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27 Cards in this Set
- Front
- Back
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Simple combustion safety controls include thermocouples and thermopiles known as _________ |
Thermoelectric devices |
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The Milli-Voltage generated by the thermoelectric energizes a power unit which is a temporary electro magnet. What does Pilot Flame On mean? |
The power unit will be engaged allowing gas to flow to the main burner. |
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Can a flame rod be used in a high heat combustion chamber? |
Yes |
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(Natural gas )Pilot light systems , continuous, interrupted and intermittent ignition systems respond to flame failure in how long? |
180 seconds |
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( Propane) Direct burner ignition by spark or hot surface systems respond to flame failure in how long? |
90 seconds |
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What 2 types of controls categories are in gas fired appliances? |
Operating controls and safety controls |
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Name 2 operating controls |
Thermostats , relays |
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Name 2 types of safety controls |
High limit safety switch Flame rollout switch |
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What are the devices that use a pilot flame to heat two dissimilar metals to create electrical power? |
Thermopiles and thermocouples, thermoelectric power generators |
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For the flame rectification circuit to be effective, the two electrodes must be at least __:__ The grounds electrodes exposed to the flame must be at least ______times larger than the flame rods surface area in order for the current to be rectified from AC input to pulsating DC output. |
1:4 |
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What are visual flame scanners? |
Sensors capable of detecting the wavelengths of light which can be seen by the human eye and are emitted by a flame. |
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What are the disadvantages of visual flame scanners? |
Very hot surfaces can emit infrared rays long after burner has been extinguished A VFS can be defeated by soot or water vapour on or inside its sensing element. |
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Direct ignition that ignite main burner fuel require no_______. |
Pilot light |
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Newer hot surface igniters are made from a material called _______ |
Silicon Nitrade |
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Spark igniters receive an activation signal from the control module, and when activated is capable of creating a rapid intermittent spark until the burner ignites. The spark must be driven by sufficient power that will jump an air gap of _______ to its receiving electrodes. |
1/8” 3mm |
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Spark igniter models will vary the time for how long the spark will be produced and discharged. The timing ranges from 4 seconds to_________ of sparking moment until lockout. |
Over 20 seconds. |
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The pilot flame and thermoelectric device must be adjusted relative to each other so the flame contacts no more than the the top __________ of the device . |
3/8”- 1/2” |
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A power unit in a safety switch is held open by an electrical output from the thermoelectric device. What happens if the pilot flame is extinguished? |
The power unit drops out and can be used to close the pilot or main burner gas supplies or used to open electrical contacts and cut power to a control circuit. |
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Flame rod tips must be placed so that approximately 1” of the of the flame rod tip is enveloped in the outer cone of the burner flame. Flame rods are most commonly with gas flames only, why? |
Clean burning and does not create deposits which can defeat the Flame rectification circuit. |
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What is the time allowed for a pilot burner or burner ignition system to safely ignite a main burner? |
Within 5 seconds of the time the pilot burner is activated |
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What type of electrical current is generated by a thermoelectric device? |
DC millivolt |
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What type of electrical current is generated by a thermoelectric device? |
DC millivolt |
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What 3 automatic systems for residential and light commercial heating are designed to save gas and only operate when a system requires heat? |
Direct spark ignition Intermittent pilot Hot surface ignition |
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What two methods are used by ignition controls to ignite fuel? |
Spark Hot surface |
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Hot surface igniters are composed of either _______ or _______. |
Silicone carbide Silicone nitride |
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Silicone Carbide is |
Quite brittle and must be handled carefully |
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Hot surface igniter systems are typically _____AC but can also be ______AC |
120 volt 24 volt |
