Code Calc Lv2 Lesson 3

A 14 AWG XHHW-2 copper conductor is connected to a circuit breaker with termination temperature limitation marked (not to exceed) 60°C. What is the allowable ampacity of this conductor now that it is connected to this circuit breaker ? .

15 A

A 3-phase, 4-wire feeder supplies a continuous load of 75 amperes and a noncontinuous load of 75 amperes to a second floor equipment distribution switchboard.

175

A 3-phase 4-wire feeder supplies a continuous load of 75 amperes and a non-continuous load of 75 amperes to a second floor equipment distribution switchboard.Second, by determining the minimum ampacity for this feeder, select the proper AWG XHHW-2 copper wire size. Assume all circuit conductors will be the same size and that reduced neutral conductors will not be considered. The terminals of the circuit breaker and switchboard are rated 75°C.

2/0 AWG

An existing 12 AWG TW copper conductor is connected to a new replacement circuit breaker with termination temperature limitation marked (not to exceed) 60/75°C. What is the allowable ampacity of this conductor now that it is connected to this circuit breaker?

20 A

A 10 AWG THWN copper conductor is connected to a circuit breaker with termination temperature limitation marked (not to exceed) 60°C. What is the allowable ampacity of this conductor now that it is connected to this circuit breaker ? .

30 A

An EMT raceway contains two 3-phase 480-volt branch circuits. Determine the minimum circuit breaker size for each of the 27 kilowatt 3-phase noncontinuous loads. Calculate to the appropriate standard size circuit breaker rating.

35 A

Two 8 AWG XHHW-2 copper conductors are connected to a two-pole circuit breaker with termination temperature limitation marked (not to exceed) 60/75°C. What is the allowable ampacity of these conductors now that they are connected to this two-pole circuit breaker?

50 A. he CB is rated for both 60 and 75 so use the 75.

The two most common conductor terminal temperature ratings associated with circuit breakers and other equipment rated 100 amperes or less are ? .

60°C and 75°C

The three most common insulated conductor temperature ratings associated with Table 310.15(B)(16) are ? .

60°C, 75°C, and 90°C

An EMT raceway contains two 3-phase 480-volt branch circuits. What minimum size THHN branch circuit conductor is required for one of the circuits when it supplies a noncontinuous load of 27 kW?

8 AWG THHN

In addition to temperature ratings of wire terminals, a circuit breaker may be marked with another temperature rating such as 25°C or maybe even as high as 40°C. This marking most likely specifies the ? temperature.

Ambient

The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the ? temperature rating of any connected termination, conductor, or device.

Lowest

Are THHN 90°C conductors permitted to be connected to the terminals of a circuit breaker and used at their 90°C ampacities as shown in Table 310.15(B)(16) if the connected load equpment is listed and approved at 90°C?

Only if the circuit breaker is listed and identified for such use

Where different temperature limitations of individual components are applied to a single circuit, the principle of the ? is often used to determine the temperature rating of the entire circuit.

Weakest Link