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G2 Gas Technician Module 12.
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G2 Gas Technician Module 12.
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G2 Gas Technician Module 12What does an Aquastat do? - ANS-Its an automatic operating switch (normally open).
Sense water temperature of a boiler and closes when temperature drops.
What does a low water cut off do? - ANS-Automatic safety control (normally closed).
Senses water level in the boiler. If level drops the switch opens and shuts off the gas
valve.
in series with gas valve.,What does a water flow switch do? - ANS-Automatic safety
control (normally open). Senses water flow and switch closes
What does a Pressure Control Switch (pressuretrol) do in a steam boiler? -
ANS-Automatic control that senses high and low steam pressure in a boiler. It closes to
start burner on low pressure and opens at high temperature to stop the burner. Controls
steam pressure in the boiler.
What does a high pressure control do in a steam boiler and at what psi does it open? -
ANS-Automatic safety control that is normally closed. It senses high pressure in the
steam boiler and opens the switch. This is at 15 psi when it opens.
How does a Thermocouple work? - ANS-Two dissimilar metals that are joined at two
junctions. Heating one of the junctions produces a DC voltage. The temp difference
between the hot and cold metals determines the quantity of the DC voltage.
sufficient to hold a solenoid like a pilot stat energized.,How much voltage will a
thermocouple produce? - ANS-It produces 25 - 30 millivolts
it should be tightened a 1/4 turn past finger tight.,Where do you screw in a
thermocouple and how tight should it be? - ANS-The thermocouple is screwed into the
pilostat coil
What are Thermopiles? - ANS-Thermopiles are a collection of thermocouples
connected in series.
How many milivolts can a Thermopile generate? What is unique about this system? -
ANS-It can generate 750 milivolts and it is sufficient to operate a milivolt gas valve
system. This system does not require power.
, Thermocouple milivolts in a open circuit what is a good range? - ANS-20-30 milivolts
Thermocouple milivolts in a closed circuit what is a good range? - ANS-10-15 milivolts
What milivolts indicates a good thermopile in an open circuit? - ANS-700-800 milivolts
What is the purpose of the pilot drop out test? - ANS-To find the minimum voltage
produced by the thermocouple that will still energize the pilot stat. Usually between 2-4
milivolts
What is the flame failure response test time for a thermocouple/thermopile residential
system. - ANS-90 seconds
Closed circuit test(thermostat OPEN) on a thermopile system. - ANS-600 milivolts
away from drafts and within the pilot flame about 3/8" to 1/2",Pilot flame installation
rules. - ANS-Must no impinge on main burner or heat exchanger
What is flame ionization? - ANS-The process of heating air molecules to allow for
separation of electrons allowing a flame to conduct an electrical current. When an AC
signal is directed through the flame it will conduct an electrical charge across the flame
to the ground.
What is flame rectification? - ANS-When you over size your ground to prevent a flame
detector from getting a false positive and thinking there is still flame present due to
carbon build up.
Closed circuit test(thermostat CLOSED) on a thermopile system. - ANS-400-450
milivolts
What does a flame rod do? - ANS-Senses a pulsating dc current that signals flame is
present.
How should you size a flame rod? Why? - ANS-Must have 4 times less surface area
then the ground. Normal practice is 10 times smaller. This causes the signal to flow
easier from the flame rod to ground.
- ANS-Flame failure response 0.8 seconds
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