7-1 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e Chapter 7 IGNITION DEVICES

7-2 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e Ignition system types Flash tube ignition Piezo ignition Electronic igniters Re-igniters

Purpose of ignition devices To provide a heat source sufficient to ignite the gas within certain flammability limits. Ignition temperature (approx.) Natural gas680°C LPG Towns gas375–425° Flammability limits Natural gas5–14% LPG2.4–9.6% Towns gas5–40% 7-3 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Flash tube ignition 7-4 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Flash tube—fault finding Incorrect air–gas mixture Check: –flash tube clear of obstructions –flash tube charging port working –correct amount of gas going into flash tube –good alignment of charging port –flash tube location not moved –primary aeration of main burner adjusted correctly –appliance working pressure adjusted correctly –charging port not partially blocked or undersized 7-5 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Piezo ignition When pressure is applied to certain types of crystals electrical current is produced. A surge of electrical current is produced each time the crystals are pressurised. 7-6 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Piezo ignition—fault finding No spark –Check mechanical striker operation. –Check continuity between piezo and burner (earthing). –Check electrode for cracks (leakage to earth). Spark but no ignition –Check spark gap (approx. 3mm). –Check spark is earthing to correct position. –Check combustible air gas mixture exists at spark location. 7-7 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Electronic igniters Electronic igniters provide a continuous spark to a single or multiple burners. Can be either 240 volt or battery operated. 7-8 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Electronic ignition—fault finding No spark –Check electrical source. –If spark is supplied to multiple burners, check if leads are faulty by swapping them around. –Check spark gap (approx. 3mm). –Check continuity from the ignition box to the burner. –Check high tension leads are in good condition. Spark but no ignition –Check spark gap (approx. 3mm). –Check spark is earthing to correct position. –Check combustible mixture is at spark location. –Check high tension leads are not coiled. 7-9 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Re-igniters These devices provide a means of ignition and can identify the presence of a flame. The electrode is a dual igniter and sensor (flame rod) Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Re-igniters—fault finding Look for faults similar to those for electronic ignition –The circuit from the micro-switch to the electrode must be to the same burner as the gas supply. –There must be flame contact with the electrode Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Ignition—Summary Ignition system must supply sufficient temperature to light gas. Types of ignition systems –Flash tube: not common with NG and LPG appliances. –Piezo ignition: single spark operation. –Electronic igniters: 240v or battery with continual, pulsating spark. –Re-igniters: Uses flame as electrical path. For igniters to work, ensure gas pressure and flame are adjusted correctly! 7-12 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e