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AIR CONDITIONING SYSTEMS A/C COMPONENTS CONTROLS & SWITCHES A/C DATA TAGS A/C TYPES, ENERGY SOURCES RATED COOLING CAPACITY AIR CONDITIONER BTU CHART SEER RATINGS OPERATING COST SYSTEM OPERATION OPERATING TEMPERATURES OPERATING DEFECTS LOST COOLING CAPACITY COMPRESSOR CONDENSER AIR HANDLER UNIT AIR FILTERS for HVAC SYSTEMS CONDENSATE HANDLING CLEANING & Legionella BACTERIA DUCT SYSTEM DEFECTS A/C REFRIGERANTS A/C DIAGNOSTIC FAQs INSPECTION LIMITATIONS CRITICAL DEFECTS Air Conditioning "How To" Books More Information InspectAPedia TM Home & Site Map AIR CONDITIONING InspectAPedia Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Bias Pledge Contact Us |
This website answers most questions about air conditioning systems. Here we discuss how to estimate the rated cooling capacity of an air conditioning system by examining various data tags and components. If your air conditioner has lost its cooling capacity or wont' start see How to Diagnose & Repair Loss of Air Conditioner Cooling Capacity. Also see How to Measure Central Air Conditioning Temperatures for a discussion of what temperatures to expect at different points in the air conditioning system. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website. 2. RATED COOLING CAPACITY - How to Determine Air Conditioning Equipment Rated Cooling CapacityThe cooling capacity of an air conditioning system is expressed in BTU's or tons. One ton of cooling capacity equals 12,000 BTU's/hour of cooling capacity. "One ton" of cooling capacity, historically, referred to the cooling capacity of a ton of ice. Tons of ice does not explain a key ingredient in the comfort produced by air conditioning systems, dehumidification of indoor air - that is, taking water out of the air. Cool air can hold less water (in the form of water molecules or gaseous form of H2O) than warm air. Think of the warmer air as having more space between the gas molecules for the water molecules to remain suspended. When we cool the air, we in effect are squeezing the water molecules out of the air. When an air conditioner blows warm humid building air across an evaporator coil in the air handler unit, it is not only cooling the air, it's squeezing out some of the water in that air. Both of these effects, cooler air and drier air, increase the comfort for building occupants. There are several ways to determine the rated cooling capacity of an air conditioning system's equipment: Air Conditioning Equipment Age and Capacity from Equipment NumbersSerial number formats vary by range of years over which equipment was manufactured, and may vary among countries of manufacture for a given company's equipment, for example between the U.S. and Canada for Carrier air conditioning equipment. Example: a Carrier Compressor/Condenser Serial# 1389E54894 on a compressor unit. Air conditioning equipment age from serial number for the example above, the equipment was made after 1980. The first four digits of the serial number are week and year of manufacture, in this case, week 13 of 1989. | |||
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AIR CONDITIONING SYSTEMS
A/C COMPONENTS CONTROLS & SWITCHES A/C DATA TAGS A/C TYPES, ENERGY SOURCES RATED COOLING CAPACITY AIR CONDITIONER BTU CHART FROM MODEL # FROM EQUIPMENT RLA # COOLING RULES OF THUMB SEER RATINGS OPERATING COST SYSTEM OPERATION OPERATING TEMPERATURES OPERATING DEFECTS LOST COOLING CAPACITY COMPRESSOR CONDENSER AIR HANDLER UNIT AIR FILTERS for HVAC SYSTEMS CONDENSATE HANDLING CLEANING & Legionella BACTERIA DUCT SYSTEM DEFECTS A/C REFRIGERANTS A/C DIAGNOSTIC FAQs INSPECTION LIMITATIONS CRITICAL DEFECTS Air Conditioning "How To" Books More Information |
FROM MODEL # - Air conditioning equipment capacity from model numberExample: Carrier A/C Compressor Condenser Model# 38XD12400 (same unit as used for the serial number example above), there is variation in how Carrier assigned these numbers but typically the numbers indicate either tonnage or MBTUH. This example has digits in the 4th and 5th positions (right hand 5 digits), so the rating is in MBTUH for this number and "24" signifies 24 MBTUH or 2 tons of capacity. Be sure to review our article on how to read the data in A/C DATA TAGS for a guide to reading the system cooling capacity either directly off of the sticker on the equipment, or for examples of how to find them model number which can be de-coded into cooling capacity and other features. A Reference Guide to Heating and Air Conditioning Equipment model numbers, serial numbers, age, and capacity: at Technical Reference Guide, is published by Carson Dunlop Weldon & Associates, Ltd., Toronto, 2006 for a $69.00 book which translates air conditioning equipment model numbers and serial numbers into date of equipment manufacture and rated BTUH capacity. | |||
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AIR CONDITIONING SYSTEMS
