8-1 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e Chapter 8 CONTROL DEVICES

Solenoid valves Solenoid valves consist of an electrical coil and an iron spindle with a gas valve attached to one end. 8-2 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Solenoid operation When electricity flows through the coil, it becomes a very strong electromagnet. The electromagnet has sufficient strength to lift the iron spindle. When the electrical supply to the coil is switched off, the gas valve loses its magnetism and the valve is returned to the off position by its own weight. 8-3 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Solenoid—uses Wherever electrical controls are used to control the supply of gas to a burner. Two solenoid valves are fitted in some cases to lessen the chance of gas leaking through. 8-4 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Relay valves Used in conjunction with safety devices, thermostats, etc., to control the flow of gas to the main burner. 8-5 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Combination controls Combination controls contain multiple valves, e.g. thermostat, regulator, safety device. They control separately and independently of each other. 8-6 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Robertshaw Unitrol 8-7 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Minisit control 8-8 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Honeywell combination control 8-9 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e