Appliance Design - July 2008 - (Page 26)

GAS TECHNOLOGY time and cause arcing and sparking everywhere but where it is supposed to happen: at the burner. Low-voltage/high-temperature wire, which is easier to apply, works well with the hot-wire system. The hot-wire system tolerates contamination well by easily burning off the contaminants. Evidence for this can be found in the gas barbecue grill industry, where the hotwire system is already being used and deftly handling contaminants such as animal fats, dirt, BBQ sauce, water, marinades, and spider webs. The ignition element powers through the contamination and ignites the burner every time – on both propane and natural gases – eliminating the need for designers to construct igniter-shielding schemes. This capacity for burning off contaminants and still igniting the burner can be observed in the sequential images in Fig. 1. The design flexibility does not end with the physical geometry of the element. The hot-wire Attribute Ignition Speed Mechanical Durability Moisture and Contaminant Resistance Corrosion Contamination Time Effects Hot-Wire Fast (3 seconds) Excellent Very Good Very Good Use causes a protective oxidation layer on the coil No effect – voltage supply is regulated ignition system is available with 10,000-cycle and 100,000-cycle elements paired with systems using a portable battery, or 12-V, 24-V, 120-V or 240-V input integrated controls. Higher life systems may also be available as required by the design or application. The application flexibility of the hot-wire ignition system makes it an excellent candidate for a variety of appliance applications. The ability to burn off contaminants makes it ideal for commercial foodservice equipment that must operate in an environment where contamination is omnipresent. The rapid time to ignition also opens up new options for cooktop applications where consumers expect flame to appear quickly. Cooking applications also can benefit from the solid ignition characteristics of the system, making the application of combination controls and relight systems less problematic. For appliances that will operate in humid or wet zones, such as certain types of spaceSpark Fast (almost immediate) Excellent Poor Poor Corrosion/scale and loss of ground Hot-Surface Slow (30 seconds +) Poor Poor Good Thermal cycling causes brittleness and change in resistance Low voltage causes longer warm-up times; High voltage causes premature element failure Almost None Not flexible, and requires shielding and protection from contaminants Normal wiring and water-heating equipment or outdoor appliances, the hot-wire igniter eliminates concerns over moisture affecting ignition, because any moisture will be boiled off instantly. The hot-wire igniter is also a fit for high-heat appliances, like low-NOx water heaters, where its low-voltage operation makes it unnecessary for design engineers to search for high-heat/high-voltage wire. The hot-wire ignition system won’t always be the optimal choice for every application, as each ignition system has its own set of considerations. Comparisons between the three systems can help appliance designers make the best decision for their application. (See Table 1.) However, having a third choice in the world of ignition increases the design flexibility for designers of gas appliances who require durability and reliability from their gas-ignition systems. < For more information, email: Sales1@channelproducts.com NEEDTS? R E PR I N Effects of Voltage Variation Can cause change in spark rate Electromagnetic Interference (EMI) None Very flexible, no need for shielding or protection Low-voltage wire can be used Large effect – special control designs needed Flexible, but needs good path to ground High-voltage wire required Have you or your company been featured in a recent issue of Appliance Design? Reprints can be a single sheet or multiple pages. They are available in color or black and white in quantities of 500 or more. Geometry/ construction Wiring and Connectivity Contact Jill DeVries for a price quote at (248) 244-1726 or Email: devriesj@bnpmedia.com BNP MEDIA 2401 W. Big Beaver Road, Suite 700 Troy, MI 48084 Fax: (248) 244-3934 Table 1. Comparison of three different ignition systems highlights advantages and disadvantages of each. Source: Channel Products. 26 applianceDESIGN July 2008 www.applianceDESIGN.com http://www.appliancedesign.com

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Appliance Design - July 2008

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