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This article explains and translates all of the data found on information tags and stickers used on air conditioning and heat pump equipment. This website answers most questions about air conditioning systems. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. Readers who need to determine the age of heating boilers and furnaces should also see AGE of HEATERS, BOILERS, FURNACES and for water heaters, see AGE of WATER HEATERS.

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A/C DATA TAGS - Air conditioner & heat pump data tags

Here we explain the meaning of each of the data names and contents of typical air conditioner system data tags. We include examples of how to make use of the data to estimate equipment age, capacity, and even its condition. (Not all of the terms we define below will appear on all equipment or motor tags.)

The photo at page top shows the main data sticker from a 1997 split system air conditioning compressor/condenser unit. This model, made by Sanyo, Inc., provides easy-to-read basic data about the system including its year of manufacture, refrigerant, electrical requirements, and service information. The photo shown here is for a conventional (non-split) residential air conditioning compressor unit. Unless it has been painted-over or lost, on most air conditioners and heat pumps, a metal, foil, or plastic tag or data sticker is usually affixed to the outdoor air conditioner or heat pump compressor/condenser housing. Depending on the age and equipment manufacturer the format and content of data on this tag varies, but typically the tag will allow you to discover some or all of the considerable amount of data listed here:

• Manufacturer: The air conditioning equipment manufacturer.
  
  Sketch at left on guessing the size of an air conditioner system is compliments of Carson Dunlop. As we cite below, Carson Dunlop also provide a Technical Reference Guide with extensive details that aid in decoding HVAC equipment serial numbers and data tags.
  
  
• Model Number, Serial Number, and Cooling Capacity: sometimes cooling capacity is coded into the model number but on most newer units including the Sanyo compressor shown here, cooling capacity is stated explicitly. On older equipment the BTUH cooling capacity may be encoded in the model numbers.
  
  RATED COOLING CAPACITY discusses how to read the cooling capacity in BTUH or tons from air conditioning or heat pump tags. The serial number of modern HVAC equipment encodes the year and month of manufacture - thus the age of the equipment is shown. For equipment where the month and year of manufacture is not stated in plain English, Carson Dunlop provides a Technical Reference Guide manual that decodes that data.
• Voltage or VAC for the compressor and separately for the blower fan. In addition to specifying voltage, the cycles (50HZ or 60HZ) and current phases (typically one phase for residential equipment) may be specified.
  
  
• Branch Circuit Selection Current- BCSC: recommended for determining the required size of the branch circuit conductors (wiring) supplying the equipment.
  
  
• Locked Rotor Amperage - LRA specifies the maximum current that the motor will draw when the motor's rotor is unable to move [locked] (or under any other condition). [NEC Table 430-152-A]. LRA on an air condtioning compressor describes the amperage drawn by the motor briefly during motor startup. Locked rotor amperage is also called inrush current. Because it takes a lot of energy (torque) to get the still parts of an electric motor turning, LRA will always be higher than the current used to keep the motor turning once it has started (FLA or RLA). This is particularly true if the motor has an additional load (resistance to turning) at startup, such as trying to start an air conditioning compressor against refrigerant head pressure inside the compressor unit.
  
  The LRA of electric motors is 700% - 850% of rated current of the motor (or in some sources 5 to 7 times greater than RLA or FLA - a lot. The motor's circuit breaker, especially on an air conditioning system which can draw high initial amps (LRA) will be sized to protect the electrical wiring of the motor circuit, but the breaker also will be chosen to tolerate a brief, high initial current draw to avoid nuisance tripping. In other words, the inrush current, because it is brief, does not need to figure in the selection of the wire sizing when wiring or fusing the motor, except to avoid nuisance tripping.
  
  The relationship between the LRA and full load amperage (FLA) varies depending on the design of the elecric motor being rated. Motors built to NEMA standards are assinged codes A through H. Each letter can be translated into multiplier x FLA to give LRA.
  
  To assist in avoiding nuisance tripping during compressor startup when high current is drawn momentarily, A/C compressor circuit breakers may be permitted to be one size larger than the circuit breaker required by the wire size itself.
  
  LRA also affects the choice of the electric motor starter. Finally, an air conditioner motor will also draw its LRA current if the motor is frozen or stuck or has bad bearings - which we hope will quickly trip the circuit breake or blow the circuit fuse. -- Thanks to Patrick Greaux for requesting clarification of LRA.
  
