve Doesn t Feed Enough No Solid Column Of Liquid Valve Can t Make Capacity Results High Superheat Loss of Coil Efficiency The Valve Must Have a Solid Column of Liquid at the Inlet Corrective Action: Add Refrigerant

36 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: High Superheat Loss Of Coil Efficiency 0 Flash Gas Bubbles At TXV Inlet Corrective Action: Remove Source Of Restriction Or Add Refrigerant

37 Valve Doesn t Feed Enough Cause: Incorrect Superheat Setting (High) High Setting Normal Setting Last Point of Liquid Refrigerant Last Point of Refrigerant Inefficient Corrective Action: Change Superheat Setting

38 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 The Valve - High Superheat P2 Diagnose: Remove Bulb And Hold In Your Hand If No Change In Valve Flow, Then The Bulb Has Lost Charge P3 Corrective Action: Replace Power Head Or Valve

39 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

40 TXV Troubleshooting Problem Sympton Cause Fix Overfeeding Overfeeding Overfeeding Overfeeding Overfeeding Low Superheat S/H Setting Oversize TXV Overcharge Bulb Location Dirty Evaporator Adjust Replace Remove Refrig. Relocate Clean Underfeeding Underfeeding Underfeeding Underfeeding Underfeeding High Superheat S/H Setting Undercharge Damaged Power Head Clogged Drier Ice Forming Adjust Add Refrig. Replace Change Change Drier Hunting Hunting Hunting Fluctuating S/H Bulb Location Oversize TXV S/H Setting Relocate Replace Adjust (See catalog section for more)