G - Pilots, pilot burners, thermocouples and Thermopiles
What is an Interrupted pilot
Ignited when there is a call for heat but goes out when the main burner is lit
What is a drop out point
A closed circuit milli voltage reading at the instant the plunger is released by the electromagnet
What is a proved pilot
Activation of a flame failure device
Can you use a joint compound on thermocouple threads
No
Can a pilot orifice be re drilled
No. It is made of pot metal
What is an intermittent pilot
Only ignited when there is a call for heat
What is an ECO
an energy cut off or high limit switch
What is power unit
Enegerized by the thermocouple or Thermopile and holds the safety gas valve open or safety switch closed
What is the main function of a pilot burner
Ignite the main burner
How do you do a safety shutdown test
Ignite the main burner and disconnect the thermocouple. The burner should then off immediately
How much power is used to operate the blower motor
Line voltage (110 or 120)
How is a pilot burner usually ignited
Manually
What is pull in voltage
Minimum milli voltage output of the Thermopile required to energize and open the gas valve to the main burner
What is a post aerated pilot burner
Most popular and common residentialy and light commercial appliances. An air duct beside the flame burns out dust and debris Also called incineration or target
What is the secondary function of a pilot
Operate flame failure devices by heating the thermocouple or Thermopile
What will excessive heat to the Thermopile cause
Premature burn out
What is an aerated pilot burner
Produces a sharp blue flame but the primary air inlet is susceptible to blockages causing the flame to carbonize. Important to frequently clean
What German physicist discovered that heat can create electricity
T.J. Seebeck
What is safe hookup
The automatic safety control is limited to only the main burner so if the pilot goes out gas will continue out of the main orifice. Prohibited for use in propane
What is an expanding pilot
The flame is always burning much like the continuous but the flame is increased when it lights the burner
How does a thermocouple work
The pilot applies heat to the thermocouple. The lead transports voltage to the power unit and if the heat is removed there is no power to hold it open
What must be done to a combination valve if an appliance is used on a propane installation
The regulator must be bypassed and the valve is operated in a fully open position
What is response time
The time it takes the thermocouple to cool sufficiently to cause the electromagnet to de energize and close the gas flow off
Where should a pilot flame be on a thermocouple
The top 3/8" to 1/2"
What is a non aerated pilot burner
Uses only secondary air to achieve combustion. Often found on gas stoves and clothes dryers Also called non linting or non primary
Where should the lead not be bent
Within 1/2" of either end it cannot be bent and shouldn't within 1" of either end
What is the maximum temperature of the ECO
the same as the temperature setting of the pressure relief valve (usually 200 to 210 F)
What is the difference between and open circuit milli volt check and a close circuit
You have to manually light the main burner to test on open You need a test adapter for closed as it will be normally operated
How is a pilots flame size adjusted
A needle valve
Where must a pilot be located
-Mounted where it can be safely lit -Properly positioned with respect to the main burner -Not exposed to falling debris during operation -Main burner flame should not touch the pilot -Must have ample air supply -Shall not recieve full force of main burner -Shall light the main burner under all conditions -never impinge on a burner or any other surface
How tight should a thermocouple be
1/4 turn more than hand tight
How much power should the thermocouple produce on an open circuit test
17 to 32 mV
What shall a response time not exceed on a unit 400,000 BTU
180 seconds on both natural gas and propane
How much power is used to operate the main control in a burner
24V
What voltages can a Thermopile produce
250 to 1000 mV
How long should it take the pilot to light the main burner
4 seconds
What shall the response time not exceed on a unit over 1 million BTU
4 seconds for both natural gas and propane
How much larger must the grounding are be than the flame sensor
4×
How much should a thermocouple produce on a closed circuit test
8 to 17 mV
What is the maximum length you should use on a Thermopile
80 feet
What shall the response time not exceed on a unit 400 MBH to 1 million BTU
90 sec natural gas 20 sec propane
What are the three pilot burner designs
Aerated Non aerated Post aerated
What is a turn down test
Also known as effective ignition test. Conducted to ensure that the pilot will satisfactorily ignite the main burner when it is reduced in size enough to prevent drop out. Factors such as a dirty pilot can cause this
How does a safety valve work on a power unit
An electromagnet attracts the plunger and holds it in the open position. A manual reset button must be depressed and held while lighting
When replacing a thermocouple what size should you use
As close as possible to the original
What is 100% safe hookup
Automatic safety control that shuts off both the main burner gas and the pilot gas
How much power should the thermocouple produce
Between 17 and 32 mV
What is a continuous pilot
Burns 24 hours a day 7 days a week whether or not the main burner is fired
What is a thermopile
Consists of several thermocouples connected in series. Therfore the total milli voltage output is higher than that produced by a single thermocouple
What are the 4 types of pilot burners
Continuous (standing) Expanding Intermittent Interupted
