I thought I understood most of this, but your outstanding video exposed my weakness. I always wondered why the white wire of a multiwire 240V circuit can be considered noncurrent carrying for the purpose of ampacity fill adjustment in table 5C. Even though it does carry current, as you say the maximal current will happen if the other leg is nonconducting, in which case you still have only two conductors! If load is balanced it carries zero, and in between the white is added to the lesser leg to equal the dominant leg, so the sum is equivalent to the ampacity of two high legs. People need to remember that this only applies with multiwire branch circuits, and with 240V appliances that carry a designated conductor for internal 120V use.
I think I misunderstood something. Five wires are in the pipe going into the panel. Why do we derate the ampacity of the wires to 75? The wires are rated 90. Once they enter the panel they're no longer in the pipe so the derating factor wouldn't apply? As long as the ampacity is still good for 75 tt.
I am confused with neutral as current carrying conductor in 63A path. First you told no need to consider neutral as current carrying , but at the end you consider it as 3 wire current carrying conductor. as i know we have to consider neutral as current carrying conductor when it is identified.
Thank you for the video I have a job site situation. I have 9 circuits (general use receptacles) to run in a 1 inch EMT. So 18 current carrying conductors. number 12 thhn. So 50 percent adjustment on 30 amp wire. Is that ok on a 20 amp breaker. Thank you.
Table “5C” apllies to all conductors not just current carrying. This includes neutrals and grounds.This in under the notes of table 2 and 4. This not give an note to current carrying conductors but all conductors . FYI.
If I had a question asking what to the ampacity of the conductor are in a similar question BUT not given the Termination temp (for the Breaker panel) would I not need to use 60 deg column according too 4-006 2) a) ? I was given a question like that but wasn't given the termination temp. I got it marked incorrect. I know breaker boxes are 75 deg termination temp but if it doesn't say it in the question am I to just assume? I was always told to never assume when working with code questions.
Yes if no termination temperatures are indicated, we would apply 4-006 2). If the load is 100amps or less we would assume 60° C, however above 100amps, we assume termination temperatures of 75° C. I would check the question to see where it falls in those two.
@@schulerruler this was the question. Eight No. 10 AWG RW90XLPE aluminum conductors Installed in a run of EMT Terminating on circuit breakers. What is the maximum ampacity rating of the conductors? a) 17.5 A b) 21A c) 24.5 A d) 30 A Using Table 4 under the 60 deg column i got 25A than went to Table 5C to derate 70% (.70) = 17.5 A The online CSA exam simulator said I was wrong and it's 21 A. Am I missing something?
I would say based on that question you've got yourself a case haha. They don't indicate anything about the breaker we would definitely use 60 and I agree with your selection. They have used the 30amp ampacity at 75 as an incorrect assumption.
@@schulerruler okay I appreciate you taking the time out of your weekend to help me. I have a hard time letting go on stuff like this. I need to know where I go wrong. Thank you again.
Apply correction factor first to determine the minimum ampacity of the load, then proceed with the Volt drop calculation to determine the minimum conductor size.
@@gbce2404 it does carry current but the three wire circuit will only ever carry the EQUIVALENT of two current carrying conductors regardless of the configuration.
Crazy that so many Electricians have not learned this..... Good Break down, Thank You
I thought I understood most of this, but your outstanding video exposed my weakness. I always wondered why the white wire of a multiwire 240V circuit can be considered noncurrent carrying for the purpose of ampacity fill adjustment in table 5C. Even though it does carry current, as you say the maximal current will happen if the other leg is nonconducting, in which case you still have only two conductors! If load is balanced it carries zero, and in between the white is added to the lesser leg to equal the dominant leg, so the sum is equivalent to the ampacity of two high legs. People need to remember that this only applies with multiwire branch circuits, and with 240V appliances that carry a designated conductor for internal 120V use.
great video, the edison 3 wire explanation was a bit confusing. I'll check the video on it.
Wonderful presentation. Thank you.
I think I misunderstood something. Five wires are in the pipe going into the panel. Why do we derate the ampacity of the wires to 75? The wires are rated 90. Once they enter the panel they're no longer in the pipe so the derating factor wouldn't apply? As long as the ampacity is still good for 75 tt.
I am confused with neutral as current carrying conductor in 63A path. First you told no need to consider neutral as current carrying , but at the end you consider it as 3 wire current carrying conductor. as i know we have to consider neutral as current carrying conductor when it is identified.
Could we have used #4awg only in the first conduit and reduce it after the junction box ? For the 63A load
I have exactly this question. did you find any answer?
Absolutely, as past that point you would not have to worry about the the additional magnetic fields from the other conductors anymore.
for 38A load if it is 120v instead of 240 .Do I count the Nature
Awesome video
Thank you for the video I have a job site situation. I have 9 circuits (general use receptacles) to run in a 1 inch EMT. So 18 current carrying conductors. number 12 thhn. So 50 percent adjustment on 30 amp wire. Is that ok on a 20 amp breaker. Thank you.
Table “5C” apllies to all conductors not just current carrying. This includes neutrals and grounds.This in under the notes of table 2 and 4. This not give an note to current carrying conductors but all conductors . FYI.
If I had a question asking what to the ampacity of the conductor are in a similar question BUT not given the Termination temp (for the Breaker panel) would I not need to use 60 deg column according too 4-006 2) a) ?
I was given a question like that but wasn't given the termination temp. I got it marked incorrect. I know breaker boxes are 75 deg termination temp but if it doesn't say it in the question am I to just assume? I was always told to never assume when working with code questions.
Yes if no termination temperatures are indicated, we would apply 4-006 2). If the load is 100amps or less we would assume 60° C, however above 100amps, we assume termination temperatures of 75° C. I would check the question to see where it falls in those two.
@@schulerruler this was the question.
Eight No. 10 AWG RW90XLPE aluminum conductors Installed in a run of EMT Terminating on circuit breakers.
What is the maximum ampacity rating of the conductors?
a) 17.5 A
b) 21A
c) 24.5 A
d) 30 A
Using Table 4 under the 60 deg column i got 25A than went to Table 5C to derate 70% (.70) = 17.5 A
The online CSA exam simulator said I was wrong and it's 21 A.
Am I missing something?
I would say based on that question you've got yourself a case haha.
They don't indicate anything about the breaker we would definitely use 60 and I agree with your selection. They have used the 30amp ampacity at 75 as an incorrect assumption.
@@schulerruler okay I appreciate you taking the time out of your weekend to help me. I have a hard time letting go on stuff like this. I need to know where I go wrong. Thank you again.
Happy to help my friend.
A question, does really matter if we have FLC or FLA?
They are the same for all intents and purposes.
hello
how the wire nuts and two way/3 way switches to be considered in box
Each pair of wire nuts will count as one conductor.
Each of the you mentioned will count as two conductors of mounted on a single strap each.
How could we apply derating to voltage drop
Apply correction factor first to determine the minimum ampacity of the load, then proceed with the Volt drop calculation to determine the minimum conductor size.
@@schulerruler Thank you
Is it possible to use #4awg only in the first conduit and reduce it after the junction box ? For the 63A load
Absolutely, as past that point you would not have to worry about the the additional magnetic fields from the other conductors anymore.
But don’t the neutral carries the unbalanced load?
It carries the unbalanced current yes, but also maintains phase voltage, and the voltage in a 120/240V circuit.
Wouldn’t it be consider a current carrying conductor then?
@@gbce2404 it does carry current but the three wire circuit will only ever carry the EQUIVALENT of two current carrying conductors regardless of the configuration.
Only in multiwire Branch circuits