  
• Minimum Circuit Ampacity - MCA: MCA can be used to determine the required size of branch circuit conductors (wiring and also control switches) supplying the equipment. [For example, using NEC Table 310-16 in the 60 degree column as required in 110-14]. However some experts recommend using BCSC. [Using the "minimum permitted" sized wire rather than the optimum-size to a compressor may save a few dollars at installation but may increase system operating costs and it may be less safe than using a larger conductor.]
  
  
• Maximum Fuse or HACR type Breaker: specifies the maximum overcurrent protection or MOP to be used to protect the equipment. The permitted ampacity of the equipment electrical circuit protection (fuse or circuit breaker amps) expressed as MOP or Maximum Overcurrent Protection. If MOP is specified, the breaker or fuse protecting the equipment should match this number.
  
  A hermetic compressor draws varying amounts of current as its internal pressure changes during operation. Current draw is higher when starting the motor, and highest if the motor is starting against its highest back pressure such as when a unit is turned off and then back on in the middle of operation. Because fusing an air conditioning compressor at the minimum level can result in blown fuses or tripped breakers during these intervals of heavy current draw during compressor startup, compressors are either protected by a slow-blow fuse or a somewhat larger than minimum circuit breaker.]
  
  On some older equipment MOP is not specified. Only in the case that MOP is not specified can the overcurrent protection required be determined by the alternative means: [RLA OR BCSC whichever is greater x 175%], or if the compressor keeps tripping that device or blowing that fuse, RLA x 225% might be used. The National Electrical Code (NEC) specifies the degree to which a breaker or fuse may exceed the RLA.
  
  
• Rated Load Amperage or Runnnig Load Amperage - RLA, also called Rated Load Current or RLC on some equipment. This is the manufacturer's anticipated load during normal usage, that is, the current drawn when the motor is running normally. RLA is usually similar to FLA in amount.
  
  Typically RLA is about about 64% of the maximum load current. See NEC section 440-2.
  
  We sometimes can guess the size (tons of cooling capacity) of an air conditioning compressor by dividing the RLA number by 6, 7, or 8. For example a compressor RLA of 21 amps may be about 3 tons of cooling capacity (21/7). For more accurate means of detemrining air conditioner cooling capacity by several means including decoding the data tag, see COOLING CAPACITY, RATED. In air conditioning systems, typically a motor provides about one horsepower (HP) per ton of cooling capacity.
  
  
• Full Load Amperage - FLA full load motor current draw, level at which the motor can be operated without damage. FLA is similar to RLA in amount. The FLA amperage is the current the motor will draw when the motor is
  loaded up to its rated horsepower. If an electric motor is running at less than its rated horsepower it will draw less than its FLA current.
  
  If an electric motor is trying to run at more than its rated horsepower, it will draw more than its FLA current. A technician can measure the actual motor amperage (current draw) and compare it to the FLA to quickly tell if a motor is overloaded - in the case of air conditioning a running current draw above FLA may mean that the compressor is near its end of life.
  
  
• Maximum Continuous Current - MCC not usually supplied, this is the most current that the compressor can draw without being damaged. [Typically about 150% of RLA.]
  
  
• BTUH Cooling Capacity: The A/C system cooling capacity, either explicitly stated in thousands of BTU's (British Thermal Units) per hour (BTUH) or implicitly given by other data, or coded in the unit's model number.
  
  
• The month and year of manufacture, possibly also encoded in the unit serial number. Since the typical life of an A/C compressor is about ten years, one would like to know the probable age of the equipment.
  
  
• The Energy Efficiency Ratio of cooling equipment is basically the amount of electricity you consume to obtain a given amount of cooling ability. It's expressed as (KW per hour of electricity used) / Thousand BTUs - this number is probably not going to be found on the equipment itself but may be in its documentation. Also see SEER RATINGS & OTHER DEFINITIONS
  
  
• Refrigerant type is shown somewhere on every air conditioner, heat pump, or other cooling compressors. The tag shown here notes that the system uses [the now obsolete] R22 refrigerant.
• Voltage - the voltage at which the motor is intended to be operated. Motors can normally operate fine at voltages withing 10% of the rated voltage level on the data plate.
• Month and year of manufacture is shown either explicitly as on the Sanyo compressor data tag shown here or this data may be encoded in the unit's serial number. Carson Dunlop provides a manual that decodes more of that data so that you can know the age of the compressor or air handler. That is, the date of its manufacture, not the date of its installation. The installation date of air conditioning equipment may be recorded on a service company's data tag, on receipts, or even inked inside of the steel cabinet of the equipment.

More Reading

• For the most complete and very detailed HVAC equipment data tag and age decoding information anywhere, Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, offer Carson Dunlop Weldon & Associates Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).

