9-1 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e Chapter 9 FLUING AND VENTILATION

9-2 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e Necessity for a flue The products of complete combustion are heat, water vapour and carbon dioxide. All are considered harmless, but if they are permitted to build up the following problems may arise in a room: 1.A hot and damp atmosphere. 2.Flame vitiation (suffocation), which causes incomplete combustion. 3.A release of carbon monoxide from the products of incomplete combustion.

Function of a flue To remove the products of combustion. Drawing air into the room by the effect of aeromotive force created within the flue. 9-3 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Factors determining the need for a flue 1.Length of time an appliance is to be used— intermittently or continuously. 2.Megajoule rating of the appliance. 3.Location of the appliance. Where an appliance is designed to be connected with a flue, it must be connected in accordance with AS 5601, plus any special local requirements. 9-4 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Operation of a flue A flue is the means of conveying the products of combustion from the appliance to the flue terminal. The energy for moving the products of combustion is generated by the heat contained by the flue gases. Hot gases become less dense and rise up the flue pipe. 9-5 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Aeromotive force The movement caused by the difference in densities between the hot gases in the flue and the colder air surrounding the flue is called aeromotive force. Aeromotive force depends on the following: 1. The temperature difference between the flue gases and surrounding air. 2. The volume of the flue gases contained within the flue. 9-6 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Parts of a flue Primary flue Draught diverter Secondary flue Terminal 9-7 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Flue design Considerations: Flue material Location of flue Appliance gas consumption Vertical height Lateral length - Refer flue size tables: AS Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Flue examples 9-9 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Multiple or combined flues Where two or more appliances are connected to a common vertical flue stack Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Flue installations (1) The installation of the flue pipe is a very important consideration when selecting or recommending the appliance location. Points to be considered 1.Locate the appliances to avoid cutting of joists and rafters. 2.Flues passing through combustible materials must have suitable clearances—refer to AS The flue pipe must be supported so that the weight of the flue is not on the appliance or flashing Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Flue installations (2) 4. A means of disconnecting the flue must be provided, e.g. bolted sleeve or slip collar. 5. Flue joints must be sealed. 6. Provision must be made to remove condensate Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Use of existing chimneys Acceptable if: they are checked for adequate size the damper is removed or fixed fully open the flue pipe does not extend into the chimney and cause restriction 9-13 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Ventilation requirements Ventilation must be sufficient to guarantee adequate air for combustion and draught diverter dilution. Ventilation may be provided by adventitious openings, e.g. spaces around doors and windows. When allowance of 3 megajoules per cubic metre of room volume is reached additional ventilation is required Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Additional ventilation Refer to AS For most rooms where the ventilation is direct to the outside atmosphere, the following formula is used: A = 3 X T A = area of free ventilation in cm² 3 = factor when ventilation is drawn from outside atmosphere T = total megajoule rating of all appliances 9-15 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Fluing—Summary Points to remember A flue is used for conveying combustion products from the appliance to the terminal. Flue design is dependent on: –Appliance location –Lateral length and vertical rise –High or low heat loss application –Gas consumption –Flue material Flue installation must be in accordance with AS 5601, manufacturer’s instructions and local authority rules. Ventilation of room must be considered Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e