Coaching Conversations from the ICC Commercial Electrical Course
These are actual coaching conversations from our online ICC Commercial Electrical course.
Our coaching system is simple and convenient. You can easily ask a question anywhere in the course. There's no need to open your email program or go to another page.
I am having difficulty understanding the quiz answer to question 9 in module 2. The correct answer given is 500 VA. It looks to me that the correct answer should be 1500 VA but is not a choice? I also do not understand how it is traceable to circuit #17. The plan shows the floor box in the office and the item is listed as being in the break room which is not listed on the plan.
Scott,
The floor box is circuited to circuit L1-35.
The panelboard schedule shows 500 VA load for circuit L1-35.
I hope this helps.
Thanks,
Aleksandar
Regarding table 230.51(C), I understand that the asterisked 1000 maximum volts row refers to those not exposed to weather, but why are there two non-asterisked rows of 1000v maximum?
Craig,
Good question! You are right, the asterisked 1000 max volts refers to the individual open conductors exposed to the weather. The two 1000 max volts without asterisks are for the two different maximum distance values between the supports. The longer the distance between the supports is, the more clearance is required between the conductors. For the maximum distance of 9 ft between the supports, the minimum clearance between conductors is 6 in. For the maximum distance of 15 ft between the supports, the minimum clearance between the conductors is 12 in. This makes sense because a longer distance between the supports means a higher chance for conductors (open conductors) to move and get in contact with each other.
I hope this helps. Let me know if you have any further questions.
Aleksandar
I am trying to understand Interrupting rating. When I look at circuit breakers which are overcurrent protection devices for branch circuits they can be rated for as low as 20 Amp. But under NEC definition (pg:70-39) of overcurrent device, branch circuit: it says that the interrupting rating to be no less than 5000 Amp. This is confusing.
The overcurrent protective devices provide overload, short-circuit, and ground fault protection (or a combination of the three). The most common combination is the overload protection (ampere rating) and short-circuit current protection (interrupting rating). In the exhibit below, you can see a Square D circuit breaker with an ampere rating of 20 amperes (see NEC 240.6) and the short-circuit current rating of 10,000 amperes (or 10 kA).
If, for example, 22 amperes flow through this breaker, the breaker will trip (immediately or eventually, depending on the breaker type, ambient temperature, and other factors).
The 10 kA value is the maximum short-circuit current rating that the device can withstand. If the short-circuit current exceeds 10 kA, the breaker may rupture, catch fire, etc.
The definition you referenced states that 5000 amperes is the minimum short-circuit current interrupting rating. If a circuit breaker has interrupting rating other than 5000 amperes, that rating must be shown on the circuit breaker (like in the exhibit below, see NEC 240.83(C)).
Also, see 110.9 for Interrupting Rating requirements.
I hope this answers your question.
Sincerely,
Aleksandar
I need help with this question.
The question is: "What is the total load of rooftop unit RTU-5?"
Answer 1: 3,492 volt-amperes
Answer 2: 5,220 volt-amperes
Answer 3: 6,984 volt-amperes
Answer 4: 10,440 volt-amperes
The correct answer is: Answer 4.
Rick,
The panelboard schedule is split into the left phase load (odd circuit numbers - 1, 3, 5...) and the right phase load (even circuit numbers - 2, 4, 6...) part. That is the industry standard. Most engineering consulting companies use similar schedules to show panelboard loads. On the right phase load side, the circuits are 18 and 20 (CU-1).
thx
2020 NFPA Handbook p261. table 310.4(A) Flame -retardant, moisture resistance, thermoplastic under insulation----what type of outer covering does a TW Type conductor have? Please explain. Your answer was "None".
See below.
Practice Test 1, Question 13.
What is the temperature adder for raceways and cables exposed to sunlight on rooftops when distance above the roof to the bottom of the raceway or cable is less than 7/8"?
The explanation given was to see 310(B)(3)(c)
Please help explain
Raymond,
Subsection 310.15(B)(3)(c) discusses the conductor ampacity adjustment factors for raceways or cables exposed to direct sunlight on or above rooftops.
It states the "Where the distance above the roof to the bottom of the raceway is less than 7∕8 in., a temperature adder of 33°C shall be added to the outdoor temperature."
I hope this helps.
Thanks,
Aleksandar
Hey I got a question on the NFPA 70 adjusting ampacity of 1/0 copper current carrying conductor single raceway exceeds 50ft dry location question.
I can follow up to why did you pick that particular table to get the 170 amps.
Thanks and let me know
If I understand your question correctly, you ask why we picked Table 310.15(B)(6).
If you carefully examine NEC Ampacity Tables 310.15(B)(16) through (21), you will see that that is the only table that addresses the THHN/THWN conductors that are installed in conduits. 310.15(B)(17), for example, addresses the THHN/THWN conductors of this same insulation that are free-aired, while 310.15(B)(18) refers to conductors with different insulation (for much higher temperatures).
I hope this answers your question.
Module 8 quiz question 15 answer "None" is incorrect. Table 310.104(A) (70-167) lists "Flame-Retardant"
Eric,
Type TW conductors do not require outer covering. You are referencing the Insulation column in Table 310.104(A). Please check the column to the right - Outer Covering.
Thanks,
Aleksandar
I am on intermediate quiz Q8.5.2 which states that the temp adjustment factor for the 90C degree column is 0.87. My 2017 NEC shows the adjustment factor as 0.95 in the 90C degree column, and 0.87 in the 60C degree column for 41-45C degree row. Which one is correct?
Jacob,
Please refer to Table 310.15(B)(2)(a). It seems that we are looking at Table 310.15(B)(2)(b) instead.
Thanks,
Aleksandar
5 ft would make it accessible so you can unplug it if you need it to
The question is: "A cord that supplies low-voltage lighting is permitted to be installed not less than _____ ft above the finished floor."
Answer 1: 5
Answer 2: 7
Answer 3: 9
Answer 4: 10
The correct answer is: Answer 2.
My answer was: Answer 1.
Albert,
The code permits not less than 7 ft as stated in 411.6.(D)(2).
Thanks,
Aleksandar
Good afternoon, where in the NEC are the electric symbols located? there are a couple of questions asked that used symbols that I didn't recognize.
Nathan,
The NEC does not have a list of electrical symbols used on electrical plans. There are a few electrical symbols scattered throughout the NEC book, but nothing like a table or list of symbols with descriptions. Engineering offices use their own electrical symbols identical or similar to the example symbols included in Module 2. You can find a simple list of electrical blueprint symbols in Ugly's Electrical References.
Thanks,
Aleksandar
In the quiz answers, it refers to using NEC content pages such as 70-2 to 70-4. Where are these pages ?
Gary,
See below for the page reference example. I hope this helps.
Thanks,
Aleksandar
