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19 Cards in this Set

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what are the furnctions of the gas-burning assembly, and what are its component parts?
to produce a proper fire at the base of the heat exchanger *gas valve *flame proving circuit *manifold and orifice *gas burners & adjustment
on the modern gas valve, there are 2 shutoff cocks.What are they used for?
*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
what is the correct natural gas pressure leaving the gas valve?
7 in. w.c. to 3.5 in. w.c.
what are the component parts of the safety shutoff equipment?
*pilot burner *thermocouple or thermopile *pilotstat power unit
what are the functions of the pilot burner?
*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.
how much voltage does the thermocouple generate?
25 to 30 millivolts (mv)
what does the acronym cgv represent?
combination gas valve
what type of valve operator has a delayed action feature?
diaphragm valve operators
describe the operation of the 2 types of pilot burners?
*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.
what type of valve requires 100% shutoff?
unit burning LP gas require 100% shutoff
what is the function of the power unit?
shut's off gas supply if pilot light is poor or nonexistent
describe a proper pilot flame?
should envelope the thermocouple 3/8 to 1/2 in. at its top
what factors are considered in sizing the main burner orifice?
*type of gas *pressure in manifold *input of gas required for each burner
describe what is meant by primary and secondary main burner air.
*primary air: air mixed with gas before combustion *secondary air: air that is supplied to the burner at the time of combustion
what is the purpose of the venturi?
to create a high velocity gas by mixing primary air & raw gas (venturi-mixing tube)
what is the function of the draft diverter?
designed to provide a balanced draft (slightly negative) over the flame in a gas-fired furnace
name & describe the various types of main gas burners.
*single-port or inshot *drilled port *slotted port *ribbon
describe the service required for gas-burning equipment.
*gas burner assembly *pilot assembly *automatic gas valve
describe the various problems that can arise with the gas burner assembly, pilot assembly, and automatic gas valve.
*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.