Glossary
Trade exam glossary
Short definitions for exam terms that appear in HVAC, electrical, welding, contractor, plumbing, crane, and home-inspection practice.
A
Acceptance Criteria
Written standard used to decide whether a weld or inspection result is acceptable.
TermAFCI
Arc-fault circuit interrupter protection intended to reduce fire risk from arcing faults.
TermAir Gap
Physical separation between a water outlet and flood level rim or receiving point.
TermAllowance
Budget amount set aside for work or materials not fully defined at bid time.
TermAmpacity
Maximum current a conductor can carry under stated conditions without exceeding its temperature rating.
TermAnti-Two-Block
Safety device or system intended to prevent block contact with the boom tip.
TermAttic Ventilation
Ventilation intended to manage attic heat and moisture conditions.
TermAzeotropic Blend
Refrigerant blend that behaves nearly like a single substance during phase change.
B
Backflow Preventer
Device or assembly used to prevent reverse flow into potable water.
TermBase Metal
Material being welded, brazed, cut, or inspected.
TermBend Test
Destructive test that bends a specimen to evaluate ductility and discontinuities.
TermBid Bond
A bond supporting the bidder's obligation to honor a bid if awarded the contract.
TermBonding Jumper
A reliable conductor used to maintain electrical continuity and fault-current path integrity.
TermBoom Angle
Angle of the boom above horizontal used in crane setup and capacity decisions.
TermBoom Length
Length of boom used with radius and angle to determine crane capacity.
TermBox Fill
Code calculation for how many conductors and devices can occupy an electrical box.
TermBranch Circuit
The circuit conductors between the final overcurrent device and the outlet or load.
TermBuilding Drain
Lowest horizontal drainage piping inside a building that receives fixture discharge.
TermBuilding Sewer
Drainage pipe extending from the building drain to the public sewer or disposal point.
C
Center of Gravity
Point where a load's weight is considered concentrated for lifting balance.
TermChange Order
A documented approval that changes contract scope, price, schedule, or conditions.
TermCleanout
Accessible opening used to clear drainage piping.
TermCombustion Air
Air required for safe and complete fuel combustion.
TermConductor Derating
Reducing conductor ampacity because of temperature, bundling, or other correction factors.
TermConduit Body
Fitting that provides access to conductors in a raceway system.
TermConduit Fill
The permitted conductor area inside a raceway based on size, type, and applicable table notes.
TermContingency
Reserved amount for uncertain scope, cost, or risk conditions.
TermContinuous Load
Load expected to run for three hours or more under maximum current conditions.
TermCounterweight
Weight used to balance crane loading and improve stability.
TermCrawlspace
Low unfinished area below a building floor that may contain structure, plumbing, wiring, or HVAC components.
TermCritical Lift
Lift requiring extra planning because of risk, load percentage, complexity, or site conditions.
TermCritical Path
Longest chain of scheduled activities controlling the project completion date.
D
Demand Factor
Ratio used to estimate likely load compared with connected load.
TermDestructive Testing
Testing that damages or breaks a specimen to evaluate properties or soundness.
TermDeveloped Length
Length measured along the centerline of pipe and fittings.
TermDouble-Tapped Breaker
Breaker terminal with more conductors than it is listed or designed to accept.
TermDrainage Fixture Unit
Sizing value used to estimate drainage discharge load.
TermDrainage Slope
Fall in drainage piping used to maintain proper flow.
TermDrip Loop
Loop in overhead service conductors intended to keep water from entering equipment.
TermDynamic Loading
Additional loading caused by motion, sudden starts, stops, impacts, or load movement.
E
F
Fault-Current Path
Low-impedance path intended to carry fault current and open the overcurrent device.
TermFeeder
Conductors between service equipment or another supply source and final branch-circuit overcurrent devices.
TermFiller Metal
Metal added during welding to help form the joint.
TermFillet Weld
Triangular weld used to join surfaces approximately at right angles.
TermFixture Unit
A plumbing sizing value used to estimate probable drainage or water-supply demand.
TermFoundation Settlement
Movement of a foundation that can cause cracks, slope, or structural distress.
TermFunction Rule
Rule that assigns each input exactly one output.
G
General Conditions
Project requirements covering administration, coordination, temporary facilities, and contract controls.
TermGFCI
Ground-fault circuit interrupter protection intended to reduce shock risk.
TermGlobal Warming Potential
Relative measure of heat-trapping effect compared with carbon dioxide.
