HVAC Electricity Exam Questions with Correct Answers

HVAC Electricity Exam Questions with Correct Answers Amp Rating and Breaker size for - #14, #12, #10, #8, #6, #3 - Answer-14-15,15 12-20,20 10-30,30 8-45,40 6-65,60 3-105,100 Residential lighting and receptacle circuits use what type of wire? - Answer-14-2 AWG (14-gauge, 2-wire, plus bond) conductors Ampacity - Answer-The amount of current a conductor is rated to handle safely. NMD - Answer-Non-metallic-sheathed cable(dry) - for exposed wiring in dry or damp locations NMW - Answer-Non-metallic-sheathed cable(wet) - for exposed wiring in wet locations Overload - Answer-Moderate increase in current beyond the rated current value. Most common method used by electrical grids to transfer power. Also for large motors and heavy loads. - Answer-Three phase electric power Grounding - Answer-Connection of all exposed non-current carrying metal parts to the earth that provides a direct path for unwanted current to earth without causing harm to people or equipment. Phase - Answer-The difference in electrical degrees between two waveforms. Three phase, four wire system wire colors - Answer-Neutral-white/natural grey Phase wire A - Red Phase wire B - Black Phase wire C - Blue How is electrical service to a building measured - Answer-Amps or kilowatts. Residential minimus is 100A. Electric heated homes need 200A Components of a residential electrical distribution system - Answer-Electric meter Main switch or breaker Distribution panel Fuses/Circuit Breaker Wire conductors How are fuses and circuit breakers sized - Answer-According to the wire they protect, and wire is sized according to load of individual branch circuits Electrical bonding - Answer-A low impedance path obtained by permanently joining all non-current-carrying metal parts to ensure electrical continuity and having the capacity to conduct safely any current likely to be imposed on it. Min size conductor required to bond gas piping systems to buildings elec system grounding conductor? - Answer-No 6 AWG Where would max Ampacity values for overcurrent protection devices be specified? - Answer-Canadian Elec Code (CEC) Wire gauge required for bonding gas piping to building's electrical system - Answer- Bare or insulated minimum No 6 AWG copper bonding conductor. No 4 AWG aluminum conductor. Purpose of protective devices (fuses/breakers) - Answer-To open the electrical circuit, stopping current flow, before damage can be done to conductors and connected equipment. They protect conductors and insulation from excess amounts of heat produced by overload and overcurrent conditions. Fuses - Answer-Simple current limiting devices that protect circuits and conductors Short circuit - Answer-Current flows outside normal path. Caused by: -failure of conductors insulation, causing conductor to touch a metal casing and crest line-to-ground fault -foreign object making contact with a conductor causing a line-to-line short Fuse color ratings - Answer-Blue 15A or less Red 20A or less Green 30A or less Max rating of a plug fuse is 30A Plug fuse not permitted in circuit w more than 125V b/w conductors Type P / Type D plug fuses - Answer-P-standard non time delay D-delay applications Low voltage ratings - Answer-0-30V - low low voltage 31-750V - low voltage Circuit breaker components - Answer-Frame (case) Operating mechanism Trip elements Contacts Terminal connection Current flow differential to trip a GFCI - Answer-0.005A = 5mA Conductors - Answer-Conductive material constructed for purpose of carrying electrical current. Best conductor carries the greatest amount of current at lowest temp rise. Ductility - Answer-Ability of a material to be drawn into wire form Malleability - Answer-Ability of a material to be formed into thin sheets Conductance - Answer-Opposite of resistance. Good conductor has high conductance and low resistance Conductor ampacity - Answer-Resistance of conductor increases with temp and as resistance increases, voltage drop increases. Ampacity rating depends on cable type, insulation, and max temp exposure. Dielectric strength - Answer-Ability if a conductors insulation to resist breakdown due to voltage stress. BX Cable (armoured cable) - Answer-Outer layer of flexible metallic sheathing to protect conductor and insulation from damage