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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
TEV installation, testing, troubleshooting & repair guide: this article describes how to install, test, or diagnose problems with a thermostatic expansion valve used on air conditioners or heat pumps or similar refrigeration equipment.
HVACR Thermostatic Expansion Valves - TEVs: this air conditioning repair article series explains the function and installation of all types of refrigerant metering devices, beginning with the most-common thermostatic expansion valve or TEV (or thermal expansion valve) that controls release of refrigerant into the evaporator coil of an air conditioning or heat pump system. We define and explain other refrigeration equipment metering devices including AEVs (Automatic Expansion Valves), manually adjusted expansion valves, capillary tubes and Low Side or High Side refrigerant float valves. Page top sketch of a thermostatic expansion valve is provided courtesy of Carson Dunlop Associates.
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Thermostatic expansion valves (TEVs) are designed to meter refrigerant into the cooling coil at the proper rate. This design can keep the proper dose of refrigerant entering the cooling coil for maximum air conditioning or heat pump system operating efficiency.
TEVs are similar to automatic expansion valves (AEVs) discussed below, but incorporate the signal from a temperature sensor mounted at the end of the evaporator coil
If you are diagnosing a problem with an air conditioner or heat pump and the TEV appears to be involved, check the TEV installation details against the information we list below.
Thermostatic Expansion Valve Location: The TEV should be installed as close as possible to the air conditioning or heat pump evaporator coil inlet. Sketch of CAPILLARY TUBE defects courtesy of Carson Dunlop. Other TEV and cap-tube defects listed below were obtained from an installation guide for TEV's provided by Singer Controls Corp.
Protect the TEV from heat during soldering or brazing by wrapping the valve body and head with a wet cloth to give 1/4" to 1/2" of thermal protection, and keep the soldering or brazing torch aimed away from the valve itself.
[Click to enlarge any image]
As with any soldering or brazing job, don't use excessive solder or flux or the excess may flow into the valve or tubing to prevent proper operation.
TEV Thermostatic Expansion Valve problems: see Thermostatic Expansion Valve (TEV) Installation, Inspection, Diagnosis & Testing Guide where we also address AEVs, float valves, manual and automatic expansion valves, etc.
Capillary Tube problems: see our separate article detailing the inspection, installation, and repair or replacement of CAPILLARY TUBES
See REFRIGERANT LEAK DETECTION where we describe the effects of dirt and moisture on TEVs and capillary tubes. A quick test for a moisture/ice jammed TEV is to add some heat to see if the device will begin working again.
Watch out: as we discuss at REFRIGERANT LEAK DETECTION, water or dirt in the system can cause serious and costly problems in the TEV or cap tube that impact the entire refrigeration system.
See THERMOSTATS for other details of the operation of primary air conditioning thermostats and switches.
At A/C - HEAT PUMP CONTROLS & SWITCHES we explain the many electrical switches and controls that control an air conditioner or heat pump system. You'll need to check these if your air conditioner won't start.
At OPERATING DEFECTS we take you through the major air conditioning problem symptoms and how to get the air conditioning system working again.
At a companion article, LOST COOLING CAPACITY, our focus is on the case in which the air conditioning system seems to be "running" but not enough cool air, or no cool air at all is being delivered to the occupied space.
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Questions & answers or comments about refrigeration controls: TEVs, AEVs, Capillary Tubes, Float Valves, & Other Refrigerant Controls
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Technical Reviewers & References
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