H1 LT1 Flashcards
What type of voltage do most appliances in residential construction use?
Single-phase voltage
Who owns the meter and meter socket?
Meter - supply authority, Meter socket - consumer
What is the name of the busses that are not connected to the ground?
Ungrounded busses
Where can service conductors connect to?
Line side of a main fusible switch
Why must the neutral wire not be fused?
For safety reasons, to prevent unequal division of voltage across loads if it were to open in an unbalanced three-wire system.
What is the voltage fixed at on the secondary winding of a single-phase system?
240 volts
What is the name of the bonding wire that connects the neutral bus to the grounding bus?
Bond strap
What is on the load side of the switch?
Fuses and load terminals
What is the purpose of fusing the line wires but not the neutral wire?
Safety, to avoid creating an unbalanced condition that could harm loads.
What is the color of the neutral wire in the secondary winding?
White or natural grey
What is the name of the section of the panelboard that contains the main circuit breaker?
Service box section
What does a load centre contain?
Circuit breakers for branch circuits
What hazard could be created if a fuse in the neutral were to open?
Shock hazard
What are the two outer wires in a three-wire circuit called?
Line wires or hot wires
What voltage level could result in a shock if a person were in contact with a grounded surface?
120 V
What is the purpose of a kilowatt-hour meter in a residential dwelling?
To record amount of electrical energy used
Why is the neutral grounded at the transformer and main power?
To limit shock hazard to 120 V
What unit is electrical energy measured in by a kilowatt-hour meter?
kWh
What is a combination panelboard?
Main circuit breaker located in the same enclosure as branch-circuit breakers
What happens if the neutral wire in an unbalanced three-wire system opens?
It creates an unequal division of voltage across the loads, possibly damaging them.
How is the 240 volts divided in a three-wire system?
To provide 120-volt and 240-volt supplies
What happens to the fuse when a high fault current flows in a circuit?
Blows to protect circuit
Where is the neutral wire grounded in a single-phase, three-wire system?
Transformer and residential service box
What are the three ways to control the power supply after it is fed through the kilowatt-hour meter?
A combination panelboard, a main circuit breaker, a main switch incorporating fuses
What are the major advantages of a single-phase, three-wire system?
Two voltages available, Improved safety, Reduced copper requirement