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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 CONTROLS SAFETY CONTROLS 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 chapter discusses basic air conditioning system operating controls, air conditioning operating defects, and both normal and abnormal air conditioner operating temperatures and how to measure them. We also review the basic air conditioning safety switches. This chapter is part of our more extensive air conditioning inspection, diagnosis, & repair document which describes the inspection, diagnosis, and repair of residential air conditioning systems (A/C systems) for home buyers, owners, and home inspectors. 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. OPERATING CONTROLS - Air Conditioning System Operating ControlsBasic air conditioning inspection and inspection report information for A/C controls:
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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 CONTROLS SAFETY CONTROLS 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 CRITICAL DEFECTS Air Conditioning "How To" Books More Information InspectAPedia TM Home & Site Map Air Conditioning Contact Us |
SAFETY CONTROLS - Air Conditioning Automatic Safety Controls - Cooling System Fuse or Circuit Breaker Size RequirementsElectric Power Controls - Safety Disconnects for Air ConditionersSafety disconnects should installed outside next to the compressor/condenser unit and are often also installed next to or mounted on the air handler/blower unit.If you cannot find an outside electrical disconnect one should be installed. These controls are recommended for safety to reduce the temptation to open the cabinet and work on the equipment with power on. Working on electrically "live" cooling equipment risks both shock and mechanical injury such as being cut by the fan if the motor starts unexpectedly. Safety shutoffs are required for new equipment. How to Specify the Breaker or Fuse Size for Air Conditioning CircuitsAmperage rating of safety disconnects and A/C circuit breakers: the safety switch on newer equipment may be a simple pull-out fuse-block type power disconnect, leaving circuit protection to be provided only at the circuit breaker or fuse for the A/C circuit where it originates in the electrical panel. Where the actual overcurrent protection is provided (at older circuit breakers used as auxiliary safety disconnects at the equipment, and at the main panel at the origin of the cooling circuit for the compressor/condenser unit) electrical overload protection size (circuit breaker or fuse amperage rating) for modern A/C equipment is specified by the manufacturer. The 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. As we explained at the beginning of this document, a hermetic compressor draws varying amounts of current (measured in amps) as its internal pressure changes during operation. We said that current draw is higher when starting the motor than when the system is in steady state operation. Current draw is highest if the motor is starting against its highest back pressure such as if the air conditioning system has been 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.] Rules of thumb for over sizing air conditioning system breakers or fuses: On some older equipment MOP is not specified. Only when MOP has not been specified can the overcurrent protection required be determined by alternative means such as [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. [For example, if the MOP or fuse size is specified by the manufacturer to be 40 amps, then a 40 amp breaker must be installed with no increase or change in that rating.] Multiple switches are often present on cooling systems. As we reminded in the previous chapter, if the air conditioning system won't run, before requesting a service call check all of the switches as well as the thermostat for proper settings. | |||
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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 CONTROLS SAFETY CONTROLS 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 CRITICAL DEFECTS Air Conditioning "How To" Books More Information InspectAPedia TM Home & Site Map Air Conditioning Contact Us |
Air Conditioner Fuse or Circuit Breaker Size DetailsGenerally, what is the ampacity we see in the field when inspecting an air conditioning compressor circuit?When the air conditioning system is running, if you measured the amperage, it would be roughly 80% of the RLA. The breaker size is typically about 125% of the total of the compressor RLA and the condenser fan FLA (full load amperage). The rationale is that the circuit breaker protecting the air conditioner compressor unit should trip in the event of a locked rotor [the revolving axle of a compressor motor, for example] or some significant electrical event, but should not trip during start up loads which, as we know can be significantly higher than the RLA momentarily [as the compressor motor draws higher amperage to get itself started]. Why can we put an "oversized" fuse or circuit breaker on an air condtioning compressor circuit?An air conditioning electrical circuit is different than a general household circuit in that we have a known current load. [There is only one device connected to the air conditioning electrical circuit, and we can read its operating characteristics.] We are not worried about an overload situation where people plug several appliances into receptacles on a single circuit. Generally speaking, the amperage draw is fine or is way too big. Section E3602.10 of the IRC says, "Branch circuits for air conditioning and heat pump equipment. The ampacity of the conductors supplying a multimotor and combination load equipment shall not be less than the minimum circuit and capacity marked on the equipment. The branch-circuit overcurrent device rating shall be the size and type marked on the appliance and shall be listed for the specific purpose." In short, do what it says on the dataplate. Thanks to Alan Carson for these details. More Reading
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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 INSPECTION LIMITATIONS SYSTEM OPERATION OPERATING CONTROLS SAFETY CONTROLS 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 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.
Technical Reviewers
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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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07/23/07 - 01/31/2006 - Created 3/28/95 www.inspect-ny.com/aircond/aircond14.htm - Web page design & content © 2007 Daniel Friedman All Rights Reserved