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 Mobile ViewAIR CONDITIONING & HEAT PUMP SYSTEMS A/C - HEAT PUMP CONTROLS & SWITCHES A/C DATA TAGS A/C - HEAT PUMP CRITICAL DEFECTS A/C DIAGNOSTIC FAQs A/C REFRIGERANTS A/C TYPES, ENERGY SOURCE AGE of AIR CONDITIONERS & HEAT PUMPS AIR CONDITIONER BTU CHART AIR CONDITIONER COMPONENT PARTS AIR CONDITIONER TYPES, ENERGY SOURCES AIR CONDITIONER NOT WORKING AIR FILTERS for HVAC SYSTEMS AIR HANDLER / BLOWER UNITS APPLIANCE EFFICIENCY RATINGS BACKUP HEAT for HEAT PUMPS BLOWER DOORS & AIR INFILTRATION BLOWER FAN CONTINUOUS OPERATION BLOWER FAN OPERATION & TESTING BOOKSTORE - Air Conditioning "How To" Books CAPACITORS for HARD STARTING MOTORS CAPILLARY TUBES CHINESE DRYWALL HAZARDS CIRCUIT BREAKER SIZE for A/C or HEAT PUMP CLEANING & Legionella BACTERIA CHINESE DRYWALL HAZARDS COMBUSTION GASES & PARTICLE HAZARDS CONDENSATE HANDLING, A/C CONDENSATION or SWEATING PIPES, TANKS COMPRESSOR & CONDENSING COIL, A/C BURNED-OUT COMPRESSOR CAPACITORS for HARD STARTING MOTORS CONDENSING COIL REPAIR REPLACE CONTACTOR RELAY DIAGNOSIS & REPAIR CONTROL CIRCUIT BOARD, A/C FAN, COMPRESSOR/CONDENSER UNIT HARD STARTING COMPRESSOR MOTORS INSPECTION CHECKLIST - OUTDOOR UNIT INSTALLATION ERRORS, COMPRESSORS LONG-ON CYCLING AC COMPRESSOR MOTOR OVERLOAD RESET SWITCH NOISES, COMPRESSOR CONDENSER Pressure Controls & Safety Switches PRESSURE READINGS, COMPRESSOR REPLACING A COMPRESSOR SHORT CYCLING AC COMPRESSOR TIGHT or SEIZED AC COMPRESSORS CONDENSATE HANDLING, A/C CONDENSATION or SWEATING PIPES, TANKS COOL OFF HEAT Thermostat Switch COOLING CAPACITY, RATED FROM MODEL # FROM EQUIPMENT RLA # COOLING RULES OF THUMB COOLING COIL or EVAPORATOR COIL COOLING LOAD REDUCTION by ROOF VENTS COMBUSTION GASES & PARTICLE HAZARDS CONDENSATE HANDLING, A/C CONDENSATION or SWEATING PIPES, TANKS DATA TAGS on AIR CONDITIONERS DEFINITION of Heating & Cooling Terms DEHUMIDIFICATION PROBLEMS DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP DUCT SYSTEM & DUCT DEFECTS DUCTS - Asbestos DUCT INSULATION, Asbestos Paper DUCT INSULATION for SOUNDPROOFING DUCT SYSTEM NOISES DUCTS, Asbestos Transite Pipe DUST CONTAMINATION FROM HVAC? EDUCATION, HVAC SCHOOLS ELECTRIC MOTOR DIAGNOSTIC GUIDE ELECTRIC MOTOR OVERLOAD RESET SWITCH ELECTRICAL POWER SWITCH FOR HEAT ENERGY SAVINGS in buildings EVAPORATIVE COOLING SYSTEMS EVAPORATOR COIL or COOLING COIL EXPANSION VALVES, REFRIGERANT FAN, AIR HANDLER BLOWER UNIT FAN AUTO ON Thermostat Switch FAN, COMPRESSOR/CONDENSER UNIT FAN CONVECTOR HEATERS - HYDRONIC COILS FAN LIMIT SWITCH FAN NOISES FURNACES WARM AIR HEATING SYSTEMS GASES, EXPOSURE, TESTING Carbon Dioxide - CO2 Carbon Monoxide - CO METHANE GAS SOURCES GAS MEASUREMENT TOOLS GAUGE, REFRIGERATION PRESSURE TEST HEAT LOSS (or GAIN) in buildings HEAT PUMPS HUMIDITY LEVEL TARGET INDOOR AIR QUALITY IMPROVEMENT GUIDE INSPECTION CHECKLIST - OUTDOOR UNIT INSPECTION LIMITATIONS LEED GREEN BUILDING CERTIFICATION LOST COOLING CAPACITY What to Check First A/C Flow Too Weak A/C Filter Problems A/C Compressor Problems A/C Off - Condensate Pan Switch A/C Cooling Coil Icing A/C Not Dehumidifying A/C Air Duct Problems Air Conditioner Won't Start Air Conditioner Refrigerant Problems Blower Fan No Start / No Stop Compressor Diagnosis: Diagnose & Repair Cooling Capacity of the Duct System Repair Guide Master List MANUALS & PARTS GUIDES - HVAC MOTOR OVERLOAD RESET SWITCH NOISY AIR CONDITIONER / HEAT PUMP OPERATING COST OPERATING DEFECTS OPERATING TEMPERATURES Air Conditioning System Temperatures Instruments Used to Measure A/C Temperatures Procedures for Making Temperature Measurements PORTABLE ROOM AIR CONDITIONERS PRESSURE READINGS, REFRIGERANT REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS REPAIR & DIAGNOSTIC FAQs for A/C REFRIGERANTS GAUGE, REFRIGERATION PRESSURE TEST REFRIGERANT CHARGING PROCEDURE REFRIGERANT DRIERS & FILTERS REFRIGERANT LEAK DETECTION REFRIGERANT LEAK REPAIR REFRIGERANT METERING DEVICES TEVs REFRIGERANT METERING CAPILLARY TUBES REFRIGERANT PIPING & DISTANCES REFRIGERANT PRESSURE READINGS RETROFIT SIZING for A/C or HEAT PUMPS SEER RATINGS & OTHER DEFINITIONS SOLAR ENERGY SYSTEMS SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS SWAMP COOLERS SYSTEM OPERATION THERMOSTATS, HEATING / COOLING THERMOSTATIC EXPANSION VALVES WATER COOLED AIR CONDITIONERS More Information |
This air conditioning repair article discusses the Diagnosing Tight or Seized Air Conditioning Compressors and how to re-start a tight air conditioning compressor. Advice for measuring amps or current draw to check for a seized or tight or failing A/C or heat pump compressor motor. InspectAPedia offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at InspectAPedia.com/Contact.htm.See the basic diagnostic steps suggested BURNED-OUT COMPRESSOR for A/C and heat pump damage indications and causes. Here we continue with details about examining and measuring A/C and heat pump compressors to continue compressor condition diagnosis. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Diagnosing Tight or Seized Air Conditioning CompressorsSometimes a compressor may be internally damaged or worn in a way that makes the piston(s) run tight in the cylinder(s) rather than loose and worn (loose or worn air conditioner compressor diagnosis is described at LOST COOLING CAPACITY). A tight or seized air conditioner compressor might occur, for example, if the compressor ran while low on oil. Or perhaps if the compressor is old and has not been run in some time. The A/C compressor may refuse to start at all, or may be hard-starting depending on when it last ran and what it's temperature is. A "hard starting" "tight" air conditioner compressor will probably draw excessive current (Amps) during startup, so that measurement may be used as part of the diagnosis of this problem. Re-Starting a Tight or Seized Air Conditioner CompressorThe service technician may try re-starting a hard-starting or tight air conditioning compressor by trying to move the motor backwards and forwards. If the compressor can be freed up enough to start at all and the oil level is made correct, the technician may install a "hard start kit" such as we introduced at HARD STARTING and see CAPACITORS for HARD STARTING MOTORS for photos, wiring diagram, and installation instructions for air conditioner compressor, fan, blower, refrigerator motor, freezer motor, or other electrical motor starting booster capacitors. If these steps work the compressor may continue to be used. If these steps do not get the tight or seized compressor running, it needs to be replaced. But even if these steps do work, the compressor has probably been damaged and you should not count on its long future life before it needs to be replaced. Amp Draw Testing for A/C or Heat Pump Compressor MotorsAlso see Basic Electrical Tests on Air Conditioner or Heat Pump Compressor Motors found at BURNED-OUT COMPRESSOR. Links there also return here. How We Measure Amps or Current Draw at the Air Conditioner CompressorBasic air conditioning compressor operation check: after the air conditioning system compressor/condenser unit has been running long enough to stabilize at its normal operating temperatures and pressures (typically 10 to 20 minutes), the service technician may measure the compressor's current draw in Amps using an ammeter or amp meter or multi-tester and appropriate connections. Watch out: the nameplate data giving FLA/RLA or LRA for an air conditioning system may include multiple electrical components combined, and even if it pertains to just the compressor motor, according to some industry experts these figures may not be an accurate diagnostic number for checking on hermetically-sealed A/C or heat pump compressor motors. Joe Marchese pointed out back in 2003:
