58 9 what are the two most common controlling

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58-9) What are the two most common controlling elements in a mechanical humidistat? Nylon strips and hair
181 58-10) How is steam humidifier operation different from evaporative humidifier operation? A steam humidifier provides the energy required to evaporate the water and does not rely on heat in the air. Steam humidifiers can control the system fan to provide humidification on demand, even if there is no call for heat. 58-11) Why should a steam humidifier be filled with water before it is energized? To avoid burning out the heating element 58-12) How can an improperly maintained humidifier contribute to bad indoor air quality issues? The water sump in some types of humidifiers can grow algae and mold if not properly maintained. 58-13) Why do steam humidifiers require heavier electrical wiring than bypass type humidifiers? The power wiring required for vaporizing and steam humidifiers is much heavier than other types of humidifiers because of the increased electrical power needed to heat the water. 58-14) What is the purpose of the flush cycle used in some steam humidifiers? To flush out minerals left behind from water evaporation 58-15) On what types of heating systems can atomizing humidifiers be used? Warm air furnaces – not heat pumps
182 UNIT 59 REVIEW QUESTIONS ANSWER KEY 59-1) List three advantages of a warm air electric furnace as compared to an oil or gas furnace. It is more compact than the equivalent gas or oil furnace. Due to cooler surface temperature, it has “zero” clearance requirements on all sides. It may, therefore, be located in small spaces such as closets. Since there is no combustion process, there are no requirements for venting pipes, chimney, or makeup air. This reduces building costs and simplifies installation. 59-2) What material are electric heater coils often made from? Nickel chrome alloy wire. 59-3) An electric furnace rated at 240 volts and 30 amps would have an output capacity of how many kW? 240 V x 30 A = 7,200 W, which is 7.2kW 59-4) What happens to the current draw as an electric heating element warms up? As the electric heating element temperature increases, its resistance also increases and the current draw decreases. 59-5) When would the blower come on in an electric furnace? The blower must come on before the first heating element and must remain on until the last heating element has been de-energized. 59-6) Why is nickel chrome alloy used for electric furnace heating elements? Nickel chrome alloy has a high electrical resistance and also resists oxidation. 59-7) How are electric heating elements rated? Electric heating elements are rated by their kW capacity. 59-8) How would a multistage thermostat operate for a heat pump system with supplemental electric heat? For heat pumps the first stage brings on the heat pump and the next stage brings on the electric strips as needed.

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