TermGrading
Ground slope around a building that affects surface drainage.
TermGroove Weld
Weld made in a groove between workpieces.
TermGross Capacity
Load chart capacity before required deductions.
TermGround Bearing Pressure
Pressure imposed on ground or support surfaces by crane loads and setup.
TermGround Fault
An unintended current path to ground or grounded parts that can create shock and fire hazards.
TermGrounding Electrode Conductor
Conductor connecting the grounding electrode system to service or separately derived system equipment.
TermGuardrail
Protective barrier intended to reduce fall risk at elevated walking surfaces.
H
I
L
Lack of Fusion
Failure of weld metal to fuse with base metal or a previous weld pass.
TermLeak Repair
Finding and correcting refrigerant leaks under service, environmental, or compliance requirements.
TermLinear Equation
Equation whose graph is a straight line, common in aptitude-test algebra.
TermLiquidated Damages
Pre-agreed damages for delay or other specified contract breaches.
TermLoad Calculation
Method for estimating electrical demand for a service, feeder, or branch circuit.
TermLoad Chart Radius
Horizontal distance from the crane rotation centerline to the load center, used in capacity decisions.
TermLoad Moment
Force effect based on load weight and radius.
TermLow-Pressure Appliance
Large low-pressure equipment commonly associated with Type III EPA 608 topics.
M
Magnetic Particle Testing
NDE method using magnetic fields and particles to find surface or near-surface discontinuities.
TermManifold Gauge
Gauge set used to read system pressures and connect service hoses.
TermMechanics Lien
Claim against property for unpaid labor, material, or improvement work under applicable law.
TermMobilization
Work required to move labor, equipment, and setup resources onto a project.
TermMoisture Intrusion
Unwanted water entry into a building system or material.
N
Net Capacity
Capacity remaining after deducting rigging, hook block, attachments, and other required weights.
TermNeutral Conductor
Grounded conductor that carries unbalanced return current in many wiring systems.
TermNumber Pattern
Sequence of numbers following an arithmetic, geometric, or mixed rule.
O
Ohm's Law
Relationship between voltage, current, and resistance.
TermOutrigger
Extendable support used to stabilize a crane during lifting.
TermOvercurrent Protection
Protection against excess current through overload, short-circuit, or ground-fault conditions.
TermOverhead
Business or project costs not directly tied to one unit of installed work.
TermOzone Depletion Potential
Relative measure of how much a substance can damage stratospheric ozone.
P
Passage Evidence
Textual support used to justify a reading-comprehension answer.
TermPayment Bond
Bond that can protect subcontractors and suppliers against nonpayment.
TermPenetrant Testing
NDE method using penetrant and developer to reveal surface-breaking discontinuities.
TermPercent Change
Change expressed as a percentage of the starting value.
TermPerformance Bond
Bond that can protect an owner if the contractor fails to perform the contract.
TermPorosity
Gas pockets or voids in weld metal.
TermPreheat
Heating base metal before welding to meet procedure or code requirements.
TermPressure Reducing Valve
Valve used to reduce incoming water pressure to an acceptable level.
TermProcedure Qualification Record
Record documenting test results used to support a welding procedure.
TermProfit Margin
Profit expressed as a percentage of revenue or price.
TermPunch List
Closeout list of incomplete or corrective items before final acceptance.
Q
R
Raceway
Enclosed channel designed to hold wires, cables, or busbars.
TermRadiographic Testing
NDE method using radiation imaging to evaluate internal conditions.
TermRated Capacity Limiter
System that warns or limits operation near rated crane capacity.
TermRatio
Comparison between two quantities.
TermReadily Accessible
Able to be reached quickly without removing obstacles or using portable ladders.
TermReading Inference
Conclusion supported by passage evidence rather than outside assumptions.
TermRecovery Cylinder
A cylinder approved for holding recovered refrigerant during service or disposal work.
TermRefrigerant Oil
Compressor oil that must be compatible with the refrigerant and system design.
TermRefrigerant Reclamation
Processing used refrigerant to a purity standard before resale or broader reuse.
TermRefrigerant Recovery
Capturing refrigerant from an appliance for proper handling instead of releasing it.
TermRefrigerant Recycling
Cleaning recovered refrigerant enough for reuse under allowed service conditions.
TermReport Limitation
Inspection condition or scope limit that affects what could be observed or reported.
TermRetainage
Portion of payment withheld until specified work or closeout conditions are satisfied.
