hvac controls operation and maintenance (3rd edition)

[...]... temperature sensor and controller When the supply fan is started, the control system is energized and the outside air damper opens to minimum position Changeover of temperature controls between cooling and heating modes may be done either automatically or manually, or the controls may be designed for sequenced operation to operate without changeover by use of different 10 HVAC CONTROLS OPERATION & MAINTENANCE. ..BASIC FUNCTIONS OF HVAC SYSTEMS AND CONTROL SYSTEMS 1 Chapter 1 Basic Functions of HVAC Systems and Control Systems T he purpose of a Heating, Ventilating, and Air Conditioning (HVAC) system is to provide and maintain a comfortable environment within a building for the occupants or a suitable environment for the process being conducted This book covers basic HVAC systems of the all-air type,... refrigerant compressor and positions a reversing valve to allow reverse cycle heat pump operation On cooling cycle, space heat is absorbed on room-side air evaporator coil and space heat plus compressor heat is rejected to loop water cooled condenser coil On heating cycle, heat is absorbed from loop 20 HVAC CONTROLS OPERATION & MAINTENANCE water by water cooled evaporator coil and absorbed heat plus... Cooling and heating coil control Humidifier control Air distribution control Fan capacity modulation and static pressure control Terminal devices control Pumping systems control Boiler and chiller plant control 23 24 HVAC CONTROLS OPERATION & MAINTENANCE AIR MOVING SYSTEM CONTROL The basic control functions for air moving systems include daily start-stop, emergency fan shutdown, smoke damper operation, ... for life safety and for safety of the contents and the structure from injury and loss due to fire and smoke The fire code most often used in the United States is NFPA 90A, Installation of Air Conditioning and Ventilating Systems HVAC EQUIPMENT-TO-CONTROL INTERACTIONS 25 NFPA 90A requires: • Manual emergency stop means for each air distribution system to stop operation of supply, return, and exhaust fans... of heating, ventilating, and air conditioning are performed by an air handling system Some functions for central hydronic cooling and heating distribution are included which also apply to air-water and allwater types of systems The principal functions of HVAC systems and control systems are: • To maintain comfortable conditions in the space by providing the desired cooling and heating outputs, while... of HVAC systems, the intended function of those components in the HVAC system, and the HVAC equipment-to-control interactions Many problems which are considered to be HVAC system design problems are found to be ATC system operating problems In order to determine whether the ATC system is functioning properly, it is necessary to determine how each control sequence is intended to function 1 2 HVAC CONTROLS OPERATION. .. left blank HVAC EQUIPMENT-TO-CONTROL INTERACTIONS 23 Chapter 2 HVAC Equipment-to-Control Interactions A complete knowledge and understanding of the interaction of HV AC equipment with the control systems which are applied to that equipment is necessary for a thorough understanding of this book SYSTEMS AND SUBSYSTEMS Systems Covered This chapter is organized to match the usual arrangement of HVAC automatic... function 1 2 HVAC CONTROLS OPERATION & MAINTENANCE Although HVAC systems must be designed to satisfy the maximum cooling and heating loads at design conditions, HVAC systems do not operate at full capacity very often Systems seem to operate for most hours of the year at near half capacity, with variations due to changes in outside conditions for time-of-day and time-of-year and to changes in internal... All-Air systems—All-Air systems perform all the conditioning processes with air The processes are cooling and dehumidification, heating and humidification, along with air cleaning and air distribution Conditioning of air is usually done in central station equipment located re- 8 HVAC CONTROLS OPERATION & MAINTENANCE motely from the space An all-air system supplies only conditioned air to the space No other . class="bi x0 y0 w0 h0" alt="" i HVAC Controls Operation & Maintenance Third Edition This page intentionally left blank iii HVAC Controls Operation & Maintenance Third Edition Guy W intended to function. T 2 HVAC CONTROLS OPERATION & MAINTENANCE Although HVAC systems must be designed to satisfy the maxi- mum cooling and heating loads at design conditions, HVAC systems do not. specific and must be obtained from the system manufacturer’s literature and training seminars. BASIC FUNCTIONS OF HVAC SYSTEMS AND CONTROL SYSTEMS 1 1 Chapter 1 Basic Functions of HVAC Systems and