The cold, snowy winter across the temperate zone of the northern hemisphere this season elicits thoughts of the importance of electronics in heating systems. Electronic controls are found in oil and gas furnaces and they sometimes fail at the worst times. Electronics engineers and technicians, of all people, have the skills to interact with these appliances of the residential infrastructure, and with some knowledge of furnace controls, can effect repairs and also customize their design. This TechNote features the author’s foray into furnace-fixing of a typical 1980s-vintage forced-air natural gas (propane, butane) furnace for an approximately 3500 square-foot (325 square meters) house in the Portland, Oregon, area of the USA. Furnaces have changed little over the intervening decades and this furnace continues to provide an example of what can typically be encountered in gas furnaces.
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