G2 Gas Technician Module 12 Revised || with 100% Error-free Solutions.

What does an Aquastat do? correct answers 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? correct answers Automatic safety control (normally closed). Senses water level in the boiler. If level drops the switch opens and shuts off the gas valve. What does a water flow switch do? correct answers Automatic safety control (normally open). Senses water flow and switch closes, in series with gas valve. What does a Pressure Control Switch (pressuretrol) do in a steam boiler? correct answers 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? correct answers 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? correct answers 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. How much voltage will a thermocouple produce? correct answers It produces 25 - 30 millivolts, sufficient to hold a solenoid like a pilot stat energized. Where do you screw in a thermocouple and how tight should it be? correct answers The thermocouple is screwed into the pilostat coil, it should be tightened a 1/4 turn past finger tight. What are Thermopiles? correct answers Thermopiles are a collection of thermocouples connected in series. How many milivolts can a Thermopile generate? What is unique about this system? correct answers 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? correct answers 20-30 milivolts Thermocouple milivolts in a closed circuit what is a good range? correct answers 10-15 milivolts What milivolts indicates a good thermopile in an open circuit? correct answers 700-800 milivolts