I have spoken with a few of the senior members (Marc, Larry, and Peter) about posting some sample electrical test questions. I have many questions that I had written to help a fellow electrician study for a licensing exam. About 50 of those questions are somewhat related to dwellings so they may be beneficial to home inspectors looking to broaden their electrical knowledge. I’ll post 5-10 at a time and then after a few days I will post the answers and If anyone has questions we can discuss the answers.
This is not related the the questions of the week so there are no prizes and it just for educational purposes and fun. Also feel free to as many questions as you like. There is no need to answer all of them.
Just a hint, many tests questions contain information that is not relevant to the answer to confuse you. Some of these questions are written that way so what may jump out at you as the obvious answer may not always be the correct answer. All questions are based on the 2020 NEC which is what the adopted electrical code here in New Jersey. Here’s the first ten questions. Enjoy.
ELECTRICAL QUESTIONS: 2020 NEC
A two family dwelling has two 200 amp service disconnects (one for each unit) and a common single riser feeding a two meter stack. The calculated load for the two units is 170 amps. What is the minimum size aluminum service conductors required to feed the meters?
a) 600 kcmil
b) #4/0
c) 250 kcmil
d) #1/0
e) #2
True or False. A grounding electrode conductor is required to be bare or insulated green or insulated green with a yellow stripe?
True or False. A white conductor pulled in a raceway can be re-identified as an ungrounded conductor if taped or otherwise marked in colors black, red, or blue?
What is the maximum number of NM cables permitted to be run through a bored hole in a wood stud?
a) Two
b) Four
c) Three
d) No limit
e) Five
True or False. A 10/32 screw used to attach a #12 AWG solid wire bonding jumper to a metal box must be green.
A dwelling has a 200 amp service which has a GEC (grounding electrode conductor) run to a CEE (concrete encased electrode), what other electrodes are required to be installed or connected to as part of the GES (grounding electrode system)?
a) Ground rod
b) Ground ring
c) Plate electrode
d) Metal gas pipe
e) None of the above
True or False. A metal switch box with a single pole switch is fed with armored cable (Type AC) therefore it must have a bonding jumper from the device to the box or be a self-grounding type.
.
An outdoor AC unit has a MCA (minimum circuit ampacity) of 24 amps and a MaxOCPD of 45 amps. What is the minimum copper conductor size required when pulling type THHN/THWN conductors in a raceway to feed this unit and using a 45 amp circuit breaker?
a) #8 AWG
b) #10 AWG
c) #12 AWG
d) #6 AWG
e) None of the above
A copper NM cable MWBC (multi-wire branch circuit) is run to provide two small appliance branch circuits for kitchen countertop receptacles. Which item from the list below is required?
a) A handle tie on two single pole circuit breakers feeding the MWBC
b) A GFCI circuit breaker
c) A 2-pole circuit breaker
d) A lock out device on the circuit breaker
e) A minimum conductor size of #14 AWG
True or False. A 240 volt window air conditioner has its own individual branch circuit. The circuit conductors are #14 NM cable, the OCPD is a 2-pole 15 amp circuit breaker. The single receptacle is permitted to be 15 or 20 amps
Illinois does not have a statewide electrical code for residential use. The local AHJ adopt the National Electrical Code (NEC) as they see fit. Most in my area of Southern Illinois are using 2017 NEC and up.
Okay so here are the answers to the first 10 questions. Feel free to post comments or questions. These answers have been pretty well vetted but if you think that the answer is incorrect let me know and we can discuss it. As with anything of this nature it is always possible that a mistake was made.
ELECTRICAL QUESTIONS: 2020 NEC/Answers
A two family dwelling has two 200 amp service disconnects (one for each unit) and a common single riser feeding a two meter stack. The calculated load for the two units is 170 amps. What is the minimum size aluminum service conductors required to feed the meters?
a) 600 kcmil b) #4/0
c) 250 kcmil
d) #1/0
e) #2
The minimum conductor size is based on the calculated load of 170 amps.
True or False. A grounding electrode conductor is required to be bare or insulated green or insulated green with a yellow stripe?
The GEC can be bare or insulated with any color insulation other than those colors designated as neutral conductors.
True or False. A white conductor pulled in a raceway can be re-identified as an ungrounded conductor if taped or otherwise marked in colors black, red, or blue?
A white conductor within a raceway cannot be re-identified as an ungrounded conductor. A white conductor within a cable assembly such as NM cable can be re-identified as an ungrounded conductor.
What is the maximum number of NM cables permitted to be run through a bored hole in a wood stud?
a) Two
b) Four
c) Three d) No limit
e) Five
There is no limit unless the hole contains fire or draft stop material.
True or False. A 10/32 screw used to attach a #12 AWG solid wire bonding jumper to a metal box must be green.
The bonding screw is not required to be any specific color.
A dwelling has a 200 amp service which has a GEC (grounding electrode conductor) run to a CEE (concrete encased electrode), what other electrodes are required to be installed or connected to as part of the GES (grounding electrode system)?
a) Ground rod
b) Ground ring
c) Plate electrode
d) Metal gas pipe e) None of the above
A CEE used to create a GES does not require any other electrodes.
True or False. A metal switch box with a single pole switch is fed with armored cable (Type AC) therefore it must have a bonding jumper from the device to the box or be a self-grounding type.
Switches connected to metal boxes via the two 6-32 screws are not required to be self-grounding and do not require a bonding jumper. The bonding jumper or self-grounding requirement would apply to receptacles.
An outdoor AC unit has a MCA (minimum circuit ampacity) of 24 amps and a MaxOCPD of 45 amps. What is the minimum copper conductor size required when pulling type THHN/THWN conductors in a raceway to feed this unit and using a 45 amp circuit breaker?
a) #8 AWG
b) #10 AWG c) #12 AWG
d) #6 AWG
e) None of the above
#12 THHN/THWN is rated for 25 amps at 75° C. The small conductor ampacity limit of 20 amps from Article 240 does not apply to this type of installation. Conductors are only required to be sized according to the MCA.
A copper NM cable MWBC (multi-wire branch circuit) is run to provide two small appliance branch circuits for kitchen countertop receptacles. Which item from the list below is required? a) A handle tie on two single pole circuit breakers feeding the MWBC
b) A GFCI circuit breaker
c) A 2-pole circuit breaker
d) A lock out device on the circuit breaker
e) A minimum conductor size of #14 AWG
Of the items on the list only a) would be correct because two single pole breakers feeding a MWBC would require a handle tie. b), c), and d), are not required. e) cannot be used on these 20 amp circuits.
True or False. A 240 volt window air conditioner has its own individual branch circuit. The circuit conductors are #14 NM cable, the OCPD is a 2-pole 15 amp circuit breaker. The single receptacle is permitted to be 15 or 20 amps.
When a single receptacle is used as the sole device on a circuit it is only required to be a minimum size of the branch circuit (there is no maximum size limit) so a 20 amp single receptacle is permitted on a 15 amp circuit.
Thanks for these questions Robert, I got most of them wrong so a great refresher
And good timing for the above OP’s report writing on those white wires being used as ungrounded conductors/feeders in a raceway. I haven’t come across that one yet