• A HREF="http://inspect-ny.com/aircond/aircond14.htm">Air Conditioning A/C System Operating Controls & Overcurrent Protection discusses the electrical power controls, fusing, fuse sizing, and amperage or current measurements on air conditioning equipment (in the section on "Safety Controls" on that page.
• CONTROLS & SWITCHES - Switches and Controls on a typical split system with indoor and outdoor components were listed in the first chapter at A/C COMPONENT LIST

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Other information tags and stickers on air conditioners and heat pumps

Service and refrigerant connections

Service information and/or refrigerant piping hook-up may be provided by a separate sticker on the air conditioner compressor/condenser unit, such as the piping arrangements shown on this split-unit compressor side. More critical service data such as refrigerant type and operating pressures are recorded in the main data tag shown earlier.

Air conditioner or heat pump basic wiring diagrams

A basic hook-up wiring diagram may be provided by the manufacturer on a separate sticker on the air conditioner compressor/condenser unit such as this one from the Sanyo unit.

Air conditioner or heat pump safety warnings

Safety warnings for consumers and service people also appear on tags or stickers on modern air conditioning and heat pump units, such as shown in the photo above.

Data information tags on commercial air conditioning and heat pumps

Commercial air conditioning or A/C/Heat pump units such as the rooftop unit from which these data tag photos were taken often provides additional and critical capacity and service data.

The first or left hand tag shows the equipment's operating capacity in both BTUH and watts, and shows a maximum air temperature at the unit. The second photo at right shows a refrigerant charging chart that must be consulted by the service technician who monitors suction line (low pressure or return line) temperature and pressure.

...

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AIR CONDITIONING & HEAT PUMP SYSTEMS
AGE of AIR CONDITIONERS & HEAT PUMPS
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
  Indoor A/C Components
  Outdoor A/C Components
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER UNIT
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - Air Conditioning "How To" Books
CLEANING & Legionella BACTERIA
COMPRESSOR CONDENSER
CONDENSATE HANDLING
CONTROLS & SWITCHES
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
DATA TAGS on AIR CONDITIONERS
DUCT SYSTEMS
DUCTS - Asbestos
DUCT SYSTEM DEFECTS
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
FAN AUTO ON Thermostat Switch
HEAT LOSS (or GAIN) in BUILDINGS
INDOOR AIR QUALITY IMPROVEMENT GUIDE
INSPECTION LIMITATIONS
LOST COOLING CAPACITY
MOTOR OVERLOAD RESET SWITCH
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
REPAIR GUIDE for AIR CONDITIONERS
REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
THERMOSTATS
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS on A/C SYSTEMS
FURNACES WARM AIR HEATING SYSTEMS
INDOOR AIR QUALITY IMPROVEMENT GUIDE

• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
• Thanks to Scott at SJM Inspect for suggesting this EPA document and for technical editing remarks regarding our air conditioning website, SJM Inspection Service LLC, serves the entire state of CT, sjminspect.com 203-543-0447 or 203-877-4774 5/16/07
• Thanks to Patrick Greaux 02/02/2009 for suggesting clarification of LRA - Locked Rotor Amperage.

Air Conditioning How-To Books on Air Conditioning Inspection, Diagnosis, & Repair

• Books, Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.
• Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
• Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
• "Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
• Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
  http://books.google.com/books?id=NAdQGV-imRAC&printsec=frontcover#PPA524,M1
• Ratib Bakera is member of Refrigeration Service Engineers Society (RSES), an International training organization for the HVACR industry provides educational and certification programs to HVACR professionals of all experience levels. www.rses.org provides information on the organization and its training materials. Independent testing and certification of HVAC technicians is provided by North American Technician Excellence - NATE - see www.natex.org. NATE is supported by ASHRAE, the US EPA, and a host of other trade and professional associations.
• Singer brand HVAC equipment brand history: Singer was bought by & became the climate control unit of Dallas-based Snyder General Corp. (founded by a former Singer HVAC manager) in 1982. The name Singer was dropped in 1984. In 1984 Snyder General operations included Arcoaire, Comfortmaker, and McQuay. In 1991 Snyder General sold Arcoaire & Comfortmaker to Inter-City Products. In 1994 Snyder General was acquired by Hong Leong Group Malaysia. Snyder General is at 2001 Ross Avenue Dallas, TX 75201.

More Information on Building Diagnostic Inspections and Repairs

• Air Conditioning Inspection, Diagnosis, Repair, Efficiency all the basics for home owners, inspectors, new repairmen
• Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
• Asbestos HVAC Ducts and Flues field identification photos and guide
• Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation

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