NRG Modules Review: Gas Technician Practice Exam

Comprehensive practice flashcards covering piping, electricity, controls, building systems, unvented appliances, water heaters, hydronics, and air distribution based on NRG lecture modules.

Pressure Drop

Working pressure at the piping inlet minus working pressure at the piping outlet.

Purge Line Termination

When using gas to purge air to the outdoors, the termination shall be at least $10$ feet from a building opening or air intake.

NPS 1 Piping Horizontal Support

The maximum allowed spacing between horizontal piping supports for NPS 1 piping is $8$ feet.

Maximum Threaded Pipe Size

The maximum allowed pipe size that can be threaded is NPS 4.

Underground Gas Piping Joints

Underground joints for gas piping shall be welded.

Underground Tubing Joints

Underground joints for tubing shall be brazed or approved flare fittings.

Plastic Piping Burial Depth

The minimum depth that plastic piping or tubing must be buried under a commercial parking lot is $24$ inches.

Standard Residential Power Supply

$240V$ / Single phase / $60$ Hertz.

Standard Residential Furnace Supply

$120V$ / Single phase / $60$ Hertz.

Potential Difference Instrument

A voltmeter is use to determine the potential difference in an electrical circuit.

Resistance Instrument

An ohmmeter is use to determine the resistance of an electrical component.

Millivolt ($mv$)

One millivolt equals $\frac{1}{1000}$ volt.

Thermocouple Open Circuit Test

The test reading should be in the range of $20$ to $30$ millivolts.

Power Pile Open Circuit Test

The test reading should be in the range of hundreds of millivolts.

Safety Limit Control

A control intended to prevent an unsafe condition of temperature, pressure, or liquid level.

High Limit Switch

A safety control that is Normally Closed ($N/C$).

NTC Thermistor

A temperature detector that senses changes via the decrease in resistance of a wire as temperature increases.

Thermostat Heat Anticipator

A device wired in series with the valve and in series with the thermostat contacts.

Aquastat

A control that responds to changes in water temperature.

Pressuretrol

A control that responds to changes in water or steam pressure.

Trial for Ignition

The time allowed to safely ignite a pilot or main burner.

Flame Failure Response Time

The time allowed for a safeguard control to de-energize shut-off valves in the event of loss of an established flame.

Flame Rectification

The process where a flame conducts electrons better from ground to flame rod than from flame rod to ground, resulting in an average $DC$ microamp signal.

Draft Intensity

The static pressure difference between the pressure in the venting system and the pressure of the atmosphere.

Stack Effect

Pressure difference caused by the temperature and density difference of indoor air versus outdoor air.

Air Barrier

A building component used to reduce air leakage into the building.

Vapor Barrier

A component used to prevent moisture travel through walls, installed on the warm side of the insulation.

Centrifugal Switch

A device used on a motor to prove it is turning, often found in dryers to prove the motor is running.

Redundant Gas Valve

A hydraulic operated gas control valve that opens to its full capacity immediately.

Bellows Meter

A meter that uses volume displacement through chambers divided by flexible material to drive dial needles.

Pressure Reducing Regulator Elements

The spring is the loading element, the diaphragm is the measuring element, and the valve/valve seat is the restricting element.

Lock-up Pressure

The pressure downstream of a regulator when there is no flow.

Propane Cylinder Retest

All refillable propane cylinders are required to be retested every $10$ years.

Absorption Refrigerator Service Factors

Three critical factors: heat input, air circulation, and leveling.

BTU (British Thermal Unit)

The amount of heat required to raise $1$ pound of water through $1^\circ F$.

Net Stack Temperature

The gross stack temperature (flue gas temperature upstream of the draft hood) minus the temperature of the air entering the burner.

Drip Tube

The component of a storage water heater that directs incoming cold water to the lower part of the tank.

Combustion Heat Requirement

The three elements required for combustion are fuel, oxygen, and heat.

Natural Gas Air Ratio

$10$ parts of air to $1$ part of natural gas are required for complete combustion.

Propane Air Ratio

$25$ parts of air to $1$ part of propane are required for complete combustion.

Primary Air

Air that is mixed with fuel prior to ignition.

Secondary Air

Air that is mixed with fuel at the point of combustion and around the flame.

Excess Air

Air in the combustion zone in addition to that which is required for theoretical combustion.

Carbon Monoxide Characteristics

Odourless, colourless, tasteless, and highly poisonous.

Sensible Heat

A change in temperature that can be felt and measured with a thermometer.

Latent Heat

Heat required to change the state of a substance (e.g., liquid to gas) without a change in temperature.

Anode Rod

An electrochemical component used in water heaters to prevent tank corrosion.

Unitrol

A gas valve on older water heaters that controls gas pressure, water temperature, and provides safety shut-off.

Low Water Cut-off ($LWCO$)

A safety control used on boilers to shut off fuel when water levels drop to an unsafe point.

AFUE (Annual Fuel Utilization Efficiency)

A measure of the seasonal efficiency of a heating appliance.

Psychrometer

An instrument with wet and dry bulb thermometers used to determine relative humidity.