Pilots, Pilot Burners, Thermocouples and Thermopiles (104c)

What is another term for a non-aerated pilot?

Non-linting/non-bunsen

What is the type of electrical current generated by thermoelectric devices?

Millivolt (mV) DC

This type of pilot burns constantly whether the main burner is fired or not

Standing pilot

What causes the electrical output of a thermoelectric device?

The difference in temperature between the hot and cold junctions when heat is applied. Known as the Seebeck effect.

How many ohms is the standard resistance of a power unit?

0.018 ohms

The recommended minimum distance from the end of a thermocouple to make a bend.

1" (1/2" if needed)

What is the normal dropout reading for a thermocouple?

1-6 mV

When the automatic safety control shuts off gas supply to both the main burner and the pilot you have what kind of hookup? This system requires manual resetting.

100% safe hookup

What Gauge of wire is to be used for mV systems located 45-80' away?

14 Gauge

What Gauge of wire is to be used for mV systems located 25-44' away?

16 Gauge

Output range for the open circuit test on a thermocouple.

17-32 mV

What Gauge of wire is to be used for mV systems located up to 24' away?

18 Gauge

What is the acceptable maximum flame response time for standing pilot applications up to 400,000 BTU/hr?

180 seconds

What should be considered for thermopile circuits exceeding 80 feet?

24-volt system

Output range for the closed circuit test on a thermocouple.

8-17 mV

The three main designs of pilot burners

Aerated Post-aerated Non-aerated

What colour of pilot flame is always trying to be achieved?

Blue flame

What is another term for an aerated pilot?

Bunsen/linting

The test used on a thermopile system to test proper ignition of main burners at a low pilot flame condition.

Effective ignition

What is the solution for a failed turn-down test?

Relocate pilot burner

How many mV are thermopiles capable of producing?

250-1000 mV

What is the acceptable closed circuit test range for a thermopile?

280-410 mV

How much of the tip of the thermocouple should the pilot flame cover?

3/8" - 1/2"

What is the acceptable open circuit test range for a thermopile?

540-800 mV

In addition to igniting the main flame, what is the secondary function of the pilot flame?

Activating a flame failure device via a thermocouple.

What is the most common problem associated with an orange pilot flame?

Combustion air impurities (dust, dirt, etc)

A temperature-actuated control that acts as a high limit to turn off the supply of gas in the event of an abnormal overheating situation. Usually set to 200-210F. Wired in series with the thermocouple and power unit.

Energy cut-off (ECO) switch

This type of pilot constantly burns at a low turndown, but is automatically increased during a call for heat.

Expanding pilot

What is a fixed element that controls the amount of gas that a pilot will burn?

Orifice

This effectively ignites the main burner

Pilot flame

This ensures the main burner is ignited under all circumstances while providing heat to the thermocouple.

Pilot flame pattern

What type of pilot uses primary and secondary air but has no mixing tube?

Post-aerated (incinerating or target)

What is an electromagnetic device used as a load in a safety circuit?

Power unit

In addition to operating the safety system (power unit) what other function does a thermopile serve?

Powers the gas valve

This type of pilot is supervised by a thermocouple.

Proved pilot

Similar to a drop-out test with thermocouples, this test is performed on thermopiles to determine the minimum voltage required to energize and open the gas valve.

Pull-in voltage test

What is the solution to an open circuit test that reads over 33 mV?

Reduce pilot flame

Name the two types of hook-ups for safety devices.

Safe and 100% safe

When the automatic safety control is limited to the main burner you have what kind of hookup?

Safe hookup

A thermopile is a number of thermocouples connected in...

Series

When reducing the pilot in a turn-down thermocouple test, when should the main burner ignite?

Within 4 seconds

This type of pilot is automatically ignited at the call for heat and remains on throughout the main burner cycle.

Intermittent pilot

This type of pilot is automatically ignited at the call for heat and is extinguished once the main burner proves lit.

Interrupted pilot

What is the adjustable component that controls the amount of gas the pilot will burn?

Needle valve or pilot regulator