Online HVAC Training

Understanding a Heat Pump Defrost Control Board – Part 3

by Ron Walker Finally we get the defrost part of the defrost control board. A heat pump’s outdoor unit will begin to frost and ice up somewhere around 40F or below outside temperature, depending on the humidity. For the heat pump to heat properly the ice must be removed. Note – Frost on the outdoor…

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HVAC Training - Defrost Control

Understanding a Heat Pump Defrost Control Board – Part 2

by Ron Walker So how exactly does a defrost control board work? If you break it down into the three different functions it performs it will be a little easier to understand. The three functions are cooling, heating, and defrost control. We’ll start with the simplest cooling. Cooling There are four inputs from the air…

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Online Air Conditioning Training

Understanding a Heat Pump Defrost Control Board – Part 1

by Ron Walker Many new air conditioning technicians are intimidated by the number of wires going to and from a heat pump defrost control board and exactly what they do. We’ll start out with a general overview of the control wiring (most defrost control boards have the same basic connections). R terminal – 24 volt…

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HVAC Training - TXV

Six Steps – Checking a TXV

By Ron Walker If you suspect you have a bad TXV, the first thing you must ensure is that the system has a proper charge. You can do this by checking that there is some subcooling happening in the condenser. If possible, check the manufacturer’s specification for the proper superheat for that particular model. As a…

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HVAC Definitions

Many HVACR terms and acronyms defined by ANSI/ACCA 5 QI – 2010 AABC: Associated Air Balance Council ACCA: Air Conditioning Contractors of America airflow:  duct airflow balance: a condition that exists when the duct system has been properly designed and assembled (i.e., sizing, friction loss, balance dampers, etc.) to ensure that the correct volume of air (in…

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