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19 Cards in this Set
- Front
- Back
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what are the furnctions of the gas-burning assembly, and what are its component parts?
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to produce a proper fire at the base of the heat exchanger *gas valve *flame proving circuit *manifold and orifice *gas burners & adjustment
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on the modern gas valve, there are 2 shutoff cocks.What are they used for?
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*A-cock:used to turn the main gas supply on and off manually. *B-cock:used to turn the gas supply to the pilot on and off manually
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what is the correct natural gas pressure leaving the gas valve?
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7 in. w.c. to 3.5 in. w.c.
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what are the component parts of the safety shutoff equipment?
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*pilot burner *thermocouple or thermopile *pilotstat power unit
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what are the functions of the pilot burner?
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*it directs the pilot flame for proper ignition of the main burner flame. *it holds the thermocouple or thermopile in correct position with relation to the pilot flame.
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how much voltage does the thermocouple generate?
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25 to 30 millivolts (mv)
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what does the acronym cgv represent?
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combination gas valve
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what type of valve operator has a delayed action feature?
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diaphragm valve operators
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describe the operation of the 2 types of pilot burners?
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*primary-aerated pilot:the air is mixed with the gas before it enters the pilot burner. *non-primary aerated pilot: the gas is supplied directly to the pilot,without the addition of primary air.
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what type of valve requires 100% shutoff?
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unit burning LP gas require 100% shutoff
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what is the function of the power unit?
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shut's off gas supply if pilot light is poor or nonexistent
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describe a proper pilot flame?
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should envelope the thermocouple 3/8 to 1/2 in. at its top
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what factors are considered in sizing the main burner orifice?
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*type of gas *pressure in manifold *input of gas required for each burner
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describe what is meant by primary and secondary main burner air.
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*primary air: air mixed with gas before combustion *secondary air: air that is supplied to the burner at the time of combustion
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what is the purpose of the venturi?
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to create a high velocity gas by mixing primary air & raw gas (venturi-mixing tube)
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what is the function of the draft diverter?
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designed to provide a balanced draft (slightly negative) over the flame in a gas-fired furnace
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name & describe the various types of main gas burners.
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*single-port or inshot *drilled port *slotted port *ribbon
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describe the service required for gas-burning equipment.
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*gas burner assembly *pilot assembly *automatic gas valve
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describe the various problems that can arise with the gas burner assembly, pilot assembly, and automatic gas valve.
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*gas burner assembly: flashback,carbon on the burners,dirty air mixture,noise of ignition,gas flames lifting from ports,appearance of yellow tips in flame. *pilot assembly: clogged air openings,dirty pilot filters,clogged orifice,defective thermocouples. *automatic gas valve: a valve that will not open,gas leakage through the valve.
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