Geothermal Alliance of Illinois Alliance of Illinois ... Thermal Expansion Valve ... Thermal...
Transcript of Geothermal Alliance of Illinois Alliance of Illinois ... Thermal Expansion Valve ... Thermal...
Geothermal Alliance of IllinoisTXVs – Theory and Fundamentals
John Haug – Senior Application EngineerEmerson Climate Technologies - Flow Controls
Emerson Flow Controls
Internal Check (Optional)
Superheat Spring
Sensing Bulb
Thermal Expansion ValveAnatomy
Power Element
Metering Pin
Valve Inlet
Diaphragm
Valve Packing
Pin Carrier
Valve Outlet
S.H. AdjustingStem (Optional)
External Equalizer
Emerson Flow Controls
ThermalBallast
Thermal Expansion ValvePower Assembly
DiaphragmStainless Steel
ThermalBallast
Buffer Plate
StainlessSteel P.E.
Emerson Flow Controls
Thermal Expansion ValveMetering Pin & Port
Metering Pin
Valve Port
Valve Inlet
Pin Carrier
Valve Outlet
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
– Responds To Temperature And Pressure Only
Does Not Control:– Space Temperature – Head Pressure– Capacity– Suction Pressure– Humidity
Controls Evaporator Superheat
Emerson Flow Controls
Thermal Expansion ValveValve Operation (Separates high side from low side)
HighPressureLiquid
Low Pressure Liquid and Vapor
Emerson Flow Controls
HighPressureLiquid
Low Pressure Liquid and Vapor
100°F
40°F
Thermal Expansion ValveValve Operation
100°F
40°F
Emerson Flow Controls
P1Remote Bulb And Power Assembly Pressure(Only Opening Force) P2
Evaporator Pressure (Closing Force)
P3 Superheat Spring(Closing Force)
Valve is in Balance When
P1=P2+P3
Thermal Expansion ValveValve Operation
Emerson Flow Controls
1 pound ofWater 72˚
1 pound ofWater 212˚
1 pound ofSteam 212˚
1 pound ofWater 212˚
1 pound ofSteam 212˚
1 pound ofSteam 220˚
+ 140 BTU =(Sensible Heat)
+ 970 BTU =(Latent Heat)
+ 8 BTU = (Sensible Heat)
Emerson Flow Controls
10°F Superheat 10°F Superheat
+ 40
+ 50
- 40
- 30
Superheat Is A Temperature DifferenceNot Just A Temperature
Emerson Flow Controls
68.5 PSIG = 40 F
65.6 PSIG = 38 F
58.5 PSIG = 33 F
Saturated Suction Pressure 58.5 PSIG
P TCHART
33°F
40°FActual Temp.
Actual Superheat = 7°F
R-22Superheat Measurement
Note: Turn ClockwiseTo 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
Turn Adjustment Stem Clockwise To Increase Superheat.
Adjustment (Superheat Change) Varies By:– Valve manufacturer– Valve family– Refrigerant– Evaporator Temperature
Thermal Expansion Valves Superheat Adjustments
NXT
Emerson Flow Controls
InternalEqualizer
ExternalEqualizer
Thermal Expansion ValveInternal Vs External Equalizers
Outlet Connection
Separate Equalizer Connection
Emerson Flow Controls
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
A Bleed Port Is An Internal Passage Directly Between The Valve Inlet And Outlet.
Thermal Expansion ValveInternal Bleed Option
Emerson Flow Controls
FlowFlow
Thermal Expansion ValveInternal Check Option
Forward (Closed) Flow(Low Leak)
Reverse (Open) Flow(High Flow)
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.
Emerson Flow Controls
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
Sensing Bulb Location
8 O’clock 4 O’clock
12 O’clock
Emerson Flow Controls
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
Why Not OK?
Horizontal Position Is Preferred
Sensing Bulb Location
OK
NotOK
Emerson Flow Controls
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
Proper Bulb and Equalizer Location
Emerson Flow Controls
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
Improper Bulb and Equalizer Location
Emerson Flow Controls
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
Improper Bulb and Equalizer Location
WRONG
Emerson Flow Controls
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
Improper Bulb and Equalizer Location
Emerson Flow Controls
Valve Doesn’t Feed Enough
Corrective Action: Add Refrigerant
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
Emerson Flow Controls
Flash Gas Bubbles At
TXV Inlet0
Valve Doesn’t Feed Enough
Corrective Action: Remove Source Of Restriction Or Add Refrigerant
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
Emerson Flow Controls
Last Point of Refrigerant
Normal Setting
Valve Doesn’t Feed Enough
Corrective Action: Change Superheat Setting
Cause: Incorrect Superheat Setting (High)
High Setting
Inefficient
Last Point of Liquid Refrigerant
Emerson Flow Controls
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
Diagnose: Remove Bulb And Hold In Your Hand
– If No Change In Valve Flow, Then The Bulb Has Lost Charge
Valve Doesn’t Feed Enough
Corrective Action: Replace Power Head Or Valve
Cause: Low or Lost Bulb Charge P1
P2
P3
Emerson Flow Controls
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
Superheat Is Erratic Or Hunts
Emerson Flow Controls
TXV TroubleshootingProblem Sympton Cause Fix
OverfeedingOverfeedingOverfeedingOverfeedingOverfeeding
Low Superheat S/H SettingOversize TXVOverchargeBulb LocationDirty Evaporator
AdjustReplaceRemove Refrig.RelocateClean
UnderfeedingUnderfeedingUnderfeedingUnderfeedingUnderfeeding
High Superheat S/H SettingUnderchargeDamaged Power HeadClogged DrierIce Forming
AdjustAdd Refrig.ReplaceChangeChange Drier
HuntingHuntingHunting
Fluctuating S/H Bulb LocationOversize TXVS/H Setting
RelocateReplaceAdjust
(See catalog section for more)