The current draw in AMPS is compared with the unit's specified FLA or "full load amps" found on the data tag or in the service manual for the unit. Remember that the total system FLA number includes the current draw of not only the compressor motor itself but also the condenser fan motor as well as the compressor motor base heater if a heater element is installed and operating. But in our table below we give example RLA/FLA (rated load amps / full load amps) and also LRA (locked rotor amps) data for both air conditioner compressor motors and heat pump compressor motors. Tables of Typical RLA / FLA and LRA Amp Draw for A/C and Heat Pump Compressor MotorsTypical FLA current draw numbers for air conditioner compressors and heat pump compressor motors (second table below) using Whirlpool data as an example, include these data:
The apparent inconsistency of Amp draw increase in these tables is most likely due to variations in compressor motor designs among the different BTUH-rated units.
Locked Rotor Amps - LRA compressor motor dataThe current draw in AMPS during compressor motor start-up can also be compared to the unit's specified LRA or "lock rotor amps" found also on the data tag we describe above. However most HVAC repair technicians look at the compressor motor FLA reading since that's the running-condition of the unit. LRA in some references is also referred to as "starting current inrush" - the amount of current drawn, in amps, when full voltage is applied to start up the electric motor, in this case in the air conditioner or heat pump compressor. Example LRA data is found for both air conditioning compressors and heat pump compressors in the two tables above. Other sources give typical LRA numbers for typical 240V A/C compressors will typically be about 33 Amps per ton or 33 Amps per 12,000 BTUH for up to 3 ton units. So a two ton unit will draw 66-67A, a 3-ton unit 100A during startup only. Larger units do not continue this almost straight line increase in current draw. So a 4-ton A/C compressor may draw a bit under 120A, and a 5-ton unit 145A. All of these current draws are only during motor start-up and are at 240V AC. [2] What's the difference between FLA and RLA Amperage Current Draw Ratings?The reason you see us using "RLA/FLA" in the center table column is that these are about the same thing. The term "Full Load Amps" or "FLA" was officially changed to "Rated Load Amps" or "RLA" back in 1976. Regardless of calling it FLA or RLA, this is the maximum current the motor should draw during any running conditions. Note that this excludes high amp load during motor start-up. On modern air conditioners and heat pumps you should see RLA marked on the motor data plate. If you are reading an older article referring to "FLA", think RLA. Some technicians and electricians apply RLA to compressor motors and still use FLA for other motors. RLA is used in circuit wire sizing. Watch out: don't mix-up RLA (running load amps) with LRA (locked rotor amps). LRA is discussed above as well. Questions & Answers regarding this articleQuestions & answers about air conditioning compressor failures: tight, hard-starting, or seized A/C compressor motors Ask a Question or Search InspectAPediaHTML Comment Box is loading comments...
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