TermRFI
Request for information used to clarify contract documents or field conditions.
TermRoof Covering
Outer roof material such as shingles, tiles, metal, or membrane.
TermRoof Flashing
Material used to direct water away from roof joints, penetrations, and transitions.
S
Sanitary Tee
Fitting commonly used to connect horizontal fixture drains to vertical drainage or vent piping.
TermSaturation Temperature
Temperature where refrigerant changes state at a given pressure.
TermSchedule of Values
Breakdown of contract price used for progress billing.
TermSediment Trap
Gas piping fitting arrangement intended to collect debris before appliance controls.
TermService Disconnect
Disconnecting means used to shut off service conductors from the premises wiring system.
TermService Drop
Overhead service conductors from the utility system to the service point.
TermService Panel
Panelboard or equipment containing service disconnects and overcurrent devices.
TermService-Entrance Conductors
Conductors from the service point to the service disconnecting means.
TermShutoff Valve
Valve used to stop water, gas, or other service flow.
TermSignalperson
Qualified person who gives crane movement signals to the operator.
TermSlag Inclusion
Nonmetallic solid material trapped in weld metal or between weld passes.
TermSling Angle
Angle affecting tension in a sling leg and total rigging capacity.
TermSlope-Intercept Form
Linear equation form y = mx + b, where m is slope and b is the y-intercept.
TermSmall Appliance
Factory-sealed appliance category often tested under EPA 608 Type I rules.
TermSubcooling
Temperature below saturation for liquid refrigerant, often used to evaluate system condition.
TermSubmittal
Contractor-provided material, product, drawing, or data submitted for review.
TermSubstitute Refrigerant
Replacement refrigerant chosen for a system under compatibility, safety, and regulatory limits.
TermSuperheat
Temperature above saturation for vapor refrigerant, used in HVAC diagnosis and charging context.
TermSwing Radius
Area swept by the rotating counterweight or superstructure.
TermSystem-Dependent Recovery
Recovery method that relies partly on the appliance compressor to move refrigerant.
TermSystem-Independent Recovery
Recovery method using separate recovery equipment instead of the appliance compressor.
T
Tagline
Line used to help control load rotation or movement.
TermTemperature Pressure Relief Valve
Safety valve that relieves excess temperature or pressure on a water heater.
TermTrap
Plumbing fitting that holds a water seal to block sewer gas.
TermTrap Primer
Device that maintains trap seal by supplying water to a trap.
TermTriple Evacuation
Evacuation method that uses repeated evacuation and nitrogen breaks to remove moisture and air.
TermType I Certification
EPA 608 category for small appliances.
TermType II Certification
EPA 608 category for high-pressure appliances other than small appliances and MVAC.
TermType III Certification
EPA 608 category for low-pressure appliances.
U
Ultrasonic Testing
NDE method using high-frequency sound to evaluate material or weld conditions.
TermUndercut
Groove melted into base metal adjacent to a weld toe or root and left unfilled.
TermUniversal Certification
EPA 608 credential covering Type I, Type II, and Type III categories.
TermUnsafe Condition
Observed condition that presents a safety hazard or unreasonable risk.
V
Vacuum Pump
Tool used to pull a system into vacuum during evacuation or dehydration work.
TermVapor Barrier
Material intended to limit moisture vapor movement.
TermVent Stack
Vertical vent pipe serving drainage system venting.
TermVisual Testing
Inspection method using direct visual examination of accessible surfaces and conditions.
TermVoltage Drop
Voltage loss in conductors caused by resistance, current, and circuit length.
W
Water Hammer
Pressure surge caused by sudden change in water flow.
TermWater-Supply Fixture Unit
Sizing value used to estimate water-supply demand.
TermWeld Procedure Specification
Written welding procedure describing variables and requirements for producing a weld.
TermWeld Reinforcement
Weld metal in excess of the surface or specified weld size.
TermWelder Performance Qualification
Qualification record showing a welder demonstrated ability within stated limits.
TermWelding Discontinuity
An interruption in weld structure that must be evaluated against acceptance criteria.
TermWelding Symbol
A drawing symbol that communicates weld type, location, size, contour, and other requirements.
TermWet Vent
Pipe that serves both drainage and venting functions under allowed conditions.
TermWire Rope
Stranded steel rope used for hoisting, boom support, or crane operation.
TermWorking Clearance
Required clear space around electrical equipment for safe access and maintenance.
TermWye Fitting
Drainage fitting with a branch entering at an angle to improve flow.