BASICS OF HVAC Ivy Tech Community College

Definitions – Page 862 HVAC systems are made up of the mechanical equipment such as the furnace, air conditioner, and ductwork. The duct is generally sheet metal pipe. Types of duct include, cylindrical, oval, rectangular and square.

Central Forced Air-Systems- Page 862 Central Forced Air Systems – are the most common systems for heating and air-conditioning. They circulate air form the living spaces through or around heating or cooling devices. Central Forced Air Systems – are the most common systems for heating and air-conditioning. They circulate air form the living spaces through or around heating or cooling devices. A Thermostat starts the cycle as a fan forces the air into the ducts. These ducts connect to openings called diffusers or air supply registers which put warm air or cold air into the room. If cool air is required, the return air is passed over the surface of a cooling coil. If warm air is required the return air is passed over the surface of a combustion chamber (gas) or heating coil (electric). A Thermostat starts the cycle as a fan forces the air into the ducts. These ducts connect to openings called diffusers or air supply registers which put warm air or cold air into the room. If cool air is required, the return air is passed over the surface of a cooling coil. If warm air is required the return air is passed over the surface of a combustion chamber (gas) or heating coil (electric).

Heat Pump- Page 864 The heat pump is forced air central heating and cooling that operates using a compressor and a circulating liquid gas refrigerant. Heat is extracted from the outside air and pumped inside the structure. The heat pump supplies up to 3x as much heat per year for the same electric consumption. It works best when outside air is greater than 20degF. In the summer the cycle is reversed and the unit operates as an air conditioner. The heat pump is forced air central heating and cooling that operates using a compressor and a circulating liquid gas refrigerant. Heat is extracted from the outside air and pumped inside the structure. The heat pump supplies up to 3x as much heat per year for the same electric consumption. It works best when outside air is greater than 20degF. In the summer the cycle is reversed and the unit operates as an air conditioner. Figure 25.6 shows how a heat pump works. What happens when outside coils freeze over? Figure 25.6 shows how a heat pump works. What happens when outside coils freeze over?

HVAC Drawings Drawings for HVAC systems show the size and location of all equipment, ductwork and components with accurate symbols, specifications, notes, and schedules. Drawings for HVAC systems show the size and location of all equipment, ductwork and components with accurate symbols, specifications, notes, and schedules. Symbols page 866. Note: ceiling supply outlet, floor supply outlet, wall supply outlet, direction of flow, and manual volume damper. Symbols page 866. Note: ceiling supply outlet, floor supply outlet, wall supply outlet, direction of flow, and manual volume damper. How does the foundation of a building affect the decision to place floor, wall or ceiling outlets? How does the foundation of a building affect the decision to place floor, wall or ceiling outlets?

HVAC Drawings- Page 868 Draw duct runs using thick.03 mm line widths. Draw duct runs using thick.03 mm line widths. Label duct sizes when appropriate. Label duct sizes when appropriate. Duct sizes can be noted as 22 X 12 for example. The first number 22 is the duct width and the second number 12 is the duct depth. Duct sizes can be noted as 22 X 12 for example. The first number 22 is the duct width and the second number 12 is the duct depth. Place notes on the drawings to avoid crowding. Use aligned techniques. Place notes on the drawings to avoid crowding. Use aligned techniques. Refer to schedules to get specific drawing information not the the sketch. Refer to schedules to get specific drawing information not the the sketch. Label equipment either block out or bold to stand out from other information on the drawing. Label equipment either block out or bold to stand out from other information on the drawing.

Single and Double Line Single line drawings are easier and faster to draw. Refer to Figure Single line drawings are easier and faster to draw. Refer to Figure Double Line drawings are often necessary when complex systems require more detail. Refer to Figure Double Line drawings are often necessary when complex systems require more detail. Refer to Figure Your assignment is a double line drawing. Your assignment is a double line drawing.

Duct Specifications. – Page 871 You will need to use reducers in your drawing. Your supply ductwork is 14” wide and is 10’ Long. The ductwork leading to the vents is 6” Long. L = D1-D2. (14”-6”=8”) Therefore your reducer Length should be 8” Long. You will need to use reducers in your drawing. Your supply ductwork is 14” wide and is 10’ Long. The ductwork leading to the vents is 6” Long. L = D1-D2. (14”-6”=8”) Therefore your reducer Length should be 8” Long.

Duct Legend – Page 872. Drawing Tips: Note the Double Line Volume Damper. A VD will be required in the drawing to dial in each vents flow. Note the Double Line Volume Damper. A VD will be required in the drawing to dial in each vents flow.

Drawing Tips: You can use Flex Duct or Round Duct to connect to your supply and return duct. You can use Flex Duct or Round Duct to connect to your supply and return duct. Figure is a good sample drawing. Figure is a good sample drawing. Use a leader line to show the CFM value and Vent Size. – Refer to Duct Legend Page 872 Use a leader line to show the CFM value and Vent Size. – Refer to Duct Legend Page 872 Show reducers as appropriate. Show reducers as appropriate.