Conductors

Question 1

The amount of current a conductor can carry is defined as its_______________.

Answer 1

ampacity

Ampacity, also described as current rating or current-carrying capacity, is the magnitude of electric current which a conductor or device can continuously carry while remaining within its temperature rating. The ampacity of a conductor depends on its material, the temperature rating of its insulation, and its operating conditions. Amperes is a unit of electric current, frequently shortened to “amp.” In practical terms, the ampere is a measure of the amount of electric charge passing a point per unit of time.

Question 2

Which one of the following lists correctly defines the parameters that affect voltage drop?
1. Circuit current, inverter type, circuit length, and main breaker size
2. Circuit length, series fuse location, array size, and circuit current
3. Wire size/gauge, circuit current, circuit voltage, and circuit length
4. Array size, inverter size, circuit voltage, and circuit current

Answer 2

2. Circuit length, series fuse location, array size, and circuit current

Voltage drop is a function of the current in a circuit, the circuit voltage and its length, as well as the size of the conductor. Wire sized to meet NEC requirements may not be large enough to yield an acceptably low voltage drop and may need to be increased in size to meet both criteria

Question 3

Which can carry more current, an 8 AWG aluminum conductor or an 8 AWG copper conductor?

Answer 3

copper

Copper has lower resistance compared to aluminum, and thus can carry more current than an aluminum wire of the same diameter because it generates less heat. To carry the same amount of current, aluminum wire would have to be up-sized. Installers will sometimes use up-sized aluminum wire on long runs because it is a less expensive conductor

Question 4

Choose three primary differences between types of wire:
1. insulation material
2. solid or stranded
3. conductor material
4. country of origin
5. VAR tolerance

Answer 4

1. insulation material
2. solid or stranded
3. conductor material

Wire types differ in conductor material, stranding type, and insulation. The two common conductor materials used in residential and commercial wiring are copper and aluminum. Most small sizes of insulated wire, as well as larger bare conductors, are available in solid or stranded wire. Stranded wire is more flexible and generally easier to install, but using appropriate terminations for the numbers of strands is an important consideration

Question 5

The equipment grounding conductor must be_____(what color)______________

Answer 5

bare wire, green, or green with yellow stripes

Proper color-coding is critical for installation safety and future maintenance. Color-coding is described in NEC, Section 250.119 & Section 200.6(A). Equipment grounding conductors must be bare wire or have green or green with yellow striped insulation

Question 6

A solidly grounded conductor must be________(what color)______________

Answer 6

white or gray

Solidly grounded conductors, like the neutral on the AC side of a PV system, must have white or gray insulation

Question 7

AWG stands for___________________________

Answer 7

American wire gauge

Question 8

true or false. 10 AWG is larger than 6 AWG

Answer 8

false

Decreasing gauge numbers correspond to increasing wire diameters up to 1 AWG. The next larger size is 1/0, pronounced “one aught”, up to 4/0, which is also sometimes written as “0000”.

Question 9

Consider two identical 3 kW PV systems. The array of one operates at twice the voltage of the other. What are two benefits of this increased voltage?
1. Decreased voltage drop
2. Higher source circuit current
3. Reduced array power (watts) required
4. Reduced shock hazard
5. Smaller wire gauge required

Answer 9

1. Decreased voltage drop
2. Smaller wire gauge required

If the power is the same—3,000 watts—but the voltage is doubled, then the current will be cut in half. Less current means smaller wire is needed to carry the same amount of power, and smaller wire is less expensive and easier to work with. The combination of less current and higher voltage is ideal for minimizing voltage drop percentage as well

Question 10

When calculating wire size for various circuits, ampacity and voltage drop calculations will often result in different sizes. Which size should be selected?
1. Always pick the wire given from the NEC calculation
2.Always pick the smaller (diameter) of the two wires
3. Always pick the larger (diameter) of the two wires
4. Always pick the wire given from the voltage drop calculation

Answer 10

3. Always pick the larger (diameter) of the two wires

Selecting the larger wire size from the results of the two calculations will ensure that the requirements of both the NEC and voltage drop are met

Question 11

The short circuit current of a PV module is adjusted by what factor to calculate maximum circuit current:

Answer 11

1.25

The short circuit current of a PV module is multiplied by 1.25 to account for array production that exceeds the rated output because of increased irradiance, due to high altitude locations and snow reflection

Question 12

Match the following circuits with the points indicated on the following diagram (IMAGE)

Answer 12

Study!

The NEC defines PV source circuits as “circuits between modules and from modules to the common connection point(s) of the DC system.” In this diagram, the common connection point is in the DC combiner box. PV output circuits are defined as “circuit conductors between the photovoltaic source circuit(s) and the inverter or DC utilization equipment.” In this diagram, the output circuits begin as they leave the combiner box and continue until they connect to the inverter. The inverter output circuit is on the AC side of the inverter, connecting the inverter to the point of interconnection at the AC service equipment