©Ted “Smitty” Smith 2008. This speed drill focuses on calculations that will be required for the journeyman and masters examination. The question slide.

©Ted “Smitty” Smith 2008

This speed drill focuses on calculations that will be required for the journeyman and masters examination. The question slide will still transition in 3 ½ minutes and will be followed by the correct answer which will stay on the screen for only 10 seconds. Do not worry about writing down the correct answer during the transition. At the end of the questions, a stop slide will appear and then that will be followed by the questions and answers without the timer so you can review them. You must click on the screen icon in the lower right hand or left corner of the tool bar to start the slide show in order for the timer to operate.

What is the minimum number of lighting branch circuits, excluding the small appliance branch circuit, that will be required for a dwelling unit that is 2385 square feet? The lighting circuits will all be 15 ampere rated circuits. The service to the home will 240V single phase. Copyright 2005 Ted "Smitty" Smith

2385 x 3= 7155/120=59.625 amperes/15=3.975 circuits Correct answer= 4 circuits minimum

What is the demand on the main service entrance of an apartment building for the cooking equipment? The apartments are each equipped with a 13.5 kW range rated at 240V. The apartment complex has a total of 10 apartments. The service to the apartment building is 240V single phase. Copyright 2005 Ted "Smitty" Smith

25000 x 1.10= 27500 watts

What is the maximum branch circuit- short circuit protection allowed for a 208V, three phase, squirrel cage motor with the following nameplate ratings: 20 hp, 51.6 A FLC, 1.15 Service Factor, and Design B The short circuit protection will be done with an inverse time circuit breaker.

150 ampere inverse time breaker.

What is the minimum trade name size conduit that can be used for a 310 foot conduit run that will contain nine 10 AWG TW conductors, five 2 AWG RHW conductors with outer covering, and two 6 AWG RHH conductors that do not have an outer covering? The wires will be installed in an intermediate metal conduit.

The total area of the conductors is 1.0934 and a 2” IMC at 31% fill will allow 1.125. 2”

A 480V three phase service is fed by four parallel runs of 250 kCMIL THHN conductors. An equally sized grounded conductor is run with each set of ungrounded conductors. The service is rated at 1000 amperes. A main bonding jumper conductor is installed between the grounded bus bar and the grounding electrode bus bar in the service. The bonding jumper is a bare copper 1/0 conductor. Is this an allowable installation? Copyright 2008 Ted "Smitty" Smith

No. Table 250.66 requires a minimum 2/0 AWG copper main bonding jumper in this application.

A pvc junction box that is permanently stamped as having a volume of 110 is installed as an underground junction box. The box has 4 pvc conduits entering the box. One conduit entering the box contains nine 10 AWG THHN conductors and one 12 AWG THHN equipment grounding conductor all of which terminate in the box. Another conduit entering contains nine 10 AWG THWN-2 conductors and one 12 AWG THHN equipment grounding conductor all of which terminate in the box. Two of the conduits entering the box contain eight 6 AWG THWN conductors and one 12 AWG equipment grounding conductors. All of the 6 AWG conductors are pulled through the box without terminating and a coil of 12 inches is left in each conductor for future maintenance. The 12 AWG equipment grounding conductors terminate in the box. No devices are present in the box. Is this an allowable installation?

No it is not. The volume of the box is 110. The conductors need a volume of 127.25

A branch circuit has a load of 17.5 amperes. The load is expected to operate at periods of 4 hours or more continuously. The branch circuit conductors are installed in a raceway that contains a total of twelve current carrying conductors. The branch circuit conductors are 8 AWG THHN copper conductors and they are protected by a 60 ampere inverse time circuit breaker for overcurrent protection. Is this an allowable installation? Copyright 2005 Ted "Smitty" Smith

Yes it is allowed. The derated and adjusted load is 43.75 amperes. An 8 AWG THHN has an ampacity of 55 amperes. Applying 110.14(C) requires we ensure that the original load of 17.5 x 1.25 for continuous duty is covered by an 8 AWG THHN in the 60 degree C column and it is. 240.4 and 240.4(B) allow the protection of the conductors to be done by the next higher standard size if all three conditions are met and this installation meets those conditions. So a 60 ampere overcurrent device is allowed. Copyright 2005 Ted "Smitty" Smith

A fixed multioutlet wiremold assembly, that is 25 feet in length, is installed in an office building with a 120V, 20A duplex receptacle installed 12 inches from the end and every two feet thereafter. The wiremold is fed with three 20 ampere branch circuits and the duplex receptacles are divided evenly between the three branch circuits. Is this an acceptable installation? The devices are expected to by used simultaneously. Copyright 2005 Ted "Smitty" Smith

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