A/C COMPONENTS CONTROLS & SWITCHES A/C DATA TAGS A/C TYPES, ENERGY SOURCES RATED COOLING CAPACITY AIR CONDITIONER BTU CHART FROM MODEL # FROM EQUIPMENT RLA # COOLING RULES OF THUMB SEER RATINGS OPERATING COST SYSTEM OPERATION OPERATING TEMPERATURES OPERATING DEFECTS LOST COOLING CAPACITY COMPRESSOR CONDENSER AIR HANDLER UNIT AIR FILTERS for HVAC SYSTEMS CONDENSATE HANDLING CLEANING & Legionella BACTERIA DUCT SYSTEM DEFECTS A/C REFRIGERANTS A/C DIAGNOSTIC FAQs INSPECTION LIMITATIONS CRITICAL DEFECTS Air Conditioning "How To" Books More Information |
FROM EQUIPMENT RLA # - Air Conditioning Equipment Capacity from Equipment RLA NumbersRLA Rule of Thumb: RLA, Rated Load Amps, or in some older texts, mis-named as "Running Load Amps" is the manufacturer's specified rated current draw when the equipment is operating, excluding the current draw during startup, but when the compressor is under load. On a single-phase 240V circuit feeding an A/C compressor/condenser unit, the equipment will draw typically 5 to 6, (7 in some cases) RLA per ton of cooling capacity. So if the data tag on a compressor shows its RLA rating=21.2 I would rate the system as 21.2/7=3 Tons. Translating Tons into BTUH, 3tons x 12 MBTUH/ton = 36,000 BTUH estimated Cooling Capacity. Details of this and related calculations are in the "Guide" book cited above. | |||
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AIR CONDITIONING SYSTEMS
A/C COMPONENTS CONTROLS & SWITCHES A/C DATA TAGS A/C TYPES, ENERGY SOURCES RATED COOLING CAPACITY AIR CONDITIONER BTU CHART FROM MODEL # FROM EQUIPMENT RLA # COOLING RULES OF THUMB SEER RATINGS OPERATING COST SYSTEM OPERATION OPERATING TEMPERATURES OPERATING DEFECTS LOST COOLING CAPACITY COMPRESSOR CONDENSER AIR HANDLER UNIT AIR FILTERS for HVAC SYSTEMS CONDENSATE HANDLING CLEANING & Legionella BACTERIA DUCT SYSTEM DEFECTS A/C REFRIGERANTS A/C DIAGNOSTIC FAQs INSPECTION LIMITATIONS CRITICAL DEFECTS Air Conditioning "How To" Books More Information |
COOLING RULES OF THUMB - determining Cooling Capacity Requirements - Rules of ThumbA home inspection does not involve the calculations of heat gain necessary to decide if the cooling capacity on a building is adequate, but the inspector is expected to examine and report on the rated system capacity (such as "36,000 BTUH") and on the presence or absence of cooling sources in the habitable rooms of the building. Air conditioning capacity requirement: A simple rule of thumb for relatively cool climates such as the Northeastern United States: one ton per 400 sq.ft. (Commercial) or one ton per 500 to 1000 sq.ft. (Residential) or one ton per 400 to 800 sq.ft. (Space Pak Systems). . Or a 3000 sq.ft. house may require a 5-ton unit. Or count the supply outlets: 10 outlets @ 100 cfm (estimated) = 1,000 cfm = 2.5 tons needed. Oversized Air Conditioning Systems: Can an air conditioning system have too much capacity? Yes. If a system is over sized for a building it may be able to drop the indoor temperature so rapidly that the cooling cycle is too short to permit adequate reduction in the humidity level. Remember that indoor comfort is a function of both temperature and relative humidity. Also, since an oversized air conditioning system will be cycling on and off more frequently, not only is the building actually less comfortable (temperatures are swinging up and down unnecessarily quickly and frequently) but it may also be harder on the equipment, thus shortening its life. (Turning electric motors on and off is hard on them.) If the "on cycle" of the A/C system seems unusually brief, or if the indoor humidity is not dropping this question merits further investigation. | |||
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AIR CONDITIONING SYSTEMS A/C COMPONENTS CONTROLS & SWITCHES A/C DATA TAGS A/C TYPES, ENERGY SOURCES RATED COOLING CAPACITY AIR CONDITIONER BTU CHART SEER RATINGS OPERATING COST SYSTEM OPERATION OPERATING TEMPERATURES OPERATING DEFECTS LOST COOLING CAPACITY COMPRESSOR CONDENSER AIR HANDLER UNIT AIR FILTERS for HVAC SYSTEMS CONDENSATE HANDLING CLEANING & Legionella BACTERIA DUCT SYSTEM DEFECTS A/C REFRIGERANTS A/C DIAGNOSTIC FAQs INSPECTION LIMITATIONS CRITICAL DEFECTS Air Conditioning "How To" Books More Information InspectAPedia TM Home & Site Map Air Conditioning Contact Us |
AIR CONDITIONING SYSTEMS Chapter IndexTo continue reading this air conditioning inspection guide, use links to the document chapters at left or below. Links shown in green font indicate where you are in this document.
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AIR CONDITIONING SYSTEMS A/C COMPONENTS CONTROLS & SWITCHES A/C DATA TAGS A/C TYPES, ENERGY SOURCES RATED COOLING CAPACITY AIR CONDITIONER BTU CHART SEER RATINGS OPERATING COST SYSTEM OPERATION OPERATING TEMPERATURES OPERATING DEFECTS LOST COOLING CAPACITY COMPRESSOR CONDENSER AIR HANDLER UNIT AIR FILTERS for HVAC SYSTEMS CONDENSATE HANDLING CLEANING & Legionella BACTERIA DUCT SYSTEM DEFECTS A/C REFRIGERANTS A/C DIAGNOSTIC FAQs INSPECTION LIMITATIONS CRITICAL DEFECTS More Information InspectAPedia TM Home & Site Map Air Conditioning InspectAPedia Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Bias Pledge Contact Us |
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06/20/07 - 01/31/2006 - Created 3/28/95 www.inspect-ny.com/aircond/aircond1123.htm - Web page design & content © 2007 Daniel Friedman All Rights Reserved
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