Appliance Design - July 2008 - (Page 22)

GAS TECHNOLOGY Fire It Up Fast Hot-wire system provides new ignition alternative. by steve hussell Steve Hussell is director of marketing and sales, Channel Products, Chesterland, Ohio. 22 applianceDESIGN July 2008 eliable ignition is the top priority for design engineers developing gas appliances, and is of utmost concern for other functions such as marketing, sales, quality assurance, and field service. Until recently, the designers of gas appliances had to choose between two on-demand ignition technologies: spark and hot surface. Now there is a third choice, a system that utilizes a low-voltage, resistive-wire coil that can be adapted to different burner systems. This adaptable technology has emerged as a strong alternative for designers seeking a higher level of ignition reliability. To fully grasp the characteristics of the hot-wire ignition system, it’s best to first review the traditionally used technologies that have preceded it. For many decades, gas appliance burners were lit by means of a standing pilot light flame. Recognizing that the always-on pilot flames wasted gas, the industry moved to on-demand ignition. The patriarch of the on-demand realm is direct-spark ignition, easily recognizable by its telltale clicking sound. Spark ignition shares its roots with piezoelectric R push-button igniters, where the mechanical impact on piezoelectric materials can provide the necessary spark for ignition without the need for a connection to an electric power source. Piezoelectric igniters continue to be used on appliances such as gas barbeque grills. The typical spark ignition system uses a transformer to generate a high voltage (15,000 V or more) spark to ground, which ignites gas flowing into the burner, usually at a spark electrode. The electrode designs are quite versatile and usually can be designed to a specific style of burner to optimize the point of ignition. The highvoltage spark works well to ignite a gas burner if the spark occurs at the proper electrode ignition point. However, a number of problems can arise that can prevent the spark from reaching this ignition point, including contamination and moisture. The electrode can become covered with scale, dirt or other foreign material. The ground plane, which is necessary for sparking to occur, can also become compromised through corrosion, improper www.applianceDESIGN.com http://www.appliancedesign.com

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Appliance Design - July 2008 Contents Editorial Shipments/Forecasts News Watch Heating Elements Gas Technology Motors & Pumps Controls & Sensors Design Marts Association Report: AHAM Advertiser's Index

Appliance Design - July 2008

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